Moderate Hypernatremia Definition
Moderate hypernatremia is defined as a serum sodium concentration of 150-155 mmol/L. 1
Classification by Severity
Hypernatremia severity is stratified based on serum sodium levels:
- Mild hypernatremia: 145-150 mmol/L 2
- Moderate hypernatremia: 150-155 mmol/L 2
- Severe (threatening) hypernatremia: >155 mmol/L 2
The threshold for hypernatremia begins at serum sodium >145 mmol/L, which represents an imbalance where the water content of body fluids is deficient compared with sodium content. 3, 1
Clinical Context and Significance
Moderate hypernatremia reflects a significant water deficit relative to sodium content and typically results from excess losses of free water rather than pure sodium excess. 4 This level of hypernatremia is associated with central nervous system dysfunction, including confusion and altered mental status in awake patients, along with pronounced thirst. 5
Special Clinical Scenarios
In certain protocols for managing cerebral edema, sodium levels of 150-155 mmol/L may be deliberately targeted therapeutically. 6 However, in patients with liver disease or cirrhosis, a sodium level of 150 mmol/L is particularly concerning as it may indicate worsening hemodynamic status. 6
Duration Classification
Hypernatremia is further classified by duration:
This distinction is critical because chronic hypernatremia (>48 hours) should not be corrected by more than 8-10 mmol/L per day to prevent osmotic demyelination syndrome, whereas acute hypernatremia can be corrected more rapidly. 5
Correction Rate Guidelines
For moderate hypernatremia that has developed slowly, the recommended correction rate is no more than 0.4 mmol/L per hour (approximately 8-10 mmol/L per 24 hours) to avoid complications from rapid osmotic shifts. 2 Close laboratory monitoring is essential during correction. 5