GENERAL AND REGIONAL CIRCULATORY RESPONSES TO CHANGE IN BLOOD PH AND CARBON DIOXIDE TENSION*

Abstract

In human subjects, alkalemia produced by intravenous infusion of hypertonic sodium bicarbonate was accompanied by significant increase in cardiac output and decrease in total peripheral resistance. Acidemia produced by intravenous ammonium chloride or lactic acid solutions was not associated with significant change in cardiac output. Neither induced alkalosis nor acidosis caused change in blood flow through the intact human forearm. With sympathetic vasoconstrictor impulses to the forearm blocked by phenoxybenzamine (Dibenzyline), both acidosis and aikalosis produced increases in forearm blood flow, larger increase being associated with aikalosis. In the intact extremity, blood flow did not change during inhalation of 5 to 7% CO2 for 5 to 10 minutes. Following blockade of sympathetic impulses by intra-arterial injection of phenoxybenzamine CO2 inhalation produced significant increase in blood flow and decrease in vascular resistance. Hypocapnia, induced by voluntary hyperventilation, was accompanied by 20% increase in blood flow in the intact forearm. Inhalation of 7% CO2 in air for 7 minutes, in 16 experiments on 10 normal human subjects, produced a 45% increase in cardiac output accompanied by rise in blood pressure and heart rate. Comparable degrees of voluntary hyperventilation without change in arterial CO2 tension caused no changes in these functions.