ArticlesEpidural anaesthesia and analgesia and outcome of major surgery: a randomised triala
Introduction
Whether epidural anaesthesia and analgesia improve the outcome of major abdominal surgery is a longrunning controversy. Proponents of the technique cite beneficial effects resulting from attenuation of the surgical stress response.1, 2 The reduction, by an effective epidural block, of intraoperative sympathetic stimulation resulting from surgical trauma has putative advantages for coagulation homoeostasis and cardiovascular, respiratory, gastrointestinal, metabolic, and immune function.1, 2 These advantages are widely believed to outweigh the rare but important morbidity risks associated with the insertion of epidural catheters.1, 2 In the mid-1980s, a randomised controlled trial by Yeager and colleagues, comparing general anaesthesia with or without perioperative epidural anaesthesia and analgesia, was stopped by the ethics committee after 53 patients had been studied, because the combined technique was associated with a significant improvement in postoperative outcome.3 Not unexpectedly, that study has generally been regarded as too small to have a significant effect on anaesthetic and surgical practice. A 1997 audit of Australian hospitals revealed a disparate pattern of practice in terms of the use of epidural techniques in four common abdominal procedures, which suggested that anaesthetists and surgeons were still divided as to the value of this approach.4
Review of published reports over the past 20 years shows several small trials that involved unselected patients at low risk of adverse outcomes and therefore lacked statistical power. In addition, many examined as endpoints transient postoperative abnormalities of doubtful clinical importance5, 6, 7, 8, 9, 10 and showed other flaws in experimental design.11 However, a systematic overview of all available randomised controlled trials over the previous 30 years showed that the use of epidural and spinal block resulted in a statistically and clinically significant reduction in morbidity and mortality after surgery.12
Reliable and valid conclusions about therapies in controversial areas of clinical practice require not only that systematic reviews or meta-analyses indicate the likely sizes of particular effects of such therapies, but also that the findings be independently confirmed in at least one, and preferably more, major randomised controlled trials, each of which is of a size and quality to permit an effect to be detected if it is truly present.13 This paper presents the results of the Multicentre Australian Study of Epidural Anaesthesia (the MASTER Anaesthesia Trial), which was designed to have adequate power to confirm the beneficial effect of epidural techniques shown by Yeager and colleagues,3 while allowing for a smaller difference observed as a result of improvements in perioperative, anaesthetic, and surgical management that have probably occurred in the time since their study.
Section snippets
Study design
We studied the highest-risk patients undergoing major abdominal operations or oesophagectomy, procedures that themselves are more prone to serious postoperative complications and fatal outcomes. This combination of high-risk patients and high-risk procedures defines an area of practice in which major perioperative complications are concentrated, and consequently maximises statistical power for a study of given size.10 Even large hospitals see few patients fitting these criteria, so a
Results
Between July, 1995, and May, 2001, we recruited and randomised 920 patients in 25 hospitals in six countries (figure 1). Five patients were randomised a second time for a subsequent eligible procedure, but the data for these second randomisations were excluded from analysis. From July, 1995, to October, 1999, we followed up all eligible patients, including those for whom consent to randomise was not obtained. A detailed analysis of trial participants and non-participants was published
Discussion
We observed no overall difference in mortality or major morbidity between patients randomly assigned general anaesthesia with intraoperative and postoperative epidural therapy or general anaesthesia with other anaesthetic and analgesic regimens for major abdominal or thoracic surgery. With one exception, respiratory failure, there was no significant difference in major postoperative morbidity between the control and epidural groups. We calculated that 15 patients needed to have epidural
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