Which primary symptom does the nurse identify as a potentially fatal complication of epidural or intrathecal anesthesia?

Journal Article

T. M. Cook,

1

Department of Anaesthesia

,

Royal United Hospital

,

Combe Park, Bath

,

UK

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Accepted:

19 November 2008

Published:

12 January 2009

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  T. M. Cook, D. Counsell, J. A. W. Wildsmith, on behalf of The Royal College of Anaesthetists Third National Audit Project, Major complications of central neuraxial block: report on the Third National Audit Project of the Royal College of Anaesthetists, BJA: British Journal of Anaesthesia, Volume 102, Issue 2, February 2009, Pages 179–190, https://doi.org/10.1093/bja/aen360

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Abstract

Central neuraxial block (CNB) techniques can produce highly effective pain relief for a wide variety of indications and may decrease patient morbidity after major surgery, although the extent of the latter benefit is not agreed universally.1,2 In recent years, both large randomized controlled trials (RCTs)3 and meta-analysis2 have led to conflicting conclusions and interpretations regarding the outcome benefit of CNB techniques. However, the risk–benefit analysis must also take into account both the rate of failure of the techniques, which may be higher than some accept,4 and the incidence of complications.5–7 In the past, these complications have been serious enough to turn the speciality away from the techniques almost entirely, particularly when reports of paraplegia after spinal anaesthesia in both the USA8 and the UK9 led to the near abandonment of CNB in the UK for more than two decades after the Second World War. With the techniques now used widely again, there are reports of, and commentaries on, major complications from both the UK and elsewhere.10–17 Most recently, Christie and McCabe18 reported a series from one hospital that, with a very high incidence of major sequelae, achieved some prominence.

Knowledge of the incidence of such complications should be an essential component of the clinical decision-making and consent processes, but there are few good data which can be quoted to support such discussions, leaving both patient and clinician in a quandary. Figures (ranging from 1:1000 to 1:100 000) are quoted, but their doubtful validity questions the ability to obtain genuinely informed consent from patients offered these procedures. Recognizing this, and that neither RCT nor meta-analysis is an appropriate method for identifying rare events, the Council of the Royal College of Anaesthetists devoted its third National Audit Project to this topic. The aim was a prospective attempt to identify both numerator (number of major complications) and denominator (number of CNB) information for a 12 month period by a review across the breadth of anaesthetic and pain management practice in the UK National Health Service (NHS). Follow-up (as far as an anonymous reporting system would allow) would extend to 6 months so that final outcome, and incidence, could be assessed and give some indication of the prognosis of such events.

Methods

A two-part project was devised: first, an assessment of the number of CNBs performed annually in the UK NHS (for denominator information); and second, an audit of the major complications of these procedures performed during a 12 month period (for numerator information). Discussions with the Centre of Research Ethics Committees (now National Research Ethics Service) indicated that ethical approval was not required, and the processes involved were agreed with the Patient Information Advisory Group of the Department of Health. The project was advertised widely throughout 2006 and 2007 through direct contact with the relevant organizations in anaesthesia, pain management, neurology, spinal surgery, radiology, and neuroradiology (Appendix 1). The aims and processes of the project were explained and the information was cascaded down to the members of those organizations at regular intervals.

Denominator data

A detailed description of the first part, the ‘snapshot’ survey (census) to determine denominator information, has been published already,19 but a brief summary is appropriate here. Between March and September 2006, the anaesthetic department of each NHS hospital believed to be performing surgery was contacted, asked to participate, and to nominate a ‘local reporter’ (LR) to co-ordinate the project locally. Each LR was asked to collect information on the number of CNBs performed over a 2 week period at the end of September 2006 or an equivalent period at about that time. The blocks were classified as epidurals, spinals, combined spinal–epidurals (CSEs), and caudals for each of the five indications: adult perioperative, obstetric (both labour analgesia and operative delivery), chronic pain, paediatric perioperative, and administered by a non-anaesthetist. We did not request data on CNB that were attempted and failed as we considered it unlikely that all cases would be recorded reliably. For each category, the reporters indicated whether their data were ‘accurate’, a ‘close estimate’, or an ‘approximate estimate’. The mechanism of data collection was not specified and reminders to return information were sent at regular intervals by post, e-mail, and telephone as necessary. Data were summed to give cumulative totals for a nominal 2 week period and, based on the annual results of one large district general hospital (Royal United Hospital, Bath), these figures were then multiplied by 25 to give an approximation of annual activity.

Event reporting (numerator data)

The same LR system was used to identify complications of CNB, but direct reports from any clinician in all relevant specialities were promoted with the aim of ensuring complete capture of all possible cases. We accepted reports even if the attempted CNB was abandoned: as such, there is a potential to slightly overestimate the incidence of complications because we did not include these attempts in the denominator. The formal audit period was September 1, 2006, to August 31, 2007, inclusive, but reporting was actively encouraged until March 31, 2008, for the same reason. Information was sought on all major complications of CNB with the potential for serious patient harm, including infection, haematoma, nerve damage, and cardiovascular collapse (detailed in Table 1). In addition, because of current concern about wrong route errors (i.e. a drug intended for the epidural or subarachnoid space inadvertently administered i.v., or vice versa),20 reports on these events were encouraged even when no injury occurred.

Table 1

Complications sought in the audit process

Table 1

Complications sought in the audit process

Primary notification of an event was by e-mail, with reports accepted from any source. The project team was able to exclude obviously irrelevant cases at this stage, but otherwise the LR for the relevant hospital was asked to obtain the details and upload them to a secure, password-protected website (the National Confidential Acute Pain Critical Incident Audit, NCAPCIA, www.ncapcia.org.uk). The information requested depended on the type of incident, but the questions were designed to gain a full picture of the procedure and the presentation, severity, and consequences of the complication. The NCAPCIA administrator (D.C.) was able to access these reports and request updates as required, being the only person who knew their source: this was essential to allow requests for clarification and updates of information while maintaining confidentiality. Each case was reviewed in detail by a panel representing all the specialities involved in the project (Appendix 2), and the following details were confirmed:

• type of block and indication for its performance (as described above). Procedures performed for the control of non-operative acute pain (e.g. fractured ribs and pancreatitis) were included in the perioperative group;

• category of complication (Table 1);

• correctness of diagnosis;

• date of CNB within the audit period;

• CNB was performed in an NHS hospital;

• severity of patient outcome (see below), initially and at 6 months (or later where such information was available);

• causation: whether the CNB was the cause of the patient injury: certain, likely, possible, unlikely, and no link.

Severity of complications

Severity of initial and final harm was recorded in a variety of ways. First, it was categorized according to the National Patient Safety Agency (NPSA) severity of outcome scale for patient safety incidents (Table 2).21 Patient harm was graded as ‘temporary’ if the incident met the NPSA criteria for moderate injury, and ‘permanent’ if the outcome was worse than this (severe injury or death). Secondly, where injury was permanent, or assumed to be so, the features were classified as follows:

• sensory only;

• motor: motor weakness of whatever severity, with or without sensory symptoms;

• paraplegia: paraplegia or tetraplegia with or without additional motor or sensory symptoms;

• death: this was classified as ‘direct’ (e.g. a cervical abscess leading to tetraplegia, respiratory failure, and death) or ‘indirect’ when the CNB was followed by a series of other events leading to death (e.g. an abscess requiring decompression with good neurological recovery, but complicated by a fatal pulmonary embolism).

Table 2

National Patient Safety Agency severity of outcome scale for patient safety incidents. *First aid, additional therapy, or additional medication. Excludes extra stay in hospital, return to surgery, or readmission. †Return to surgery, unplanned re-admission, prolonged episode of care as in or out patient or transfer to another area such as ICU. ‡Permanent lessening of bodily functions, sensory, motor, physiologic, or intellectual

Table 2

National Patient Safety Agency severity of outcome scale for patient safety incidents. *First aid, additional therapy, or additional medication. Excludes extra stay in hospital, return to surgery, or readmission. †Return to surgery, unplanned re-admission, prolonged episode of care as in or out patient or transfer to another area such as ICU. ‡Permanent lessening of bodily functions, sensory, motor, physiologic, or intellectual

Interpretation of reports

In a proportion of cases, LRs were not able to provide full details of cases and patient progress, and some information was incomplete in spite of follow-up requests. Therefore, the reports required some ‘interpretation’ by the review panel, which assumed the worst, unless there was evidence to refute it:

• Diagnosis: where this was uncertain, cases were included: only those with clear evidence of incorrect diagnosis were excluded.

• Causation and outcome: these were particularly difficult to judge in a number of cases, and this led to a decision to quote rates of complications in two ways, that is, in terms of both ‘worst’ and ‘best’ case scenarios, defined in the results as ‘pessimistic’ and ‘optimistic’ incidences. When causation was judged certain, likely, possible, or unlikely, cases were included in the ‘pessimistic’ analysis, but those judged as unlikely were excluded from the ‘optimistic’ analysis. Similarly, efforts were made to determine the patient outcome at 6 months after the CNB. Where outcome at 6 months (or later) was available, this was used in the final judgement, but if such outcome information was only available from an earlier date, that outcome was assumed to have persisted—the ‘pessimistic’ outcome.

• Thus, the results are presented both cautiously (the ‘pessimistic’ figures) and pragmatically (the ‘optimistic’ figures).

Validation of data

Requests were made to several organizations for information which might validate (i.e. confirm the completeness of) both denominator and numerator data. For the denominator, this included the National Joint Registry, the National Obstetric Anaesthesia Database, and the Department of Health Hospital Episodes Statistics. For the numerator, we sought evidence of relevant cases from the NHS Litigation Authority (NHSLA) and National Reporting and Learning Service (NRLS) of the NPSA, the Medical Protection Society, and the Medical Defence Union. Medical journals were checked for reports of relevant cases and authors contacted as necessary. The internet search engine ‘Google’ was used to search for news items published on the internet with the words (epidural, spinal, death, abscess, haematoma, and infection).

Incidence calculations

Cases were included in the numerator where a complication of CNB led to permanent patient harm and the CNB had been performed within the audit period and in an NHS hospital.

