Heated carrier fluids in decreasing propofol injection pain: a randomized, controlled trial

BACKGROUND Propofol is a commonly used intravenous drug during anesthetic induction because of its rapid onset and short duration. However, the injection pain that patients experience is so severe that they recall the induction of anesthesia as the most painful part of the perioperative period. Therefore, the objective of this study was to determine the effect of heated carrier fluids (40℃) in decreasing propofol injection pain. METHODS A randomized, controlled clinical trial was conducted in 90 patients aged 18 to 65 who were scheduled for either elective or urgent surgery under general anesthesia classified as American Society of Anesthesiologists physical status I or II. Patients were allocated into the following 3 groups: 1) Group W (n = 30) who received 200 ml of heated carrier fluids for 20 minutes prior to propofol injection; 2) Group L (n = 30) who received 200 ml of heated carrier fluids for 20 minutes prior to 0.5 mg/kg 1%lidocaine 1 minute before propofol injection; 3) Group C (control group, n = 30) who received 200 ml of room temperature fluids prior to propofol injection. Pain was evaluated using verbal pain score (VPS). RESULTS Group W and Group L showed significant reduction (P = 0.001) in the incidence and severity of injection pain compared to Group C. VPS scores were significantly lower in Group W and Group L compared to those of Group C. Incidence of propofol injection pain was statistically different between Group W (P = 0.005) and Group L (P = 0.037) compared to Group C, but not statistically different between Group W and Group L (P = 0.432). CONCLUSIONS Both sole injection of heated carrier fluids and the combination of 0.5 mg/kg 1%lidocaine pretreatment effectively reduced propofol injection pain.