BLOOD pH/PLASMA CATECHOLAMINE RELATIONSHIPS: RESPIRATORY ACIDOSIS

Abstract

SUMMARY Infusions of hydrochloric acid in ventilated, intact dogs were associated with increases in plasma noradrenaline and adrenaline in proportion to the fall in arterial pH. Down to about pH 6.7 the rise in noradrenaline predominated, largely due to extra-adrenal liberation. During more extreme acidosis the adrenal medulla released large amounts of adrenaline, with some noradrenaline, apparently resulting partly from a local effect on the adrenal medullary cells. From the results of hexamethonium infusion it is concluded that during non-respiratory acidosis hexamethonium has a greater dampening effect on the extra-adrenal sympathetic system than on the adrenal medullary synapse. The plasma catecholamine responses to respiratory and to non-respiratory acidosis appear to be broadly similar. There was evidence, however, in the range of pH 6.7-6.9, that more noradrenaline is liberated during respiratory acidosis, and that during hexamethonium administration the adrenal medulla can be excited to a greater extent by carbon dioxide than by acid infusion.