The data were entered into a Microsoft Excel 2007 spreadsheet (Microsoft Corporation, USA) and incidences were calculated (by dividing the numerator for a given group by the relevant denominator). Confidence intervals (CIs) were derived using binomial probability tests with the stat-conf programme (Handbook of Biological Statistics 2008, http://udel.edu/~mcdonald/statconf.html). The primary end-points of the study were the incidences (both ‘pessimistic’ and ‘optimistic’) of permanent harm due to complications of the various types of CNB performed within the 1 yr audit period in an NHS hospital. The incidence of decompressive laminectomy in adult patients undergoing a perioperative epidural block was also calculated.

Results

This report focuses primarily on the quantitative aspects of the project. A full report, with expanded clinical details and analysis to identify clinical learning points will be published simultaneously by the Royal College of Anaesthetists (www.rcoa.ac.uk).

By September 2006, all 309 hospitals which had been contacted had agreed to participate and had appointed an LR.

Denominator data (snapshot returns)

The original publication of ‘snapshot’ data was based on reports from 97% of hospitals,19 but since then returns have been received from the final 3%. Thus, the denominator data (Table 3) used in the calculation of incidences of complications are based on returns from all the hospitals surveyed, 92% of them grading their figures as ‘accurate’. Extrapolating to annual activity by using a multiplier of 25 (see comment above) suggests that a total of just more than 700 000 CNB procedures [∼325 000 (46% of total) subarachnoid blocks, 293 000 (41%) epidurals, 42 000 (6%) CSEs, and 47 000 (7%) caudals] are performed annually in the UK. The majority of CNBs were performed for obstetric (45%) or perioperative care (44%) indications.

Table 3

Census phase: estimate of the number of CNB procedures performed annually in 309 UK NHS hospitals (100% return). Figures in parentheses are percentages: in the right column, the percentage of all CNB that were of the type of block of the relevant row, and in the penultimate row, the percentage of all CNB that were performed for the clinical indication of the relevant column. ‘Non-anaesthetists’ include neurosurgeons, spinal surgeons, orthopaedic surgeons, rheumatologists, ‘physicians’, and general practitioners. The bottom row indicates the percentage of returns recorded as ‘accurate’: others were close estimates, or estimates

Table 3

Census phase: estimate of the number of CNB procedures performed annually in 309 UK NHS hospitals (100% return). Figures in parentheses are percentages: in the right column, the percentage of all CNB that were of the type of block of the relevant row, and in the penultimate row, the percentage of all CNB that were performed for the clinical indication of the relevant column. ‘Non-anaesthetists’ include neurosurgeons, spinal surgeons, orthopaedic surgeons, rheumatologists, ‘physicians’, and general practitioners. The bottom row indicates the percentage of returns recorded as ‘accurate’: others were close estimates, or estimates

None of the databases consulted in an attempt to validate these data provided information that could be used for that purpose.

Numerator data (complications reported)

Event returns and validation of completeness

In total, 108 cases were reported directly to the project team or through NCAPCIA, with 84 of these being considered appropriate for panel review. The 24 cases eliminated by the project team before panel review were all minor complications of no relevance to the problems under consideration: when there was the slightest doubt, the cases were included for review.

The NHSLA and NRLS databases were screened by the NPSA for all reports relating to CNB performed in the audit period. This identified ∼1700 cases reported to the NRLS (of which 13 were reported to have a serious or fatal outcome) and five cases notified to the NHSLA. The audit lead (T.M.C.) reviewed an unselected subset of 200 of the NRLS cases, all NRLS cases with a serious or fatal outcome, and all NHSLA cases. The NRLS review identified only one case meeting the criteria of the current project (in the 13 serious cases): this had already been reported. Two NHSLA cases were potentially relevant. One (a wrong route injection error) clearly met NAP3's inclusion criteria, but did not match the details of any cases reported at that time. A second case (of nerve injury) possibly met the inclusion criteria, but it was not clear whether it had been reported or not. Both hospitals were contacted by the NPSA and asked to report the case if it met inclusion criteria and had not been reported already. The wrong route injection case was subsequently reported to NCAPCIA and is included with those reviewed in detail.

Review of the literature identified three potential cases for inclusion, but discussion with the authors of the papers indicated that they did not meet the criteria. Internet-based news ‘alerts’ identified the wrong route injection case also identified by NHSLA screening. Other sources of validation did not identify any further cases.

Sources and timing of reports

Although the methodology of the system meant that anonymous reporting was possible, the majority (67) of cases were from identified individuals: 56 anaesthetists, nine neurologists, and two acute pain nurses. Similarly, other details cannot be described in full, but reports were received from all areas of the UK. Four hospitals reported more than one event, but two of these had neurosurgical units and were reporting complications of CNBs which had been performed elsewhere. It was not possible to obtain detailed information about the dual reports from the other two hospitals.

Events were notified throughout the audit period, but only one was reported after December 2007 and that was in August 2008, 5 months after the formal closure date. However, review indicated that it should be included in the analysis, even at a late stage.

Review panel assessments

Eighty-four cases were reviewed. Thirty-two cases were either performed outside the period of the audit, not performed in the NHS, or the complication did not meet the diagnostic criteria of the audit (wrong diagnosis, no link between CNB and notified complication, or full recovery of the complication at the time it was notified). Fifty-two cases therefore met all of the audit's inclusion criteria and efforts were made to follow-up these cases for a minimum of 6 months (Table 4). All 84 were reviewed for learning points for the clinical report to be published elsewhere (www.rcoa.ac.uk), but the remaining 52 are the focus of this analysis of the determination of permanent injury after CNB. Of these 52 patients, 22 made a fully documented complete recovery from their serious complication (NPSA classification ‘moderate’, Table 2): seven epidural abscesses, seven nerve or spinal cord injuries, three cardiovascular collapses [requiring cardiopulmonary resuscitation or admission to intensive care (ICU)], three cases of meningitis, one vertebral canal haematoma, and one other (intrathecal opioid overdose leading to respiratory arrest). These cases are not considered further. The remaining 30 events were used in the calculation of the ‘pessimistic’ incidences of permanent harm after CNB techniques. Detailed review indicated that in 16 cases, the patients were either likely to make a good recovery or the attribution of the permanent harm to the block was tenuous. This left 14 events for the calculation of the ‘optimistic’ incidences.

Table 4

Summary of cases reviewed and their classification by review panel. Exclusion from review was due to wrong diagnosis, minor injury, full recovery before notification, and procedure performed outside the dates of the audit or in a non-NHS hospital. See text for definitions of ‘pessimistic’ and ‘optimistic’ categories

Table 4

Summary of cases reviewed and their classification by review panel. Exclusion from review was due to wrong diagnosis, minor injury, full recovery before notification, and procedure performed outside the dates of the audit or in a non-NHS hospital. See text for definitions of ‘pessimistic’ and ‘optimistic’ categories

Patient characteristics

Events were distributed across both genders and the range of ASA status, with the majority of events occurring after elective surgical procedures and about half the CNBs having been performed by consultants and half by other grades (Table 5). There were no children in the 52 patients in the audit, and the majority of cases occurred in patients aged more than 50 yr. In the 30 patients with permanent harm (judged ‘pessimistically’), the complications were spread across all types of CNB: 18 (60%) followed epidural block and seven (23%) spinal anaesthesia. As far as clinical indication was concerned, 25 (83%) were in the perioperative group (Table 6).

Table 5

Patient characteristics data of cases reviewed by panel. See text for definitions of ‘pessimistic’ and ‘optimistic’ categories. *Based on reporter's data with some interpretation. †Not all data were requested for groups of complications (e.g. operator details were not requested for cardiovascular collapse, wrong route errors, or miscellany)

Table 5

Patient characteristics data of cases reviewed by panel. See text for definitions of ‘pessimistic’ and ‘optimistic’ categories. *Based on reporter's data with some interpretation. †Not all data were requested for groups of complications (e.g. operator details were not requested for cardiovascular collapse, wrong route errors, or miscellany)

Table 6

Complications used in calculation of ‘pessimistic’ (see text for explanation) incidences related to type of block and clinical indication

Table 6

Complications used in calculation of ‘pessimistic’ (see text for explanation) incidences related to type of block and clinical indication

Incidence of permanent harm

Considering the overall totals first, the incidence of any permanent injury (NPSA classifications serious and fatal, Table 2) after all CNBs in this survey is 4.2 per 100 000 (95% CI 2.9–6.1; equivalent to 1 in 23 500) using the ‘pessimistic’ assessment of outcome, and 2.0 per 100 000 (95% CI 1.1–3.3; 1 in 50 500) with the ‘optimistic’ assessment. However, there was a considerable variation between the incidences after different types of block. In both ‘pessimistic’ and ‘optimistic’ assessments, epidural and CSE were associated with higher incidences than both spinal and caudal blocks. Looking at clinical indication also revealed similar variation.

By using the subgroups we used in the census phase (Table 3), it is possible to calculate incidences for each of the subgroups. We report these for completeness (Tables 7–10), but as discussed below caution against their over-interpretation. The incidence of complications was highest after perioperative use and considerably lower in other groups (Tables 7 and 8). The incidence of permanent injury after adult perioperative epidural anaesthesia or analgesia was ‘pessimistically’ 17.4 per 100 000 (95% CI 7.2–27.8; 1 in 5800) and ‘optimistically’ 8.2 per 100 000 (95% CI 3.5–16.1; 1 in 12 200). Twelve patients in this category underwent decompressive laminectomy (seven for abscess, four for vertebral canal haematoma, and one as a result of nerve injury in association with spinal stenosis), an incidence of 12.3 per 100 000 cases (95% CI 6.3–21.4, 1 in 8100). One patient declined laminectomy.

