Functional Cardiac Deterioration During Development of Hemorrhagic Circulatory Deficiency

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Abstract
A massive infusion test has been devised to evaluate the functional capacity of the heart. In five dogs extensive surgical procedures followed by episodes of arterial hypotension at 30 mm Hg and lasting 90 minutes caused severe cardiac incapacity, which was demonstrated by failure of rate of cardiac work to increase throughout the infusion together with a large rise in left atrial pressure. This incapacity was not evident in tests made immediately after the hypotensive episode. The damage became more and more severe in tests performed 90 and 150 minutes after the end of the hypotension even though mean arterial pressure was maintained at 100 mm Hg. Operated control dogs did not show cardiac deterioration in tests timed as above. The rate of cardiac work continued to increase throughout the infusion with a relatively small rise of left atrial pressure. In a series of five dogs, flow to the coronary arteries and to those supplying the head and forelimbs was maintained by normal blood pressure while the rest of the animal was made hypotensive for 90 minutes. The arterial pressure in the whole animal was then returned to an average level of 100 mm Hg. Tests made at intervals after the hypotension showed equivocal evidence of cardiac deterioration. In another series of four dogs, prepared as above, the partial hypotension lasted 150 minutes before the arterial pressure was returned to normal. Tests at intervals after hypotension showed cardiac damage in all the animals and severe damage in three. Evidence is presented indicating that the peripheral vascular bed had deteriorated functionally as a result of 150 minutes of partial hypotension.