Combined Intrathecal Morphine and Dexmedetomidine for Postoperative Analgesia in Patients Undergoing Major Abdominal Cancer Surgery

Objective. To compare the analgesic effect of combined intrathecal morphine and dexmedetomidine with either drug alone for postoperative analgesia in patients undergoing major abdominal cancer surgery. Methods. Ninety patients were allocated to receive intrathecal 10mg bupivacaine 0.5% (bupivacaine group, n=30), 10mg bupivacaine 0.5% and 0.5mg morphine (Morphine Group, n=30), or 10mg bupivacaine 0.5%, 0.5mg morphine and 5 mg dexmedetomidine (morphine-Dex group, n=30). The groups were compared with time to first postoperative analgesia, iv patient-controlled analgesia (PCA) morphine consumption, pain scores, hemodynamics, sedation, and adverse events in the first 48h postoperative. Results. The time to first use of morphine PCA was longer in morphine (22.13 +/- 5.21h, P=0.000) and morphine-Dex (23.46 +/- 4.69h, P=0.000) groups compared with bupivacaine group (0.50 +/- 0.09h). Dexmedetomidine addition increased the duration of intrathecal morphine (ITM) analgesia by 1.33 h (P=0.485). Morphine consumption was less in morphine (10.83 +/- 2.96 mg, P=0.000) and morphineDex (11.00 +/- 3.32 mg, P=0.000) groups than in bupivacaine group (27.5 +/- 4.30 mg), with a nonsignificant difference between morphine and morphine-Dex groups (P=0.375). Morphine and morphine-Dex groups showed lower pain scores (P<0.001). Intraoperative blood pressure and heart rate were lower in morphine and morphine-Dex groups (P<0.05) with no significant difference between groups in postoperative hemodynamics. Patients in bupivacaine group showed a higher incidence of postoperative nausea (P<0.03) and vomiting (P <0.01), while patients in morphine and morphine-Dex groups had a higher incidence of pruritus (P<0.02). Conclusions. Our results do not support improved analgesia with the combination of intrathecal morphine and dexmedetomidine, despite the absence of significant adverse effects.