A 52-year-old man from Delhi presents with a 3-month history of epigastric pain, heartburn, and regurgitation. He has been self-medicating with sodium bicarbonate antacid powder 3–4 times daily. On examination, blood pressure is 148/92 mmHg (previously 130/85 mmHg), and he appears mildly edematous. Serum sodium is 148 mEq/L (normal 135–145), serum bicarbonate is 32 mEq/L (normal 22–26), and pH is 7.48. Urine chloride is low. What is the most likely adverse effect of his current antacid regimen?

Explanation

## Clinical Presentation Analysis The patient's laboratory findings and clinical signs point to a specific electrolyte and acid-base disturbance caused by chronic sodium bicarbonate use. ### Key Laboratory Findings | Parameter | Patient Value | Normal Range | Interpretation | |-----------|---------------|--------------|----------------| | pH | 7.48 | 7.35–7.45 | Alkalemia | | HCO₃⁻ | 32 mEq/L | 22–26 | Elevated (metabolic alkalosis) | | Na⁺ | 148 mEq/L | 135–145 | Hypernatremia | | Urine Cl⁻ | Low | — | Chloride-responsive alkalosis | | BP | 148/92 | — | Hypertension (new) | **Key Point:** Sodium bicarbonate antacids cause metabolic alkalosis by increasing serum HCO₃⁻. The excess sodium load leads to volume expansion and hypertension. Low urine chloride indicates the kidneys are attempting to conserve chloride, which is characteristic of chloride-responsive (contraction) alkalosis. ### Pathophysiology of Sodium Bicarbonate Toxicity 1. **Metabolic alkalosis**: Direct HCO₃⁻ loading from repeated dosing 2. **Hypernatremia**: Sodium load exceeds water intake 3. **Hypokalemia**: Alkalosis shifts K⁺ intracellularly; increased renal K⁺ wasting via increased distal Na⁺ delivery 4. **Hypertension**: Volume expansion from excess sodium 5. **Chloride depletion**: Renal chloride conservation (low urine Cl⁻) **High-Yield:** The combination of metabolic alkalosis + hypokalemia + hypertension + hypernatremia from chronic sodium bicarbonate is a classic NEET PG scenario. The low urine chloride confirms chloride-responsive alkalosis, which improves with saline (not bicarbonate restriction alone). ### Clinical Pearl Sodium bicarbonate should be avoided in chronic acid reflux because: - It is poorly buffered (CO₂ escapes, leaving HCO₃⁻) - Systemic absorption causes alkalosis - Sodium load worsens hypertension - Better alternatives: aluminum/magnesium hydroxide, calcium carbonate, or PPIs ### Why Not Milk-Alkali Syndrome? Milk-alkali syndrome requires concurrent high calcium intake (milk + absorbable alkali). This patient took only sodium bicarbonate powder, not milk. Hypercalcemia and AKI are not evident. ### Why Not Hypermagnesemia or Hypophosphatemia? The patient was not taking magnesium-containing antacids (Mg(OH)₂) or aluminum-containing ones (which cause hypophosphatemia). Sodium bicarbonate does not cause these mineral disturbances.