randomised trial comparing the incidence of unintended sciatic nerve block following ultrasound guided pudendal nerve block with two different volumes of ropivacaine for hemorrhoidectomy

30 patients undergoing elective hemorrhoidectomy would be dived randomly divided into to two groups.Written informed consent would be obtained from the patient.All the patients would be fasted pre operatively for 6 hours.On the day of surgery ,the motor power  and sensation of the sciatic nerve would be noted.An intravenous cannula would be started and the patient would be loaded with 10ml/kg RL.The patients vitals would be monitored and the patient would be place in the prone position.For patient belonging to group I ,the pelvis would be scanned with a 3-6 mega hertz ultrasound probe starting from the Posterior superior illiac spine and advanced down to identify the Greater sciatic foraman and the Piriformis.Once when the piriformis is identified then the probe is still moved caudally until the piriformis disappears and the sacrospinous and the sacrotuberous ligament is noted.The probe is adjusted such that the sciatic nerve is visualised lateral to the ischial spine and the pudendal nerve and artery is visualised medial to the ischial spine in the interligamentous plane.the neerdle is advanced under real time ultrasound guidance till the tip reaches the inter ligamentous plane medial to the pudendal artery.Once when the position is confirmed 10 ml of 0.25% of ropivacaine is injected incrementally after repeated aspiration for blood and the spread of injectate to the sciatic nerve would be noted.The same procedure would be repeated in the opposite side.For patients belonging to group II the same procedure would be repeated but the volume of 0.25% ropivacaine injected would be 5ml on each side.Following the block the patient would be turned to supine position and general anaesthesia induced and appropriate sized LMA would be inserted and the surgical procedure would be completed.After the procedure the patient would be reversed from general anaesthesia and the outcomes would be assessed.