Biochemical changes following suxamethonium. Serum myoglobin, potassium and creatinine kinase changes before commencement of surgery.

Forty patients were investigated for serum myoglobin changes following induction of anaesthesia but before the commencement of surgery. Blood was drawn for potassium, creatinine kinase and serum myoglobin immediately prior to and 5, 10 and 20 minutes after administration of thiopentone 4 mg/kg and suxamethonium 1.2 mg/kg. Twenty patients were given either 2 mg alcuronium or 20 mg gallamine as pretreatment 2 to 3 minutes before the suxamethonium to reduce the fasciculations. Anaesthesia was maintained with artificial ventilation and alcuronium, or spontaneous ventilation with halothane. Serum myoglobin was assayed by radioimmunoassay. All pre-induction myoglobin levels were within the normal range. Of the 20 patients who were not pretreated, six showed a marked rise of serum myoglobin within 5 minutes, increasing to 150-200 micrograms/litre at 20 minutes. The remaining 14 patients had no such rise. No patients in the pretreatment group had any significant rise in serum myoglobin, suggesting that although the fasciculations were not completely abolished, there was protection against one of the effects of suxamethonium on the muscle. Although there was no clear relationship between intensity of fasciculations and increase in serum myoglobin, there was no marked rise in serum myoglobin values in any patient who did not have muscle fasciculations. There were no consistent changes in potassium or creatinine kinase in any group during the period of study.