Pierre M. Galletti

Laboratory experience with 24 hour partial heart-lung bypass

Summary Eight out of eleven dogs were long term survivors when submitted to 24 hours of partial heart-lung bypass using a membrane oxygenator with a low priming volume. It was possible to maintain an adequate metabolic balance in these animals and tests of hepatic and renal function after perfusion gave normal results. Blood damage during perfusion remained well within limits of compensation by the organism. However, the survival time of erythrocytes tagged at the end of the procedure was shortened, explaining the occurrence of hemolytic anemia in the first week after perfusion. Nonsurvivors showed pulmonary damage, water and electrolyte retention, splanchnic congestion and impairment of liver function. These experiments suggest that extracorporeal blood oxygenation can be offered safely for clinically useful periods with simple equipment requiring little or no priming blood.

Physiologic principles of partial extracorporeal circulation for mechanical assistance to the failing heart

Abstract Partial heart-lung bypass is one form of artificial circulation proposed for assisting the failing heart. Since it involves extracorporeal gas exchanges, respiratory as well as circulatory functions must be considered during the procedure. Our studies reveal that an accurate knowledge of the systemic blood volume is necessary to control the distribution of blood flow between the intracorporeal and extracorporeal circuits. The systemic blood content also influences the pulmonary ventilation. Partial heart-lung bypass can be performed in such a manner that it completely fulfills the metabolic requirements of the body tissues. Whether abnormal hemodynamic conditions in heart failure can be relieved by partial heart-lung bypass after the period of active circulatory assistance is still to be evaluated.

Influence of Blood Temperature on the Pulmonary Circulation

Innervated, nourished and ventilated dog lungs were perfused in situ with a technic which afforded adequate control of blood flow, pressures, pH and temperature. Variations of the pulmonary (hut not of the systemic) blood temperature was followed by pronounced changes of the pulmonary vascular resistance, believed to be attributable to pulmonary vasomotion.

Studies of Myocardial Actomyosin and Myosin After Shock, Acute Hemorrhage, Acute Hypoxia, and Cardiopulmonary Bypass

Decreases in cardiac efficiency have been observed in experimental endotoxic shock, acute hemorrhage, and cardiopulmonary bypass. Diminished coronary blood flow, tissue anoxia, or metabolic alteration may affect the contractile protein which, in turn, causes cardiac inefficiency. To test this hypothesis, cardiac actomyosin and myosin were extracted with Guba-Straub solution, and intrinsic viscosity, ATP (adenosinetriphosphate) activity, ATP sensitivity, the rate of ATP hydrolysis, and myosin-ATPase activity were determined. Under these experimental conditions, both myosin and actin were altered.In order to exclude the possible effect of hypoxia of the arterial blood upon the cardiac contractile system, acute hypoxia was produced in dogs and the physicochemical properties of actomyosin and myosin were studied. During acute hypoxia, the myosin-ATPase was affected, but actin appeared to remain unaltered.These changes of actomyosin and myosin may cause insufficient energy utilization by the contractile system and thereby affect the cardiac efficiency.

Cardiovascular Adaptation to Partial Heart-Lung Bypass

Partial heart-lung bypass was performed in open-chest dogs, using the gravity arterial in-fusion technique. Arterial infusion pressure, venous suction and pressures in the left ventricle, aortic arch, and airways were phasically recorded. The mean flow in the aortic arch and the blood content of the extracorporeal circuit were continuously recorded. According to the height of the bag oxygenator above the heart level, partial heart-lung bypass resulted in a shift of blood either from the extracorporeal circuit into the animal or vice versa. When the body blood volume was increased by the bypass procedure, the cardiac output decreased only slightly. When the body blood volume was diminished by the bypass procedure, the cardiac output dropped markedly. It was found that when the systemic arterial pressure was maintained at approximately normal levels, independent of cardiac output, the change in cardiac output was proportional to the change in the body blood volume.

STUDIES OF MYOCARDIAL CONTRACTILE PROTEINS AND MITOCHONDRIAL SUCCINATE DEHYDROGENASE DURING PARTIAL HEART-LUNG BYPASS.

Under certain clinical conditions of &dquo;cardiovascular failure,&dquo; a primary hemodynamic change may lead to metabolic alterations which, in turn, disturb the cardiovascular functions. Mechanical assistance of the heart-lung bypass procedure may be applicable to break this vicious cycle.’ During the procedures of partial heart-lung bypass, however, gas exchange and blood pumping occur simultaneously in the heart and lungs of the animal, and in the extracorporeal circuits. As a result, the hemodynamic and metabolic responses of the animal may be complicated.2 2