Role of intramuscular injections of vasopressors in combating spinal hypotension during caesarean sections: A prospective, randomized, double-blinded controlled clinical trial

Background: Hypotension following spinal anaesthesia (SA) is a common problem. Vasopressors play an important role in its management. The common approach in the routine clinical setting is immediate action after detection of hypotension rather than as a preventive measure. There are studies which compare bolus and intravenous (IV) infusion in the management of maternal hypotension, but literature about comparison of efficacy of intramuscular (IM) vasopressors is very limited. Hence, this study was planned in elective caesarean deliveries to compare the efficacy of IM phenylephrine, ephedrine, and mephentermine for the maintenance of arterial pressure during SA. Materials and Methods: A prospective, randomized, double-blind study was conducted where 120 parturients belonging to American Society of Anaesthesiologists II undergoing elective caesarean section under SA were evaluated after being randomized into four groups receiving either preemptive phenylephrine 4 mg IM, ephedrine 45 mg IM, mephentermine 30 mg IM, or normal saline 0.9% 2 ml IM as placebo, immediately following SA. The mean arterial blood pressure and heart rate were primarily evaluated and any other complications were also recorded. Results: It points toward significantly decreased incidence of hypotension in phenylephrine group compared to the other groups (P = 0.034). The incidence of rescue IV ephedrine requirement was maximum with the placebo group, least with mephentermine compared to ephedrine and placebo group. However, there was no statistical difference between the groups with respect to doses of IV ephedrine used (P = 0.08). Maternal nausea, vomiting, and newborn Apgar score were also comparable. Conclusion: All the vasopressors are effective in reducing the severity of hypotension, though phenylephrine was found to be better for the prevention of hypotension