Mixed Acid-Base Disturbances: Core Curriculum 2025.

Mixed acid-base disorders are frequently encountered in clinical practice and due to their complexity, diagnoses and treatment are challenging. The opposing effects of multiple disturbances can lead to blood pH levels that are near normal or separate acid-base disturbances can have an additive effect leading to more significant changes in blood and intracellular pH. A systematic evaluation of patient history, physical examination, and laboratory results (including acid-base balance, anion gap, electrolytes, and urine parameters) enables the rapid diagnosis of mixed acid-base disorders by analyzing the appropriateness of compensatory mechanisms, assessing changes in serum and urine electrolytes, and estimating urinary acid excretion. Eight cases are provided to illustrate the approach to mixed acid-base disturbances. Examples include mixed metabolic and respiratory acid-base disorders, mixed respiratory acid-base disorders, and mixed metabolic acid-base disorders.