Table 7

Incidence of permanent harm (including death) after CNB with ‘pessimistic’ (see text for explanation) interpretation of data: events per 100 000 cases (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot’ phase of the project)

Table 7

Incidence of permanent harm (including death) after CNB with ‘pessimistic’ (see text for explanation) interpretation of data: events per 100 000 cases (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot’ phase of the project)

Table 8

Incidence of permanent harm (including death) after CNB with ‘optimistic’ (see text for explanation) interpretation of data: events per 100 000 cases (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot’ phase of the project)

Table 8

Incidence of permanent harm (including death) after CNB with ‘optimistic’ (see text for explanation) interpretation of data: events per 100 000 cases (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot’ phase of the project)

Table 9

Incidence of paraplegia or death after CNB with ‘pessimistic’ (see text for explanation) interpretation of data: events per 100 000 (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot’ phase of the project)

Table 9

Incidence of paraplegia or death after CNB with ‘pessimistic’ (see text for explanation) interpretation of data: events per 100 000 (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot’ phase of the project)

Table 10

Incidence of paraplegia or death after CNB with ‘optimistic’ (see text for explanation) interpretation of data: events per 100 000 (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot phase’ of the project)

Table 10

Incidence of paraplegia or death after CNB with ‘optimistic’ (see text for explanation) interpretation of data: events per 100 000 (95% CI). N/A, zero denominator (i.e. no cases reported in this group in the ‘snapshot phase’ of the project)

Paraplegia and death are the worst possible outcomes so figures for these (13 ‘pessimistic’ and five ‘optimistic’) were extracted and analysed in the same way. The overall incidence of these two complications in this series is ‘pessimistically’ 1.8 per 100 000 (95% CI 1.0–3.1; 1 in 54 500) and ‘optimistically’ 0.7 in 100 000 (95% CI 0–1.6; 1 in 141 500) (Tables 9 and 10). The patterns revealed are similar to those seen in the analysis of all permanent complications.

Six patient deaths were reported (two abscesses, three cardiovascular collapses, and one wrong route error). All were included in the ‘pessimistic’ assessment, giving a rate of <1 in 100 000 (0.8 per 100 000: 95% CI 0–1.8), and three in the ‘optimistic’ group, a rate of <1 in 200 000 (0.4 per 100 000: 95% CI 0–1.2). Four of the deaths were considered to be directly associated with CNB and two indirectly.

Consideration of the cases with a fatal outcome (Table 11) may clarify how determinations of ‘pessimistic’ and ‘optimistic’ decisions were made, and illustrate the need to present the outcome data in both ways.

Table 11

Case summaries of deaths due to CNB

Table 11

Case summaries of deaths due to CNB

We followed the progress of those patients reported to the project with an initially serious neurological injury in whom we were able to determine a final outcome (Table 12). Patients were included even if they did not meet inclusion criteria (e.g. incidents occurring outside the audit dates or in private hospitals).

Table 12

Prognosis, at 6 months, of all significant injuries with early neurological injury after CNB: numbers (%). Cases include those occurring after CNB performed outside the audit period or in non-NHS hospitals. Immediately fatal cases are not included

Table 12

Prognosis, at 6 months, of all significant injuries with early neurological injury after CNB: numbers (%). Cases include those occurring after CNB performed outside the audit period or in non-NHS hospitals. Immediately fatal cases are not included

Discussion

The results of this large prospective project are largely reassuring with the incidence of permanent injury being lower than in other equivalent or related studies.18,22–24 Assessed ‘pessimistically’ the incidence of permanent injury after CNB was 4.2 per 100 000, and of paraplegia/death was 1.8 per 100 000. ‘Optimistically’ the incidence of permanent injury was 2.0 per 100 000 and of paraplegia/death 0.7 per 100 000. The incidence of complications of epidural and CSE were at least twice those of spinals and caudals.

Previous studies have focused on the neurological complications of CNB, but this project took a broader approach and included all major complications of CNB, whether leading to neurological or other major sequelae. As a result, several deaths and major complications from wrong route errors or cardiovascular collapse were identified.

An internal NPSA paper describes epidural anaesthesia and its multiple potential complications well: ‘a complex amalgam of clinical judgement, technical skills, materials and equipment, drug delivery systems, patient supervision and care pathways. In addition to inherent complications in the procedure, each of these facets has the potential to generate patient harm through a combination of patient characteristics, human error or shortfalls in performance, equipment dysfunction and broader system failures. As a consequence, an enormous number of injuries can result’.25 This description is applicable to all forms of CNB and encapsulates the complexity of these seemingly simple procedures. The results of this national project reflect the complexities of both CNB and the interpretation of its sequelae.

Data interpretation

The data contain both clinical uncertainty and statistical uncertainty. We have presented the results in both ‘pessimistic’ and ‘optimistic’ terms to acknowledge the clinical uncertainty. As the case descriptions of the patients who died illustrate, in many cases, the interpretation of clinical descriptions was difficult because causation may be uncertain within a complex train of events. In other cases, the degree to which CNB led to final outcome may be uncertain. As an example we do not know whether spinal cord ischaemia after general anaesthesia in elderly frail patients who also have an epidural in place is caused by the CNB or simply coincidental: there were four such cases. Further, the final outcome was not always clear. One option would have been to be more decisive and simply present one ‘best guess’ result, but this would be an inappropriately simplistic response to the reality of complex clinical data. In 11 of 84 cases, interpretation was hampered by incomplete information: gaps were interpreted pessimistically even though this may mean that some patients were included inappropriately.

The statistical uncertainty is accommodated by the use of 95% confidence intervals (CIs) for all calculated incidences. In many cases, CIs are large, an inevitable consequence of the low or zero numerators of some groups. The data with the narrowest CIs are those with larger numerators and large denominators. Data with low or zero numerators are difficult to interpret.26,27 For zero numerators, we used the recommended ‘rule of 3’ (which states that for n observations with a zero numerator, the upper 95% confidence limit is 3/n) to calculate the upper confidence limit.26 The importance of this is that the main results have quite narrow CIs (e.g. pessimistic incidence of permanent injury from any CNB; 4.2 per 100 000 cases, 95% CI 2.9–6.1). In contrast, some of the sub-classifications of the data have very wide CIs (e.g. optimistic incidence of death or paraplegia after spinal anaesthesia in children 0 per 100 000 cases, 95% CI 0–921.8). This makes such data, particularly those with zero numerators, very difficult to interpret, and we would advise extreme caution in doing so.

The nature of this project means that whatever incidence is calculated from our data, it can only be a minimum incidence: unreported or wrongly excluded cases would increase the rates. Each additional case would increase the pessimistic incidence by ∼3%.

Data reliability and validation

The first and most obvious question is, ‘are the results robust?’ We consider the denominator(s) to be robust because they are based on a census of activity of the entire relevant population not a sample. All UK NHS hospitals committed to the project and all returned census data with more than 92% of these data being reported as ‘accurate’. Therefore, any error in the denominator is small.

Within the numerator data, there are both ‘known unknowns’ and ‘unknown unknowns’.28 The known unknowns are those cases which were reported, but where detail was inadequate for robust decisions on the nature or outcome of the event. In 11 cases (13%), insufficient information prevented determination of long-term outcome: in each, no recovery was assumed. Therefore, several cases have been classified ‘pessimistically’ as suffering permanent injury when full recovery may have occurred: this will have increased the resulting incidence of such complications. The unknown unknowns are those cases which may exist, but were not notified and therefore have not been included in incidence calculations. Inevitably, it is impossible to determine their number and futile to speculate on numbers, but every effort was made to disseminate widely information about the project, both within and outside the anaesthetic speciality. That 100% of hospitals volunteered an LR to the project, 100% returned census data, and more than 10% of cases were notified by non-anaesthetists attests to wide awareness and enthusiasm for the project.

Several sources were searched in an effort to validate the denominator (the number of procedures performed annually) and numerator (the number of relevant complications). These sources were either incomplete, from different populations, not validated themselves, or were impossible to correlate with the data presented here. None of the sources searched provided any information which conflicted with this project's data. Validation attempts showed that most cases of significant injury after CNB had not been notified to other national databases of clinical incident (e.g. NRLS). This raises concerns over the current under reporting of serious clinical incidents to the NRLS. It is, however, recognized that a number of data sources are required to fully capture and characterize clinical incidents.29 In contrast, validation attempts only identified one case that had, at that time, definitely not been reported to us and we subsequently learned of this case by other means also.

In spite of the inability to validate data externally, comparisons are possible with other data published recently. A UK audit of more than 10 000 paediatric epidurals reported a similarly low number of major complications, no deaths, and a permanent neurological injury incidence of 1 in 10 663,30 and thus is consistent with this survey. A survey of UK hospitals by Meikle and colleagues,31 identified knowledge of 40 vertebral canal haematomas occurring in a 6 yr period. Their annual rate of seven cases per year is very similar to that of this project: eight cases of vertebral canal haematoma were reported in 1 yr, with five meeting full inclusion criteria. In a Canadian series, the rate of decompressive laminectomy was 21 per 100 000 cases.32 In our equivalent subgroup (adult, non-obstetric perioperative epidurals), the incidence of decompressive laminectomy was 12.3 per 100 000: within the confidence limits of the Canadian data. It should be noted that Canadian and UK practice in selecting patients for laminectomy may well differ and our cohort contains nine cases which might have undergone laminectomy if the threshold for it was lower.

Comparison with other studies

The burden of neurological complications from CNB compared with other causes such as general anaesthesia and surgery is not well reported. A recent review of 54 cases from a UK medical defence organization found 72% were ‘surgical’ and 28% ‘non-surgical’.33 This, somewhat limited report indicates that neurological injury associated with regional anaesthesia is much less frequent than that related to surgery. Further, the incidence of such injury may differ little between regional and general anaesthesia.34

The best information available previously on major complications after regional anaesthesia comes from surveys in two Scandinavian countries, Finland and Sweden, both having ‘no fault’ compensation schemes and populations small enough to allow for central reporting systems. In Finland, a survey of 720 000 procedures performed between 1987 and 1993 found that the incidence of major complications was one in 22 000 after spinal anaesthesia and one in 19 000 after epidural block.22 In Sweden, a survey of 1.7 million procedures performed between 1990 and 1999 found an incidence of severe neurological complications of one in 20 000–30 000 after spinal anaesthesia, one in 25 000 after obstetric epidural, and one in 3600 after non-obstetric epidural.23 Both reviews were retrospective.

In the UK, Christie and McCabe18 retrospectively recorded 12 major complications after 8100 perioperative epidurals (1 in 675) in one hospital. This approximates to 148 per 100 000 epidurals. As nine patients made a full recovery, permanent injury was three in 8100 (37 per 100 000, 95% CI 7.6–108). Our point estimates for permanent injury after adult perioperative epidural are: pessimistic 17.4 per 100 000 (95% CI 7.2–27.8) and optimistic 8.2 per 100 000 (95% CI 3.5–16). Although the CIs from these data are narrower than those of Christie and McCabe, there is significant overlap. The figures reported here come from a population some 12 times larger so that the point estimates and CIs are likely to be more robust.

