The effect of dexmedetomidine and midazolam on combined spinal-epidural anesthesia in patients undergoing total knee arthroplasty

BACKGROUND: Intravenous dexmedetomidine has been reported to potentiate the anesthetic effect of local anesthetics and improve the quality of postoperative analgesia when used as an adjuvant in neuraxial block. We compared the effects of intravenous dexmedetomidine and midazolam for sedation on combined spinal-epidural (CSE) anesthesia. METHODS: This study included 50 patients undergoing total knee arthroplasty. CSE anesthesia was given using 10 mg bupivacaine for all patients. After checking the maximum sensory and motor levels, the patients were randomly allocated into two groups of 25 each to receive intravenous continuous infusion of dexmedetomidine (Group D) or midazolam (Group M) for sedation during surgery. Regression block level, hemodynamic changes, and sedation score were compared between the groups when the patients entered the postanesthetic care unit (PACU). For patient-controlled epidural analgesia, 0.2% levobupivacaine with 650 µg of fentanyl (150 ml in total) was infused at a rate of 1 ml/h, in addition to a 3-ml bolus dose with a 30-min lockout time. The visual analogue scale scores, additional analgesic demand, patient satisfaction, and adverse events between the two groups were also compared postoperatively. RESULTS: A significant difference was observed in relation to the sensory block level in the PACU (Group D: 6.3 ± 2.1; Group M: 3.2 ± 1.9) (P = 0.002). The motor block level and other outcomes showed no significant intergroup differences. CONCLUSIONS: Intravenous injection of dexmedetomidine, rather than midazolam, for procedural sedation is associated with prolonged sensory block, with comparable incidences of adverse events during CSE anesthesia.