Effect of Ultrasound Guided Sciatic Nerve Block on Post Operative Analgesia in Patients undergoing below Knee Orthopedic Surgeries under Spinal Anaesthesia – Prospective Randomized Study

Background and Aims: Ultrasound (US) guided sciatic nerve block has been found to provide adequate post operative analgesia for below knee procedures. The present study was designed to assess the effect of US guided sciatic nerve block on post operative analgesia in knee and below knee surgeries. Methods: This was prospective randomized double blind study involving 51 ASA physical status I and II patients undergoing knee and below knee orthopedic surgeries under subarachnoid block, randomly divided into 2 groups. Group A received Sciatic nerve block and group B received intravenous fentanyl 2 mcg/ kg in preoperative room. All patients received subarachnoid block 20 min after intervention. Pain during mobilization to operation theatre, positioning for SAB, and post operative pain and was noted using visual analogue scale First request for post operative analgesia and post operative 24 hour analgesic consumption was also noted. Results: The demographic parameters were comparable in both the groups. The duration of analgesia in Group A [mean ± SD - 285.80 ± 18.47 min(95% CI 279 to 293 min)] was prolonged compared to Group B [mean ± SD - 180.20 ± 10.94 min(95% CI 176 to 184 min)] (p <0.001). The 24 hour analgesic consumption of paracetamol and tramadol were lower in Group A [2,360.00 ± 489.90 (95% CI 2170 to 2550) gms] [106.00 ± 30 mg (95% CI 94.2 to 118 mg)] compared to Group B [3,160.00 ± 472.58 (95% CI 2980 to 3350)] gms, [160.00 ± 32.27 mg (95% CI 147 to 173 mg)] (p <0.001). The decrease in VAS scores [median(IQR)] was 5(4-5) and 2(2-3) at the time of positioning in group A and B respectively (p <0.001). None of the patients had any neurological deficits post operatively. Conclusion: Preoperative administration of US guided sciatic nerve block resulted in decreased pain scores while positioning for spinal anaesthesia, prolongation of analgesia and reduction in post operative analgesic requirements.