Effect of three different doses of intrathecal dexmedetomidine on subarachnoid block: a prospective randomized double-blind trial

Background: Dexmedetomidine has increasingly been used in regional anesthesia as an adjuvant, but there is still no consensus on the optimum dose when it is used intrathecally. We conducted this study to elucidate the dose-response relation between three different doses of intrathecal dexmedetomidine (2.5, 5, or 10 µg) as an adjuvant to 0.5% hyperbaric bupivacaine in patients undergoing elective lower abdominal and lower limb surgeries. Methodology: 90 patients, aged 18-60 y, were randomized into three groups of 30 patients each. Group A received 0.5% hyperbaric bupivacaine 12.5 mg (2.5 ml) with 2.5 µg dexmedetomidine, Group B received 5 µg dexmedetomidine with bupivacaine, and Group C received 10 µg dexmedetomidine with bupivacaine. Duration of the spinal sensory blockade (primary outcome), onset of the blockade, time to rescue analgesia, level of sedation, duration of motor blockade, comparison of hemodynamic variables and complications, if any were assessed. Results: There was a significant dose dependent prolongation of sensory block; Group A - 250.67 ± 51.39, Group B - 286 ± 52.76, and Group C - 351.00 ± 47.00 min; (p < 0.001), motor block; Group A - 255.53 ± 44.25, Group B - 312 ± 29.64, and Group C - 361.4 ± 16.14 min (p < 0.001). Time to two segment regression was 132.33 ± 48.29, 148.77 ± 48.89, 171.57 ± 25.46 min (p = 0.002) and time for rescue analgesia was 351.33 ± 101.19, 472.00 ± 24.41, 738.00 ± 67.79 min (p < 0.001). VAS was significantly low in Group C (p < 0.05). Intergroup hemodynamic parameters were comparable (p > 0.05) without any appreciable side effects. Conclusion: Spinal dexmedetomidine increases the sensory and motor block durations as well as time to first analgesic use, and decreases analgesic consumption in a dose-dependent manner, when used with hyperbaric bupivacaine. Abbreviations: IT - Intrathecal; ITD - Intrathecal Dexmedetomidine; SAB - Subarachnoid Block; VAS - Visual Analogue Scale; BMI - Body Mass Index; NIBP - Non-Invasive Blood Pressure; RSS - Ramsay Sedation Score; TSSR - Two segment sensory regression; ANOVA - Analysis of Variance; OSB - Onset of sensory block, TSSRT - Two segment sensory regression time; Duration of sensory blockade; OMB - Onset of motor block; DMB - Duration of motor blockade Key words: Dexmedetomidine; Bupivacaine; Anesthesia, Spinal; Dexmedetomidine; Post-operative analgesia Citation: Mowar A, Singh V, Pahade A, Karki G. Effect of three different doses of intrathecal dexmedetomidine on subarachnoid block: a prospective randomized double-blind trial. Anaesth. pain intensive care 2021;26(1):8–13; DOI: 10.35975/apic.v26i1.1759 Received: July 24, 2021, Reviewed: November 18, 2021, Accepted: November 28, 2021