Incidence of insufficient intraoperative neuromuscular paralysis. A retrospective registry analysis

Muscular tone that inhibits anesthetic or surgical care characterizes insufficient neuromuscular block. The incidence of insufficient neuromuscular block is unknown, therefore we developed novel electronic search strategies to identify occurrences of insufficient neuromuscular block. Our primary goal was to determine the incidence of intraoperative insufficient neuromuscular block in abdominal and neurovascular surgery. Our secondary goal was to assess factors independently associated with insufficient block.

Retrospective cohort.

Operating rooms in a tertiary care center.

Adults having abdominal, laparoscopic, and interventional neurovascular procedures under general anesthesia with endotracheal intubation between April 2005 and February 2013.

An expert panel of anesthesiologists used a Delphi process to develop criteria to identify insufficient intraoperative neuromuscular block. 10 final criteria were agreed upon and used to determine the incidence of insufficient neuromuscular block.

48,315 surgeries met our inclusion requirements. Intraoperative insufficient neuromuscular block was identified in 13,538 cases, representing 28% (95% CI: 27.6%, 28.4%) of the operations. Younger age, male sex, type of surgery, longer duration of surgery, pre-existing conditions, and use of volatile anesthetics were independently associated with insufficient block after Bonferroni correction.

Our results suggest that episodes of insufficient block occur in over a quarter of operations that are generally thought to require muscle relaxation. Without neuromuscular monitoring, it is difficult to separate inadequate anesthesia from inadequate neuromuscular block, and both presumably contributed in many cases.