Laparoscopic surgery and muscle relaxants: is deep block helpful?

Abstract

It has been hypothesized that providing deep neuromuscular block (a posttetanic count of 1 or more, but a train-of-four [TOF] count of zero) when compared with moderate block (TOF counts of 1-3) for laparoscopic surgery would allow for the use of lower inflation pressures while optimizing surgical space and enhancing patient safety. We conducted a literature search on 6 different medical databases using 3 search strategies in each database in an attempt to find data substantiating this proposition. In addition, we studied the reference lists of the articles retrieved in the search and of other relevant articles known to the authors. There is some evidence that maintaining low inflation pressures during intra-abdominal laparoscopic surgery may reduce postoperative pain. Unfortunately most of the studies that come to these conclusions give few if any details as to the anesthetic protocol or the management of neuromuscular block. Performing laparoscopic surgery under low versus standard pressure pneumoperitoneum is associated with no difference in outcome with respect to surgical morbidity, conversion to open cholecystectomy, hemodynamic effects, length of hospital stay, or patient satisfaction. There is a limit to what deep neuromuscular block can achieve. Attempts to perform laparoscopic cholecystectomy at an inflation pressure of 8 mm Hg are associated with a 40% failure rate even at posttetanic counts of 1 or less. Well-designed studies that ask the question "is deep block superior to moderate block vis-à-vis surgical operating conditions" are essentially nonexistent. Without exception, all the peer-reviewed studies we uncovered which state that they investigated this issue have such serious flaws in their protocols that the authors' conclusions are suspect. However, there is evidence that abdominal compliance was not increased by a significant amount when deep block was established when compared with moderate neuromuscular block. Maintenance of deep block for the duration of the pneumoperitoneum presents a problem for clinicians who do not have access to sugammadex. Reversal of block with neostigmine at a time when no response to TOF stimulation can be elicited is slow and incomplete and increases the potential for postoperative residual neuromuscular block. The obligatory addition of sugammadex to any anesthetic protocol based on the continuous maintenance of deep block is not without associated caveats. First, monitoring of neuromuscular function is still essential and second, antagonism of deep block necessitates doses of sugammadex of ≥4.0 mg/kg. Thus, maintenance of deep block has substantial economic repercussions. There are little objective data to support the proposition that deep neuromuscular block (when compared with less intense block; TOF counts of 1-3) contributes to better patient outcome or improves surgical operating conditions.