Acid-Base Disorders

Maintaining a normal physiologic acid-base balance is essential for the functioning of every organ system in the body. The renal and pulmonary systems are the primary regulators of acid-base balance. There are four principal acid-base disorders: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis. A systematic approach to evaluation is critical to identify potential etiologies. A history, physical examination, metabolic profile, and arterial blood gas measurement provide a full assessment of acid-base status. However, availability of arterial blood gas measurements is usually limited outside of inpatient and emergency department settings. Calculation of an anion gap is a crucial first step for evaluating laboratory test results. Changes in serum pH, Pco₂, serum bicarbonate concentration, and anion gap suggest the primary disorder, and predictable compensatory changes indicate whether a secondary acid-base disturbance is present. Mixed acid-base disorders involving the renal and pulmonary systems can occur, underscoring the importance of a systematic approach to evaluation. In the outpatient setting, primary care physicians play a vital role in identifying and treating these disorders based on initial evaluation. Prompt recognition and management of acid-base disorders can help prevent morbidity and mortality.