Comparison of Prolongation of Spinal Anesthesia Produced by Intravenous Dexmedetomidine and Midazolam: A Randomized Control Trial

CONTEXT: Various intravenous (i.v.) adjuvants have been used along with spinal anesthesia to delay the onset of postoperative pain. AIMS: To compare effects of i.v. dexmedetomidine with midazolam on duration of spinal anesthesia. SETTINGS AND DESIGN: This prospective randomized control trial was conducted in a tertiary care institution. SUBJECTS AND METHODS: Forty-three patients presenting for elective infraumbilical surgery under spinal anesthesia were randomly allocated into two groups. Group A received a loading dose of 0.5 μg/kg followed by 0.5 μg/kg/h of i.v. dexmedetomidine. Group B received a loading dose of 0.03 mg/kg followed by 0.03 mg/kg/h of i.v. midazolam. Two dermatomal regressions, regression to S(1) level, and sedation score were noted. STATISTICAL ANALYSIS USED: To test the statistical significance of duration of sensory blockade, Mann–Whitney U-test was applied. The incidence of bradycardia and hypotension was analyzed using Pearson's correlation coefficient test. RESULTS: The mean time for two dermatomal regressions was significantly prolonged in Group A (2.3 ± 0.4 h) than Group B (1.6 ± 0.5 h, P = 0.001). Mean time for sensory regression to S(1) dermatome was also prolonged in Group A (5.2 ± 0.83 h) than in Group B (4.4 ± 0.87 h, P = 0.01). Glycopyrrolate was administered in 45% of patients in Group A and 21% in Group B, which was statistically significant (P = 0.039). CONCLUSION: Conscious sedation with i.v. dexmedetomidine at a loading dose of 0.5 μg/kg followed by 0.5 μg/kg/h prolongs duration of spinal anesthesia than i.v. midazolam at a loading dose of 0.03 mg/kg followed by 0.03 mg/kg/h in patients undergoing infraumbilical surgeries. However, dexmedetomidine is associated with higher incidence of hemodynamic instability.