Laparoscopic Surgery and Muscle Relaxants

摘要

To the Editor: I have read the review by Kopman and Naguib1 with great interest! However, although comprehensively written by 2 of the most distinguished authors in their field, I dare to disagree with the format in which some of the studies are represented and with the review's conclusions. I will confine my detailed criticism to the 3 most relevant headings from the original review. NONLAPAROSCOPIC SURGERY: ARE RELAXANTS ALWAYS NECESSARY? The authors make the point that "lessons learned from general surgery have applicability to laparoscopic surgery as well."1 The first reference discussed in detail is a study by Tammisto and Olkkola,2 which concludes that "as anesthesia deepened, less intense block was required." In the context of volatile-based anesthesia, this is not surprising. However, I would like to draw attention to a quote from the same article2: "We conclude that there is a linear relationship between the end-tidal concentrations of enflurane and the degree of neuromuscular block … However, due to huge interindividual variation, certain 'overdosing' of neuromuscular blocking drugs is necessary to guarantee adequate muscle relaxation of abdominal muscles during all stages of upper abdominal surgery." Depth of anesthesia therefore appears to be not sufficiently predictive to avoid unsatisfactory operating conditions. The discussion of the study also states that tightness of abdominal muscles might have gone unnoticed because surgeons only complained when surgical conditions were grossly unacceptable (i.e., coughing). Therefore, I agree with the review's authors that lessons can be learned from this study; however, my conclusion would be that depth of anesthesia is an unreliable predictor of surgical working conditions. It may also be mentioned that in the light of ongoing intense (and admittedly controversial) research into the possible side effects of "too deep" anesthesia, mentioning deep anesthesia as an easy way to improve surgical conditions may be seen as somewhat counterintuitive. In the review article, the authors also quote an investigation by King et al.3 as stating that 70% of patients did not require a neuromuscular-blocking agent to achieve good or excellent operating conditions. In response, I will highlight another statement by King et al.3: "Nonetheless, vecuronium significantly increased the proportion of patients in whom at least adequate (# grade 3) surgical field ratings were maintained throughout the procedure, from 72% (placebo group) to 98%." In my view, at least this significantly changes the representation of the study, because it implies the question of whether nonadequate surgical conditions can and should really be tolerated in 30% of patients. DOES DEEP NEUROMUSCULAR BLOCK PROVIDE BETTER LAPAROSCOPIC SURGICAL CONDITIONS THAN MODERATE LEVELS OF BLOCK? Kopman and Naguib1 commence this section by quoting the study by Chassard et al.4 as finding no differences in surgical conditions in patients receiving either a neuromuscular-blocking agent to a twitch depression of 10% of control or no blocking drugs. According to a previous article by Kopman et al.5 as well as the authors' definition of block levels in their review, this constitutes at best a "moderate versus no block study" and may hence be misplaced in the section of the review. Another larger study by Chen et al.6 is quoted in the same context. Although the review acknowledges many of the shortcomings of this article (i.e., no depth of block monitored), it quotes that "Satisfactory conditions for ventilation and operation were consistently achieved with and without muscle relaxants…"1 The readers should know that this study makes no mention of a standardized assessment of surgical working conditions. Are "satisfactory" conditions optimal or even "good"? The latter remains speculative. Two further articles7,8 referenced in the same context investigated paralyzed versus nonparalyzed patients. In both studies, nonparalyzed patients were al