Residual neuromuscular block as a risk factor for critical respiratory events in the post anesthesia care unit

Residual neuromuscular block is an important postoperative complication associated to the use of neuromuscular blocking drugs. The purpose of this study was to access the incidence of residual neuromuscular block in a post-anesthesia care unit and to evaluate its association with critical respiratory events.

Prospective cohort study was conducted in a Post Anesthetic Care Unit (PACU) for a period of 3 weeks. Two hundred two adult patients who submitted to scheduled non-cardiac and non-intracranial surgery were eligible to the study. The primary outcome variable was residual neuromuscular block after arrival to PACU that was defined as train-of-four ratio <0.9 and objectively quantified using acceleromyography. Demographic data, perioperative variables, lengths of hospital and recovery room stay and critical respiratory events were recorded. Inadequate emergence was classified in its different forms according to the Richmond agitation and sedation scale 10 min after admission to the recovery room.

Residual neuromuscular block incidence in the post-anesthesia care unit was 29.7% (95% confidence interval: 23.4, 36.1). Patients with residual neuromuscular block had more frequently overall critical respiratory events (51% versus 16%, P<0.001), airway obstruction (10% versus 2%, P=0.029), mild-moderate hypoxemia (23% versus 4%, P<0.001), severe hypoxemia (7% versus 1%, P=0.033), respiratory failure (8% versus 1%, P=0.031), inability to breathe deeply (38% versus 12%, P<0.001) and muscular weakness (16% versus 1%, P<0.001). Residual neuromuscular block was more common after high-risk surgery (53% versus 33%, P=0.011) and was more often associated with post-operative hypoactive emergence as defined by the Richmond Agitation and Sedation Scale (21% versus 6%, P=0.001).

This study suggests that residual neuromuscular block is common in the PACU and is associated with more frequent critical respiratory events.