Fluid loading during spinal anesthesia can reduce bradycardia after intravenous dexmedetomidine infusion

Background: Dexmedetomidine has been widely used during spinal anesthesia to provide sedation. However, dexmedetomidine frequently causes significant bradycardia. This study was designed to evaluate whether fluid loading could reduce the incidence of bradycardia after intravenous dexmedetomidine infusion in patients under spinal anesthesia. Methods: A total of 99 patients, 18 to 65 years of age, with American Society of Anesthesiologists physical status 1 or 2, who were scheduled for elective total knee replacement or internal fixation of lower leg fracture under spinal anesthesia were enrolled. The patients were randomly assigned into one of the three groups, and fluid was loaded as follows: group LOW - 4 ml/kg, group MID - 8 ml/kg, and group HI - 12 ml/kg. After fluid loading and spinal anesthesia, dexmedetomidine was infused as follows: 1 µg/kg of loading dose for 10 minutes, thereafter continuous infusion at 0.4 µg/kg/h. Results: The heart rate of group HI was significantly higher than that of group LOW (P = 0.049). The dosage of atropine administration was significantly lower in group HI than in group LOW (P = 0.003). The change in thoracic fluid contents was significantly higher in group HI than in group LOW (P = 0.018). Conclusions: Fluid loading during spinal anesthesia can reduce the incidence and extent of bradycardia after intravenous dexmedetomidine infusion. Keywords: Bradycardia; Dexmedetomidine; Fluid therapy; Heart rate; Spinal anesthesia