Warmflo warming system overheats fluids in simulated clinical conditions

To evaluate the Warmflo fluid warming system at various flow rates of crystalloid solution simulated to clinical conditions.

Prospective analysis and laboratory investigation.

Operating room and technical laboratory of a university-affiliated hospital.

The Warmflo WF-100 fluid warming (heat exchanger) cassette of the Warmflo FW-538 fluid warming system was primed with lactated Ringer's solution. The fluid warming system was adjusted to temperature set points of 38 degrees C or 42 degrees C. The temperature of the solution flowing through the warming system was measured inside the infusion line downstream from the heat exchanger cassette at the proximal and distal sites, with flow rates of two, 10, and 100 mL/min and simultaneously inside the warming housing between the heater plates.

Average temperature of the solution measured inside the infusion line at the proximal site ranged between 33.4 (+/-1.35) degrees C and 34.0 (+/-2.23) degrees C at a flow rate of two mL/min when the temperature set point was 38 degrees C. At all other flow rates at either set point, the solution temperature was above 37.5 degrees C inside the infusion line, reaching up to 43.9 degrees C at a flow rate of 100 mL/min and a set point of 42 degrees C. Temperatures inside the warming housing ranged from 40.6 (+/-0.26) degrees C to a maximum of 48.0 (+/-0.85) degrees C at a set point of 42 degrees C after the flow stopped.

The Warmflo fluid warming system can overheat fluids at temperatures considerably above normal body temperatures.