Recovery of the acute hypoxic ventilatory response after reversal of a minimal neuromuscular block. A randomized, controlled trial in healthy, non-obese volunteers.

Background: Neuromuscular blocking agents inhibit the peripheral chemoreflex. We examined the effect of sugammadex 2 mg/kg and 4 mg/kg compared to spontaneous recovery of neuromuscular block (NMB) on the recovery of the acute hypoxic ventilatory response (AHVR). Methods: This was a 2-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 NMB). Thereafter, NMB was allowed to recover spontaneously in the first experiment, while in experiment 2, volunteers were randomized to receive sugammadex 2 mg/kg or 4 mg/kg for reversal. The depth of neuromuscular block was assessed with electromyography at the adductor pollicis muscle. AHVR was measured at baseline; during stable NMB; and at 0-, 20-, and 40-minutes post-recovery. Results: Thirty-seven volunteers were enrolled; data from 27 volunteers were eligible for analysis. AHVR was reduced by 32% (mean difference versus baseline (MD) –0.22 L.% -1 .min -1 , 95% CI –0.32 to –0.12) during symptomatic NMB (mean train of four ratio 0.42 ± 0.22;). At the disappearance of all symptoms, AHVR remained on average depressed by 23% (MD –0.16 L.% -1 .min -1 , 95% CI –0.28 to –0.04). In 57% of volunteers following spontaneous recovery versus 28% following sugammadex reversal, AHVR did not return to baseline values during the measurement period. In addition, the magnitude of residual AHVR depression was greater following spontaneous recovery compared to reversal with sugammadex. However, on average AHVR was not significantly different from baseline at 20 and 40 minutes post-recovery in any group. Conclusions: The AHVR after reversal of a minimal NMB with sugammadex did not significantly differ with spontaneous recovery of NMB. 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 minutes after recovery.