EFFECTS OF CHRONIC HYPERCAPNIA ON ELECTROLYTE AND ACID-BASE EQUILIBRIUM. II. RECOVERY, WITH SPECIAL REFERENCE TO THE INFLUENCE OF CHLORIDE INTAKE*

Abstract

Balance studies have been carried out in eight dogs during recovery from chronic respiratory acidosis induced by a high CO2 atmosphere. Four animals received a high-salt diet and four others a low-salt diet during the period of exposure to CO2 and throughout the recovery period. At the end of the CO2 period, plasma bicarbonate concentration ranged from 35 to 38 mEq per 1 in both groups; plasma chloride concentration was depressed. After being returned to room air, the high-salt dogs showed a prompt reduction in plasma bicarbonate concentration to a normal range of 21 to 24 mEq per 1, and chloride concentration rose simultaneously to a normal level. By contrast, the low-salt dogs had a significantly smaller reduction in plasma bicarbonate concentration, to values of approximately 27 to 30 mEq per 1, and became mildly alkalotic; plasma chloride concentration showed little or no change. During the subsequent 6 days, the low-salt dogs stabilized their plasma bicarbonate levels in a range consistently above the normal; the plasma chloride concentration in these animals remained grossly subnormal. The persistent elevation of plasma bicarbonate concentration in the low-salt animals indicates that an elevated rate of hydrogen ion secretion persisted despite a normal plasma carbon dioxide tension. Potassium deficiency did not appear to be a factor in the difference observed between the low-and high-salt groups. When salt was added to the diet of the low-salt dogs, the plasma bicarbonate fell to normal and there was a reciprocal rise in plasma chloride concentration. The reduction in bicarbonate was achieved without urinary bicarbonate loss, but was associated with a marked suppression of acid excretion. Two additional studies of animals given a diet low in sodium but containing a moderate amount of chloride demonstrated that the acid-base disturbance and hypochloremia could be corrected solely by the provision of chloride.