A 2-year-old with severe hypernatraemic dehydration (serum Na 168 mEq/L) after several days of inadequate fluid intake is being rehydrated. Which is the MOST important principle guiding fluid therapy?
- A Rapid correction with 0.9% saline boluses to lower Na quickly
- B Use 5% dextrose to correct hyperosmolality quickly
- C Oral rehydration is contraindicated; IV fluids must be used exclusively
- D Slow correction reducing serum Na by no more than 10–12 mEq/L per day ✓
Correct answer: D. Slow correction reducing serum Na by no more than 10–12 mEq/L per day
Explanation
In hypernatraemic dehydration, correction must be slow — no more than 10–12 mEq/L/day — to avoid cerebral oedema. The brain adapts to hyperosmolality by generating idiogenic osmoles; rapid correction creates an osmotic gradient driving water into brain cells, causing paradoxical cerebral oedema and seizures. Isotonic saline or half-normal saline is used to restore circulating volume before gradual oral/IV water repletion. Rapid correction with hypotonic solutions is dangerous. Oral rehydration can be used in mild-moderate hypernatraemic dehydration.
Reference: Ghai Essential Pediatrics, 10th ed.
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