Studies on hypertension. 2. Influence of acid-base imbalance on the distribution of electrolytes and its relationship to hemodynamics

Abstract

In a previous paper the author reported that the acid-base equilibrium plays an important role in the mechanism of hemodynamics in hypertension. It was concluded that in metabolic acidosis systolic and diastolic blood pressures did not show any change, but total peripheral resistance elevated moderately, while in metabolic alkalosis systolic and diastolic blood pressures indicated a significant decrease in normotensive and hypertensive subjects. From the point of the electrolyte distribution of plasma and red cells it seems to be important to elucidate the mechanism of the changes of hemodynamics in hypertension induced by the acid-base equilibrium. In this report, therefore, the author has attempted to determine the influences of metabolic acidosis on the electrolyte distributions in plasma and red cells and investigate their relationships to the hemodynamics in normotensive and hypertensive subjec〓s. Materials and Methods The study was done on 33 subjects, of whom 16 were normotensives and 17 had apparent essential hypertension without evidences of cardiac or renal failures. Three hundred ml of 0.01 N hydrochloric acid solution was infused intravenously to induce metabolic acidosis and one hundred and fifty ml of 7 per cent bicarbonate solution to induce metabolic alkalosis. Sodium, potassium, chloride and bicarbonate concentrations in plasma, and sodium and potassium concentrations in the red blood cells were measured before and after the infusion. The red blood cells were separated by centrifugation at 3, 600 g for 30 minutes. Results Serial electrolyte changes in metabolic acidosis and their relationship to hemodynamics : Arterial blood pH fell after the intravenous infusion of 0.01 N hydrochloric acid in normotensive and hypertensive subjects. Sodium concentration in plasma decreased slightly in both groups after the influsion. Potassium concentration rose in normotensives and conversely fell in hypertensives, but the differences between them were not significant. Plasma concentration of chloride did not change after the infusion in normotensives while it was elevated insignificantly in hypertensives. Bi-carbonate concentration rose in both groups, but a statistical significance was noted only in the hypertensive group. Since sodium concentration in red blood cells slightly decreased in both groups of patients, the ratio of plasma sodium to sodium in red blood cells, Nae/Nai, increased insignificantly. Potassium concentration in the red blood cells increased slightly in both groups and the ratio of plasma potassium to potassium in red blood cells, Ki/Ke, had no remarkable change in the normotensive group but showed a mild increase in the hypertensive groups. Interestingly there was a close relationship between changes in systolic blood pressure and/or total peripheral resistance and Ki/Ke in the hypertensive group.