Comparison of Postoperative Analgesic Effect of Dexmedetomidine and Morphine as an Adjuvant to Intrathecal Bupivacaine in Infraumbilical Surgeries: A Randomised Clinical Trial

Abstract

Introduction: Regional anaesthesia is the standard technique for lower limb infraumbilical procedures. To provide a better analgesic profile, adjuvants are added to local anaesthetics to enhance their action. Opioids have been used as an adjuvant for a long-time. With evolving pharmacology, various drugs satisfy the criteria of being an adjuvant. One such drug is Dexmedetomidine, a novel alpha-2 agonist. Aim: To compare the duration of analgesia of intrathecal Morphine and Dexmedetomidine as an adjuvant to bupivacaine in a subarachnoid block for lower limb infraumbilical surgeries. Materials and Methods: In this randomised clinical, doubleblinded study conducted in a multispecialty hospital over the period of June 2020 to February 2021, 70 patients were randomly divided into two groups: Group M received Morphine 125 µg, and Group D received dexmedetomidine 5 µg as an adjuvant to 15 mg of 0.5% hyperbaric bupivacaine. The primary outcome was to compare the duration of postoperative analgesia. The secondary results assessed the block characteristics, haemodynamic parameters, rescue analgesic consumption, sedation score, and side-effects like bradycardia, hypotension, nausea, vomiting, pruritus, and respiratory depression. Data was spread in an Excel sheet and descriptive analysis done. Normally distributed continuous variables were compared using a Student’s t-test, and discrete variables were compared using a Chi-square test. A p-value of <0.05 was considered significant. Results: Both groups were similar with respect to age, sex, body mass index, American Society of Anaesthesiologists grading, and duration of surgery. The duration of analgesia was 956.97±120.043 minutes in group M and 392.83±50.354 minutes in group D (p-value <0.001). The total consumption of paracetamol was 1984.71±499.111 mg in group M and 3543.86±406.17 mg in group D. The onset and regression were significantly faster in group D. There was significant hypotension and bradycardia up to the 40th minute and an increase in heart rate, respiratory rate, and mean arterial pressure between 5-7 hours in group D. The sedation score was more in group D for the initial two hours. Postoperatively, the incidence of nausea, vomiting, and pruritus was more in group M. Conclusion: It can be concluded that 125 µg of intrathecal morphine is a better adjuvant to spinal bupivacaine, providing excellent postoperative analgesia compared to 5 µg of intrathecal dexmedetomidine. However, dexmedetomidine had more incidence of hypotension, bradycardia, and sedation when compared to morphine intrathecally.