A comparative study of blood warmer performance.

Massive transfusions of refrigerator-temperature blood may induce hypothermia and life-threatening arrhythmias; for this reason a variety of devices have been developed for rapid blood warming. Blood warmers available in the United States use one of three warming technologies: dry heat, water bath, or countercurrent heat exchange. In the current study we evaluated blood warmers representative of each technology for speed and extent of heat transfer: the Fenwal blood warmer (Fenwal Laboratories; dry heat), the DW-1000 (American Pharmaseal Co.; dry heat), the FloTem IIe (DataChem Inc.; dry heat), the Hemokinetitherm (Dupaco Inc.; water bath), and the H250 and H500 (Level 1 Technologies; countercurrent heat exchange). Only one countercurrent heat instrument (the H500) was able to heat blood > or = 33 degrees C at target flow rates > or = 250 ml/min. Dry heat and water bath blood warmers were unable to warm blood > or = 33 degrees C at target flow rates > or = 100 ml/min. High resistance to flow with the proprietary tubing required for one instrument (the Hemokinetitherm) prevented tests of blood warming at rates > 150 ml/min. We found that instruments that used countercurrent technology warmed blood and saline more effectively than did blood warmers that used either dry heat or water bath technology. Our study also demonstrated the need for close control and standardization of experimental conditions in the evaluation of blood warming devices.