Reduction in spinal induced hypotension with ondansetron in parturients undergoing caesarean section

Abstract

Background: Spinal anaesthesia is the preferred method of anesthesia for caesarean section. However, hypotension and bradycardia are the most common side effects seen after spinal anesthesia. One of the mechanism involved in these side effects is Bezold-Jarisch reflex which is mediated by serotonin (5HT₃) receptors. Ondansetron, a 5HT₃ receptor antagonist, has been safely used to blunt the Bezold-Jarisch reflex resulting in less hypotension and bradycardia in parturients undergoing spinal anesthesia.

Objectives: The aim of this study was to evaluate the efficacy of ondansetron in reducing the incidence of post spinal hypotension and bradycardia in parturients undergoing elective caesarean section.

Study Design: Observational case control study.

Participants: The included patients were parturients scheduled for elective caesarean section under spinal anesthesia.

Methods: In our study, 60 parturients were enrolled. Before spinal anesthesia, group1(ondansetron group, n=30) had received ondansetron 4mg diluted in 10ml saline over 1 minute and group 2 (saline group, n=30) had received 10ml normal saline over 1 minute. Blood pressure, heart rate and vasopressor requirements were assessed at regular intervals of time after spinal anesthesia.

Results: Group1and group 2 were comparable with respect to age, weight, time to onset of block, highest sensory level achieved and duration of surgery. The decrease in mean heart rate was significantly lower in group 1 than group 2 from 10 minutes to 30 minutes (p=0.004). The decrease in mean systolic and diastolic blood pressure was significantly lower in group 1 than group 2 from 8 minutes to 30 minutes (p<0.001). Compared to group 2, parturients in group1 required significantly less vasopressor (phenylephrine) (p<0.001) and had significantly lower incidences of nausea (p=0.005) and vomiting (p=0.024).

Conclusion: We conclude that prophylactic IV administration of 4mg ondansetron 5 minutes before spinal anesthesia is effective in reducing the incidence of spinal induced hypotension and bradycardia in parturients undergoing caesarean section.

Implication: Intravenous ondansetron given before spinal anesthesia can be part of a multi-modal methodology to reduce incidence of post spinal hypotension and bradycardia.