A comparative study of buprenorphine in two different doses as an adjuvant to levobupivacaine in US-guided lumbar plexus block for postoperative analgesia

Background
Lumbar plexus block (LPB) is a proven modality to provide analgesia following lower limb surgeries. The present study compared the effect of buprenorphine in different doses viz. 150 μg and 300 μg as an adjuvant to levobupivacaine in unilateral lumbar plexus block. In this prospective, controlled, and double-blind study, ninety patients undergoing hip, thigh, and knee surgeries under subarachnoid block were enrolled. The patients were randomly allocated into three groups of thirty each, to receive LPB with 0.25% levobupivacaine plain (group L), 0.25% levobupivacaine with 150 μg buprenorphine (group BL), or 0.25% levobupivacaine with 300 μg buprenorphine (group BH), after the sensory level of subarachnoid receded to T10. Total volume administered was 30 ml. The duration of analgesia post LPB, total pain-free period, cumulative rescue analgesic doses per patient, number of patients requiring rescue analgesic, pain scores using visual analog scale (VAS), and sedation levels were noted at protocolized predetermined intervals in each case.
Results
The duration of analgesia post LPB was significantly prolonged in both the buprenorphine groups (9.76 ± 1.39 h in group with 150 μg buprenorphine and 10.13 ± 1.5 h in group with 300 μg buprenorphine) as compared to 4.25 ± 0.93 h in the control group ( < 0.001). The total pain free-period of 12.81 ± 1.49 h was maximum in group BH as compared to 12.42 ± 1.47 h in group BL and 7.01 ± 0.89 h in group L and was statistically significant with the control group ( = 0.001). The cumulative rescue analgesic doses per patient was also significantly higher in control group L (3.10 ± 0.40) as compared to groups BL (1.77 ± 0.5) and BH (1.33 ± 0.48). There was significant decrease in pain scores in patients of both buprenorphine groups compared to the control group up to 24 h ( < 0.001). In group BH, patients were sedated in the first hour with a modified Ramsay Sedation Score of 1.93 ± 0.86 which was statistically significant from the group L (modified RSS of 1.00 ± 0.00, = 0.003) as well as from group BL (modified RSS of 1.47 ± 0.50, = 0.043).
Conclusions
Buprenorphine in either of the doses (150 μg or 300 μg) as an adjuvant to levobupivacaine in lumbar plexus block provided comparable postoperative analgesia. A dose of 300 μg, however, resulted in significant sedation and respiratory depression. Hence, buprenorphine 150 μg appears to be an optimal dose providing prolonged postoperative analgesia and minimal sedation.