Use of infrared thermometry to measure lavage and intravenous fluid temperature

A study was conducted to determine the accuracy of tympanic thermometers for measuring the temperature of warmed fluids in fluid bags and in tubing at the delivery site (ie, beside the intravenous [IV] catheter). One-liter 0.9% saline bags were warmed in a microwave oven. A thermocouple electronic temperature probe was then used to measure the reference temperature. The probe was inserted into each bag and bathed in the fluid. Temperature changes were recorded simultaneously over a 20-minute period using the probe and a First Temp Tympanic Thermometer (Intelligent Medical Systems, Inc, Carlsbad, CA). The warmed fluid was then allowed to run through microdrip IV tubing. Temperature of the effluent was measured in the tubing using the tympanic thermometer externally and the probe internally at the same point. The two measures were compared using linear regression and Student's t tests. Overall, the correlation between the two probes was r = 0.99 for both the fluid bags and the IV tubing. The overall mean differences were small, 0.7°C and 1.2°C for the bags and tubing, respectively, but they were statistically different (P > .05). Data were analyzed in three temperature ranges: <36°C, 36°C to 41°C, and >41°C. Again, small differences were found on the order of 1°C. It was concluded that infrared thermometry is an accurate method for measuring the initial and delivery temperature of warmed fluids. Although tympanic thermometer measurements were statistically different from reference readings in certain temperature ranges, these differences were small and not clinically significant. Tympanic thermometers can measure the temperature of warmed fluid bags and lavage and IV effluent adjacent to the catheter site, ensuring that hypothermic patients receive fluid at therapeutic temperatures.