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.