Performance characteristics of Ultratherm fluid warmer

Area of Science:

• Biomedical Engineering
• Medical Devices
• Fluid Dynamics

Background:

• The Ultratherm Infusion Fluid Warmer (Model 3703-1) is a disposable device for warming intravenous fluids.
• It lacks temperature monitoring and audible alarms, relying on air-activated chemical heating elements.
• Direct contact between heating elements and i.v. tubing raises concerns about temperature control.

Purpose of the Study:

• To evaluate the warming performance and safety of the Ultratherm Infusion Fluid Warmer.
• To assess the impact of the warmer on blood integrity (hemolysis) and fluid temperatures at various flow rates.
• To determine the limitations and appropriate clinical applications for the Ultratherm device.

Main Methods:

• Intratubing thermocouple wire probes were used to measure internal warmer chamber temperatures.
• Blood and saline warming were studied at different flow rates (30, 100, 500 mL/h).
• Free hemoglobin measurements quantified hemolysis in blood samples exiting the warmer.

Main Results:

• Internal warmer chamber temperatures reached a plateau of approximately 65°C and were sustained for hours.
• Blood samples exiting at 47°C and 53°C showed 0.6% and 7% hemolysis, respectively.
• Warming of refrigerated blood at 500 mL/h was insufficient (below 19°C), while room temperature saline reached up to 52°C.

Conclusions:

• High, unmonitored internal temperatures pose a risk of heat damage to blood and sensitive fluids.
• The Ultratherm warmer's use should be limited to clear fluids, room temperature fluids, and specific flow rates (100-500 mL/h) and times (1-6 hours post-activation).
• Clinical application requires careful consideration of these limitations to ensure patient safety.