Cameron and colleagues35 reported a similar, retrospective, single hospital series, from Australia. Two vertebral canal haematomas and six epidural abscesses followed 8210 ‘acute pain’ epidurals. One laminectomy was required and there were no cases of permanent neurological injury. The incidences of vertebral canal haematoma (24 per 100 000, 95% CI 3–88), abscess (73 per 100 000, 95% CI 27–159), laminectomy (12 per 100 000, 95% CI 1–68), and permanent neurological harm (0 in 100 000, 95% CI 0–45) are again broadly consistent with those reported here.

Clinical implications

In the current series, as in the Swedish study, most complications of CNB occurred when epidural block was used in the perioperative period. Whether this was because it was used in higher risk patients is not something that this project can identify, but a higher (or lower) incidence of complications in one subgroup does not necessarily equate to the procedure being less (or more) appropriate for them. There are both statistical and clinical reasons for this. First, Moen and colleagues’23 figure of one in 1800 major complications in women having epidural anaesthesia for knee arthroplasty is often quoted, but the absence of any complications in men having the same procedure for hip arthroplasty or spinal anaesthetic for knee arthroplasty is rarely mentioned. Denominators for these groups were as low as 7000 and are too small for robust point estimates of incidences.

Secondly, the clinical perspective of the appropriateness or safety of a CNB procedure must recognize the potential benefits of that procedure (compared with other techniques) and risks other than the major ones reported here. Such risk–benefit analyses will differ between subgroups of patients and procedures so, for both statistical and clinical reasons, comparisons between subgroups should be made with considerable caution.

The patient characteristics are also relevant. More complications were reported in females than in males, but permanent injury was of equal incidence. Although many patients experiencing complications were aged >70 yr, a significant proportion was <50 yr of age (Table 5). More than half of the patients were fit and well (estimated ASA grades I–II), and most patients were undergoing major, elective surgery with CNB being performed by consultants. However, denominator data for these observations were not collected, so the extent (if any), to which these factors are associated with, or causal of, adverse outcomes cannot be determined. Notwithstanding this, patients who developed spinal cord ischaemia, vertebral canal haematoma, and epidural abscess were usually elderly, many were infirm and most undergoing major surgery. In contrast, patients suffering (non-ischaemic) nerve injury were more frequently young and healthy. These differences reinforce that comparisons between subgroups may not be valid.

Accepting these cautions, several clinical findings are of note. More complications occurred with perioperative epidural than in any other subgroup, although the four perioperative deaths all occurred in association with spinal or CSE block. Obstetric, chronic pain, and paediatric groups had a low incidence of major complications. This series includes one of the largest cohorts of each subgroup and, as such, those results are reassuring.

Concerns have been raised previously about the safety of CSE,36–38 and in this series, it had a relatively high incidence of complications. It represented only 5.9% of all CNBs performed, but led to 13–14% of permanent injuries and 15–40% of cases of paraplegia/death. Two of the deaths followed its use.

Of perhaps greater concern is the continuing problem with ‘wrong route’ injection errors: nine cases are reported here, six in obstetric practice. There was one death, but no other patient harm. A further similar death occurred in an obstetric unit shortly before this audit started:16 judged by the coroner to be an ‘unlawful killing’.39 Subsequently, an NPSA-published safety alert20 and multi-professional best practice guidance40 have highlighted the problem and identified measures to reduce its occurrence. That one in four respondents to a recent survey of 206 UK obstetric units reported knowledge of such an event indicates that this may be a major problem.41 Several alternatives, to remedy these potentially fatal mix-ups, have been advocated, but until a robust solution is universally in place, these events are likely to continue. This might be termed a national ‘systems error’. It is beyond the remit of this review to evaluate solutions, but clearly one must be found.

Prognosis of neurological complications

Most reviews of serious complications of CNB do not report their prognosis. All major complications are important, but the incidence of permanent harm is the most critical outcome. In Christie's series, three-quarters of identified patients made a full recovery. In this project, it was possible to monitor the progress of 41 initially major neurological complications of CNB (Table 12), and in 25 (61%) complete, or almost complete, recovery was documented. Neurological injury associated with spinal cord ischaemia or vertebral canal haematoma had a notably poor prognosis, whereas all patients with meningitis and the majority of patients experiencing nerve injury and abscess recovered fully. As we did not set out to identify all mild or moderate complications of CNB, unreported minor cases will have occurred and some may have resulted in permanent harm.

Overview

This project attempted to identify the incidence of major complications resulting in permanent harm after CNB in NHS hospitals in the UK. The number of such procedures was estimated in a 2 week census, and the complications of all CNBs performed over 1 yr in the NHS were identified, followed up, and analysed in detail. Analysis of the data suggests a lower incidence than reported previously in other series, usually of smaller numbers of patients, but there can be no certainty that all relevant cases were identified. There would need to be a considerable number of additional cases for the results of this project to be changed significantly, but if anyone is aware of such an unreported case meeting the inclusion requirements (see Methods section), the review panel would welcome further reports (in confidence to Professor Wildsmith at ). If a substantial number of reports is made, the results will be updated in the future.

Funding

The project was funded by The Royal College of Anaesthetists. It would not have been possible without time and support given freely by many individuals and organizations.

Acknowledgements

First, our thanks go to the network of local reporters who collected the data for this project and supplied the detailed clinical reports, as well as the other individuals who notified us of cases. The following organizations were represented at a preliminary meeting and their unanimous support contributed to the development and success of the project: Association of Anaesthetists of Great Britain and Ireland (Professor Mike Harmer), British Pain Society (Dr Beverley Collett and Dr Andrew Vickers), European Society of Regional Anaesthesia, Great Britain and Ireland Section (Dr Barrie Fischer), National Confidential Acute Pain Critical Incident Audit (Dr David Counsell), Patient Liaison Group of the Royal College of Anaesthetists (Mrs Anne Murray), Acute Pain Nurses (Ms Sharon Kitkatt), National Patient Safety Agency (Mrs Joan Russell), Council of the Royal College of Anaesthetists (Dr Anne May, Professor Tony Wildsmith). We are also indebted to the President, Council, and the Head of Professional Standards (Mr Charlie McLaughlan) at the Royal College of Anaesthetists. We would also like to acknowledge the advice of Mrs Karen Thomson, Patient Information Advisory Group at the Department of Health and Ms Alexandra Cronberg, statistician at the National Patient Safety Agency. Finally, special thanks go to the chief administrator for the project at the Royal College of Anaesthetists, Ms Shirani Nadarajah.

Appendix 1: supporting organizations

The project was endorsed by the following organizations and specialist societies which played an important role in the promotion and dissemination of information about the project: Association of Anaesthetists of Great Britain and Ireland, Association of British Neurologists, Association of Paediatric Anaesthetists, British Association of Spinal Surgeons, British Pain Society, British Society of Neuroradiologists, European Society of Regional Anaesthesia (Great Britain and Ireland Section), Medical Defence Union, Medical Protection Society, National Confidential Acute Pain Critical Incident Audit, National Patient Safety Agency, Obstetric Anaesthetists Association, Royal College of Radiologists, and Society of British Neurological Surgeons. The project was also endorsed by the Chief Medical Officers of England (Sir Liam Donaldson), Northern Ireland (Dr Elizabeth Mitchell), Scotland (Dr Harry Burns), and Wales (Dr David Salter).

Appendix 2: the review panel

The review panel was composed of experts in CNB and its complications, as follows (in alphabetical order with their nominating groups): Dr David Bogod (Obstetric Anaesthetists Association), Dr Iain Christie (Association of Anaesthetists of Great Britain and Ireland), Dr David Counsell (National Confidential Acute Pain Critical Incident Audit), Dr Max Damian (Association of British Neurologists), Dr Barrie Fischer (European Society of Regional Anaesthesia: Great Britain and Ireland Section), Dr Richard Howard (Association of Paediatric Anaesthetists), Professor Ravi Mahajan (Royal College of Anaesthetists), Dr Angelique Mastihi (Medical Protection Society), Mrs Anne Murray (Patient Liaison Group, Royal College of Anaesthetists), Mrs Joan Russell (National Patient Safety Agency), Dr Nick Scott (European Society of Regional Anaesthesia: Great Britain and Ireland Section), Dr Andrew Vickers (British Pain Society), Professor Tony Wildsmith (Royal College of Anaesthetists). Several panel members also brought medico-legal expertise to the review panel. The panel was chaired by Dr Tim Cook (Project Lead, Royal College of Anaesthetists) who obtained additional expertise, as required, from individuals nominated by specialist microbiological or radiological organizations.

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Author notes

†

This article is accompanied by Editorial I.

© The Board of Management and Trustees of the British Journal of Anaesthesia 2009. All rights reserved. For Permissions, please e-mail:

© The Board of Management and Trustees of the British Journal of Anaesthesia 2009. All rights reserved. For Permissions, please e-mail:

Supplementary data

Comments

10 Comments

Central Neuraxial Blockage: practicalities of risk definition . A reply

9 February 2010

Tim M cook (with [David Counsell], and [Tony Wildsmith])

Consultant in Anaesthesia and ICM., Royal United Hospital, Bath

Dear Editor

We thank Kirkham and colleagues for their interest in the Third Audit Report from the Royal College of Anaesthetists (NAP3). 1,2

They raise several issues, but all stem from their finding that 40% of their colleagues were not aware of the results of the project, and attributing this to the complexity of presentation of results in this journal. However, the methodologies used were those considered correct scientifically, and nothing else would have been appropriate. Data were presented primarily as the number of events in the population (N per 100,000 patients) as recommended by statisticians at the National Patient Safety Agency, and secondarily as frequency of occurrence (1 in N,000 patients) because some clinicians prefer this. Confidence intervals were added to indicate the possible range of the ‘true’ incidence in the population as a whole rather than in our ‘sample’. Difficulties in judging final outcome required that the results were further presented in terms of both ‘optimistic’ and ‘pessimistic’ assessment. This all resulted in there being a lot of numbers in the paper, with more being generated by need to present data according to the broad indications for central nerve block (CNB), differences in ‘risk’ being recognised before we started NAP3. The importance of reporting data by indications and type of intervention is self evident if once compares the results for peri-operative epidural with for instance peri-operative spinal, or paediatric caudal. We believe the manner in which we analysed and reported the data enables clinicians to extract data that is pertinent to their practice and relevant to discussions with individual patients.

