Reversal of neuromuscular blockade (NMB) with sugammadex can cause marked bradycardia and asystole. Administration of sugammadex typically occurs in a dynamic period when anesthetic adjuvants and gas concentrations are being titrated to achieve emergence. This evaluation examined the heart rate (HR) responses to sugammadex to reverse moderate to deep NMB during a steady-state period and sought mechanisms for HR changes.
Patients with normal sinus rhythm, who were undergoing elective surgery that included rocuronium for NMB, were evaluated. After surgery, while at steady-state surgical depth anesthesia with sevoflurane and mechanical ventilation, patients received either placebo or 2 or 4 mg/kg of sugammadex to reverse moderate to deep NMB. Study personnel involved in data analysis were blinded to treatment. Continuous electrocardiogram (ECG) was recorded from the 5 minutes before and 5 minutes after sugammadex/placebo administration. R-R intervals were converted to HR and averaged in 1-minute increments. The maximum prolongation of an R-R interval after sugammadex was converted to an instantaneous HR.
A total of 63 patients were evaluated: 8 received placebo, and 38 and 17 received 2 and 4 mg/kg sugammadex. Age, body mass index, and patient factors were similar in groups. Placebo did not elicit HR changes, whereas sugammadex caused maximum instantaneous HR slowing (calculated from the longest R-R interval), ranging from 2 to 19 beats/min. There were 7 patients with maximum HR slowing >10 beats/min. The average HR change and 95% confidence interval (CI) during the 5 minutes after 2 mg/kg sugammadex were 3.1 (CI, 2.3–4.1) beats/min, and this was not different from the 4 mg/kg sugammadex group (4.1 beats/min [CI, 2.5–5.6]). HR variability derived from the standard deviation of consecutive R-R intervals increased after sugammadex.
Sugammadex to reverse moderate and deep NMB resulted in a fast onset and variable magnitude of HR slowing in patients. A difference in HR slowing as a function of dose did not achieve statistical significance. The observational nature of the investigation prevented a full understanding of the mechanism(s) of the HR slowing.