Randomized trial comparing the incidence of unintended sciatic nerve block following ultrasound-guided pudendal nerve block with two different volumes of ropivacaine for hemorrhoidectomy: A pilot study

Abstract

Aim: To compare the incidence of unintended sciatic nerve block following pudendal nerve block in the interligamentous plane with two different volumes of ropivacaine for post hemorrhoidectomy pain. Materials and Methods: 30 patients undergoing hemorrhoidectomy were enrolled for the study and randomly divided into two groups. Prior to the block a scout scan was performed and the pudendal artery, nerve and the sciatic nerve were identified in the interligamentous plane. All the patients received bilateral pudendal nerve block under ultrasound guidance with 5ml of 0.25% ropivacaine in group 1 and 10 ml in group 2. The spread of local anaesthetic to the ipsilateral sciatic nerve was noted under ultrasound imaging. The time of first rescue analgesia (FRA) and total analgesic requirement(TAR) were noted in both groups. The overall patient satisfaction was assessed with a three point scale.The unintended motor and sensory block of the sciatic nerve was noted. Results: The right pudendal artery was visualized in all cases where but left pudendal artery was not visualized in 1 case. The right & left pudendal nerve was visualized in 40% & 46.7% of cases in group I and 40% in both sides of group 2. The incidence of spread of drug towards the right and left sciatic nerve was more in group II (73.3% & 66.6%) than group I (40% & 33.3%). Statistically significant difference was not noted in the time for FRA (P value 0.684) & TAR (P value 0.579). There was no clinically significant sciatic nerve block. Conclusion: We conclude that less volume of local anaesthetic can achieve effective pudendal nerve block minimizing the spread to ipsilateral sciatic nerve.