In fact Kirkham and colleagues finding was not that 40% of their colleagues misunderstood our results, but that they were not “aware” of them, a significant difference and one implying a failure of dissemination. The results were published both in this journal and in a much fuller report from the College (which also produced Powerpoint presentations). All of these resources were sent to every anaesthetic department in the UK. A press release resulted in coverage of the audit in many UK national newspapers, and we have delivered a number of invited lectures, one even resulting in a short video about NAP3 and peri- operative CNB on Youtube™. For those wishing to revisit the detailed results, all of these resources remain readily available, at no cost, at the links listed below.3-5 We have recently added a table of point estimates to the College website and continue to explore methods to increase dissemination.

All of this effort was expended because it is recognised that both the rate of dissemination of published information, and its subsequent absorption, can be slow. Whether the 60% of anaesthetists in Gloucester who knew about NAP3 was the peak of awareness, whether it is representative of other departments, and whether this is better or worse than other published papers are all unknown. We suspect that information accrual persists well beyond 6 months after publication, that the figure may well be typical, and that we have done quite well compared to others (well, we would wouldn’t we!). It may be unrealistic to expect that that all anaesthetists in the UK (and elsewhere) have taken the opportunity to read both the NAP3 paper and report, but the fact that two thirds of those responding to Kirkham and colleagues found the results “useful” and more than one third have changed their practice is rather encouraging.

Their suggestion of a national survey of the impact of NAP3 is timely: one was planned for the first anniversary of its launch. It is now ready to start and, to inform future projects, will seek feedback on the dissemination of the results of NAP3, as well as on their impact. We look forward to a good response.

Dr TM Cook, NAP3 College lead Consultant Anaesthetist, Royal United Hospital, Bath

Dr D Counsell Consultant Anaesthetist, Wrexham-Maelor Hospital, Wrexham.

Professor JAW Wildsmith Emeritus Professor, University of Dundee , Dundee

References

1. Kirkham L, Payne S, Cooper R. Central Neuraxial Blockage: practicalities of risk definition. BJA eletters http://bja.oxfordjournals.org:80/cgi/eletters/102/2/179#5567

2. Major complications of central neuraxial block: report on the 3rd National Audit Project of the Royal College of Anaesthetists. Cook TM, Counsell D, Wildsmith JAW. On behalf of the Royal College of Anaesthetists Third National Audit Project. British Journal of Anaesthesia 2009: 102: 179-90

3. www.rcoa.ac.uk/index.asp?PageID=717

4. http://bja.oxfordjournals.org/

5. http://www.youtube.com/watch?v=ng3Qp7_fRkU

Conflict of Interest:

None declared

Submitted on 09/02/2010 7:00 PM GMT

Central Neuraxial Blockage: practicalities of risk definition

31 January 2010

Sonja M Payne

Lucy Kirkham, Robin Cooper

Editor – We read with great interest the 3rd National Audit Project by Cook et al regarding the major complications of central neuraxial blocks (CNBs). This audit was the largest ever prospective audit in this clinical area and was no small feat indeed.

Cook et al state, “Knowledge of the incidence of complications should be an essential component of the clinical decision-making and consent process, but there are few good data which can be quoted to support such discussion, leaving both patient and clinician in a quandary (1)”. With this objective in mind, the results of this audit demonstrated a reassuringly low incidence of complications due to CNBs in the UK.

Six months following the publication of these results, we distributed surveys to all anaesthetists working in the Gloucestershire Royal Hospital to determine awareness of the audit findings and to ascertain if they had led to a change in the practice of gaining informed consent. The department consisted of 35 consultants, 12 staff grades, 6 specialist trainee (ST) grades 3 to 7 and 3 ST grades 1 and 2. We received a response from 67% of clinicians, all of which perform CNBs as part of their routine practice. Of those surveyed, only 60% of responders were aware of the audit findings. This lack of awareness cannot be attributed to underexposure as all UK anaesthetic departments partook in the acquisition of data and the results were widely disseminated in both this journal and the Royal College website. The more likely explanation may be due to the relatively complex, and daunting, format in which the findings are presented.

As differences in the incidence of complications in the patient sub- populations became apparent, the national audit results were divided into perioperative, obstetric, chronic pain, paediatric and non-anaesthetist. Seventy-nine percent of those surveyed appreciated the differing risks between patient populations. Participants were asked to provide the risk figures they currently present to patients when discussing CNBs. Quoted figures for permanent injury varied from 1 in 5000 to 10 000 for perioperative CNB and 1 in 5000 to 15 000 for obstetric CNB. When compared to the findings of the audit, these figures appear to be largely over-estimating risk with permanent injury in the perioperative population determined as 1 in 12 500, pessimistically, to 1 in 24 000, optimistically, and 1 in 83 000, pessimistically, to 1 in 330 000, optimistically, in the obstetric population. However, patients still appear to be willing to undergo these procedures for the attributed benefits.

Audit data was presented as ‘permanent harm’ and paraplegia or death’. For the incidences determined in the national audit to be usable in the consent process, one arguably needs to use these terms. Permanent harm is defined according to National Patient Safety Agency guidelines and includes sensory or motor deficits, paraplegia or death. Seventy-one percent of anaesthetists surveyed felt confident in the connotation of the term ‘permanent harm’. Fifty-five percent were currently using this term in the consent process. Of those not currently using this term, 24% were willing to use this term in view of the audit results. As stated previously, ‘permanent harm' includes the data subset of ‘paraplegia or death’; therefore, ‘paraplegia or death’ represents incidents on the most severe end of the complication spectrum. Less than a fifth of those polled currently used this term when obtaining patient consent and none of the other responders were willing to start using this term. Despite the reluctance of anaesthetists to routinely declare paraplegia or death as risks of CNBs, it could be argued that this risk is inherently encompassed under ‘permanent harm’. However, is this evident to the patient who is providing their consent? Should we be openly discussing these specific risks?

The audit results were deemed clinically useful by 64% of the anaesthetists surveyed and 38% had altered the statistics provided to patients in line with the audit findings. An overwhelming consensus of those surveyed requested further clarification on what we, as a professional group, should be quoting to patients as perceived risks of CNBs. Available on the Royal College website is open access to a patient information leaflet entitled ‘Information for patient and relatives: Risks associated with your anaesthetic’ (2). This document describes the risks of any CNB, updated October 2009 in accordance with the audit results, as 1 in 23 500 to 50 500 for permanent harm and 1 in 54 500 to 141 500 for paraplegia or death. This practical guide fulfills the need for clear, nationalised figures to be used to garner informed consent, although this risk is not differentiated between patient sub-populations.

The 3rd National Audit has accomplished its’ objective of providing more robust figures for the incidence of major complications of CNBs. We feel a national follow-up survey to determine the clinical impact of this project would be an interesting extrapolation of our study.

L. Kirkham, S. Payne, R. Cooper Gloucester, UK

References:

1. Cook TM, Counsell D, Wildsmith JA. Major complications of central neuraxial block: report on the Third National Audit Project of the Royal College of Anesthetists. Br J Anaesth 2009; 102(2); 179-190.

2. Wiggins S, Turner J. Risks associated with your anaesthetic: Nerve damage associated with a spinal or epidural injection. Royal College of Anaesthetists, October 2009. (see: www.rcoa.ac.uk/docs/Rick_11nerve-spinal.pdf).

Conflict of Interest:

None declared

Submitted on 31/01/2010 7:00 PM GMT

Re: Antiseptic solutions for central neuraxial blockade ? which concentration of chlorhexidine in alcohol should we use?

Antiseptic solutions for central neuraxial blockade – which concentration of chlorhexidine in alcohol should we use?

Dear Editor We thank Dr Scott and colleagues for their kind comments regarding the Royal College of Anaesthetists’ 3rd National Audit Project (NAP3).1 Their primary point does not relate directly to the audit, but is both topical and important. We cannot provide a definitive answer, but would offer an overview of the relevant information.

The US Physician’s Desk Reference Manual, a commercially published compilation of manufacturers' prescribing information, has (since 1984) warned that “chlorhexidine gluconate is for external use only. Keep out of eyes and ears and avoid contact with meninges”. Two studies are relevant: In 1955, Weston-Hurst reported that CHG (as well as other detergents) produced neurotoxicity when injected into the CSF of monkeys 2; In 1984, Henschen and Olsen showed that injection into the anterior chamber of the eye produced adrenergic nerve degeneration in rats, and suggested that neurotoxic effects on thin myelinated fibres should be investigated.3 Both studies used much larger amounts of CHG than are likely to contaminate neuraxial block equipment, and obviously there are no equivalent human data. Studies of the use of CHG antiseptic solution or CHG-impregnated dressings for epidural insertion sites have reported clinically important reductions in bacterial colonisation of skin and catheter without any adverse effects, but the numbers of patients studied were small as far as safety issues are concerned.4,5

Conversely, the evidence regarding the anti-septic efficacy of this compound is not in doubt and an American Society of Regional Anesthesia and Pain Medicine Practice Advisory Panel considering ‘The Infectious Complications Associated with Regional Anesthesia and Pain Medicine’ concluded that CHG is the most effective one.6 In spite of this, the product characteristics summary for ChloroPrep (Chloraprep ® instruction leaflet, Entura Inc, Leawood KS66211 USA http://www.enturia.co.uk/pdf/9886_SPC_vfinal_290908.pdf) states quite clearly that the product should not be used for lumbar puncture and that “contact with the brain (and) meninges….must be avoided”. We contacted the manufacturers about this. Their helpful response confirms the current guidance, but does indicate that there are plans to seek removal of the lumbar puncture exclusion from the license for tinted chloraprep and replace it the statement 'do not bring into contact with the meninges'. Some product literature refers extensively to the EPIC study, but this related only to the use of CHG in vascular access and urethral catheterisation.7

However, the evidence of CHG actually causing adhesive arachnoiditis is weak. A review listing all the possible causes included ‘detergents and contaminants’ as one of eight groups of causes8 elicited five strongly worded letters to the Editor, but none referred specifically to CHG as a cause. In the 12 month period of our audit we received 26 reports (not all meeting audit criteria) of infective complications, but only one report of adhesive arachnoiditis (for which we could only speculate about the aetiology): of note where the specific antiseptic used was specified it was CHG in all cases. In the medico-legal case referred to by Scott and colleagues, no evidence was presented that CHG contamination was responsible for the arachnoiditis: the diagnosis was, rather, one of exclusion. In the words of Sherlock Holmes “When you have eliminated the impossible, whatever remains, however improbable, must be the truth”. On this occasion, that conclusion may have been wrong.

