Recovery of the Acute Hypoxic Ventilatory Response after Reversal of a Minimal Neuromuscular Block: A Randomized Controlled Trial in Healthy, Nonobese Volunteers.

Background: Neuromuscular blocking agents inhibit the peripheral chemoreflex. This study examined the effect of 2 and 4 mg/kg sugammadex compared to spontaneous recovery of neuromuscular block on the recovery of the acute hypoxic ventilatory response (AHVR).

Methods: This was a two-experiment, randomized, controlled trial in healthy volunteers. Participants received a continuous infusion of rocuronium, to achieve stable symptoms of neuromuscular block in the head and neck region (symptomatic neuromuscular block). Thereafter, neuromuscular block was allowed to recover spontaneously in the first experiment, while in experiment 2, volunteers were randomized to receive 2 mg/kg or 4 mg/kg sugammadex for reversal. The depth of neuromuscular block was assessed with electromyography at the adductor pollicis muscle. AHVR was measured at baseline, during stable neuromuscular block, and at 0, 20, and 40 min after recovery.

Results: A total of 37 volunteers were enrolled; data from 27 volunteers were eligible for analysis. AHVR was reduced by 32% (mean difference vs. baseline, -0.22 l · % -1 · min -1 ; 95% CI, -0.32 to -0.12) during symptomatic neuromuscular block (mean train-of-four ratio, 0.42 ± 0.22;). At the disappearance of all symptoms, AHVR remained on average depressed by 23% (mean difference, -0.16 l · % -1 · min -1 ; 95% CI, -0.28 to -0.04). In 57% of volunteers after spontaneous recovery versus 28% after sugammadex reversal, AHVR did not return to baseline values during the measurement period. In addition, the magnitude of residual AHVR depression was greater after spontaneous recovery compared to reversal with sugammadex. However, on average AHVR was not significantly different from baseline at 20 and 40 min after recovery in any group.

Conclusions: The AHVR after reversal of a minimal neuromuscular block with sugammadex did not significantly differ with spontaneous recovery of neuromuscular block. However, fewer patients had residual depression of AHVR when sugammadex was used. In all groups, a considerable proportion of patients had residual depression of the AHVR 40 min after recovery.