Reversal of vecuronium with neostigmine: a comparison between male and female patients

We investigated the differences between males and females in the reversal effect of neostigmine on neuromuscular blockade. Thirty male and 30 female patients undergoing elective general anesthesia were studied. Vecuronium was given in all patients anesthetized with nitrous oxide, oxygen, and sevoflurane. After the surgical procedure, when T1 (1st response in train-of-four (TOF))/control returned to 0.25, neostigmine 40 microg/kg in combination with atropine 20 microg/kg was given to antagonize residual neuromuscular blockade. Three, six, nine, 12, and 15 minutes after neostigmine reversal, T1/control or TOF ratio (T4/T1) did not significantly differ between the sexes. Also, 15 minutes after neostigmine administration, the number of patients in whom recovery from neuromuscular blockade was sufficient to guarantee good respiratory function, i.e., TOF ratio > 0.74, did not significantly differ between the sexes. In contrast, 15 minutes after neostigmine, the number of patients in whom recovery from neuromuscular blockade was adequate to ensure satisfactory recovery from neuromuscular blockade including the return of the faculty of sight, i.e., TOF ratio > 0.9, was significantly less in the males than in females (6 vs. 14, P = 0.028). In conclusion, 15 min after neostigmine, TOF ratio less often returns to a value of more than 0.9 in males than in females.