Effects of Differences in Epidural Needle Entry Point and Angle of Rotation of Needle Hub on the Onset and Duration of Sensory Blockade in Lower Limb Orthopaedic Surgeries: A Randomised Controlled Trial

Abstract

Introduction: Epidural anaesthesia is a boon for providing prolonged analgesia for postoperative pain relief. The influence of epidural needle insertion on the onset of the block, which has not been studied previously, is significant. Aim: To analyse the effect of epidural needle entry and rotation of the needle on the onset and duration of the block. Materials and Methods: This double-blinded randomised controlled trial was conducted at the Department of Anaesthesiology, SRM Institute of Science and Technology, Chennai, Tamil Nadu, India from March 2020 to August 2021 on 70 patients undergoing leg and ankle surgeries. They were randomised into Group-ML (midline approach) and Group-PM (paramedian approach). In Group-ML, midline epidural needle entry was followed by catheter insertion. In Group-PM, the needle entry was paramedian, and the bevel was turned 45º towards the surgical site for catheter insertion. A 10 mL of 0.5% bupivacaine was administered. Postoperatively, epidural infusion was initiated using 0.125% bupivacaine with 2 μg/mL fentanyl. The time taken for catheter placement, onset of motor and sensory blockade, maximum sensory level attained, duration of sensory blockade, consumption of local anaesthetics, haemodynamic profile, and the need for rescue analgesia were monitored. Continuous data were analysed using the Student's t-test, and categorical data were analysed using the Chi-squared test with International Business Machines (IBM) statistical product and service solutions software version 27.0 Results: Both groups were comparable with respect to demographics. The mean age in Group-ML was 40.9±25.93 years, while in Group-PM it was 41.028±20.576 years, with a p-value of 0.981. The mean BMI in Group-ML was 24.91±2.998 kg/m2 , while in Group-PM it was 24.96±2.527 kg/m2 , which was statistically insignificant with a p-value of 0.944. A total of 21 males in Group-ML and 28 males in Group-PM participated in the study; the distribution was found to be statistically insignificant with a p-value of 0.067. The time taken for the placement of the epidural catheter was around 288 seconds in Group-ML and 322 seconds in Group-PM, with a p-value of 0.0035. The onset of sensory block was around 17 minutes in Group-ML and 13 minutes in Group-PM, respectively, with a p-value of 0.0001. The duration of sensory block or the time taken for two-segment regression of level was around 102 minutes and 128 minutes in Group-ML and Group-PM, respectively (p-value 0.0001). The rescue analgesic was required in seven patients of Group-ML and none in Group-PM, with a p-value of 0.005. The haemodynamic profile intra and postoperatively and postoperative VAS score were statistically insignificant between the groups. Conclusion: The paramedian approach and epidural catheter insertion with the needle rotated at an angle of 45º towards the surgical side provide a rapid onset of the sensory and motor block with extended duration of the sensory blockade and reduced consumption of local anaesthetics.