Determination of an effective dose of intrathecal morphine for pain relief after cesarean delivery

Very small doses of intrathecal (IT) morphine (25-200 mu g) have been used in an effort to provide effective postoperative pain relief while minimizing side effects after cesarean delivery. We performed a double-blinded study in 40 patients presenting for elective cesarean delivery in which IT morphine was administered along with oral hydrocodone/acetaminophen and other medications commonly administered after cesarean delivery. We administered IT morphine by up-down sequential allocation of doses. For the purposes of this study, adequate postoperative analgesia was defined as comfort not requiring IV morphine for 12 h after spinal anesthesia with bupivacaine, fentanyl, and morphine. In addition, a time and cost comparison was performed for study patients receiving intrathecal morphine compared with a historical group of patients receiving patient-controlled analgesia with IV morphine. We were unable to determine with meaningful precision a dose of IT morphine to provide analgesia in this context. However, very small doses of IT morphine combined with oral hydrocodone/acetaminophen and other medications commonly prescribed after cesarean delivery provided postoperative pain relief with no more time commitment than patient-controlled analgesia (148 +/- 61 vs 150 +/- 57 min) and with significantly less acquisition cost($15.13 +/- $4.40 vs $34.64 +/- $15.55). Implications: When used along with oral analgesics, very small doses of spinal morphine provide adequate pain relief after cesarean delivery. Spinal anesthetics, oral analgesics, and other medications commonly prescribed to treat side effects after cesarean delivery contribute significantly to this analgesia. When small doses of spinal morphine are used in this setting, they provide adequate analgesia and patient satisfaction that is time-and cost-effective.