Comparison of Two Different Dexmedetomidine Doses and Their Effect on the Duration of Spinal Anesthesia in Lower Limb Amputation Surgeries.

Background: Spinal anesthesia is a very common technique used in lower limb surgeries. Dexmedetomidine is a highly selective α2-adrenergic agonist which has been used as pre-medication and as an adjuvant to general anesthesia. It is found that injection of dexmedetomidine intrathecally prolongs both sensory and motor block and has antinociceptive action for both visceral and somatic pain by depressing the release of nociceptive C fibers transmission and hyperpolarization of post synaptic dorsal horn cells. Objective: To compare the effect of addition of different doses of dexmedetomidine to bupivacaine on the duration of spinal anesthesia, quality of block, intraoperative and postoperative complications and postoperative analgesia in patients undergoing lower limb amputation surgeries. Methods: This prospective double blind randomized controlled clinical trial was done on sixty six adult patients of both sexes, aging from 21 to 60 years old, ASA I and II presented to Ain Shams University Hospitals for lower limb amputation surgeries were involved in this study during the period from July 2021 till May 2022. Results: The addition of dexmedetomidine to bupivacaine in spinal anesthesia significantly prolonged both sensory and motor blockades duration compared with bupivacaine alone. It was significantly faster in group B (2.1 ± 0.124) compared with A and C groups (2.64 ± 0.34) and (4.72 ± 0.31) respectively and in group A compared with group C. They also prolonged the time of postoperative analgesia as evidenced by significantly longer time to first rescue analgesia Time to first call for rescue analgesia was significantly longer in group B (350 ± 45 mins) compared with A(287.41 ± 40.83 mins) and C(192 ± 42 mins) groups and in group B compared with group A. Also, there was significant difference in number of analgesic doses in group B compared to A and C groups and in group B compared to group A. Lower VAS scores with minimal adverse effects and hemodynamic stability. Comparing two different doses of dexmedetomidine showed that 15 µg dexmedetomidine caused more prolongation of the spinal block duration and the time of postoperative analgesia than dexamethasone. It also decreased shivering during spinal anesthesia with only 4 patients compared to group A with 8 patients and group C with 9 patients. Conclusion: 5 µg dexmedetomidine seems to be an attractive as an adjuvant to spinal bupivacaine in surgical procedures. It provided good quality of intraoperative analgesia, hemodynamically stable conditions, minimal side effects, and excellent quality of postoperative analgesia. Unfortunately, it had not any effect on incidence or severity of phantom pain and sensation in lower limb amputation surgery, but 15 µg had better time of analgesia and longer time till the patient needed rescue analgesia with lower VAS score with no remarkable difference in the side effect as revealed. [ABSTRACT FROM AUTHOR]