endocrine and metabolic disorders
Acid Base Disorders
Key Points
Acidosis and alkalosis refer to physiologicprocessesthat cause accumulation or loss of acid and/or alkali; blood pH may or may not be abnormal. Acidemia and alkalemia refer to an abnormally acidic (pH<7.35) or alkalotic (pH>7.45) serum pH. Acid-base disorders are classified asmetabolicif the change in pH is primarily due to an alteration in serum bicarbonate (HCO3−) andrespiratoryif the change is primarily due to a change in Pco2(increase or decrease in ventilation). The pH establishes the primary process (acidosis or alkalosis), changes in Pco2reflect the respiratory component, and changes in HCO3−reflect the metabolic component. All acid-base disturbances result incompensationthat tends to normalize the pH. Metabolic acid-base disorders result in respiratory compensation (change in Pco2); respiratory acid-base disorders result in metabolic compensation (change in HCO3−). More than one primary acid-base disorder may be present simultaneously. It is important to identify and address each primary acid-base disorder. Initial laboratory evaluation of acid-base disorders includes measurement of arterial blood gases and serum electrolytes and calculation of the anion gap. Use one of several formulas, rules-of-thumb, or an acid-base nomogram to determine if laboratory values are consistent with a single acid-base disorder (and compensation) or if a second primary acid-base disorder is also present. Treat each primary acid-base disorder. 