Neuraxial morphine is commonly used to help control pain after cesarean section. While pain control is important, the risk of apnea with neuraxial opioids is always a cause of concern. There is particular concern if the patient has risk factors for respiratory depression and hypoxia, such as obesity or sleep apnea.
Previous studies have looked at the incidence of apnea following neuraxial morphine for cesarean section. However, most of these studies are at least 20 years old. Since the time they were published, patient weight has increased, as has the recognition of sleep apnea. Dr. Ashraf S. Habib, Anesthesiology-Womens Division, Duke University Medical Center, Durham, North Carolina, and colleagues studied the incidence of apnea after cesarean section and use of neuraxial morphine, based on the need for naloxone, in over 5,000 patients who underwent the procedure at their institution between December 1, 2006, and December 31, 2011. Their article, “A Retrospective Assessment of the Incidence of Respiratory Depression After Neuraxial Morphine Administration for Postcesarean Delivery Analgesia,” appeared in this month’s edition of Anesthesia & Analgesia.
About 20% of the patients received epidural morphine and the remainder received spinal morphine. The typical morphine dose for epidural analgesia was 3 mg and for spinal analgesia was 0.15 mg. About 63% of the patients had a BMI ≥30 kg/m2 (i.e., they were obese). No patient needed naloxone for treatment of respiratory depression, although though two received naloxone to treat pruritus. One patient became hypotensive and needed oxygen 55 hours after delivery after receiving 60 mg nifedipine XL. This patient did not require naloxone.
There might have been instances of minor hypoventilation or hypoxia where naloxone was not needed. Also, monitoring was not as stringent as it is in the operating room. Nonetheless, given those caveats, it appears that neuraxial morphine to manage pain after cesarean section is safe.
Hopefully, patient weights in the next 20 years will not increase more than they have already, requiring yet another study in an increasingly obese population.