Discussion
nausea, nausea and dizziness, vomiting, constipation, dizziness, pruritus, neuraxial morphine-induced, nausea,, urinary retention
ADVERSE REACTIONS
This prospective, double-blinded, randomized dose–response trial is the first study focusing on the infusion dose of butorphanol for preventing morphine-induced pruritus in women having elective caesarean delivery. Our results showed that prophylactic administration of 0.25 mg palonosetron significantly decreases the required dose of butorphanol, reduces the severity of pruritus at 6h after epidural morphine administration, and lowers the incidence of post-operative nausea and dizziness. Butorphanol is considered an appropriate prophylactic measure against neuraxial morphine-induced pruritus. However, high doses of butorphanol can cause adverse reactions such as dizziness, drowsiness, nausea and vomiting, which might limit its clinical use [Although the effectiveness of epidural morphine for post-caesarean analgesia has been well established, morphine can produce undesired side effects, including pruritus, nausea, vomiting, urinary retention, and constipation [Continuous infusion was chosen as the route of butorphanol administration due to its short duration of action. We chose palonosetron for its high affinity for the 5-HT3 receptor and longer plasma half-life (approximately 40h) than other antagonists, such as ondansetron (approximately 3.8 h) [For the regimen and dose of neuraxial morphine, all the participants in this study received 2 mg epidural morphine. The dosage was set based on the protocol in similar studies and our routine clinical experience in practice. Epidural morphine is usually administered at a dose of 1 mg to 3 mg, which is approximately 10 times that in other studies using intrathecal morphine [Our study has some limitations. First, the dose of palonosetron used in the P + B group was fixed at 0.25 mg. Different doses of palonosetron might have different impacts on the ED50 of butorphanol. Second, our study compared the ED50 value for butorphanol infusions. However, in clinical practice, ED90 or ED95 is more preferable. Third, the study only consisted of parturients, the results may be different in other populations. To increase generalizability of the current findings, further studies are needed to focus on the dosage of palonosetron and butorphanol in preventing pruritus induced by epidural neuraxial administration of morphine in other patient populations.