An effective antiseptic is only one of the required elements of a good aseptic technique.

It is recognised that anything which kills bacteria is potentially harmful to nerves so the user must be meticulous in taking measures to prevent CHG from reaching the CSF. CHG solution (and any alternative for that matter) must be kept well away from the drugs and equipment to be used, and the solution must be allowed to dry first. The use of a concentration of CHG greater than 0.5% cannot be supported; this concentration is evidently effective, but a greater one might increase the risk of neurotoxicity from inadvertent contamination, and should be avoided.

Which ever antiseptic agent is chosen it should be used in a manner that minimises the risk of it entering the neuraxis. Use of an effective anti-septic is only one component of aseptic technique.

It is our opinion (a poor level of evidence!) that, on the limited evidence available to us, 0.5% chlorhexidine in 70% alcohol is the optimal skin preparation for neuraxial procedures. It is an ‘off label’ indication. In the absence of guidance from central authorities clinicians must judge how best to balance the very rare risk of neurotoxicity against the more likely, although still rare, hazard of vertebral canal sepsis. Departments may choose to formally identify CHG for discretionary off- label use. and then audit the occurrence of any problems.

TM Cook, Bath B Fischer, Reddich D Bogod, Nottingham JA Wildsmith, Dundee D Counsell, Wrexham I Christie, Plymouth M Damien, Leicester

1. Cook TM, Counsell D, Wildsmith JAW. Major complications of central neuraxial block: report on the 3rd National Audit Project of the Royal College of Anaesthetists. On behalf of the Royal College of Anaesthetists Third National Audit Project. Br J Anaesth 2009: 102: 179-90 2. Weston-Hurst E. Adhesive arachnoiditis and vascular blockage caused by detergents and other chemical irritants: an experimental study. In: Stewart MJ, Cameron GR, Oakley CL, Collins DH, MacDonald A, eds. The Journal of Pathology and Bacteriology. London, Oliver and Boyd Ltd., 167- 178, 1955. 3. Henschen A, Olson L. Chlorhexidine-induced degeneration of adrenergic nerves. Acta Neuropathol 1984; 63: 18-23. 4. Kinirons B, Mimoz O, Lafendi L, Naas T, Meunier J-F, Nordmann P. Chlorhexidine versus povidone iodine in preventing colonization of continuous epidural catheters in children. Anesthesiology 2001; 94: 239- 44. 5. Shapiro JM, Bond EL, Garman JK. Use of a chlorhexidine dressing to reduce microbial colonization of epidural catheters. Anesthesiology 1990; 73: 625-31 6. Hebl JR. The importance and implications of aseptic techniques during regional anaesthesia. Regional Anesthesia and Pain Medicine; 2006; 31: 311 -23 7. Pratt RJ, Pellowe C, Loveday HP et al. The epic Project: Developing National Evidence-based Guidelines for Preventing Healthcare associated Infections. Phase 1: Guidelines for Preventing Hospital-acquired Infections. J Hosp Inf 2007; 65: (suppl.) S1-S64 (http://www.epic.tvu.ac.uk/) 8. Rice I, Wee MJ, Thomson K Obstetric epidurals and chronic adhesive arachnoiditis. Br J Anaesth 2004; 92: 109-20.

Conflict of Interest:

None declared

Submitted on 15/06/2009 8:00 PM GMT

Antiseptic solutions for central neuraxial blockade ? which concentration of chlorhexidine in alcohol should we use?

10 May 2009

Michael J Scott (with John G Stones, Nigel E Payne)

Consultant in anaesthesia and ICM, Royal Surrey County Hospital, Guildford

We have read the article on the national audit conducted by the Royal college of Anaesthetists by T. M. Cook and colleagues and congratulate the whole group on an outstanding piece of work which has enlightened the whole anaesthetic community and no doubt will lead to improved patient safety.

We have noted that the NAP 3 audit reinforces that sterile technique in regional anaesthesia is an important aspect of reducing complications from infection of neuraxial blockade. In chapter 9 it states that ‘chlorhexidine in alcohol is the solution of choice for regional anaesthesia’ although the concentration of chlorhexidine is not stated. A review article by Dr. Urdaneta, published in Regional Anesthesia and Pain Medicine in 2006 also considered that its use be considered a Grade A recommendation.¹ A photo in the text shows a bottle of Chlorhexidine 0.5% with alcohol 70% solution. In our trust we have been using this chlorhexidine 0.5% with alcohol 70% solution for over 14 years without complication and understand the importance of letting the alcohol dry prior to attempting regional anaesthesia.

As of 2008 some chlorhexidine-based topical cutaneous skin antiseptics have the warning “do not use for lumbar puncture” or “do not use in contact with the meninges.”³ In our trust we have recently been asked to introduce Chloraprep ® 2% chlorhexidine in 70% alcohol to use as a cleaning solution before spinal and epidural insertion rather than 0.5% with 70% alcohol following the recommendations of the EPIC study ² We are concerned that if the policy of using 2% chlorhexidine in alcohol 70% is introduced around the country that we may see an increase in complications of arachnoiditis secondary to chlorhexidine contamination. A recent publicised case of arachnoiditis due to chlorhexidine contamination was settled for £5million (ref Daily Mail ‘Mother paralysed after being injected with cleaning fluid during childbirth will win up to £5m in damages’.4) with the suggestion that only one ten thousandth of a litre of chlorhexidine was needed to cause the problem. Our concern is that with the introduction of higher concentrations of chlorhexidine solution there will be more chlorhexidine residue left on the skin after the alcohol has dried.This may be introduced into the CSF on the tip of the spinal or epidural needle causing potential arachnoiditis secondary to chlorhexidine contamination.

Can the editors please comment on whether they have reached any conclusion following their audit on which concentration of chlorhexidine in alcohol is the safest antiseptic solution to use? We look forward to your reply.

Dr Michael Scott Consultant in Anaesthesia and Intensive Care Medicine Royal Surrey County Hospital Egerton Rd Guildford GU2 7XX

John Stones RGN, MSc Nurse Specialist Pain Management Royal Surrey County Hospital Egerton Rd Guild ford GU2 7XX

Dr Nigel Payne Consultant in Anaesthesia and Pain Medicine Royal Surrey County Hospital Egerton Rd Guildford GU2 7XX

1 Hebl JR. The importance and implications of aseptic techniques during regional anesthesia. Reg Anesth Pain Med 2006;31: 311-23 2 EPIC Study Pratt RJ et al. J Hosp Inf 2007 65;(suppl.) s1-s64 3 Chloraprep ® instruction leaflet, Entura Inc, Leawood KS66211 USA 4 Daily Mail online 22 February 2008

Conflict of Interest:

None declared

Submitted on 10/05/2009 8:00 PM GMT

Re: Is the outcome for central neuraxial blockade really reassuring?

Dear Editor

Is the outcome for central neuraxial blockade really reassuring?

We welcome Dr Grounds’s interest in the report of the 3rd National Audit Project of the Royal College of Anaesthetists (NAP3),[1] but would dispute most of his arguments although agreeing completely that the profession must seek to eliminate harm associated with central nerve block (CNB). Each complication reported to NAP3 was studied in considerable detail and avoidable factors were identified in some. The full report, which we encourage Dr Grounds to read, emphasises these issues and indicates where the employment of ‘best practice’ (e.g. risk assessment, scrupulous asepsis and management of unexpected leg weakness after CNB) might have prevented some complications. [2]

First a correction because Dr Grounds quotes selectively: it was only with the pessimistic interpretation of the findings that six deaths occurred in association with CNB during the year; the optimistic interpretation was of three deaths in association with CNB and a mortality risk of less than 1 in 220,000 (0.4 per 100,000, 95% confidence interval 0 -1.2). If we are to argue about statistics it is important to do so accurately.

Dr Grounds takes issue with the description of the results of the project as ‘reassuring’. The estimated risks derived from the project are considerably lower than several recent estimates (derived from considerably smaller cohorts) [3,4] and all fall into the category of risk described as ‘rare’ [5]. On any fair judgement we therefore find these results reassuring. He further suggests that the report is reassuring for the narrow audience which comprises the advocates of CNB, but not for its recipients: patients. We find this argument perverse because anaesthetists are effectively the servants of their patients and, by inference, only what is good for patients can be good for anaesthetists.

The paper which appeared in the British Journal of Anaesthesia is, of necessity, only a précis of a larger work, the full report of the project [2]. Because of the nature of the British Journal of Anaesthesia the paper is a technical document likely to be of more relevance to a physician than a patient, but the report is targeted at both anaesthetists and the patients they serve. The report is not an ‘apologia’ for CNB, but we hope it represents a balanced view of the potential harm and potential benefits of the various procedures, and in varying clinical circumstances. It is for this reason that the full report was widely advertised in the lay press and is freely available to the public for downloading from the College website.

Further, Dr Grounds focuses entirely on the (now better defined) estimates of the risk of harm associated with (and not necessarily caused by) CNB. The debate over the various proven and potential benefits of CNB is complex and requires careful examination of published literature and its methodological limitations. Dr Grounds appears to brush over this important area (discussed in some depth in Chapter 3 of the full report) and, perhaps more importantly, the potential consequences of omission of CNB. When CNB is used it is rare that the option is simply not to perform it because an alternative will be needed. Without CNB, labour pain requires potent opioids. Without CNB, Caesarean section will be performed under general anaesthesia. Without CNB, post-operative pain control will likely require potent opioids (often delivered by infusion) and increased use of non-steroidal anti-inflammatory drugs. Without CNB, as Dr Grounds concedes, pain relief is less effective and uncontrolled pain has its own physiological impact. In each case the alternative interventions will have their own consequences with possible negative impact on outcome. While some instances of such negative impact have been highlighted by Confidential Enquiry into Maternal & Child Health and the National Patient Safety Agency [6,7], most remain unquantified. What the profession has achieved corporately through NAP3 is a clearer quantification of the risks associated with CNB. It was never the aim of the project to quantify accurately the risks associated with other forms of anaesthesia, other forms of analgesia or inadequate analgesia. This remains a task in waiting.

