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TECHNOLOGY, COMPUTING, AND SIMULATION

Flow Rates and Warming Efficacy with Hotline and Ranger Blood/Fluid Warmers

Department of Anesthesiology, College of Medicine, University of South Florida, Tampa, Florida

Address correspondence and reprint requests to Peter E. Horowitz, MD, 12901 Bruce B. Downs Blvd., MDC Box 59, Tampa, FL 33612-4799. Address e-mail to phorowit{at}hsc.usf.edu

The heating capabilities of a water bath blood/fluid warmer, Hotline, have proven superior to those of other devices. The dry heat warmer Ranger has not previously been compared with the Hotline. We evaluated these devices in terms of flow rates and efficacy of warming. We delivered room temperature (21°C) saline and 10°C packed red blood cells (RBCs) by using 90 mm Hg (gravity equivalent) and 300 mm Hg bag pressure and various sizes of IV catheters. The outflow from each device was connected to an inline thermistor, and simultaneous measurements of outflow temperature and flow volume per minute were recorded. Additional data points were obtained with a roller pump that delivered flows of 1–6 L/h through each device. We calculated the effect of these flow rates and outflow temperatures on the mean body temperature (MBT) of a 70-kg patient. The Hotline and Ranger had similar flow rates at 90 and 300 mm Hg pressure infusion when studied with various sizes of IV catheters. Hotline was able to deliver warmer RBCs and saline at slower flow rates (1–4 L/h), but because changes in MBT were almost identical, there was no clinically important advantage, and almost no heat was transferred at these slower flow rates. At more rapid flow rates (>4 L/h), the Ranger warmed RBCs and saline better and produced smaller decreases in MBT than the Hotline. The use of the Hotline for rapid infusions, especially of cold RBCs, is not recommended because of low outflow temperatures and decreases in MBT that were three times larger than those seen with the Ranger.

IMPLICATIONS: We compared the ability of a new dry heat blood/fluid warmer (Ranger) with the water bath warmer Hotline in terms of flow rates and outflow temperatures by using room temperature saline and 10°C diluted packed red blood cells (RBCs). Flow rates were similar, but the Ranger provided higher outflow temperatures at flows >4 L/h, especially during rapid pressurized infusions of both RBCs and saline.