THE REDISTRIBUTION OF CARDIAC OUTPUT DURING CONGESTIVE HEART FAILURE IN NEWBORN ANIMALS

Abstract

The two purposes of this study were to assess the efficacy of a new technique to produce a controlled state of congestive heart failure (CHF) in newborn animals, and to assess alterations in organ flow during CHF. One to 10 day old Spanish goats were studied during general endotracheal anesthesia (Ethrane and N₂O). Flows were measured using the radioactive microsphere technique. CHF was produced with a continuous infusion of sodium citrate (C) into the left atrium. Phenylephrine (P) was used to maintain arterial pressure as cardiac output (CO) fell after addition of C. Hemodynamic changes in this experimental preparation simulate a cardiomyopathy. Flow measurements during C + P infusions compared to control or P periods reflected a sparing of brain flow until total CO fell to extremely low levels. Control flow =0.61 ml/min · gm⁻¹ ± 0.14 SE. Brain flow during C + P = 0.48 ml/min · gm₋₁ ± 0.16 (NS) with normal pressure and mild drop in CO. Myocardial flow increased signficantly (p< 0.01) during P infusion and with P + C flow was maintained until CO fell; then subendocardial perfusion was most reduced. Renal flow was the first to fall as CO dropped, followed by skin and skeletal muscle flows. Small bowel perfusion increased with P but fell as CO was reduced by C. During shock systemic arterio-venous shunting occurred, suggested by a rise in the percentage of recirculating microspheres.

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