Duration of muscle relaxant action depends on many factors. However, we found no studies devoted to the influence of menstrual phase on neuromuscular block.

OBJECTIVE

To study the influence of menstrual phase on duration of non-depolarizing neuromuscular block under rocuronium bromide.

MATERIAL AND METHODS

The study included 40 women ASA class I—II, who were either in follicular (group 1, n=20) or luteal (group 2, n=20) phases of menstrual cycle. They underwent laparoscopic cholecystectomy. Demographic and anthropometric data were similar. Patients received propofol (1.5—2.0 mg∙kg^–1) and fentanyl (2—3 μg∙kg^–1) for induction of general anesthesia. Muscle relaxation was performed with rocuronium bromide (0.6 mg∙kg^–1). TOF monitoring was performed at all stages of anesthesia.

RESULTS

Serum progesterone was 0 (0; 0.5) and 20 (17; 22) nmol∙l^–1, respectively (p<0.001). Tracheal intubation was successful in all patients on the first attempt with mean duration 43 (35; 45) sec in the 1^st group and 104 (98; 108) sec in the 2^nd group (p<0.001). Neuromuscular conduction recovery time between induction dose of rocuronium bromide and appearance of the first TOF response was 36 (33; 40) and 23 (19; 23) min, respectively (p<0.05). Recovery of neuromuscular conduction from the first muscle response to extubation took 30 (28; 33) and 20 (18; 22) min, respectively (p<0.05). Six patients in the 1^st group required decurarization. There were no similar cases in the 2^nd group (p<0.05).

CONCLUSION

Duration of non-depolarizing neuromuscular block provided by rocuronium bromide is reduced in luteal phase of menstrual cycle compared to follicular phase.