Cardiovascular and respiratory function values in hyperthermia: the effect of beta-receptor blockade with bunitrolol

During hyperthermia in water, the rectal temperature of 12 healthy young test subjects rose by on average 1.16 degrees C. Under treatment with placebo, the pulse rate increased by 40.6 beats/min, systolic pressure by 14.6 mm Hg, oscillatory respiratory resistance fell by 0.29 hPa/1/s and time-averaged flow ventilation increased by 3.62 1/min. Under treatment with a beta-receptor blocker (10 mg of bunitrolol) there was no change in the tachycardiac response, there was slightly less of a rise of blood pressure, slightly less of a fall of oscillatory respiratory resistance and time-averaged flow ventilation remained low (2p less than 0.05). The response of the cardiovascular parameters and oscillatory respiratory resistance is discussed in connection with redistributions of blood volume during hyperthermia. The less pronounced hyperventilation is considered to be due to the effect of beta-receptor blockade in warding off external stress-induced factors.