[Muscular rigidity caused by alfentanil: prevention]

We studied three groups of 30 patients each, undergoing minor orthopaedic surgery, anaesthetized with alfentanil (30 micrograms/kg bolus followed by an infusion of 0.3 micrograms/kg/min), thiopental 3 mg/kg and 70\% N2O via facial mask. Patients in group I were treated, three minutes before induction, with vecuronium 0.02 mg/kg i.v., while those in group II were premedicated with diazepam 0.15 mg/kg i.m. 30-45 minutes before induction. Group III served as control. Muscular rigidity was evaluated clinically with a subjective score based on a scale of 0 (no rigidity) to 3 (severe rigidity). Diazepam did not give significant protection from muscular rigidity. Vecuronium administration did not significantly reduced the number of patients who became rigid, but significantly decreased the incidence of severe rigidity (p less than 0.005), the mean rigidity score (p less than 0.05) and the incidence of rigidity at the induction of anaesthesia (p less than 0.0005). We also observed a progressively increasing incidence of rigidity with increasing age (not significantly) and body weight (p less than 0.05 total rigidity, p less than 0.01 severe rigidity).