Effect of Ondansetron on Maternal Hypotension During Spinal Anesthesia With Ropivacaine for Cesarean Sections: A Randomized, Double-Blind Trial

Introduction: Ondansetron, a selective 5-hydroxytryptamine 3 (5-HT3) receptor antagonist, has been proven to be effective in the prevention of spinal-induced hypotension for elective cesarean section. Methods: A total of 138 primigravida parturients scheduled for elective cesarean section were randomly assigned to three groups. Groups ONDA4 and ONDA8, respectively, received 4 and 8 mg of ondansetron in 100 mL normal saline, before spinal anesthesia with 1.7 mL ropivacaine 0.75% and 15 mcg of fentanyl, whereas the CONTROL group received an equal volume of normal saline. Noninvasive blood pressure and heart rate were recorded upon arrival, before and after spinal injection, and thereafter every minute for a time period of 10 minutes along with total doses of phenylephrine (mcg) or ephedrine (mg). Time required for the spinal anesthesia to achieve a sensory and motor block at the T4 level and Bromage 3 scale respectively, as well as to regress to the T7 level and a Bromage 1 scale were noted. Maternal nausea/vomiting or shivering, umbilical artery pH, and neonatal Apgar score at 1 and 5 min were also recorded. Results: There were no differences between groups in systolic, diastolic blood pressure, heart rate (p=0.355, p=0.550, p=0.474 respectively), doses of phenylephrine or ephedrine, (p=0.920, p=0.142 respectively), time for the block to reach T4 (p=0.889) and Bromage scale 3 (p=0.269), or to regress to T7 (p=0.273) and Bromage scale 1 (p=0.392), the incidence of nausea/vomiting (p=0.898/p=0.365), umbilical artery pH (p=0.739), neonatal Apgar score at 1 and 5 min (p=0.936 and p=0.907 respectively). Conclusion: Our results showed no significant effect of two different doses of ondansetron, in preventing maternal hypotension, following spinal anesthesia with ropivacaine for cesarean section.