A Comparison of the Effect of Fractionated and Bolus Dose Injection on Spinal Anesthesia for Lower Limb Surgery: A Randomized Clinical Trial

Background: In previous clinical trials and a small number of studies, the fractional injection of anesthetics led to reduced physiological complications and hemodynamic stability and increased duration of anesthesia. Objectives: The present study intended to compare the effect of fractionated and bolus dose injection of bupivacaine and fentanyl on spinal anesthesia for lower limb fracture surgeries. Methods: In this randomized, double-blind clinical trial, 70 patients with lower limb fractures were divided into groups of bolus spinal anesthesia (Group A) and fractional spinal anesthesia (Group B). Group A received a bolus dose of 25 µg fentanyl plus 15 mg bupivacaine 0.5% intrathecally at a rate of 0.2 mL/sec and were laid down in supine position after 45 seconds. In Group B, a half dose of the mixture, i.e., 25 µg fentanyl plus 15 mg bupivacaine 0.5% mixture, was injected intrathecally, and then, the other half was injected after 45 seconds while the needle was still in place. Afterward, the patients were immediately laid down in the supine position. Hemodynamic changes in the sensory and motor blockage parameters were recorded in both groups. Results: The motor blockage onset time was shorter in Group B compared to Group A (P = 0.026). Moreover, the sensory blockage duration was longer (P = 0.035), and the highest level of sensory blockage was lower (P = 0.008) in Group B compared to Group A. Conclusions: Fractional spinal anesthesia led to a longer duration and more favorable levels of sensory blockage compared to the bolus method. In addition, hemodynamic changes and complications occurred less frequently following this procedure. Keywords: