STUDY OF PROPHYLACTIC ROLE OF ORAL MIDODRINE ON INCIDENCE OF HYPOTENSION AFTER SUBARACHNOID BLOCK IN ELECTIVE LOWER ABDOMINAL SURGERY

Abstract

Background and Aim: Hypotension is a common and significant complication following subarachnoid block (SAB), resulting from sympathetic blockade and peripheral vasodilation. Oral midodrine, an α1-adrenergic agonist, may help maintain hemodynamic stability and reduce the incidence of spinal anaesthesia-induced hypotension.This study aimed to evaluate the prophylactic role of oral midodrine in preventing hypotension following subarachnoid block in patients undergoing elective lower abdominal surgery and to assess its associated adverse effects. Materials and Methods: This prospective randomized controlled trial was conducted in a tertiary care hospital. Seventy ASA I–II patients undergoing elective lower abdominal surgery under subarachnoid block were randomized into two groups (n=35 each). Group M received oral midodrine 5 mg, while Group C received an identical placebo tablet 60 minutes before spinal anaesthesia. Hemodynamic parameters, incidence of hypotension, vasopressor requirement, and adverse effects were recorded and compared between the groups. Results: Baseline demographic characteristics were comparable between the groups. Heart rate was similar before drug administration and before SAB; however, Group M demonstrated significantly lower HR values from 6 minutes onward (p<0.05). Mean arterial pressure was significantly better maintained in Group M following SAB, with higher MAP values observed at 3, 6, 9, and 12 minutes compared to Group C (p<0.05). Rescue mephentermine was required in only 3 patients (8.57%) in Group M compared with 18 patients (51.43%) in Group C (p<0.0001). The incidence of adverse effects, including nausea, vomiting, shivering, and hypothermia, was low and comparable between the groups. Conclusion: Oral midodrine effectively reduces the incidence of spinal anesthesia-induced hypotension, improves hemodynamic stability, and significantly decreases vasopressor requirements without increasing adverse effects. It is a safe and effective prophylactic agent for patients undergoing elective lower abdominal surgery under spinal anesthesia.