Efficacy of Bupivacaine with Morphine versus Bupivacaine with Dexamethasone for Ultrasound Guided Caudal Block in Patients undergoing Lumbar Discectomies: A Randomised Control Study

Introduction: Patients scheduled for spinal surgeries often complain of severe pain postsurgery. Using an additive to the caudal local anaesthetic can provide better pain relief and facilitate early ambulation. Adding an opioid like morphine extends pain relief, while using a steroid like dexamethasone also contributes to prolonged pain relief. Aim: To compare the combination of morphine with bupivacaine and the combination of dexamethasone with bupivacaine in order to assess which provides better pain relief postsurgery. Materials and Methods: In this randomised controlled study, ninety patients in American Society of Anaesthesiologists (ASA) grade I and II categories, scheduled for single-level lumbar discectomies, were randomised into three groups. Patients in group A received an ultrasound-guided caudal injection of 25 mL of morphine (3 mg) and bupivacaine (0.25%). Patients in group B received 25 mL of dexamethasone (8 mg) and bupivacaine (0.25%). Lastly, patients in group C received 25 mL of bupivacaine (0.25%) pre-surgery. Postoperative pain was assessed periodically using Visual Analogue Scale (VAS) scores. The time to ambulation, need for rescue analgesics, and side effects were also studied. Data were collected and analysed using Statistical Package for Social Sciences (SPSS) software. Qualitative variables between the groups were compared using the Chi-square test of significance. A p-value of <0.05 was considered statistically significant. Results: Age (p-value=0.997), sex (p-value=0.928), ASA grades (p-value=0.312), fentanyl consumption during surgery (p-value=0.224), and surgery duration were comparable across all groups (p-value=0.082). VAS static scores were significantly lower in the early postoperative period in group A (p-value=0.021) compared to group B (p-value=1.49) and group C (p-value=0.341). VAS dynamic scores were significantly lower in all groups (p-value <0.01); however, intergroup comparison showed that none of the scores were statistically significant (p-value >0.05 at all times). The time to ambulate was significantly shorter in group A (27.23±11.13 hours) compared to group B (32.87±13.55 hours) and group C (36.07±14.61 hours) (p-value=0.03). The need for rescue analgesics was recorded, with the time taken for rescue analgesics in group A being (8.23±4.56 hours), in group B (8.00±3.67 hours), and in group C (8.77±3.37 hours). The difference in time required was not statistically significant (p-value=0.73). Side effects, including nausea and vomiting, were recorded, with statistical significance observed (p-value=0.03). Conclusion: Ultrasound-guided caudal block provides effective pain relief in lumbar surgeries. In our study, the addition of morphine to bupivacaine provided better pain relief than dexamethasone. However, side effects are not uncommon and should be considered when using such combinations.