An Investigation of the Thermal and Athermal Effects of Microwave Irradiation on Erythrocytes

Erythrocytes heated by either microwave irradiation or conventional techniques were examined for loss of hemoglobin (Hb) and potassium (K+). In all experiments, microwave heated red blood cells (RBC´s) were directly compared with RBC´s warmed to the same temperature by use of an adjustable incubator and with RBC´s maintained at room temperature. Microwave irradiation was carried out at either 2.45 GHz or in selected 0.5 GHz swept frequency regions in the 12.5-18 GHz range. Sample temperature was continuously monitored in both microwave heated and conventionally heated samples by use of a relatively nonperturbing liquid crystal optic fiber temperature probe. When rabbit RBC´s were warmed by 3.7°C for 45 min by either irradiation (2.45 GHz, 10 mW/cm2) or conventional heating, no additional Hb or K+ was released into the supernatant. In contrast, when rabbit RBC´s were rapidly warmed from room temperature to 37°C by either technique, the heated erythrocytes lost significantly more of both Hb and K+ than equivalent RBC´s maintained at room temperature. In addition, RBC´s warmed to 41.5°C by either technique lost far more Hb and K+ than those warmed to 37°C. In all experiments, Hb and K+ were lost in equal amounts by microwave heated and conventionally heated erythrocytes warmed at the same rate to the same final temperature. Thus, at all frequencies and power levels tested, any increased loss of either Hb or K+ from microwave irradiated rabbit RBC´s should be ascribed to thermal effects on the stability and/or permeability of the erythrocyte membrane.