Evaluation of outflow temperatures generated by a dry heat fluid warmer at low fluid rates

To evaluate the output temperature of a dry heat fluid warmer at fluid rates typically used in small animal veterinary patients.

Prospective in vitro study.

None.

Ambient temperature lactated Ringer's (17.9-18.8 °C) was delivered via a dry heat fluid warmer. A temperature probe was used to measure fluid outflow temperature from the compatible giving set at 5, 10, 20, 50, 70, 80, 100, 200, 300, 400 and 500 mL hour^-1. Outflow fluid temperature at plateau (two consecutive readings within 0.1 °C) was compared with baseline fluid temperature (fluid warmer turned off) to calculate temperature changes at each rate. Kruskal-Wallis test was used to compare changes in temperature and time to plateau temperature. Dunn's post hoc test was used to test for significant differences in temperature compared to 5 mL hour^-1; p value < 0.05.

Median plateau outflow temperature increased as fluid rate increased, with temperatures of 18.5, 18.6, 18.7, 18.8, 19.4, 19.4, 21.5, 25.3, 28.5, 30.7 and 32.6 °C, at flow rates of 5, 10, 20, 50, 70, 80, 100, 200, 300, 400 and 500 mL hour^-1. Fluid rates > 100 mL hour^-1 showed significant increases from baseline (p = 0.021) There was no difference in temperature change from baseline at fluid rates < 100 mL hour^-1 (p > 0.05). Compared to plateau temperature at 5 mL hour^-1, there was a statistical difference in plateau temperature above 100 mL hour^-1(p = 0.0207). Maximum outflow plateau temperature was 32.6 °C at 500 mL hour^-1.

A dry heat fluid warmer has significantly decreased efficacy at low fluid rates, with no statistically significant increase in fluid temperature at fluid rates below 100 mL hour^-1 at the end of a compatible fluid line. Inline dry heat fluid warmers are ineffective at fluid rates below 100 mL hour^-1.