Approach to Acid Base Disorders - Evaluation and Differential Diagnosis 1) Start with the Anion Gap (AG). 2) Next, are they more acidotic or alkalotic than expected based on the AG? Compare the change in bicarb to the change in AG (delta/delta) to see! 3) Now, look at the gas. Do you need an ABG? Generally, for acid/base, a VBG approximates an ABG by adding ~0.05 to pH and ~5 mmHg to pCO2. 4) The final step is to assess for the chronicity (acute, chronic, or acute on chronic) of the disorder and for the appropriate compensation which can be done by using formulas. Differential Diagnosis: • Anion Gap Metabolic Acidosis: Lactic Acidosis, Ketoacidosis, Renal Failure, Toxic Ingestion • Non-Anion Gap Metabolic Acidosis: GI loss of bicarb, Renal loss of bicarb, Bicarb shift • Metabolic Alkalosis: GI loss of H+, Renal loss of H+, Bicarb retention • Respiratory Acidosis: CNS depression, Obstructive Lung Disease, Neuromuscular Disease, PE, Decreased Mechanical Ventilation • Respiratory Alkalosis: CNS stimulation, Compensatory for Metabolic Acidosis, Pregnancy, PE, Increased Mechanical Ventilation Dr. Meredith Greer @EmmGeezee #Acid #Base #Disorders #Evaluation #workup #Differential #Diagnosis #acidosis #alkalosis