Dr Grounds’s lengthy discussions of the airline industry and Reye’s syndrome have no relevance in this debate. NAP3 neither studied air travel nor the management of children’s fevers. We believe the statistics of the NAP3 report are clear and speak for themselves.

Finally the debate over the risks and benefits of CNB and particularly peri-operative epidurals will undoubtedly continue, but it has been informed recently by both the NAP3 report and the publication of the paper by Wijeysundera and colleagues in the Lancet last summer [8]. Those authors used a somewhat complex methodology and studied only patients undergoing elective surgery with an overall mortality of less than 2%. They reported an 11% relative reduction in mortality in those patients who received peri-operative epidural anaesthesia. Notwithstanding the low baseline mortality of this cohort of patients this equates to a NNT of less than 450 patients to save one life. Marrying the results of Wijeysundera’s paper with those of NAP3 leads to the interpretation that even in relatively low risk elective patients use of a peri-operative epidural is more than 10-20 times more likely to save a patient’s life than to lead to any degree of permanent harm. We await equivalent figures in higher risk emergency patients who have the greater potential to benefit.

We find this analysis very reassuring.

Yours sincerely

Dr TM Cook, Bath

Dr D Counsell, Wrexham

Professor JAW Wildsmith, Dundee

Conflict of Interest:

None declared

1. Cook T M, Counsell D, Wildsmith J A W. Major complications of central neuraxial block: report on the Third national Audit Project of the Royal College of Anaesthetists. Br J Anaesth 2009; 102: 179 – 90.

2. http://www.rcoa.ac.uk/index.asp?PageID=717

3. Christie IW, S. McCabe S. Major complications of epidural analgesia after surgery: results of a six-year survey. Anaesthesia 2007; 62: 335–41

4. Cameron CM, Scott DA, McDonald WM, Davies MJ. A review of neuraxial epidural morbidity: experience of more than 8,000 cases at a single teaching hospital. Anesthesiology 2007; 106: 997–1002.

5. Jenkins K, Barker AB. Consent and anaesthetic risk. Anaesthesia 2003: 58: 962-84

6. Cooper GM, McClure JH. Anaesthesia. Chapter 9 in: Why Mothers Die: Sixth Report of the Confidential Enquiries into Maternal Deaths in the United Kingdom. London: RCOG Press, 2004

7. Reducing Dosing Errors with Opioid Medicines. National Patient Safety Agency. Rapid Response Report. NPSA/2008/RRR05. 04 July 2008 (http://www.npsa.nhs.uk/patientsafety/alerts-anddirectives/rapidrr/)

8. Wijeysundera DN, Beattie WS, Austin PC, Hux JE, Laupacis A. Epidural anaesthesia and survival after intermediate-to-high risk non- cardiac surgery: a population-based cohort study. Lancet 2008; published online Aug 11. DOI:10.1016/S0140-6736(08)61121-6.

Conflict of Interest:

None declared

Submitted on 01/03/2009 7:00 PM GMT

Re: Concerns regarding the infectious complications of neuraxial block

Dear Editor

Concerns regarding the infectious complications of neuraxial block

We welcome Dr Narasimha’s interest in the report of the 3rd National Audit Project of the Royal College of Anaesthetists (NAP3) [1]. Dr Narasimha raises concerns over the infective complications reported to NAP3.

While elimination of healthcare associated infection is a laudable goal it is probably an unattainable one. We believe the issues around reuse of spinal needles, repeated attempts at central neuraxial block (CNB) and choice of antiseptic solution are not well represented by Dr Narasimha’s letter and these topics are discussed in detail in the relevant chapters of the full NAP3 report (Chapter 7: Vertebral canal abscess and Chapter 8: Infective meningitis) which is available on-line [2].

It is notable that few of the cases of infective complications of CNB reported to NAP3 were associated with the classic risk factors associated with such infective complications. In all there were 20 cases of infective complications (meningitis and abscess) notified to the project (including those eventually excluded on the basis of full recovery, hospital funding or date of procedure). Of these 20 cases aseptic technique was documented in 18: it was complete in 13 and incomplete in five (28%). The finding of gaps in aseptic technique was common in non-infective reports too and overall 27% of cases notified to NAP3 had evidence of such gaps. CNB was successful on first attempt in 13 cases, required more than one attempt in five and was not documented in two. The procedure was considered ‘blameless’ (full asepsis and success on first attempt with no immediate complications) in 13 cases. Seven had evidence of some infection at the time the CNB was performed. Fifty percent of the procedures were performed by consultants and 50% were emergencies. Only in a small minority of these 20 cases was care deemed remediable.

So while we agree with Dr Narasimha that asepsis and good technique are important factors in minimising infective (and other) complications of CNB, it is evident that infective (and other) complications of CNB will unlikely be eliminated even by optimal care. The consequence is that while performance of CNB (including aseptic technique) demands the highest possible standards the possibility of complications will always remain and thus demands equally high standards of post-procedure monitoring and supervision in order to detect such complications and manage them promptly. Yours sincerely

Dr TM Cook, Bath

Dr D Counsell, Wrexham

Professor JAW Wildsmith, Dundee

References

1. Cook T M, Counsell D, Wildsmith J A W. Major complications of central neuraxial block: report on the Third national Audit Project of the Royal College of Anaesthetists. Br J Anaesth 2009; 102: 179 – 90.

2. http://www.rcoa.ac.uk/index.asp?PageID=717

Conflict of Interest:

None declared

Submitted on 01/03/2009 7:00 PM GMT

Concerns regarding the infectious complications of neuraxial block

24 February 2009

Prasad K Narasimha

Associate professor, Dept of Anaesthesiology, Kasturba Medical College, Manipal

We read the most thought provoking article on the national audit conducted by the Royal college of Anaesthetists by T. M. Cook and colleagues. It is definitely reassuring that the incidence of major complications associated with central neuraxial block has reduced and many of them resolve. It does assure us that if the technique can be safely practiced if all the necessary precautions are taken. However, it is appalling to note that one of the leading complications resulting in permanent squeal is epidural abscess either from extrinsic contamination or intrinsic infective focus. It is definitely true that the incidence of extrinsic contamination is more if multiple attempts at spinal or epidural is required. The sterility of the needle cannot be assured when the anaesthesiologist takes longer time than usual and patient suffers for the desperation of the anaesthesiologist. There has been a debate on chlorhexidine solution used as skin disinfectant and the product information forbidding its use for lumbar puncture or close to meningeal structures1. Chlorhexidine is recommended as the skin disinfectant of choice by the American society of Regional Anesthesia and Pain medicine. Whether Povidone- iodine or chlorhexidine is used, adequate time should be given for the action of the same so that disinfection is proper. The use of multi- use Povidone iodine solution should be discouraged to avoid contamination2. Proper guidelines have to be drawn up for prevention of contamination when multiple attempts at neuraxial block are necessary. 1. Cynthia T Crosby. Is Chlorhexidine Prep Appropriate for Peridural Anesthesia? APSF NEWSLETTER Fall 2008, pg 38, 47 2. Ismail Serhat Kocamanoglu MD, E. Bengi Sener MD. Streptococcal meningitis after spinal anesthesia: report of a case, Canadian Journal of Anesthesia 50:314-315; 2003.

Conflict of Interest:

None declared

Submitted on 24/02/2009 7:00 PM GMT

Re: Incidence of severe complications after centroneuraxial block

19 February 2009

Tim Cook (with Dave Counsell, Wrexham, Tony Wildsmith, Dundee)

Consultant anaesthetist, Royal United Hospital, Bath

Dear Editor

We would like to thank Dr Fowler for his interest in and compliments about the 3rd National Audit Project of the Royal College of Anaesthetists (NAP3).1 His letter2 raises several points which we will respond to in order.

First we would endorse his inference that informed consent requires accurate and specific information about risk. It was the primary aim of NAP3 to generate this information for central neuraxial block (CNB). NAP3 generated both optimistic and pessimistic estimates of the incidence of permanent harm after CNB ‘overall’ and for each of four types of CNB with four broad clinical indications. This generates more than 30 incidences of harm for specific blocks types and specific indications, each with relevant 95% confidence intervals. For many anaesthetists this provides enough (and for some too many) figures to quote to patients during the consent process.

We would respectfully disagree that the patients with fully recovered complications should be included in calculations of incidence because “these complications had the potential to cause a permanent motor deficit or death”. Taken to its logical conclusion Fowler would have us include all patients receiving CNB because all may ‘potentially be harmed’. The patients who were excluded from analyses were those who made a full and documented recovery within six months. As our endpoint was permanent harm (conservatively defined as persisting deficit 6 months after CNB) it would be quite wrong to include those patients who clearly did not meet this definition. Had we chosen an endpoint such as ‘material risk’ or ‘major harm’ a minority of these cases may indeed have been included, but we did not: in part because of the impracticality of defining and determining such endpoints with clarity. We consider it an important learning point from the project that more than 60% of those patients with initially important neurological complications made a full documented recovery within 6 months. As Buggy’s editorial points out, our pessimistic incidences may indeed over-estimate risk because we included some patients either lost to follow-up (where recovery may well have occurred) and some where causation was not proven.3 Of note, our quoted incidence of laminectomy does include some of the patients referred to by Dr Fowler, who were initially harmed but made a subsequent full recovery.

Dr Fowler suggests that the project might (ideally) have been used to determine the risk of CNB for each surgical specialty (and by extrapolation perhaps for each operation). This would have required collection of data such as the indication for every CNB performed in the UK for a whole year. This is also true regarding resolving such interesting questions as whether CNB performed awake or anaesthetised is associated with more harm. We spent a considerable time deciding how much information to request from our colleagues in the census stage of the project, because it is only by determining denominator data that one can then calculate an incidence. We eventually decided that there was more to be gained by return of a limited amount of data from all hospitals, than extensive details from only a few. We believe we were vindicated in this decision by a 100% return rate in the census stage, but this figure should not hide the enormous amount of effort required to achieve such a return. We have no doubt at all that had we attempted to gain considerably more information at the census stage of the project, returns would have been low and the project would have failed.

