Intrathecal Dexmedetomidine, Ketamine, and their Combination Added to Bupivacaine for Postoperative Analgesia in Major Abdominal Cancer Surgery.

BACKGROUND Intrathecal ketamine has been studied extensively in animals, but rarely in humans. Intrathecal dexmedetomidine prolongs the duration of spinal anesthesia. OBJECTIVE To investigate the efficacy and safety of intrathecal dexmedetomidine, ketamine, or both when added to bupivacaine for postoperative analgesia in major abdominal cancer surgery. DESIGN Double-blinded, randomized, controlled trial. SETTING Academic medical center. METHODS Ninety patients were randomly allocated to receive either intrathecal 10 mg of hyperbaric bupivacaine 0.5% and 5 µg of dexmedetomidine (group I, n = 30), 10 mg of hyperbaric bupivacaine 0.5% and 0.1 mg/kg ketamine (group II, n = 30), or 10 mg of hyperbaric bupivacaine 0.5% and 5 µg of dexmedetomidine plus 0.1 mg/kg of ketamine (group III, n = 30). Hemodynamics, pain score, time to first request of analgesia, total PCA morphine consumption, sedation score, and adverse effects in the first 24 hours postoperatively were recorded. RESULTS Time to first request of analgesia was longer in group II (7.42 ± 1.43 h) and group III (13.00 ± 7.31h) compared to group I (3.50 ± 1.57 h). PCA morphine consumption was less in group III (6.67 ± 2.8 mg) compared to group I (9.16 ± 3.63 mg) and group II (8.66 ± 3.49 mg). Group III showed lower postoperative pain scores, and a higher incidence of postoperative sedation (P < 0.03). LIMITATIONS This study is limited by its relatively small sample size. CONCLUSION In conclusion, the combination of intrathecal dexmedetomidine and ketamine provided superior postoperative analgesia, prolonged the time to first request of rescue analgesia, and reduced the total consumption of PCA morphine, without serious side effects compared to either drug alone.