An improved approach to the patient with metabolic acidosis: a need for four amendments.

Clinicians should identify life-threatening issues in patients with metabolic acidosis. These threats may be present before therapy begins and/or anticipated after therapy commences. By adding four amendments, short-comings in the commonly used clinical approaches for the diagnosis of metabolic acidosis can be overcome. First, a definition of metabolic acidosis should consider not only the concentration of bicarbonate but also the content of bicarbonate in the extra cellular fluid compartment. The latter requires a quantitative estimate of the ECF volume, which can be obtained using the hematocrit and/or the total protein concentration in plasma. Second, to determine if the basis for metabolic acidosis was the addition of acids or the loss of NaHCO 3 , one must hunt for new anions, not only in plasma, but also in the urine. Third, it is important to measure the venous as well as the arterial PCO2 to assess the capacity to buffer H+ while minimizing H + binding to intracellular proteins. Fourth, to assess the role of the kidney in a patient with metabolic acidosis, the urine osmolal gap and the concentration of creatinine in the urine should be measured to provide an estimate of the rate of excretion of ammonium.