Efficacy of Intravenous Ondansetron on Hemodynamic Complications in Women Undergoing Spinal Anesthesia for Cesarean Section: A Randomized Placebo Controlled Clinical Trial

Several methods are used for the prevention or decreasing the incidence of spinal anesthesia hemodynamic complications. Ondansetron is a 5HT3 receptor antagonist with known efficacy on preventing nausea and vomiting and probably on intrathecal opioid-induced pruritus. The present study aims to evaluate the effects of intravenous Ondansetron on the attenuation of blood pressure and heart rate, by 5HT3 blocking in vagal nerve endings and effect on Bezold Jarish reflex.
Material and One hundred and two candidates for elective cesarean section were randomized into 2 groups of 51 cases, the Ondansetron group received 4mg Ondansetron intravenously before performing spinal anesthesia, and placebo group received 2cc sterile water. Hypotension was defined: Systolic blood pressure less than 100 MmHg or fall more than 20% from primary BP which was treated by administration of Ephedrine in case of any. In both groups, Ondansetron effect was studied on hypotension occurrence, bradycardia, consumed Ephedrine amount, pruritus, nausea and vomiting.
There were no statistically significant differences in systolic/diastolic blood pressure, Mean Arterial Pressure, heart rate and pruritus in both groups (P=0.081).Nausea and vomiting in the first 10 minutes after spinal anesthesia were lesser in Ondansetron group (P= 0.001). Mean consumed Ephedrine was significantly lesser in Ondansetron group (5.8 mg in Ondansetron and 10.7 mg in placebo group, P=0.009).
Ondansetron given intravenously with antiemetic dose (4 mg) decreases mean consumed Ephedrine and nausea and vomiting after spinal anesthesia, but does not have an influence on blood pressure, heart rate and pruritus.