Effect of irrigation fluid temperature on perioperative hypothermia and metabolic acidosis during unilateral biportal endoscopic spine surgery.

PURPOSE: Perioperative hypothermia is a recognized yet often overlooked complication of endoscopic spine surgery, where continuous fluid irrigation is required for adequate visualization and hemostasis. Despite the substantial volumes of saline used during unilateral biportal endoscopic (UBE) procedures, the systemic effects of irrigation fluid temperature remain poorly characterized. We evaluated its impact on perioperative body temperature, venous blood gas parameters, and pain outcomes after UBE surgery. METHODS: In this retrospective cohort study sixty consecutive patients with lumbar disc herniation (LDH) or lumbar spinal stenosis (LSS) undergoing UBE surgery were analyzed in two groups: a warm group (n = 30) in which saline was warmed to 36-37 °C, and a cold group (n = 30) in which room-temperature saline (20-22 °C) was used. Tympanic body temperature, venous blood gas parameters (pH, lactate, bicarbonate, base excess), and back and leg Visual Analog Scale (VAS) scores were compared at standardized time points. RESULTS: No significant between-group differences were observed preoperatively (p > 0.05), but marked differences emerged from the 30th intraoperative minute onward and progressed throughout surgery (all p < 0.001). Postoperatively, the cold group showed lower body temperature (35.45 ± 0.37 vs. 36.25 ± 0.13 °C), lower pH (7.28 ± 0.03 vs. 7.38 ± 0.01), higher lactate (2.88 ± 0.35 vs. 1.40 ± 0.15 mmol/L), and lower bicarbonate (19.65 ± 1.56 vs. 23.26 ± 0.83 mmol/L). No significant differences were found in VAS scores or hemoglobin changes. CONCLUSION: Warming irrigation fluid to near-body temperature may prevent intraoperative hypothermia and associated metabolic acidosis during UBE surgery, representing a simple, low-cost strategy to support perioperative physiologic stability.