Comparison of Morphine and Clonidine as Adjuncts to Bupivacaine in Spinal Anaesthesia- A Double Blind Randomised Control Trial

Abstract

Introduction: Spinal anaesthesia is a preferred choice for infraumbilical surgery. Various drugs have been added intrathecally to augment analgesia in the postoperative period. Morphine an opiate was among the first to be introduced. More recently the alpha-2 agonist Clonidine. Aim: To compare Clonidine and Morphine as adjuncts to bupivacaine in spinal anaesthesia on the quality of the block, the duration of postoperative analgesia, haemodynamic changes and complication. Materials and Methods: In this randomised double blind controlled study, one hundred patients between age 20-40 years of age and American Society of Anaesthesiologists (ASA) physical status 1 and 2 undergoing lower limb Orthopaedic procedures were studied to compare the effect of preservative free morphine (100 mcg) (Group BM) and clonidine (30 mcg) (Group BC) as an adjunct to 0.5% bupivacaine in spinal anaesthesia. Group BM received a mixture of 2.6 mL (13 mg) of hyperbaric bupivacaine (0.5%) with 0.1 mL of preservative free Morphine and 0.1 mL 0.9% saline. Group BC received a mixture of 2.6 mL (13 mg) of hyperbaric bupivacaine (0.5%) with 0.2 mL of clonidine (30 mcg). Total volume of solution in both the groups was 2.8 mL. The groups were compared for the onset and duration of sensory and motor blockade. Duration of analgesia, Sedation, Haemodynamic variations viz., Pulse rate, blood pressure and complications. Data obtained was analysed using Student t-test, Pearson chi-square test and ANOVA as appropriate. Results: Onset of sensory block was faster and duration of the sensory as well as motor block was more after addition of Clonidine (30 µg) to bupivacaine in spinal anaesthesia. The duration of postoperative analgesia was significantly prolonged to 10-13 hours in patients receiving Bupivacaine and morphine combination as compared to 6-8 hours noted in patients receiving Bupivacaine and Clonidine only. Incidence of hypotension, bradycardia, shivering, nausea and vomiting was not statistically significant. None of the patients in both groups showed any other side effects like respiratory depression, hypoxia, excessive sedation or any other spinal consequences. Conclusion: Clonidine improves the quality of spinal anaesthesia in terms of faster onset of sensory block and longer duration of sensory as well as motor block compared to morphine, when added as an adjunct. However, the duration of postoperative analgesia was prolonged more with the addition of Morphine compared to Clonidine.

Keywords

• alpha-2 agonists
• block quality
• intrathecal adjuvants
• opiates
• postoperative analgesia