Gender differences in rocuronium-induced neuromuscular blockade in patients undergoing abdominal surgery

Objective To evaluate the gender differences in neuromuscular blockade induced with rocuronium in patients undergoing abdominal surgery. Methods Twenty-four ASA Ⅰ or Ⅱ patients aged 20-59 yrs undergoing abdominal surgery under general anesthesia were enrolled in this study. Their body mass index (BMI) ranged between 18.5-25 kg·m-2. Patients with neuromuscular disease were excluded and no patient was taking any drug that might influence the effect of muscle relaxant. The patients were divided into male group ( n = 12) and female group (n = 12). The neuromuscular function was monitored and recorded using accelerography (DK-5210, Biometer, Denmark). The response of adductor pollicis muscle to train-of-four (TOF) stimulation of ulnar nerve were recorded. Body temperature was maintained at 36.0-36.9℃ and room temperature at 24-26℃ during surgery. The premedication included intramuscular atropine 0.01 mg·kg-1 and oral diazepam 10 mg. Anesthesia was induced with fentanyl 2-4 μg·kg-1, propofol 2-3 mg·kg-1 and rocuronium 0.6 mg·kg-1. The patients were intubated and mechanically ventilated (VT = 7-10 ml RR = 12-14 bpm). PET CO2 was maintained between 35-45 mm Hg. Anesthesia was maintained with propofol by TCI (effect-site concentration was set at 3-4 μg·ml-1) and intermittent i.v. boluses of fentanyl. Rocuronium (1 mg·ml-1) was infused and T1 was maintained at 5%-10% of the control height. At the end of surgery rocuronium infusion was terminated and neostigmine 0.05 mg·kg-1 was given i.v. .Results There were significant differences in body weight and height between male and female groups ( P 0.05) . The onset time following intubating doses of rocuronium (0.6 mg·kg-1 ) was significantly shorter in female group than in male group. The duration of maximal effect and the time needed for T1 to return to 10% of control height were significantly longer in females than in males ( P 0.05) . The amount of rocuronium needed to maintain T1 at 5%-10% of the control height during the 1st 10 min was significantly larger in males than in females ( P 0.05) . Conclusion Females are more sensitive to rocuronium than males.