Chloride-responsive metabolic alkalosis

This condition is far less common than chloride responsive metabolic alkalosis and is almost always associated with either an underlying disease (primary hyperaldosteronism, Cushing s syndrome, or Bartter s syndrome) or with excess addition of exogenous base. In these conditions, urine CL will usually be >20 mmol/L. 

The patient s response to volume replacement may be predicted by the urine chloride concentration, and permits the differential diagnosis of metabolic alkalosis. 

TABLE 51—8. Courses of Metabolic Alkalosis Differentiated on the Basis of Their Responsiveness to Sodium Chloride... 

Although the pH may not deviate significantly from normal, treatment may need to be initiated to maintain Pa02 and PaC02 at acceptable levels. Because it is often difficnlt to correctly identify this mixed disorder, it is helpful to observe the patient s response to discontinuation of diuretics and administration of sodium and potassium chloride. If the patient has a simple metabolic alkalosis, the PaC02 will normalize, but it will only minimally affect the PaC02 if it is a mixed disorder. Treatment should be aimed at decreasing the plasma bicarbonate with sodium and potassium chloride therapy. 

Conclusion. The acidity of the urine is (appropriate, inappropriate) as a response to metabolic alkalosis. The preservation of electrolyte and fluid volume (takes precedence, is subservient) to the correction of the acid-base disturbance. Cautious intravenous infusion of isotonic sodium chloride solution is likely to (improve, have no effect on, adversely affect) the patient s condition. 

Metabolic compensation occurs when respiratory alkalosis persists for more than 6 to 12 hours. In response to the alkalemia, proximal tubular bicarbonate reabsorption is inhibited and the serum bicarbonate concentration falls. Renal compensation is usually complete within 1 to 2 days. The renal bicarbonaturia, as well as decreased NH4+ and titratable acid excretion, are direct effects of the reduced PaC02 and pH on renal reabsorption of chloride and bicarbonate. The... 

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