Single-pump techniques for assisted circulation in cardiogenic shock: experimental evaluation and case report.
Acute cardiogenic shock or bridging to transplantation often involves the need for circulatory and cardiac support systems that are more effective than the intraaortic balloon pump. Biventricular failure, which is present in many cases, is generally treated with total cardiac replacement or with a complex of pumps and oxygenator that makes application difficult. With the goal of developing a universally applicable method of cardiac and circulatory support, we undertook a series of canine experiments designed to evaluate the effect of various treatment methods on survival, hemodynamics, and metabolic function. The series involved 123 dogs, in which cardiogenic shock was induced by means of multiple coronary artery ligations. The individual animals were then subjected to bypass, treated medically, or left untreated, depending on random selection. Each treatment lasted for 4 hours and was followed by a 2-hour period of observation. The following single-pump methods were tested: 1) left ventricular (LV) bypass, 2) left atrial (LA) bypass, 3) left ventricular and right atrial (LV + RA) bypass, 4) left atrial and right atrial (LA + RA) bypass, 5) LV + RA bypass, plus treatment with substrates (cysteine and ribose), and 6) LV + RA bypass, plus treatment with fluosol. Each bypass system incorporated a single reservoir and a centrifugal pump, and blood was returned to a femoral artery. Medical therapy consisted of either 1) treatment with sodium nitroprusside alone or 2) treatment with substrates alone. With respect to survival and hemodynamic effects (as reflected by oxygen consumption), LV + RA bypass and LA + RA bypass proved superior. During the posttreatment period, LV + RA bypass was associated with the highest survival rates and, therefore, with the most satisfactory recovery of myocardial or cardiac function. Despite the limited desaturation produced during venous shunting from the right atrium, perfusion of the entire body and consumption of oxygen were least in the LV + RA bypass group. The addition of substrates, or even of fluosol, caused a reduction in oxygen consumption. Our experience also includes one clinical case in which LA + RA bypass was used to support a 57-year-old man for 32 hours, after left atrial bypass alone proved inadequate. The dual-chamber technique brought about an improvement not only in hemodynamics but also in blood-gas values and pH. On the basis of this case and the canine experiments, we conclude that LV + RA and LA + RA bypass techniques offer safe, effective means of long-term temporary support for patients in severe cardiogenic shock.
Lefemine
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Department of Surgery, Veterans' Administration Medical Center, Johnson City, Tennessee, USA.
Dunbar
J
J
Delucia
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Low
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