Jaw relaxation after a halothane/succinylcholine sequence in children.

BACKGROUND

Lack of complete jaw relaxation after a halothane-succinylcholine sequence has been described in the literature. To date, however, most existing studies are retrospective, and lack agreement on the magnitude and incidence of this phenomenon. This prospective study examined the incidence and degree of incomplete jaw relaxation in 500 children who were given intravenous succinylcholine during halothane anesthesia.

METHODS

Five hundred consecutive unmedicated children received a minimum dose of 2 mg/kg intravenous succinylcholine after induction of anesthesia with halothane. The degree of jaw relaxation was assessed 45-60 s later by the same observer using a standardized clinical scale. The degree of relaxation was correlated with the type of surgical procedure, and the presence and intensity of fasciculations.

RESULTS

Complete relaxation (mouth opened easily and fully) occurred in 95.4% of study patients. Incomplete relaxation (firm manual separation required to open the mouth fully) was seen in 4.4% of the patients. One child (0.2%) had masseter muscle rigidity (mouth could not be fully opened but intubation possible). There were no incidents of trismus (teeth clamped shut and intubation via direct visualization impossible). The incidence of incomplete relaxation and masseter muscle rigidity did not correlate with the presence or degree of fasciculations or the type of surgical procedure. There were no clinical signs of a hypermetabolic state or myoglobinuria in any patient.

CONCLUSIONS

Incomplete jaw relaxation after a halothane-succinylcholine sequence is not uncommon in children, and is considered a normal response.