Comparative study of intrathecal dexmedetomidine with intrathecal magnesium sulfate used as adjuvants to bupivacaine.

Background: No drug, used as adjuvant to spinal bupivacaine, has yet been identified that specifically inhibits nociception without its associated side-effects.

Aims: This prospective randomized double-blind study was conducted to evaluate the onset and duration of sensory and motor block as well as perioperative analgesia and adverse effects of dexmedetomidine and magnesium sulfate given intrathecally with 0.5% hyperbaric bupivacaine for spinal anesthesia.

Materials And Methods: A total of 90 patients classified as American Society of Anesthesiologists status I and II scheduled for lower abdominal and lower limb procedures were prospectively studied. Patients were randomly allocated to receive intrathecally either 15 mg hyperbaric bupivacaine plus 0.1 ml (10 μg) dexmedetomidine (group D, n=30) or 15 mg hyperbaric bupivacaine plus 0.1 ml (50 mg) magnesium sulfate (group M, n=30) or 15 mg hyperbaric bupivacaine plus 0.1 ml saline (group C, n=30) as control. The onset time to reach peak sensory and motor level, the regression time for sensory and motor block, hemodynamic changes and side-effects were recorded.

Statistical Analysis Used: All statistical analyses were performed using INSTAT for windows. Continuous variables were tested for normal distribution by the Kolmogorov-Smirnov test. Data was expressed as either mean and standard deviation or numbers and percentages. Continuous covariates (age, body mass index and height) were compared using analysis of variance (ANOVA). For the times to reach T10 dermatomes, Bromage 3 scale and the regression of the sensory block to S1 dermatome and Bromage scale 0, one-way ANOVA was used to compare the means. The level of significance used was P<0.05.

Results: The onset times to reach T10 dermatome and to reach peak sensory level as well as onset time to reach modified Bromage 3 motor block were significantly different in the three groups. The onset time to reach peak sensory and motor level was shorter in group D as compared with the control group C, and it was significantly prolonged in group M. We also found that patients in group D had significant longer sensory and motor block times than patients in group M, which was greater than in the control group C.

Conclusion: It was found that onset of anesthesia was rapid and of prolonged duration in the dexmedetomidine group (D). However, in the magnesium sulfate group (M), although onset of block was delayed, the duration was significantly prolonged as compared with the control group (C), but to a lesser degree than in the dexmedetomidine group (D). The groups were similar with respect to hemodynamic variables and there were no significant side-effects in either of the groups.