Cardiac Denervation Effect in Hypoxia and Hypercapnia

The effects of hypoxia on the circulatory system involving changes in heart rate, cardiac output, and arterial blood pressure have received considerable attention. Most studies have been made in intact anesthetized dogs by varying the gas mixture used to ventilate the animal, and changes in cardiac function have been attributed to both the direct effect of oxygen deficit on the heart and to reflex neurogenic stimuli. Studies using separate perfusion systems for the systemic and cardiac circulations have shown little initial effect on the perfused heart with moderately hypoxic blood, whereas isolated perfusion of the carotid receptors with desaturated blood results in bradycardia during the period of hypoxia to the chemoreceptors.³Similarly, Austen and associates¹have shown that systemic hypoxia could cause severe cardiac arrhythmia even when the heart was receiving fully oxygenated blood. It was originally shown by Harrison and coworkers⁹that thoracic sympathectomy did not