Efficacy of ultrasound-guided classical versus parasacral parallel shift technique of sacral plexus block for lower limb surgeries – A randomised controlled trial

Background and Aims: Ultrasound-guided sacral plexus block has been used for anaesthesia and analgesia in lower limb surgeries. This study aimed to compare the block performance characteristics after ultrasound-guided (USG) sacral plexus nerve block (SNB) using the parasacral parallel shift (PSPS) approach versus the classical approach in patients undergoing orthopaedic below-knee limb surgeries. Methods: In this randomised study, 144 adult patients were randomised to receive USG SNB either by the classical approach (Group C) or the PSPS approach (Group P). A fixed dose of 20 ml of 0.5% ropivacaine was administered. Patients also received USG femoral nerve block with 10 ml of 0.5% ropivacaine. The primary outcome was the scanning time between the two groups. Secondary outcomes were the needling time, sensory and motor block onset and postoperative analgesic characteristics between the two groups. A P value of <0.05 was considered statistically significant. Results: The needling time and the scanning time were significantly lesser in Group P than in Group C ( P < 0.05). Complete sensory and motor nerve blockade of the sciatic nerve was significantly higher in Group P ( P = 0.029). Block performance time, time for sensory block and time for motor block were significantly less in Group P compared to Group C ( P < 0.001). The postoperative analgesic characteristics were comparable between the two groups. Conclusion: The sacral plexus block with ultrasound-guided parasacral parallel shift technique had a lower block performance time with lesser needling and scanning time than the classical approach.