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E-letters: Electronic letters published:
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Re: Antiseptic solutions for central neuraxial blockade – which concentration of chlorhexidine in alcohol should we use?
- Tim M Cook, Barrie Fischer, David Bogod, Tony Wildsmith, David Counsell, Iain Christie and Max Damien (16 June 2009)
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Antiseptic solutions for central neuraxial blockade – which concentration of chlorhexidine in alcohol should we use?
- Michael J Scott, John G Stones, Nigel E Payne (11 May 2009)
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Re: Concerns regarding the infectious complications of neuraxial block
- Tim M Cook (2 March 2009)
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Re: Is the outcome for central neuraxial blockade really reassuring?
- Tim M Cook (2 March 2009)
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Concerns regarding the infectious complications of neuraxial block
- Prasad K Narasimha (25 February 2009)
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Is the outcome for central neuraxial blockade really reassuring?
- R Michael Grounds (20 February 2009)
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Re: Incidence of severe complications after centroneuraxial block
- Tim Cook, Dave Counsell, Wrexham, Tony Wildsmith, Dundee (20 February 2009)
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Incidence of severe complications after centroneuraxial block
- Steven J Fowler (2 February 2009)
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Tim M Cook Royal United Hospital, Bath, Barrie Fischer, David Bogod, Tony Wildsmith, David Counsell, Iain Christie and Max Damien
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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 |
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Michael J Scott, Consultant in anaesthesia and ICM Royal Surrey County Hospital, Guildford, John G Stones, Nigel E Payne
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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 |
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Tim M Cook
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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 |
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Tim M Cook
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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 |
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Prasad K Narasimha, Associate professor Dept of Anaesthesiology, Kasturba Medical College, Manipal
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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 |
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R Michael Grounds, Consultant in Anaesthesia and Intensive Care Medicine St Georges Hospital. Tooting. London SW17 0QT
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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 |
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Tim Cook, Consultant anaesthetist Royal United Hospital, Bath, Dave Counsell, Wrexham, Tony Wildsmith, Dundee
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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 |
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Steven J Fowler, Specialist Anaesthetist The Alfred Hospital, Melbourne, Australia
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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: steven.fowler@alfred.org.au 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 4. Moen V, Dahlgren N, Irestedt L. Severe neurological complications after central neuraxial block in Sweden 1990-1999. Anesthesiology 2004; 101: 950-9 5. Sage D, Fowler SJ. Major neurologic injury following regional anesthesia. In: Finucane BT, ed. Complications of regional anesthesia. 2nd ed. New York: Springer, 2007; 333–53 Conflict of Interest:None declared |
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