A Prospective Comparative Study Between Ultrasound-Guided Combined Sciatic-Femoral Nerve Block Versus Spinal Anesthesia for the Patients Undergoing Elective Below-Knee Surgeries

Introduction The scope of anesthesia has shifted from general anesthesia (GA) and spinal anesthesia (SA) for below-knee surgery to peripheral nerve blocks (PNB). Combined sciatic-femoral nerve block (SFNB) with ultrasound (USG) guidance can be a better format for use. Objectives The primary objectives were to compare the duration of onset of sensory and motor blockade, total duration of sensory and motor blockade, and time of first analgesic requirement between both groups. Methods A prospective, randomized comparative study was carried out at a tertiary care teaching hospital in Odisha, India, from April 2019 to April 2021 in the Department of Anaesthesiology. Patients admitted for elective below-knee surgeries with American Society of Anesthesiology (ASA) grade II or less were divided into two groups (Group A receiving USG-guided SFNB and group B receiving SA) by computer-generated sampling. The block randomization method was used to ensure equal samples in both groups. Data collection was done using the Magpi software (Magpi, Inc., Washington, D.C., United States) on android-based mobile phones. Data were analyzed using Stata Statistical Software: Release 12 (2011; StrataCorp LP, College Station, Texas, United States) for analysis. Relevant statistical tests were used to compare the results between the groups (independent sample t-test or Wilcoxson signed-rank test). Repeated measures ANOVA (RM-ANOVA) was used to check the hemodynamic stability within the groups. Results Thirty-seven subjects were enrolled in each arm (Group A and Group B). Baseline parameters in both groups were comparable. The most common indication among the study subjects was single or multiple meta-tarsal fractures (20, 27.0%) followed by malleolus (15, 20.3%) and calcaneum fractures (13, 17.6%). Most of the study subjects were from ASA grade I (around 80%). The time of onset of sensory and motor block was found to be more for USG-guided SFNB (8.08±2.11 minutes and 11.35±1.84 minutes, respectively) as compared to the SA group (3.03±0.50 minutes and 4.89±0.52 minutes, respectively) (p<0.001). Total anesthesia and time to first analgesic requirement were, however, more in USG-guided SFNB (349.43±53.49 minutes and 339.73±54.24 minutes, respectively) as compared to the SA group (137.30±34.21 minutes and 137.30±34.21 minutes, respectively) (p<0.001). The mean time to first urination in USG-guided SFNB (178.92±20.92) was significantly less (p<0.001) compared to the SA group (419.19±40.30). There were no adverse events (0%) in USG-guided SFNB while 64.9% of the subjects in the SA group experienced adverse events (p<0.001). The most common adverse events were nausea/vomiting and hypotension (around 50% for both). Hemodynamic stability was present in both the groups of anesthesia subjects, though fluctuations in blood pressure may be seen more frequently in cases of SA. All the subjects in both the groups had achieved a Bromage score of 3 universally. The grand mean score of pain by SA (2.347±0.044) was more (p<0.001) in comparison to that in subjects with USG-guided SFNB (1.961±0.073) and this was significant in both the groups. The mean increase in pain score at 24 hours in comparison to baseline was, however, significantly more (p<0.05) in the SA group (1.784±0.111) in comparison to those receiving USG-guided SFNB (1.324±0.190). Conclusion USG-guided SFNB is a better option for below-knee surgeries as compared to SA.