Figure 630

Ninety-five percent confidence intervals for metabolic alkalosis. Metabolic alkalosis is the acid-base disturbance initiated by an increase in plasma bicarbonate concentration ([HCO3]). The resultant alkalemia dampens alveolar ventilation and leads to the secondary hypercapnia characteristic of the disorder. Available observations in humans suggest a roughly linear relationship between the steady-state increase in bicarbonate concentration and the associated increment in the arterial carbon dioxide tension (PaCO2). Although data are limited, the slope of the steady-state APaCO2 versus A[HCO^] relationship has been estimated as about a 0.7 mm Hg per mEq/L increase in plasma bicarbonate concentration. The value of this slope is virtually identical to that in dogs that has been derived from rigorously controlled observations [21]. Empiric observations in humans have been used for construction of 95% confidence intervals for graded degrees of metabolic alkalosis represented by the area in color in the acid-base template. The black ellipse near the center of the figure indicates the normal range for the acid-base parameters [3]. Assuming a steady state is present, values falling within the area in color are consistent with but not diagnostic of simple metabolic alkalosis. Acid-base values falling outside the area in color denote the presence of a mixed acid-base disturbance [4]. [H+]—hydrogen ion concentration.

Excess alkali

Alkali gain

Source?

Enteral

— Milk alkali syndrome

— Calcium supplements

— Absorbable alkali

— Nonabsorbable alkali plus K+ exchange resins

Parenteral

— Ringer's solution

— Bicarbonate

— Blood products Nutrition

H+ loss

Gastric

Intestinal

Suction

Villous adenoma Congenital chloridorrhea

Renal

H+ shift

— Chloruretic diuretics

— Inherited transport defects

— Mineralocorticoid excess

— Posthypercapnia

K+ depletion

Reduced GFR

Mode of perpetuation?

Increased renal acidification t

Cl responsive defect Cl- resistant defect

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