The next most appropriate test to order in a patient with a pH of 7.1, Pco2 of 40, sodium of 132, potassium of 4.2, and chloride of 105 is:a. Serum bicarbonate
Metabolic acidosis results from an increased intake of acids, an increased generation of acids, or an increased loss ofbicarbonate. In evaluating a patient with a low serum bicarbonate level and metabolic acidosis, first measure the AG, an index of unmeasured anions.
AG = [Na] - [Cl + HCO3]
Metabolic acidosis with an increased AG occurs from either exogenous acid ingestion (ethylene glycol, salicylate, or methanol) or endogenous acid production of β-hydroxybutyrate and acetoacetate in ketoacidosis, lactate in lactic acidosis, or organic acids in renal insufficiency.