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Neuraxial morphine is the most common long-acting opioid for prolonged analgesia after a cesarean delivery.1 However, it is associated with pruritus and postoperative nausea and vomiting (PONV).1,2 Both of these side effects are common after neuraxial morphine, and the side effects are more common with intrathecal doses greater than 150 µg. Few parturients experience a severe form of pruritus, PONV or both, and would rather experience pain than pruritus and/or PONV; thus, it is important to treat both in a timely manner.
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The reported incidence of pruritus is between 30% and 100%, making it the most common side effect post-cesarean delivery. The pruritus is often localized to the trunk and facial areas innervated by the trigeminal nerve. The exact mechanism is unknown. It is thought to be due to interaction between neuraxial opioids and 5-Hydroxytryptamine subtype 3 (5-HT3) receptors in the dorsal horn of the spinal cord and the spinal tract of the trigeminal nerve in the medulla. Activation of the mu- and kappa-opioid receptors in the same location is believed also to cause pruritus. Importantly, pruritus after neuraxial morphine administration is not due to histamine release.
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No single agent has been found to be completely effective in preventing or treating intrathecal opioid-associated pruritus. Several classes of medications can be used to treat pruritus. In women with a history of severe intrathecal morphine-induced pruritus, other analgesic modalities should be considered.
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Prophylaxis (if history of severe pruritus):
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Consider minimal effective intrathecal morphine dose of 100 µg or morphine via epidural (3 mg) instead of intrathecal route.
Consider neuraxial dexmedetomidine (Chapter 6, “Dexmedetomidine”).3
Avoid neuraxial morphine, and discuss use of oral/intravenous (IV) opioids.
Use regional techniques with bupivacaine such as transversus abdominis plane or quadratus lumborum blocks.
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Assess the patient, often assurance is a good start before treatment.
Nalbuphine (partial mu-receptor agonist/antagonist) 2.5 mg IV. Studies have shown that doses may be repeated up to 7.5 mg total dose without an effect on analgesia.
Naloxone 40 to 80 µg IV or infusion of 0.25 to 2.4 µg/kg/h; be aware of reversal of analgesia.
Ondansetron (5-HT3 receptors antagonist) 4 to 8 mg IV.4-8
Dexmedetomidine 10 µg IV.
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Diphenhydramine does NOT improve pruritus associated with neuraxial opioids but will worsen sedation.
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POST-CESAREAN DELIVERY NAUSEA AND VOMITING
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Post-Cesarean Delivery Nausea and Vomiting9
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PONV are common side effects following cesarean delivery under neuraxial anesthesia, with incidence up to 60% to 80%. Etiology is multifactorial. Nausea and vomiting associated with intrathecal opioids are due to their vascular uptake and are dose related. There are dopaminergic, muscarinic, serotonergic, histaminergic, neurokinin-1, and opioid receptors in the central nervous system, particularly in the chemoreceptor trigger zone ...