Extended duration of action of rocuronium in postpartum patients

We studied the time course of action of a single bolus of 600 micrograms/kg rocuronium given during anesthesia with propofol, fentanyl, and nitrous oxide was studied in 12 nonpregnant and 12 postpartum patients. Neuromuscular effects were quantified by recording the indirectly evoked twitch response of the adductor pollicis muscle after ulnar nerve stimulation. In all patients, the trachea was intubated 60 s after administration of rocuronium. Onset time was similar in both groups (nonpregnant: 91 +/- 28 s vs. postpartum: 95 +/- 30 s), with the time to 25% twitch recovery being significantly longer (P < 0.001) in the postpartum patients (31.1 +/- 3.6 min) compared with the nonpregnant group (24.9 +/- 4.0 min). The time required for recovery from 25% to 75% of the control twitch response after reversal with neostigmine and atropine was significantly longer (P = 0.003) in postpartum (4.8 +/- 0.9 min) than in nonpregnant patients (3.2 +/- 0.6 min). These data suggest that pregnancy-induced changes result in prolonged effects of rocuronium in postpartum patients.