Blood warmers
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Blood Warmers: Efficacy, Safety, and Performance
Introduction to Blood Warmers and Hypothermia Prevention
Blood warmers are essential devices used during blood transfusions to prevent hypothermia, a condition that can lead to severe complications such as cardiac arrhythmias and coagulopathy. These devices heat the blood to near body temperature before administration, ensuring patient safety and comfort.
Hemolysis and Blood Warmers: Safety Considerations
One of the primary concerns with blood warmers is the potential for hemolysis, the destruction of red blood cells, which can occur if the blood is overheated. A systematic review and meta-analysis found that blood warming at temperatures up to 43°C, and even up to 45-46°C, is generally safe and causes hemolysis only in clinically negligible proportions1. Factors influencing hemolysis include blood age, type of anticoagulant, duration of heat exposure, and the type of infusion pump used1.
Performance of Prehospital Blood Warmers
In prehospital settings, warming blood is crucial for trauma patients. A study comparing improvised warming methods (body heat, sunlight exposure, gel heat pads) with a commercial blood warmer (Belmont Buddy Lite) found that only the commercial device reliably warmed blood to near physiological levels2. Improvised methods, while better than no warming, did not achieve the same effectiveness2.
Evaluation of Portable Blood Warmers
Portable blood warmers are vital for prehospital and emergency use. A study comparing four devices (Thermal Angel, Hypotherm X LG, °M Warmer, Buddy Lite) under simulated conditions showed that all devices performed better than the control, with the °M Warmer providing the most consistent temperature increase across various flow rates4. Importantly, there was no significant association between warming and hemolysis across different devices and flow rates4.
Comparative Performance of Blood Warming Technologies
Different technologies are used in blood warmers, including dry heat, water bath, and countercurrent heat exchange. A comparative study found that countercurrent heat exchange devices, such as the Level 1 H500, were more effective at warming blood to ≥33°C at high flow rates compared to dry heat and water bath devices5. This technology's superior performance makes it suitable for rapid transfusions where maintaining blood temperature is critical.
Specific Blood Warmer Models and Their Efficacy
The Medimpact electronic in-line blood warmer has been shown to effectively warm blood to 32°C at a flow rate of 560 ml/hr, making it suitable for massive transfusions in infants and neonatal exchange transfusions3. Similarly, the Level 1 blood warmer series, particularly the 500 series, can warm up to 80 units of blood per hour to near body temperature, demonstrating high efficiency7.
Conclusion
Blood warmers are indispensable in both clinical and prehospital settings to prevent hypothermia during transfusions. While various devices and technologies are available, those using countercurrent heat exchange and commercial portable warmers generally offer superior performance. Ensuring the safe use of these devices, particularly regarding hemolysis, is crucial, and current evidence supports their safety at recommended temperatures.
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Most relevant research papers on this topic
Blood Warming and Hemolysis: A Systematic Review With Meta-Analysis.
Blood heating at temperatures below 43°C and up to 45-46°C is safe and causes hemolysis in clinically negligible proportions.
Meta-AnalysisPerformance comparison of improvised prehospital blood warming techniques and a commercial blood warmer.
The Buddy Lite is the only commercial blood warmer that reliably warms blood to a near normal physiological level, making improvised warming methods insufficient for prehospital blood transfusions.
RCTA new blood warmer.
The Medimpact electronic in-line blood warmer effectively warms cold stored blood to 32° C, making it suitable for massive blood transfusion in infants weighing up to 14 kg and neonatal exchange transfusion.
Comparison of portable blood‐warming devices under simulated pre‐hospital conditions: a randomised in‐vitro blood circuit study
Portable blood warming devices perform differently at clinically relevant flow rates, with the °M Warmer providing the most substantial temperature change.
RCT
Rigorous JournalA comparative study of blood warmer performance.
Countercurrent heat exchange blood warmers effectively warm blood and saline more effectively than dry heat or water bath devices, but close control and standardization of experimental conditions are crucial for accurate evaluation.
Non-RCT