Effect of ondansetron on spinal anesthesia induced hypotension

Hypotension and bradycardia are the common side effects seen after spinal anesthesia. Multiple strategies are tested to prevent the post spinal anesthesia induced hypotension. Recently, ondansetron, a 5-HT3 antagonist commonly used as an antiemetic was found to be effective in preventing spinal anesthesia induced hypotension. The aim of this study is to evaluate the effect of ondansetron in the prevention of spinal anesthesia induced hypotension

Following spinal anesthesia, hypotension results mainly from a decrease in systemic vascular resistance secondary to a blockage of sympathetic fibers and an increase in vagal tone. This reduction in venous return can trigger the Von Bezold-Jarisch (BJ) reflex, mediated by serotonin receptors (subtype 5-HT3), resulting in increased efferent vagal signaling and bradycardia, ultimately exacerbating hypotension

Ondansetron is a drug employed as prophylaxis for Postoperative Nausea and Vomiting (PONV), whose antiemetic activity involves the selective inhibition of the 5-HT3 receptors. As a result, ondansetron can suppress the BJ reflex, and it has been postulated as a therapeutic strategy to prevent hypotension in patients undergoing spinal anesthesia Patients will be randomized using computer generated random sequence of numbers. On the day of surgery patient will be shifted to OT and all standard monitors would be attached. Peripheral IV line will be inserted. All the patients were preloaded with 500 mL of lactated Ringer’s solution IV. Patient’s peripheral oxygen saturation, blood pressure(systolic, diastolic, and mean arterial pressure), and electrocardiogram will be monitored. Basal values will be recorded. Group A- received 0.1mg/kg max upto 8mg ondansetron intravenously (IV) 10 min before spinal anesthesia. Group B- received 4 mL saline IV 10 min before spinal anesthesia The patients were placed in lying down lateral position, and dural puncture was performed at L3–L4 interspace under full aseptic precautions. A total volume of 15 mg of 0.5% hyperbaric bupivacaine was injected intrathecally and adjuvant opiods(fentanyl) at the discretion of the anesthesiologist. Supine position was adopted after the administration of spinal anesthesia. Parameters such as age, sex,height, weight, surgery timing and amount of iv fluids given would be included and level of spinal block The primary outcome was the proportion of patients with hypotension during surgery. Hypotension was defined as mean arterial pressure(MAP) below 20% of initial value. Secondary outcomes included the proportion of patients with bradycardia, vasopressors usage, and variations in blood pressure and Heart Rate (HR). Baseline Systolic Blood PressureDiastolic Blood Pressure Mean

Arterial Pressure Heart Rate values will be recorded, as well as after anxiolysis, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes after spinal anaesthesia and every 30 min till the end of surgery. Incidence of nausea and vomiting until shift from icu, fluid requirement ,level of spinal blockage were

also noted. Care was also taken so that the surgeries are similar.