Effect of Ondansetron on Maternal Hypotension During Spinal Anesthesia With Ropivacaine for Cesarean Sections

Spinal anesthesia is now the preferred technique for cesarean section because it has a rapid onset and poses considerably reduced anesthetic risks for both the mother and the fetus. A recent study aimed to investigate the effectiveness of ondansetron in preventing maternal hypotension during spinal anesthesia with ropivacaine for cesarean sections. A total of 138 primigravida parturients were randomly assigned to three groups: one received 4 mg of ondansetron, another received 8 mg of ondansetron, and the control group received normal saline. Noninvasive blood pressure, heart rate, doses of phenylephrine or ephedrine, and various other parameters were recorded.

The study concluded that there were no significant differences between the groups in terms of blood pressure, heart rate, doses of phenylephrine or ephedrine, time for the block, incidence of nausea/vomiting, umbilical artery pH, and neonatal Apgar scores at 1 and 5 minutes, showing that ondansetron did not have a significant effect in preventing maternal hypotension following spinal anesthesia with ropivacaine for cesarean section. The paper highlighted that spinal anesthesia is the preferred technique for cesarean sections due to its fast onset and lower anesthetic risks. However, the sudden decrease in afterload following lumbar sympathetic blockade may cause hypotension and fetal compromise. Ondansetron, a selective 5-hydroxytryptamine 3 (5-HT3) receptor antagonist, was suggested as a potential preventative measure for spinal-induced hypotension. Although previous studies have shown some beneficial effects of ondansetron, particularly when used with bupivacaine, the current study specifically focused on its interaction with ropivacaine and its impact on hemodynamic parameters.

The study followed ethical standards and included 138 parturients. Group allocation was concealed, and the solutions were prepared to ensure blinding. The results indicated no significant differences in blood pressure, heart rate, and doses of vasopressor agents among the different groups. Furthermore, there were no significant differences in the sensory and motor block characteristics, incidence of nausea/vomiting, shivering, and neonatal outcomes. The authors discussed potential reasons for the lack of significant differences, such as the slower onset of the spinal block after ropivacaine, the better hemodynamic profile of ropivacaine compared to bupivacaine, and the lower intrathecal volume of ropivacaine used in the study, all of which may have impacted the results. In conclusion, the study found that neither 4 mg nor 8 mg of ondansetron prevented hypotension in parturients undergoing spinal anesthesia with ropivacaine for cesarean section. The authors suggested the need for further studies to better understand the interaction between ropivacaine-induced neuraxial blockade and the preventive role of ondansetron for post-spinal hypotension, particularly with an emphasis on the pharmacokinetics of the administered drugs.

Key Points

• The study aimed to investigate the effectiveness of ondansetron in preventing maternal hypotension during spinal anesthesia with ropivacaine for cesarean sections. 138 primigravida parturients were randomly assigned to three groups: one received 4 mg of ondansetron, another received 8 mg of ondansetron, and the control group received normal saline.
• The study concluded that there were no significant differences between the groups in terms of blood pressure, heart rate, doses of phenylephrine or ephedrine, time for the block, incidence of nausea/vomiting, umbilical artery pH, and neonatal Apgar scores at 1 and 5 minutes, showing that ondansetron did not have a significant effect in preventing maternal hypotension following spinal anesthesia with ropivacaine for cesarean section.
• Spinal anesthesia is the preferred technique for cesarean sections due to its fast onset and lower anesthetic risks, but it may cause hypotension and fetal compromise. Ondansetron, a selective 5-hydroxytryptamine 3 (5-HT3) receptor antagonist, was suggested as a potential preventative measure for spinal-induced hypotension.
• The authors discussed potential reasons for the lack of significant differences, such as the slower onset of the spinal block after ropivacaine, the better hemodynamic profile of ropivacaine compared to bupivacaine, and the lower intrathecal volume of ropivacaine used in the study, all of which may have impacted the results.
• In conclusion, the study found that neither 4 mg nor 8 mg of ondansetron prevented hypotension in parturients undergoing spinal anesthesia with ropivacaine for cesarean section. The authors suggested the need for further studies to better understand the interaction between ropivacaine-induced neuraxial blockade and the preventive role of ondansetron for post-spinal hypotension, particularly with an emphasis on the pharmacokinetics of the administered drugs.

Reference

Karachanidi S, Paraskeva A, Theodosopoulou P, et al. (July 22, 2024) Effect of Ondansetron on Maternal Hypotension During Spinal Anesthesia With Ropivacaine for Cesarean Sections: A Randomized, Double-Blind Trial. Cureus 16(7): e65073. DOI 10.7759/cureus.65073