Comparison of Intravenous Bolus and Infusion of Dexmedetomidine on Characteristics of Subarachnoid Block.

Aims: Dexmedetomidine is very dynamic drug, used for analgesia, sedation, blunting the laryngoscopic responses and as adjuvants in regional anesthesia. Studies have shown that intravenous (iv) dexmedetomidine given during spinal anesthesia increases the quality of subarachnoid block (SAB). In this study, we compare the two iv regimen of dexmedetomidine on analgesic effect of spinal anesthesia. One is bolus dose of dexmedetomidine and other is infusion during the surgery, both given after induction of spinal anesthesia.

Subjects and Methods: Sixty American Society of Anesthesiologists I and II patients scheduled to undergo surgeries under SAB were randomly allocated into two groups namely B and I. After SAB with 3.0 ml of bupivacaine 0.5% heavy, Group B received 0.5 μg/kg of dexmedetomidine bolus over 15 min, Group I received 0.5 μg/kg/h of dexmedetomidine infusion until the end of surgery.

Statistical Analysis Used: All parametric data were statistically analyzed using Student's t -test and nonparametric data analyzed using Chi-square test and Fischer exact test as appropriate. P < 0.05 was considered as statistically significant. Statistical analysis was performed using the SPSS.

Results: Time to reach desired level T10 was quick in Group B compared to Group I. Regression of sensory and motor was prolonged in Group I compared to Group B. Total duration of analgesia was significantly prolonged in Group I 230.39 ± 16.20 compared to Group B 196.01 ± 14.32 and the difference is statistically significant ( P = 0.0001). Both groups had Ramsay sedation score of 3 which lasted for 45 min in Group B while it was maintained in Group I. Side effects profile of both groups was comparable with few incidence of bradycardia and hypotension in both groups requiring treatment.

Conclusions: We conclude that the continuous infusion of dexmedetomidine after SAB results in prolonged analgesia than just a bolus dose. Therefore, we suggest use of the maintenance dose of iv dexmedetomidine after SAB for prolonging the duration and achieving adequate sedation.