Time course of neuromuscular blockade after rocuronium - A comparison between women and men

Background. We studied 40 patients (20 female and 20 male) undergoing elect ive surgery under general anaesthesia to evaluate the effect of gender on t he pharmacodynamics of rocuronium. Methods. Using electromyography (EMG) we determined the maximal neuromuscul ar block and time course of action of 0.45 mg/kg rocuronium (1.5xED(95)). Results. Age and body mass index were comparable between females and males (38 (+/-8) vs.37 (+/-10) years and 24.2 (+/-2.9) vs. 25.2 (+/-1.7) kg/m(2). However, significant differences in weight and height were found between f emales and males (65.7+/-9.3 kg vs. 77.5+/-5.5 kg; p<0.01 and 178+6.8 cm vs . 164+/-6.7 cm; p<0,01). Onset time was shorter in females (168+/-65 s vs.2 11+/-56 s; p<0.05). Maximal neuromuscular blockade after 0.45 mg/kg rocuron ium was 94 (+/-3) % in females and 89 (+/-6) % in males; p<0.01. Clinical d uration was increased in females (23+/-5 min vs. 17+/-5 min; p<0.05), while the recovery index was comparable between both groups (9+/-4 min in female s and 9+/-3 min in males; n.s.). Conclusion. Compared to men neuromuscular blockade after 0.45 mg/kg rocuron ium was more pronounced in women. The onset time was shortened and the clin ical duration increased in female patients.