AN EXPERIMENTAL STUDY OF THE IMMEDIATE HEMODYNAMIC ADJUSTMENTS TO ACUTE ARTERIOVENOUS FISTULAE OF VARIOUS SIZES 1

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Abstract
Some of the immediate circulatory adjustments to the opening and closing of arteriovenous fistulae of different sizes were studied in the anesthetized dog. An increase in stroke volume and cardiac output was observed in all experiments. With the smaller fistulae, i.e., fistulae accommodating less than 20% of the control cardiac output, the cardiac output was increased by the full amount of the fistula flow. Greater increases in cardiac output occurred with larger fistulae, but the amount of the increase in output was less than the amount of the fistula flow which resulted in a decrease of the blood flow to the systemic capillary bed. Vasoconstriction supervened, which prevented a fall in the mean arterial blood pressure in some of the fistulae accommodating up to 60% of the control cardiac output, but with larger fistulae the arterial blood pressure fell despite vasoconstriction.