Hypothermic Myocardial Oxygenation

¹ From the Department of Surgery, The Johns Hopkins Hospital and University, Baltimore, Maryland

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.