How do you correct acute hypernatremia?

Correcting Acute Hypernatremia

For acute hypernatremia (developing over <48 hours), correct rapidly at a rate of at least 1 mmol/L/hour using hypotonic fluids, as the brain has not yet adapted and rapid correction prevents cellular dehydration and neurologic damage without risk of cerebral edema. 1

Distinguishing Acute from Chronic Hypernatremia

• Acute hypernatremia develops when serum sodium increases at a rate exceeding 0.5 mmol/L/hour, typically occurring within 48 hours 1
• Acute hypernatremia commonly results from massive sodium intake (hypertonic NaCl or NaHCO3 solutions), iatrogenic causes, or rapid water losses 2
• Chronic hypernatremia develops slowly over days, requiring slower correction rates (no more than 0.4 mmol/L/hour or approximately 10 mmol/L per 24 hours) to prevent cerebral edema 2

Treatment Strategy for Acute Hypernatremia

Rapid Correction Protocol

• Administer hypotonic fluids rapidly to lower serum sodium at a rate of at least 1 mmol/L/hour 1
• Hypotonic fluid options include 0.45% NaCl (half-normal saline), 0.18% NaCl (quarter-normal saline), or D5W (5% dextrose in water) 3
• For massive acute sodium ingestion, consider aggressive free-water replacement: in documented cases, 6 liters of free water over 30 minutes successfully corrected sodium levels as high as 196 mmol/L without neurologic sequelae 4

Rationale for Rapid Correction

• In acute hypernatremia, the brain has not yet activated adaptive mechanisms to restore intracerebral osmolytes, which take approximately 48 hours to fully develop 5
• Rapid correction improves prognosis by preventing the effects of cellular dehydration and CNS dysfunction 2
• There is no risk of cerebral edema with rapid correction of acute hypernatremia because brain cells have not yet accumulated organic osmolytes 5, 1

Treatment Based on Volume Status

Hypervolemic Hypernatremia

• Results from excessive sodium intake (hypertonic saline, sodium bicarbonate) 2
• Treat with diuretics plus hypotonic fluid replacement to remove excess sodium while correcting water deficit 2

Euvolemic Hypernatremia

• Typically caused by diabetes insipidus (neurogenic or nephrogenic) 2
• Replace free water deficit with hypotonic fluids while addressing underlying cause 2

Hypovolemic Hypernatremia

• Results from renal or extrarenal water losses exceeding sodium losses 2
• Initial volume resuscitation with isotonic saline to restore hemodynamic stability, followed by hypotonic fluids to correct hypernatremia 2

Monitoring During Correction

• Check serum sodium every 1-2 hours during rapid correction of acute hypernatremia 4
• Monitor for neurologic improvement as sodium normalizes 4
• Adjust fluid administration rate based on sodium response and clinical status 2

Special Considerations for Pediatric Patients

• Hypernatremic dehydration in children carries the highest morbidity and mortality rate among electrolyte disorders, primarily due to CNS dysfunction 6
• Even in acute cases, monitor serum electrolytes frequently during correction 6
• CNS damage can result either from the hypernatremia itself or from overly rapid correction if chronicity is misjudged 6

Critical Distinction from Chronic Hypernatremia

• If hypernatremia has developed slowly over days, correction must be slow (maximum 0.4 mmol/L/hour or 10 mmol/L per 24 hours) to prevent cerebral edema from rapid osmotic shifts 2
• When timing is uncertain, assume chronic hypernatremia and correct slowly unless clear history of acute massive sodium intake or rapid water loss is documented 1
• In chronic hypernatremia, brain cells have accumulated organic osmolytes; rapid correction causes water to shift into brain cells faster than osmolytes can be extruded, resulting in cerebral edema 5