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Reliable detection of epidural haematomas
- Jeremy J Nightingale, Jo Miekle, Scott Bird (24 October 2008)
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Reliable detection of epidural haematomas
- Andrew J Toner, [Pradip Prabhu] (14 October 2008)
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Jeremy J Nightingale, Anaesthetist Portsmouth hospitals NHS Trust, Jo Miekle, Scott Bird
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We thank Doctors Toner and Prabhu for their correspondence, and agree that the timely diagnosis of epidural haematomas presents a significant challenge, especially in hospitals without 24-hour access to MRI scans. We too agree with the opinion expressed in the editorial [1] that the results of our survey suggest that the incidence of epidural haematoma may be significantly higher than suggested by reported cases: we reported an increase of 40 units in which an epidural haematoma had presented over a 6 year period. This suggests an incidence of approximately 7 per year, assuming that only one case presented in each unit and ignoring the possibility that further cases had presented in the 32 units that reported cases 6 years previously. This is almost certainly an under-estimate, as it is likely that some cases have gone unreported. We also agree that, aside from logistical problems, transferring postoperative patients from hospitals that lack 24-hour access to MRI facilities in order to investigate the cause of motor block presents significant risk, and avoiding the need to do so wherever possible constitutes good management. Excluding subarachnoid placement or migration of the epidural catheter and avoiding epidural top-ups with high concentrations of local anaesthetic (LA) may contribute to this. However, defining an appropriate maximum concentration of LA to be used for top-ups presents difficulties, owing to significant inter-individual differences in sensitivity to local anaesthetics. The limit of 0.15% bupivacaine proposed by the authors is not supported by the data from the research to which they refer: Lacassie et al [2] used the Bromage 4-point scale of motor function, and considered a score of 3 or below to constitute motor block. They reported no cases of motor block with 20 ml bolus doses of 0.25% bupivacaine. The extent to which data from obstetric patients translate to postoperative analgesia is debatable, but there is a case for the use of concentrations up to 0.25% for epidural top-ups. We consider the documentation of the dosage and timing of epidural top-ups as crucial to the avoidance of unnecessary investigation of abnormal motor function, especially as we move ever more towards shift working, and our epidural prescription charts in Portsmouth include areas for this information to be recorded. PCEA compared to continuous epidural infusion (CEI) is known to reduce analgesic consumption and motor block in surgical patients [3]. It is not clear what definition of PCEA Wu et al [4] used, i.e. whether they excluded studies that included a background infusion from their meta- analysis. The inferences that can be drawn from this meta-analysis concerning analgesic efficacy are limited by the heterogeneity of included studies – in particular, the wide range of local anaesthetics and opioids used for epidural analgesia. Our own research [5] shows that PCEA with a background infusion produces significantly better analgesia than CEI, and it may be that the optimal compromise between analgesic efficacy and motor block is achieved with a combination of PCEA and a low rate background infusion. 1. Bedforth NM, Aitkenhead AR, Hardman JG. Editorial I Haematoma and abscess after epidural analgesia. Br J Anaesth 2008; 101: 291-3 2. Lacassie HJ, Columb LO, Lacassie HP, Lantadilla RA. The Relative Motor Blocking Potencies of Epidural Bupivacaine and Ropivacaine in Labor. Anesth Analg 2002; 95: 204-8 3. Standle T, Burmeister M-A, Ohnesorge H et al. Patient-controlled analgesia reduces analgesic requirements compared to continuous epidural infusion after major abdominal surgery. Can J Anaesth 2003; 50: 258-64 4. Wu CL, Cohen SR, Richman JM et al. Efficacy of Postoperative Patient-controlled and Continuous Infusion Epidural Analgesia versus Intravenous Patient-controlled Analgesia with Opioids - A Meta-analysis. Anesthesiology 2005; 103: 1079-88 5. Nightingale JJ, Knight MV, Higgins B, Dean T. Randomized double- blind comparison of patient-controlled epidural infusion vs nurse- administered epidural infusion for postoperative analgesia in patients undergoing colonic resection. BR J Anaesth 2007; 98: 380-4 Conflict of Interest:None declared |
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Andrew J Toner, Anaesthetist , [Pradip Prabhu]
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Editor – We thank Dr Meikle and colleagues for their informative article on the detection and management of epidural haematomas and we agree with the suggestion in the allied editorial that the true incidence of haematomas is much higher than one every two years in the UK. At our institution we have a high rate of elective epidural insertion and in the last six months there have been two cases that highlight the difficulties in this area of practice. Firstly, a patient developed an epidural haematoma which remained undetected for greater than 24 hours, and tragically was associated with a poor neurological outcome. Several months later, we transferred a second patient to a tertiary centre for a diagnostic MRI following 5 hours of complete motor block after cessation of the epidural infusion. On arrival at the neurosurgical unit the motor block was receding, no further investigations were performed and the patient was returned the following day. The two transfers for this patient were within 24 hours of an elective laparotomy and were not without considerable risks. On reflection there are further strategies for improved detection of epidural haematomas in addition to those proposed by Meikle et al. Perhaps most importantly, by avoiding strong concentrations of epidural local anaesthetic solutions for top-ups (greater than 0.15% Bupivacaine or equivalent) at any point in the perioperative period the development of complete motor block can be more reliably interpreted as pathological. In the obstetric population, the concentration of a 20ml bupivacaine bolus that caused motor block in 50% of patients was 0.326% (95% confidence interval, 0.285-0.367)[1]. Although the incidence of complete motor block with infusions of low concentrations of bupivacaine only is not clear, it is rare enough that if encountered, it should justifiably trigger a protocol for detection of epidural haematoma. A further strategy to minimise local anaesthetic induced motor block is to use patient controlled epidural analgesia (PCEA) in appropriate patients that are alert and cooperative. A recent meta-analysis of postoperative analgesia for all surgery compared continuous epidural infusion, PCEA and patient controlled analgesia with intravenous opioids[2]. Whilst continuous epidural infusions provided marginally better analgesia than PCEA (visual analogue pain scores 2.0 vs. 2.3, p<0.001) there was a much higher incidence of motor block (28.3% vs. 3.2%, p<0.001). Finally, it is worth noting that the differential diagnosis of complete motor block with epidural infusions includes inadvertent subarachnoid placement or migration of the catheter. An aspiration test has good positive predictive value in this instance, and may prevent unnecessary MRI scanning. Although we accept many anaesthetists will continue to use higher concentrations of local anaesthetic for epidural top-ups we feel that the above strategies can minimise premature investigation of abnormal neurology in patients with epidurals and lead to prompt initiation of protocols if complete motor block arises. A. Toner* P. Prabhu Guildford, UK *E-mail: toner@doctors.org.uk 1. Lacassie HJ, Columb MO, Lacassie HP, Lantadilla RA. The Relative Motor Blocking Potencies of Epidural Bupivacaine and Ropivacaine in Labor. Anesth Analg 2002;95: 204-8 2. Wu CL, Cohen SR, Richman JM, et al. Efficacy of Postoperative Patient-controlled and Continuous Infusion Epidural Analgesia versus Intravenous Patient-controlled Analgesia with Opioids – A Meta-analysis. Anesthesiology 2005; 103: 1079-88 Conflict of Interest:None declared |
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