acidemia

Acidemia is the condition in which the blood has a pH below the normal range, typically defined as less than 7.35. It is a state of acidemia, and may result from disturbances that increase acid production, decrease bicarbonate, or impair the removal of carbon dioxide. It can arise from metabolic causes, respiratory causes, or a combination of both (mixed disorders). The body may attempt partial compensation, such as increasing ventilation in metabolic acidosis or increasing bicarbonate retention in respiratory acidosis, but acidemia persists unless the underlying problem is addressed.

Pathophysiology involves the balance between carbon dioxide, a volatile acid, and bicarbonate, a base. In metabolic acidosis, there is a primary loss of bicarbonate or an excess production of nonvolatile acids, leading to low bicarbonate and low pH. In respiratory acidosis, elevated carbon dioxide from hypoventilation lowers pH. Evaluation often uses arterial blood gas measurements to determine the primary disorder and the degree of compensation. The anion gap calculated from serum electrolytes helps classify metabolic acidosis as high-gap or normal-gap, guiding the search for causes such as lactic acidosis, ketoacidosis, renal failure, or toxin ingestion.

Common causes include lactic acidosis from shock or hypoxia, diabetic or alcoholic ketoacidosis, renal failure, diarrheal bicarbonate loss, toxins, and respiratory conditions like COPD, pneumonia, or airway obstruction that impair ventilation. Treatment centers on addressing the underlying cause, ensuring adequate oxygenation and ventilation, correcting electrolyte and fluid abnormalities, and, in selected cases, administering bicarbonate therapy for severe metabolic acidosis or significant acidemia. Prognosis depends on the cause, severity, and the patient’s overall condition.