Hypothermic Myocardial Oxygenation

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Abstract
Coronary blood flow together with corollary functions were determined in 11 anesthetized dogs at normal body temperature and in 9 of these animals after cooling to 20°C. The arterial ph was kept in the normal range by controlled ventilation. At 20°C coronary blood flow/100 gm left ventricle decreased to 29% of the normothermic control value. Myocardial oxygen consumption decreased to 24%, coronary A-V oxygen difference to 82%, total body oxygen consumption to 24%, cardiac output to 21%, and calculated left ventricular work to 10.7%. Systemic A-V oxygen difference did not vary significantly. Pulmonary vascular resistance increased to 306% of the normothermic control, peripheral resistance to 304% and coronary vascular resistance to 193%. Coronary blood flow appeared to be sufficient to maintain an adequate supply of oxygen to the myocardium for the work performed by it at 20°C.