Alterations of cardiovascular functional parameters after onset of heat stroke in rats.

The effects of heat stroke formation on electrocardiogram (ECG) and blood pressure (BP) waveform parameters were assessed in rats under urethane anesthesia. Heat stroke was induced by exposing anesthetized rats to an environmental temperature of 42 degrees C. The movement in which arterial pressure began to decrease was taken as the onset of heat stroke. It was found that the duration of either P were, Q wave, R wave, S wave, T wave or QRS complex, as well as the amplitude of either P wave, Q wave, S wave or T wave were not affected after onset of heat stroke. However, the amplitude of R wave, the P-P interval, the R-R interval and the Q-T interval were significantly decreased after onset of heat stroke. In addition, the peak amplitude of systolic wave, dicrotic notch, diastolic wave, the duration of either systolic wave, a whole BP cycle, diastolic wave or dicrotic wave, the pulse pressure, as well as the mean arterial pressure were also decreased after onset of heat stroke. On the other hand, heat stroke formation increased the heart rate. The results demonstrated that alterations of these ECG and BP waveform parameters occurred after onset of heat stroke in rats.