Which electrolyte disturbance is expected with prolonged nasogastric output?

• A. Hypokalemia
• B. Hyperkalemia
• C. Hyponatremia
• D. Hypophosphatemia

Answer: (A)

Prolonged loss of gastric juice through an NG tube removes large amounts of hydrogen and chloride, which drives a metabolic alkalosis and leaves the body chloride-depleted. The accompanying volume depletion stimulates aldosterone, promoting sodium reabsorption and potassium excretion by the kidneys, leading to hypokalemia. This combination—hypochloremic metabolic alkalosis with low potassium—is the typical pattern with extended NG output. The other options don’t fit this classic derangement: hyperkalemia isn’t expected with gastric drainage, hyponatremia isn’t the primary consequence of prolonged gastric losses, and hypophosphatemia is not a direct result of NG suctioning.