Foundations of acid-base analysis: primary process, compensation, and normal values

Apuntes

CME Acid-Base Interpretation: A Practical Approach Masahiro J. Morikawa, MD, MPH, and Prakash R. Ganesh, MD, MPH Acid-base disorders are prevalent in critically ill patients, and a systematic approach is essential for evaluation. The first step is to determine the primary process based on a patient’s pH, partial pressure of carbon dioxide, and bicarbonate measurements. After this is complete, the next step is to evaluate for respiratory or metabolic compensation. Devi- ations from expected compensation may indicate additional acid-base processes. For metabolic acidosis, anion gap calculation distinguishes between anion gap metabolic acidosis and non–anion gap metabolic acidosis. The evaluation for anion gap metabolic acidosis includes calculating the osmolal gap and conducting a gap-gap analysis. Evaluating non–anion gap metabolic acidosis involves urine anion gap calculation. These analyses identify potential etiologies and additional acid-base disturbances. Metabolic alkalosis assessment begins with measuring urine chloride levels to determine whether the process is a result of chloride depletion. Respiratory acidosis, caused by hypoventilation, often results from chronic lung di...