Prophylactic ephedrine during spinal anaesthesia: double-blind study in patients in ASA groups I-III.

Forty-eight patients scheduled to undergo spinal anaesthesia were allocated to three groups of 16 each according to ASA classification I-II-III. Each patient received a fluid load of 7 ml kg-1 and either ephedrine 12.5 mg i.v. and 37.5 mg i.m., or placebo. Twelve patients in the placebo groups developed a maximal decrease in mean arterial pressure exceeding 20%. Five of these (one in ASA II and four in ASA III) developed a decrease exceeding 33% and required treatment. In ASA risk group III, all patients in the placebo group had a decrease in mean arterial pressure exceeding 20%; in 50% of these patients, the decrease exceeded 33%. We conclude that prophylactic ephedrine is desirable for spinal anaesthesia, especially in ASA III patients.