Haematoma and abscess after epidural analgesia
The survey by Meikle and colleagues1 published in this month's British Journal of Anaesthesia highlights the uncommon but catastrophic complication of epidural haematoma. Although the incidence of symptomatic epidural haematoma may appear small, amounting, they suggest, to one case every 2 yr in the UK, it appears that the use of epidural infusions is increasing, alongside an increase in prophylactic anticoagulation and low-dependency care of patients with indwelling epidural catheters.2 The results of this survey indicate that the incidence of epidural haematoma may, in fact, be significantly higher than suggested by reported cases, and the ongoing national audit by the Royal College of Anaesthetists may give us a better indication of the true risk of this complication.Similar catastrophic injury may result also from epidural abscess, which has been reported in one UK hospital to occur with a frequency of 1 in 800, when epidural catheters were inserted for postoperative pain management.3 Our experience from forensic practice is that Meikle (and previous authors) underestimate the incidence of epidural haematoma considerably, but that the experience of Phillips and colleagues overestimates the risk of abscess nationally. The incidence of epidural haematoma and abscess probably varies in different patient populations; Scott and Hibbard4 reported two haematomas and one abscess after 505 000 epidural blocks in obstetric practice. The incidence in higher risk patients is likely to be greater. For example, Ngan Kee and colleagues5 reported a higher incidence after thoracic epidural analgesia and Okano and colleagues6 noted 11 out of 30 patients with epidural abscesses had an underlying illness or were receiving steroid therapy.
Two of us (A.R.A. and J.G.H.) have encountered, in medicolegal practice, 11 cases of epidural haematoma in an 11 yr period (the events occurred between 1997 and 2007) and eight cases of epidural abscess in a 10 yr period (between 1995 and 2004). Failure to discontinue epidural infusions after the presentation of new neurological signs (especially leg weakness) and failure to recognize the urgency of diagnosis and surgery after suspicion of epidural haematoma appear frequently in such cases. In contrast to epidural haematomas, which usually present during the epidural infusion,7 abscesses often present late and after the patient has left hospital,3 8–10 but for those which present before discharge and for the large majority of epidural haematomas, our experience is that there is usually a significant delay before diagnosis because junior surgical trainees, inexperienced anaesthetists, or both wrongly attribute the onset of weakness and increasing numbness to the effects of the local anaesthetic. The infusion is usually continued for hours,7 and sometimes for several days, before the opinion of an experienced anaesthetist is sought, resulting in permanent neurological damage. It is impossible to educate all trainee surgeons and nurses to recognize the significance of these clinical signs, and we agree that strict protocols offer the best solution to early diagnosis, investigation, and treatment.
Although reporting-bias affects the incidence calculated from reported cases, examination using closed-claim analysis has similar flaws. Closed-claim analysis allows a glimpse of cases that would usually not be reported. However, the technique must also underestimate the true incidence of complications because not all patients who suffer complications sue. Patients who decide to sue have usually suffered a significant and long-lasting injury, and have been able to secure funding for their claim. In addition, the true incidence of a complication which leads to litigation cannot be estimated accurately from the experience of two individuals. The number of other patients who have entered litigation proceedings in relation to epidural haematoma or abscess in the UK in the last 10–11 yr is unknown.
Another method of estimating the extent of damage caused by specific anaesthetic techniques is to consider the costs of claims handled by large insurance or indemnity organizations. Between April 1995 and October 2005, the Clinical Negligence Scheme for Trusts (CNST), which deals with litigation for all NHS hospitals in England, handled 251 claims associated with epidural blocks.11 The claims had a total value of £32 346 737 (an average of £128 871 each). There were lower incidences of brain damage and fatality in claims related to epidural block than in those associated with general anaesthesia. However, there were higher incidences of nerve damage, paraplegia, partial paralysis, spinal damage, and unnecessary pain. We have been unable to establish how many of these claims were related to delay in recognizing the symptoms and signs of epidural haematoma or abscess, but the size of the settlements suggests that the proportion of these 251 patients suffering debilitating neurological injury was not inconsiderable.
Meikle and colleagues1 recommend that patients should receive neurological observations at least every 4 h and that these observations should continue for at least 24 h after removal of the epidural catheter. This recommendation seems valid in view of the previously reported cases of haematoma and abscess formation after catheter removal.5 8 12 Every department should have readily available written guidelines regarding the use of neuraxial techniques in patients with potentially altered coagulation.13 The authors also recommend the cessation of the epidural infusion after the presentation of new neurological signs, with suspicion of epidural haematoma if these signs do not resolve. The authors do not recommend a minimum time interval between the suspicion of haematoma or the cessation of the infusion and MRI scanning; we suggest that no more than 4 h should elapse between the onset of new neurological signs and MRI scanning, and this scan (and ideally, the patient) should be assessed by an expert. Should there be a delay in stopping the epidural infusion after the presentation of new signs, then MRI scanning may need to take place before the local anaesthetic effect of the epidural may be expected to resolve.
In hospitals without expertise to carry out surgical decompression, protocols and procedures need to be in place to ensure that patients are transferred to a unit where surgery can be performed within 12 h of the onset of weakness or increasing numbness to optimize the chance of recovery. In the absence of focal neurological signs, conservative management of epidural abscess may be successful14–17 but frequently urgent surgical evacuation is required.9 18–22
Owing to the low incidence of epidural haematoma, we will never be in a position to introduce true, evidence-based practice. Even if studies of sufficient size are conducted, their relevance will be limited by constant evolution in practice. Thus, we are obliged to apply common-sense and learning to help our patients avoid a life-damaging event. The relative rarity of epidural haematoma and abscess means that expensive and laborious additions to current practice are not appropriate, but the simple measures suggested by Meikle and colleagues need not be expensive or laborious, and we wholly commend them to practising anaesthetists in the UK. It is likely that the introduction of strict protocols would minimize or prevent the development of permanent and disabling neurological injury in a considerably larger number of patients than they suggest.
1 Department of Anaesthesia
Queen's Medical Centre
Nottingham NG7 2UH
UK
2 University Department of Anaesthesia
Queen's Medical Centre
Nottingham NG7 2UH
UK
* E-mail: j.hardman{at}nottingham.ac.uk
References
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