Effect of heat on stored red cells during non-flow conditions in a blood-warming device

Background and Objectives: While blood is flowing within a transfusion-warm ing device, the blood temperature is usually less than that applied externa lly. If the flow is temporarily stopped, the temperature can rise above 37 degrees C in some warming devices. We sought to determine whether temperatu res near 45 degrees C achieved during prolonged non-flow conditions in a bl ood warmer are harmful to red cell integrity. Materials and Methods: After 42 days of storage at 4 degrees C, red cells were exposed to 44.7 degrees C for 30 min while stationary in a blood warming device (Augustine Medical, Inc., 241 Fluid Warming Set) and examined for cell counts, hemolysis and os motic fragility. Results: Red cell, white cell and platelet counts, hemoglo bin, PCV and potassium were unchanged following heat treatment. Plasma hemo globin was 508+/-132 mg/dl following heat treatment compared to 396+/-188 f or the control (p>0.05). In the osmotic fragility test, hemolysis remained within normal limits when tested at 0.60 and 0.65% sodium chloride (NaCl) a nd was unchanged at the 0.5% NaCl level. At the 0.75% NaCl level, there was 16+/-5.1% hemolysis of heated 42-day-old red cells compared to 11+/-3.4% f or the control (both of which being above the 9% upper limit for fresh cont rol red cells). Conclusions: We conclude that elevated temperatures achieve d during temporary cessation of flow in the Augustine Medical, Inc., 241 Fl uid Warming Set for as long as 30 min do not cause notable hemolysis or oth er damage to red cells.