Which of the following is the most common primary acid-base disorder encountered in clinical practice?

Explanation

## Epidemiology of Acid-Base Disorders **Key Point:** Metabolic acidosis is the most frequently encountered primary acid-base disturbance in both acute and chronic clinical settings. ### Frequency Distribution in Clinical Practice | Disorder | Frequency | Common Causes | |----------|-----------|---------------| | Metabolic acidosis | 40–50% | DKA, lactic acidosis, renal failure, diarrhea | | Respiratory acidosis | 20–25% | COPD, hypoventilation, airway obstruction | | Respiratory alkalosis | 15–20% | Hyperventilation, sepsis, anxiety, hypoxemia | | Metabolic alkalosis | 10–15% | Vomiting, diuretics, contraction alkalosis | **High-Yield:** In hospital populations, metabolic acidosis accounts for approximately 40–50% of all primary acid-base disorders, making it the single most common presentation. ### Why Metabolic Acidosis Is Most Common 1. **Multiple etiologies**: DKA, lactic acidosis (sepsis, shock, metformin), renal failure, GI bicarbonate loss (diarrhea), and uremia all cause metabolic acidosis. 2. **Acute and chronic disease**: Both acute presentations (DKA, lactic acidosis in sepsis) and chronic conditions (CKD, ESRD) commonly manifest as metabolic acidosis. 3. **Severity**: Metabolic acidosis often indicates serious underlying pathology (shock, organ failure), prompting earlier detection and reporting. **Clinical Pearl:** When a patient presents with an acid-base abnormality in the ICU or emergency department, metabolic acidosis should be your first differential consideration until proven otherwise. **Mnemonic: HARDUPS** — causes of metabolic acidosis: - **H**yperalimentation - **A**cetazolamide / Addison's disease - **R**enal tubular acidosis - **D**iarrhea - **U**reteral diversions - **P**ancreatic fistula - **S**alicylates