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The effect of ondansetron on acute opioid tolerance in patients receiving intrathecal opioids prior to cesarean delivery
Abstract Number: S-50
Abstract Type: Original Research
Background: Opioids are commonly added to local anesthetic solution in spinal anesthesia for cesarean delivery. The addition of intrathecal (IT) fentanyl improves intraoperative analgesia but may induce acute tolerance to opioids resulting in increased postoperative pain and analgesic requirements (1,2). The 5-hydroxytryptamine type 3 receptor has been identified as a novel target for treating opioid dependence, and ondansetron (a well known antiemetic) has been shown to prevent and reverse opioid-induced hyperalgesia and tolerance in mice (3,4). No study to date has investigated whether or not these results can be generalized to a human population. The purpose of this study is to investigate whether administration of intravenous (IV) ondansetron prior to spinal anesthesia will have an attenuating effect on IT fentanyl-induced acute opioid tolerance and decrease pain scores and postoperative analgesic requirements. Our null hypothesis is that the addition of IV ondansetron prior to spinal anesthesia, including IT fentanyl, will not change postoperative pain scores or analgesic use.
Methods: Eighty-six patients undergoing elective cesarean delivery were recruited and randomly allocated to receive either 8 mg IV ondansetron (n=44) or placebo (n=42) in a prospective, double-blind design. All patients received the same study protocol regimen for spinal anesthesia consisting of 15 mg bupivacaine, 20 micrograms of IT fentanyl, and 100 micrograms of preservative free morphine. This is a secondary analysis, using linear mixed-effects models to assess the difference in pain and opioid consumption in the first 24 hours after surgery between the groups.
Results: No differences between the two groups were found in age, ASA scores, duration of surgery, or sensory and motor block characteristics. There was no difference between the groups in postoperative pain scores (p=0.920) or opioid consumption (p=0.539).
Discussion: In patients undergoing cesarean section under spinal anesthesia, including IT fentanyl, the addition of IV ondansetron prior to spinal anesthesia did not significantly affect post-operative pain scores or opioid consumption. The administration of ondansetron did not have an effect on acute opioid tolerance in this sample.
1.Gupta K et al. Saudi J Anaesth. 2014;8(1);64-8.
2.Carvalho B et al. Int J Obstet Anesth. 2012;21;29-34.
3.Chu LF et al. Pharmacogenet Genom. 2009;19(3);193–205.
4.De-Yong Liang et al. Anesthesiology. 2011;114(5);1180-9.