A 58-year-old man with severe traumatic brain injury develops serum sodium of 162 mEq/L with polyuria and altered sensoriology. Free water deficit is calculated at 4 litres. Which intravenous fluid is most appropriate for initial correction of this hypernatraemia?
- A 5% Dextrose in Water (D5W) ✓
- B 0.9% Normal Saline
- C Ringer's Lactate
- D 0.45% Normal Saline with Dextrose
Correct answer: A. 5% Dextrose in Water (D5W)
Explanation
Hypernatraemia represents free water deficit, and D5W provides free water once dextrose is metabolised. Normal saline is isotonic and does not correct free water deficit. Half-normal saline contains sodium and corrects more slowly than D5W. Correction rate should not exceed 10 to 12 mEq/L per 24 hours to avoid cerebral edema.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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