Comparison of Norepinehrine Versus Phenylepherine Infusion for Prevention of Post-spinal Hypotension

Overview

This prospective randomized double-blinded clinical trial aims to compare the efficacy and hemodynamic effects of prophylactic norepinephrine infusion versus phenylephrine infusion for prevention of spinal anesthesia-induced hypotension in elderly patients undergoing elective orthopedic hip surgery under subarachnoid block. Sixty-two patients aged 60 years or older will be randomly assigned into two equal groups to receive either norepinephrine infusion (8 µg/min) or phenylephrine infusion (100 µg/min) immediately after spinal anesthesia. The primary outcome is the mean heart rate during vasopressor infusion, while secondary outcomes include incidence of hypotension, severe hypotension, bradycardia, reactive hypertension, intraoperative fluid requirements, blood loss, transfusion requirements, and postoperative nausea and vomiting. Hemodynamic parameters will be monitored throughout surgery to evaluate the safety and effectiveness of both vasopressor strategies.

Spinal anesthesia-induced hypotension is a common and clinically significant complication in elderly patients undergoing orthopedic hip surgery. Age-related physiological changes, impaired autonomic responses, and reduced cardiovascular reserve increase susceptibility to hypotension after subarachnoid block, which may result in organ hypoperfusion, myocardial ischemia, nausea, vomiting, and increased perioperative morbidity. Phenylephrine is traditionally used for prevention and treatment of spinal anesthesia-induced hypotension because of its potent alpha-adrenergic vasoconstrictive effect. However, its use may be associated with reflex bradycardia and reduction in cardiac output. Norepinephrine, which possesses both alpha-adrenergic and mild beta-adrenergic activity, may provide better maintenance of heart rate and cardiac output while effectively preserving blood pressure. This prospective randomized double-blinded clinical trial will be conducted at the Department of Anesthesia, Intensive Care and Pain Management, Sohag University Hospitals, after approval from the Institutional Ethics Committee. Elderly patients aged 60 years or older, classified as ASA physical status I-III and scheduled for elective orthopedic hip surgery under spinal anesthesia, will be enrolled after obtaining written informed consent.