Effectiveness of intravenous boluses of phenylephrine, ephedrine and mephentermine as vasopressors for management of perioperative hypotension in elective lower segment caesarean section under spinal anaesthesia – A prospective comparative study

Hypotension after subarachnoid block for caesarean section is the commonest but serious complication encountered by anaesthesiologists. Various vasopressors are used to prevent/treat this complication. This study was done to compare the efficacy of three commonly used vasopressors – phenylephrine, ephedrine, mephentermine for treatment of perioperative hypotension. Sixty American Society of Anaesthesiologists (ASA) physical status class II parturients undergoing elective caesarean section under subarachnoid block were randomly allotted three groups (P, E, M) (n = 20) to receive intravenous boluses of phenylephrine 100 mcg, ephedrine 6mg & mephentermine 6mg respectively, following hypotension. Maternal Haemodynamic parameters, complications & neonatal APGAR scores were recorded. P-value < 0.05 was considered significant and P-value < 0.001 considered highly significant. Demographic values, baseline vital parameters and mean number of vasopressor boluses required were similar in the three groups (P > 0.05). The mean trends of systolic blood pressure (P = 0.06), diastolic blood pressure (P = 0.7) and mean arterial pressure (P = 0.6) were similar in the three groups. Heart rate was raised during periods of hypotension; the mean heart rate was lower in the phenylephrine group after vasopressor administration. The overall trend was similar (P = 0.1) among the three groups. There was (P = 0.003) higher incidence of bradycardia in the phenylephrine group. The neonatal APGAR scores were > 7 in the three groups at the 1st and 5th minute (P = 0.5). All three vasopressors effectively maintained arterial blood pressure during the subarachnoid block for caesarean section. Phenylephrine caused a significant reduction in heart rate compared to ephedrine or mephentermine.