Effect of Dexmedetomidine IV on the Duration of Spinal Anesthesia with Prilocaine: A Double-Blind, Prospective Study in Adult Surgical Patients.

BACKGROUND: The duration of spinal anesthesia with prilocaine has been poorly documented and no English-language study has been published regarding the effects of dexmedetomidine on the duration of anesthesia with spinal prilocaine.

OBJECTIVE: The aim of this study was to assess the effects of dexmedetomidine IV on the duration of action of prilocaine and its associated adverse events (AEs) in spinal anesthesia.

METHODS: In this double-blind, prospective study, patients classified as American Society of Anesthesiologists grade I to II who were to undergo lower abdominal, anorectal, or extremity surgery with a spinal anesthetic were assigned to 1 of 2 groups. All patients were administered prilocaine 2% for spinal anesthesia. Within 10 minutes after spinal anesthesia was initiated, group 1 received a loading dose of dexmedetomidine 1 μg/kg IV, followed by a maintenance dose of 0.4 μg/kg · h for 50 minutes; group 2 (control) received the same amount of physiologic saline in the same time frame. Mean arterial pressure (MAP), heart rate (HR), duration of sensory and motor blockade, and sedation scores were tracked. Patients were observed for 4.5 hours after surgery, with follow-ups occurring up to 96 hours after surgery.

RESULTS: Eighty-three patients were assessed for study inclusion, 23 of whom were excluded. Sixty patients (42 men, 18 women; mean [SD] age, 40.56 [16.86] years) were included in the study. MAP was similar in the 2 groups throughout the study. Mean (SD) HR was significantly lower in group 1 compared with group 2 at 20 minutes (70.43 [19.28] vs 77.63 [18.14] beats per minute, respectively; P = 0.02). The mean (SD) duration of the persistence of sensory anesthesia (ie, the time required for the maximal level of anesthesia to regress 2 dermatomes) was significantly longer in group 1 compared with group 2 (148.33 [21.18] vs 122.83 [18.73] minutes; P < 0.001). The mean (SD) time to complete abolishment of motor blockade was also significantly longer in group 1 than in group 2 (215.16 [25.10] vs 190.83 [18.57] minutes; P < 0.001). The average sedation score in group 1 was significantly higher than in group 2 (P < 0.001) during anesthesia. Significantly more patients in group 1 required atropine than those in group 2 (9 vs 2 patients; P < 0.001) to treat bradycardia. There was no significant between-group difference in the number of patients who received ephedrine to treat hypotension. One patient in each group reported waist and back pain; 2 patients in each group reported nausea. Shivering occurred in 0 and 5 patients in groups 1 and 2, respectively; the between-group difference in AEs was not statistically significant. Paresthesia, postdural puncture headache, allergic reactions, total spinal anesthesia, urinary retention, or vomiting-AEs commonly associated with spinal anesthesia-were not observed or reported by either group.

CONCLUSIONS: The results of this study suggest that dexmedetomidine IV significantly prolonged the duration of spinal anesthesia and provided a significantly higher level of sedation compared to placebo in this group of adult surgical patients. The treatment was generally well tolerated in all patients.