Influence of the amount of skeletal muscle mass on rocuronium-induced neuromuscular block.

OBJECTIVE

To evaluate the effects of skeletal muscle mass on the rocuronium-induced neuromuscular block.

DESIGN

A prospective, double-blinded, observational study.

SETTING

A tertiary care university hospital.

POPULATION: One hundred one patients aged 18-65 years who were scheduled to undergo major surgery lasting more than 1 h under general anaesthesia.

METHODS

All participants underwent body composition analysis before anaesthesia and were allocated into two groups; the muscular and non-muscular group, according to skeletal muscle mass. During anaesthesia induction, rocuronium 1.0 mg kg-1 of total body weight was injected followed by neuromuscular monitoring using train-of-four stimulation every 15 s.

MAIN OUTCOME MEASURES: The onset time of rocuronium included the elapsed time from the rocuronium injection until 95% depression of first twitch (T1) and the time to no response to TOF stimulation. The duration was evaluated as the elapsed time from the rocuronium injection to 25% recovery of the final T1 (TDUR25), and the time to the reappearance of T1 (TTOF1) and T4 (TTOF4). These pharmacologic data were compared between two groups.

RESULTS

There was no significant difference in the onset time of rocuronium between the two groups. However, TDUR25 (min) was significantly shorter in the muscular group than in the non-muscular group (p =  0.035 and p =  0.014 in males and females, respectively). TTOF1 and TTOF4 were also shorter in the muscular group than in the non-muscular group.

CONCLUSIONS

Total body weight-based dosing of rocuronium might prolong the neuromuscular relaxation effect in patients with a small amount of skeletal muscle.