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The effect of ondansetron on cardiac output in elective cesarean deliveries under spinal anesthesia: A randomized controlled trial
Abstract Number: F-61
Abstract Type: Original Research
Maintenance of cardiac output (CO) is essential to ensuring adequate placental perfusion prior to delivery. A drop in cardiac preload, secondary to sympathetic block, may trigger the Bezold-Jarisch reflex (BJR) increasing maternal hypotension and bradycardia (1,2). As serotonin antagonists (e.g. ondansetron) can attenuate the BJR (3,4), we hypothesized that pre-spinal administration of ondansetron would maintain or increase maternal CO relative to placebo in elective cesarean delivery (CD) under spinal anesthesia.
Following informed consent, 52 women having an elective CD under spinal anesthesia were enrolled in this randomized, blinded, placebo controlled trial. Subjects were randomized to receive either 4mg of IV ondansetron or placebo five minutes prior to spinal anesthesia. The spinal anesthetic dose, intravenous fluids, prophylactic phenylephrine infusion, and additional vasopressor administration were standardized. CO data was acquired using the Non-Invasive Cardiac Output Monitor (NICOM®, Cheetah Medical, Vancouver, WA). The primary outcome was the maximum change in CO from baseline following spinal anesthesia until uterine incision, expressed as change in L/min and %. Secondary outcomes included maternal hemodynamic changes, phenylephrine dosage, phenylephrine side effects, umbilical cord gases, and Apgar scores.
There was no significant difference between the groups with respect to the primary outcome measure (Figure). The mean (SD) maximum change in CO in the ondansetron group was -2.05 (1.43) versus -1.92 (1.41) in the placebo group (p = 0.74). The mean (SD) maximum percentage change in CO in the ondansetron and placebo groups was 28.2 (18) and 28.4 (20.0) respectively (p = 0.97). The total dosage of phenylephrine administered was similar between groups. There were no significant differences in fetal outcomes or the other secondary outcomes.
Administration of ondansetron 4mg IV prior to spinal anesthesia for elective CD conferred no advantage over placebo in mitigating the maximum decrease in CO. Future research directions may include examining varying doses of ondansetron or alternative serotonin antagonists.
1. Liu SS et al. Anesthesiology 2001; 94: 888-906
2. Campagna JA et al. Anesthesiology 2003; 98: 1250–1260
3. Yamano M et al. Jpn J Pharmacol 1994; 65: 241–248
4. Yamano M et al. Jpn J Pharmacol 1995; 69: 351–356