The effect of infusion rate and catheter length on the temperature of warming fluid

BACKGROUND: We used warming fluid for maintenance of body temperature in operating room or intensive care unit. This study was aimed to investigate the effect of infusion rate and catheter length on the temperature of warming fluid. METHODS: Normal saline was used for testing infusion and temperature of infusion was maintained by a warmer as 40℃. The temperatures of solution in infusion line were measured at 0, 25, 50, 75, and 100 cm apart from warmer at six different flow rates (100, 200, 300, 700, 1,400, and 2,100 ml/h). We also measured the temperature changes at room temperature (RT) and 5℃, 10℃, and 15℃ above RT. RESULTS: The time to maintain solution temperature as 40℃ was 165, 122, 37, 37, 21, and 19 s at flow rate 100, 200, 300, 700, 1,400, and 2,100 ml/h. The peak temperature was 43.58 ± 0.58, 44.43 ± 1.18, 44.37 ± 0.70, 43.79 ± 0.61, 42.82 ± 0.97, and 42.11 ± 0.92℃ according to increasing flow rate. The temperature at 100 cm apart from warmer was 23.96 ± 1.53, 25.46 ± 2.76, 29.32 ± 3.47, 31.40 ± 5.38, 31.39 ± 6.75, and 38.14 ± 0.96℃ according to increasing flow rate. CONCLUSIONS: These results suggested that the decreasing rate of temperature was related inversely to the flow rate and directly to the catheter length. There may be needed a rapid infusion pump with adequate heating system at a high flow rate and to locate the warmer close to patient for reserving a heating effect.