Acid–Base Balance Disorders

Abstract

Abnormalities in maintaining the pH of the blood in a range that is incompatible with sustaining metabolic processes are known as acid–base balance disorders. Here, we define normal acid–base balance and describe the four basic acid–base balance disorders including metabolic acidosis, metabolic alkalosis, respiratory acidosis and respiratory alkalosis that occur. We suggest a diagnostic approach in defining the disorders and a differential diagnosis to their causes. Routine management of these disorders is also discussed. Key Concepts: Normal Physiologic function depends on the maintenance of a systemic arterial pH between 7.35 and 7.45. The coordination of renal and respiratory regulatory mechanisms is responsible for maintaining physiologic pH. The use of simple equations can differentiate between different acid–base disorders. The causes of metabolic acidosis can be divided among those that lead to a high anion gap and those that present with a normal anion gap. An approach to differentiating the causes of metabolic alkalosis is based on assessing volume status. Respiratory acidosis develops in the setting of hypoventilation. Respiratory alkalosis occurs when carbon dioxide output in the lungs exceeds its metabolic production in the tissues. The ultimate treatment of acid–base disorders is focused on identifying and managing their underlying cause.