To assess the safety and efficacy of 37.5 mg ephedrine i.m. in preventing hypotension associated with spinal anaesthesia for Caesarean section.
In a double-blind randomised controlled study, 40 patients (20 in each group) were given either 37.5 mg ephedrine or placebo i.m. The following parameters were recorded: (i) blood pressure; (ii) heart rate; (iii) ephedrine i.v. supplementation; (iv) umbilical venous blood gases and neonatal Apgar scores.
The incidence of hypertension in the study group was 30% compared with 20% for the control group (P:NS). There was no difference in mean highest blood pressure or mean highest heart rate between the groups. The incidence of hypotension was lower but not significantly lower in the study group (50%) than in the control group (80%) (P:NS). However, the incidence of delayed hypotension was only 10% in the study group patients compared with 50% in the control group patients (P < 0.05).
Giving 37.5 mg ephedrine i.m. prior to spinal anaesthesia was not associated with reactive hypertension or tachycardia. Intramuscular ephedrine provided more sustained cardiovascular support than intravenous ephedrine.