SUSTAINED 35-GHZ RADIOFREQUENCY IRRADIATION INDUCES CIRCULATORY FAILURE

The objective of this study was to determine the thermal distribution and concomitant cardiovascular changes produced by whole-body exposure of ketamine-anesthetized rats to radiofrequency radiation of millimeter wave (MMW) length. Rats (n = 13) were implanted with a flow probe on the superior mesenteric artery and with a catheter in the carotid artery for the measurement of arterial blood pressure. Temperature was measured at five sites: left (T-sl) and right subcutaneous (sides toward and away from the MMW source, respectively), colonic (T-cl), tympanic, and tail. The animals were exposed until death to MMW (35 GHz) at a power density that resulted in a whole-body specific absorption rate of 13 W/kg. During irradiation, the T-sl increase was significantly greater than the T-c increase. Heart rate increased throughout irradiation. Mean arterial pressure (MAP) was well maintained until T-sl reached 42 degrees C, at which point MAP declined until death. Mesenteric vascular resistance tended to increase during the early Stages of irradiation but began to decrease at T-sl greater than or equal to 41 degrees C. The declines in both mesenteric vascular resistance and MAP began at T-c < 37.5 degrees C; death occurred at T-c = 40.3 +/- .3 degrees C and T-sl = 48.0 +/- .4 degrees C. These data indicate that circulatory failure and subsequent death may occur when skin temperature is rapidly elevated, even in the presence of relatively normal T-c.