Effect of Deep Versus Moderate Neuromuscular Block During Sevoflurane Anesthesia on Intraoperative Surgical Conditions in Patients Undergoing Laparoscopic Renal Surgery

Neuromuscular blocking agents (NMBAs) are routinely administered during general anaesthesia to facilitate endotracheal intubation and to optimize surgical conditions. Increasing data suggest superiority of a deep neuromuscular block (defined by a post-tetanic count of 1-2 twitches) in creating optimal working conditions for the surgical team. However, it is unknown whether other aspects of the anaesthetic technique, most notably the choice of anaesthetic (for example, total intravenous versus inhalational anaesthesia), influence the relationship between the depth of the neuromuscular block and surgical conditions, particularly in laparoscopic surgery. Volatile anaesthetics are known for their ability to potentiate neuromuscular blocking agents an effect that is less existent with propofol. We previously showed that surgical working conditions in laparoscopic surgery during propofol anaesthesia are highly reliant on the depth of the neuromuscular block. Whether such a relationship also exists for inhalational anaesthetics, is unknown. To investigate this, we conducted a prospective, randomized, double blind study in which patients scheduled for laparoscopic renal surgery were randomized to receive either a moderate or a deep neuromuscular block during sevoflurane anaesthesia. The primary outcome was the intraoperative surgical condition assessed by a surgeon using the validated Leiden-Surgical Rating Scale. We hypothesized that the use of an inhalational anaesthetic would obviate the need for a deep NMB due to its intrinsic muscle relaxant potentiating properties to produce optimal working conditions.