Warming efficacy and blood damaging of blood and infusion warmers

Question: Inadequately warmed blood or infusions contribute to the development of perioperative hypothermia. Therefore we analysed the efficiency of several infusion warmers. Method: Tested infusion warmers: Model Autoline(R) (Barkey) 500OR(R)/241(R) (Arizant), BW385L(R) (Biotest), H250(R)/D50(R) und D60(R) (Level-1), H500(R)/D300(R) (Level-1), Warmflo FW537-I(R)/HEC40(R) (Tyco). Different solutions (saline, colloid solution and packed red blood cells PRBC) were tested varying the infusion flow, temperature of the solution and infusion pressure. Effective warming was defined as an infusion temperature greater than or equal to 33 degreesC. Haemolysis was measured by the increase of free plasma haemoglobin. Results: The infusion warmers were effective within the following flow ranges: Low flow rate (< 250ml/h): Autoline(R), 500OR(R)/241(R) and H250(R)/D60(R). Medium flow rate (250-2500 ml/h): Autoline(R), 500OR(R)/241(R) BW385L(R) (> 480ml/h), H250(R)/D60(R) und D50(R) (greater than or equal to 1300 ml/h), FW537-I(R)/HEC40(R) (> 950 ml/h. High flow rate (2500-10 000 ml/h): BW385L(R) (up to 5000 ml/h), H 250(R)/ D50(R), H250(R)/D60(R), H500(R)/D300(R) and FW537-I(R)/HEC40(R). Highest flow rates(> 10000ml/h): H250(R)/ D60(R), H500(R)/D300(R) and FW537-I(R) HEC40(R). Colloidal solutions were warmed nearly as good as saline, cooled PRBC had a smaller range of effective warming. There was no relevant haemolysis in any of the tested systems (plasma free haemoglobin raise < 24 mg/dl in all systems). Conclusion: The warming capacity of the system and the length of the uninsulated infusion system determine the efficiency of an infusion warmer. The range of effective warming of an infusion warmer should be known for proper application.