Study objective: To establish the relationship between train-of-four (TOF) nerve stimulation and the number of posttetanic twitches (posttetanic count [PTC]) during neuromuscular blockade caused by rocuronium in males and females.
Design: Prospective, observational, clinical comparison.
Setting: Operating room of a university hospital.
Patients: 60 ASA physical status I and II patients (30 women and 30 men), aged 18 to 60 years, who were scheduled for elective orthopedic surgery and ear, nose, throat surgery with a planned duration of 2 hours. INTERVENTIONS; During fentanyl, propofol, and nitrous oxide (N(2)O) anesthesia, neuromuscular blockade was evaluated with accelerometry of the thumb using TOF and posttetanic twitch stimulation (PTTS) of the ulnar nerve in patients who received rocuronium 1 mg.kg(-1).
Measurements and main results: The first responses to PTTS were seen at mean times of 34.9 and 37.7 minutes after rocuronium injection in male and female patients, respectively (NS). The average interval between the appearance of a posttetanic response and the first response to TOF stimulation (T1) was not significantly different between male and female patients (15.4 +/- 4.8 min (SD) vs. 15.9 +/- 4.9 min, respectively). There was a significant negative correlation between PTC and the time to first response to TOF nerve stimulation (r = -0.83; p = 0.0001). Gender did not have a statistically significant effect on this relation (F = 0.9; p = 0.34). The intervals from administration of rocuronium to the first appearances of T1 and T2 were not significantly different between the two groups, but the intervals to the first appearances of T3 and T4 were significantly longer in female patients.
Conclusions: Even though the times from initial administration of rocuronium 1 mg.kg(-1) to the first appearances of T3 and T4 are significantly longer in female patients, the intervals to the first detectable responses to PTTS and TOF are not significantly different between females and males. Gender has no significant effect on the relation between PTC and the time to T1.