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

Abstract

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 10 mg bupivacaine 0.5% (bupivacaine group, n = 30), 10 mg bupivacaine 0.5% and 0.5 mg morphine (Morphine Group, n = 30), or 10 mg bupivacaine 0.5%, 0.5 mg morphine and 5 µg 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 morphine-Dex (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.

Trial registration: ClinicalTrials.gov NCT02435537.

Keywords: Acute Pain; Analgesic; Intrathecal; Morphine.