A reply

Abstract

Dr Scott has raised some interesting issues and I think these are worth exploring. Firstly, I refer Dr Scott to a review done the same year on the same topic with very similar references [1] to the one that he has quoted. It found very little benefit of epidural analgesia in colorectal surgery. The authors in the reference quoted by Dr Scott state that they were unable to comment on the increase or decrease in anastomotic dehiscence using thoracic epidural analgesia and also comment on the fact that many of the proposed benefits to epidural analgesia were unable to be proven [2]. So we do not believe that the evidence that he has provided supports the safety or efficacy of epidural analgesia in patients who have had colorectal surgery. Regarding the use of the study by Gould et al. [3], we chose this as it is the only study that we are aware of that has clearly demonstrated the relationship between cardiac output, blood pressure and gastro-intestinal tract perfusion. Gould et al. clearly showed that gut perfusion is not related to cardiac output but is related to an increase in perfusion pressure. Most therapies used to treat epidural induced hypotension are based on either fluid loading or decreasing the epidural infusion rate. Fluid loading will optimise cardiac output but will do very little to improve vascular resistance and relying on pain driven catecholamines to increase the blood pressure seems somewhat perverse. It is, of course, very difficult for us to comment on Dr Scott’s 3500 cardiac patients who have had thoracic epidural analgesia. As far as we are aware he has not published any data regarding these patients. This is not the group that we were addressing and they will have different levels of post operative monitoring and therapy to standard laparotomy patients. Without knowing Dr Scott’s definitions, therapy and completeness of the data set, it is impossible to draw any conclusions on the safety of epidurals from his data. The review quoted earlier found an odds ratio of 13.5 for hypotension with epidural analgesia compared to opioid techniques [1]. We would therefore say there is quite a high level of concern. Thirdly we reiterate our point made in the editorial about the MASTER study. We did not say it was a perfect study. We said that it was the most credible study in this area that has been performed. It demonstrates a number of important points but most significantly, how difficult it is to provide adequate epidural analgesia in these patients. Regarding the significant reduction in pulmonary morbidity and pain, we commented in our editorial that there was a statistically significant reduction in pain scores, but that in both groups the pain scores were low. We still feel that a reduction in pain score of 1 cm on a visual analogue score was not clinically significant. Our comment on the MASTER study being a victim of its own success refers to the fact that it is very difficult to prove benefit in terms of pain scores if your background pain score is so low. Failure rates for post-operative epidurals are high. The failure rate in the MASTER study was 42.5%. This is in the context of a study with enthusiasts involved. It is difficult to see that it will be any less in the UK. The study that you quoted suggesting a 20% failure rate in UK hospitals is not reflective of normal UK practice [4]. This survey was performed when patients with epidural analgesia were routinely admitted to High Dependency Unit for post operative care. This, as you pointed out, is no longer the case. The authors also only looked at epidural analgesia for 48 h which we consider to be inadequate. We therefore stand by our figures of 50% of epidurals failing and possibly even higher. We do however agree with Dr Scott that if you are going to provide an epidural service you must have the ability to adequately assess the effect of your epidural analgesia, strive for total dynamic analgesia and be able to rapidly resite or adjust the epidural. This is both costly and time consuming to provide this service on a 24 h basis. Considering both the decrease in the numbers and experience of junior trainees, it is likely that this role is going to fall to consultants. We are not sure that the cost of providing this service is justified.