Finally Dr Fowler refers to work relating to lower limb arthroplasty and raises the possibility that total joint replacement and epidural anaesthesia are a particularly hazardous combination.4 Moen’s data has also been reported in support of this contention.5 We discuss in some detail in our report why such subgroup analyses are potentially misleading, particularly when numerators and denominators are small, with the consequence of increasingly wide confidence intervals around any point estimate of risk. Regarding joint arthroplasty, in the period during which NAP3 ran more than 100 000 lower limb arthroplasties were performed in the NHS in England and Wales (personal communication Mr Ian Mulcahy, National Joint Registry). As NAP3’s denominator also included Scotland and Northern Ireland the denominator will considerable exceed 100 000 operations. Although the NJR data does not allow us to state, with confidence, how many of these operations were performed under CNB, nor how many under epidural, we can state that only one of the 50 adult peri-operative non- obstetric cases reviewed by NAP3 (including those later excluded on the grounds of date of CNB or hospital funding) was a lower limb arthroplasty in which epidural anaesthesia was the CNB. Of these 50 cases, 13 underwent orthopaedic surgery including eight primary joint replacements and two revision joint replacements. Six spinals and two combined spinal epidurals (CSEs) were used for primary arthroplasty and one CSE and one epidural for the revision arthroplasties. Permanent harm (pessimistically interpreted) occurred after two spinals, three CSEs and one epidural. Without robust denominators interpretation of this data is difficult, but we can be reassured we did not uncover an epidemic of epidural related harm following orthopaedic arthroplasty.

Dr TM Cook, Bath

Dr D Counsell, Wrexham

Professor JAW Wildsmith, Dundee

References

1. Cook TM, Counsell D, Wildsmith JAW. Major complications of central neuraxial block: report on the 3rd National Audit Project of the Royal College of Anaesthetists. On behalf of the Royal College of Anaesthetists Third National Audit Project. Br J Anaesth 2009: 102: 179-90

2. Fowler S. Incidence of severe complications after centroneuraxial block http://bja.oxfordjournals.org/cgi/eletters/102/2/179

3. Buggy DJ. Editorial: central neuraxial block: defining the risk more clearly. Br J Anaesth 2009; 102: 151-3

4. Fowler SJ, Symons J, Sabato S, Myles PS. Epidural analgesia compared with peripheral nerve blockade after major knee surgery a systematic review and meta-analysis of randomised trials. Br J Anaesth 2008;100:154-64

5. Moen V, Dahlgren N, Irestedt L. Severe neurological complications after central neuraxial blockades in Sweden 1990–1999. Anesthesiology 2004;101:950–9

6. Howes B, Clarke PA, Cook TM. The National Joint Registry may fail to collect accurate, validated anaesthetic data. Anaesthesia in press 2009

Conflict of Interest:

None declared

Submitted on 19/02/2009 7:00 PM GMT

Is the outcome for central neuraxial blockade really reassuring?

19 February 2009

R Michael Grounds

Consultant in Anaesthesia and Intensive Care Medicine, St Georges Hospital. Tooting. London SW17 0QT

Letter to the Editor

Sir, The authors of the recent ‘Major complications of central neuraxial block: report on the Third National Audit Project of the Royal College of Anaesthetists (ref.1) suggest that the results of this project are “largely reassuring”. However, I would submit that the use of the word “reassuring” may be comforting for those enthusiasts who advocate a wider use of central neuraxial blockade (CNB) but their results may not be quite so well received by the wider audience, their patients. The authors correctly identify that large randomised controlled trials (RCT’s)(ref.2) and meta-analaysis (ref.3) have led to conflicting conclusions and interpretations regarding outcome benefit of CNB techniques. The reduction in pain following the use of CNB is not contested but the improvement of outcome is not well established (if it does exists) and the well established risks of CNB (some serious) are all too often not considered in studies examining surgical outcome (ref.4) . The authors on behalf of the National Audit Project of the Royal College of Anaesthetists suggest that the incidence of complications is reassuring, but is this actually the case? They report 30 cases (pessimistic interpretation) or 14 cases (optimistic interpretation) with permanent injury and six deaths associated with CNB in a total of 707,425 CNB’s performed during a 12 month period1. They suggest that in the United Kingdom the incidence of permanent injury following CNB is between 4.2 per 100 000 (pessimistic) and 1.8 per 100 000 (optimistic) with a death rate of approximately 0.85 per 100 000. This may be reassuring to the enthusiasts. However, the conduct of anaesthesia and pain relief is often compared to the airline industry with it moments of stress interrupting long periods of inactivity but more importantly the industry’s constant aim to improve safety by a balance of safety checks and reduction of the risk of harm to their passengers by identifying the areas of potential risk and ensuring those risks are quantified, minimised or eliminated and their customers informed. If we were to take the results of this study and compare them to the airline industry then the results may be very sobering! According to the National Air Traffic Services, there are some 220 million passengers overflying the United Kingdom every year in passenger aircraft(ref.5). If these passengers were subject to the same rates of permanent injury or death then we would have between 3960 (optimistic estimate) and 9240 (pessimistic estimate) permanent complications of which 1870 of these would be death. If that were to happen then there would be a public outcry and the airlines industry would be expected to reduce the risk and solve the problem immediately. Using an example from clinical medicine, Reye’s Syndrome was reported to be associated with the use aspirin in children with a viral illness. The incidence of Reye’s Syndrome was variously reported to between 0.6 per 100 000 and 0.3 per 100 000 (refs.6,7,8) when aspirin was used as an anti-pyretic in children with viral illness. This syndrome has a mortality of approximately 30%. However, it is notable that where a complication of medical treatment (with a reported incidence of death less that one quarter of that of CNB) was considered to have potential to cause harm the various national Medicines agencies requested that physicians ceased using the treatment. In this review of the incidence of complications associated with CNB in the United Kingdom the authors suggest that there may be as many as six deaths per year associated with this form of analgesia. Given the lack of convincing evidence as to the benefit to surgical outcome, would the authors agree that “reassuring” is perhaps a word used by the enthusiasts but the reality is that this is worthy of careful investigation to see if we as anaesthetists can reduce these unfortunate deaths and complications. Were CNB’s of unique and essential value in anaesthesia, then no patient should be deprived of the benefit, but that is not the case. 1. Cook T M, Counsell D, Wildsmith J A W. Major complications of central neuraxial block: report on the Third national Audit Project of the Royal College of Anaesthetists. Br J Anaesth 2009; 102: 179 – 90. 2. Rigg J A R, Jamrozik K, Myles P S, et al., for the MASTER Anaesthesia Trial Study Group. Epidural anaesthesia and analgesia and outcome of major surgery: a randomised trial. Lancet 2002; 359: 1276 – 82. 3. Rodgers A, Walker N, Schug S, et al., Reduction of postoperative mortality and morbidity with epidural or spinal anaesthesia: results of overview of randomised trials. Br Med J 2000; 321: 1493 – 7. 4. Ballantyne J. C. Does epidural analgesia improve surgical outcome? Br J Anaesth, 2004; 92: 4-6. 5. National Air Traffic Services. www.nats.co.uk/faq/231/freqently_asked_questions.html 6. Arrowsmith J B, Kennedy D L, Kuritsky J N, Faich G A. National Patterns of Aspirin Use and Reye Syndrome Reporting, United States, 1980 to 1985. Pediatrics 1987; 79: 858 – 63. 7. Hurwitz E S. The Changing Epidemiology of Reye’s Syndrome in the United States: Further Evidence for a Public Health Success. JAMA 1988; 260: 3178 – 80. 8. Autret-Leca E, Jonville-Bera A-P, Llau M E, et al., Incidence of Reye’s Syndrome in France: A Hospital-based Survey. J Clin Epidemiology 2001; 54: 857 – 62.

Conflict of Interest:

None declared

Submitted on 19/02/2009 7:00 PM GMT

Incidence of severe complications after centroneuraxial block

1 February 2009

Steven J Fowler

Specialist Anaesthetist, The Alfred Hospital, Melbourne, Australia

Editor - Cook and colleagues’ important prospective audit confirms that epidural procedures are associated with permanent harm much more frequently in the general perioperative population than in the obstetric setting and that spinal anaesthesia is relatively safe(1). An individualised approach to the informed consent process is emphasised in the accompanying editorial(2), where the risk discussed with a particular patient is tailored to the clinical indication instead of providing the overall headline figure.

It can be argued that the 22 patients who made a complete recovery (as well as the other cases with full recovery before notification) should have been included in the analysis because these complications had the potential to cause a permanent motor deficit or death. Undoubtedly the clinicians involved (as well as the patients themselves) would categorise the complication as “major” in view of the complex multidisciplinary care often required to avoid a poor outcome. It follows that these cases should be taken into account when discussing material risk but from the published data it is not possible to calculate a revised incidence for each subgroup.

Ideally the type of surgery would have been recorded during the snapshot derivation of the denominator(3), allowing a subgroup analysis for each surgical specialty. This sort of information is very useful clinically when deciding which anaesthetic technique to recommend to a particular patient. For example, it is thought that the presence of multiple “red flags” such as degenerative spine and concurrent anticoagulant treatment among patients undergoing total joint replacement greatly increases the risk of a serious complication after epidural blockade(4,5).

With 100% participation from NHS hospitals, the project has achieved its aim of providing good quality, up-to-date data for clinicians and the authors are to be congratulated.

Steven J Fowler

The Alfred, Melbourne, Australia

Email:

References:

1. Cook TM, Counsell D, Wildsmith JAW. Major complications of central neuraxial block: report on the Third National Audit Project of the Royal College of Anaesthetists. Br J Anaesth 2009; 102: 179-190

2. Buggy DJ. Editorial: central neuraxial block: defining the risk more clearly. Br J Anaesth 2009; 102: 151-3

3. Cook TM, Mihai R, Wildsmith JAW. A national census of central neuraxial block in the UK: results of the snapshot phase of the Third National Audit Project of the Royal College of Anaesthetists. Anaesthesia 2008: 63: 143-6

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Conflict of Interest:

None declared

Submitted on 01/02/2009 7:00 PM GMT

Which nursing action is required before a client in labor receives epidural anesthesia?

Which of the following would be a danger signal for a woman in labor?

Which complication occurs as a result of ineffective breathing patterns?

Which are the causes of somatic pain in a client who is in the second phase of labor?