Signs and Symptoms of Hypernatremia
Hypernatremia presents with a spectrum of neurological manifestations ranging from mild cognitive changes to life-threatening cerebral edema, with severity depending on the rapidity of onset and degree of sodium elevation.
Neurological Manifestations
Mild to Moderate Symptoms
- Confusion and altered mental status
- Lethargy and dizziness
- Irritability and restlessness
- Muscle weakness
- Hypotonia
- Anorexia
- Nausea and vomiting
- Headache (often migraine-like) 1
- Tremors, ataxia, and dysarthria 1
Severe Symptoms
- Progressive deterioration in mental status
- Seizures
- Coma
- Potential collapse
- Death due to acute cerebral edema 1
- Acute brain shrinkage leading to vascular rupture
- Cerebral bleeding and subarachnoid hemorrhage 2
Pathophysiology-Related Signs
Hypernatremia reflects a net water loss or hypertonic sodium gain, resulting in hyperosmolality 2. The brain adapts to hypernatremia by accumulating organic osmolytes to minimize cerebral dehydration. This adaptation is crucial but can lead to complications if correction occurs too rapidly 2.
Risk Factors and Special Populations
Hypernatremia is particularly dangerous in:
- Patients with altered mental status
- Those with hypothalamic lesions affecting thirst sensation
- Infants and elderly people who may have reduced thirst sensation 2
- Neurosurgical patients who may develop central diabetes insipidus 1
Clinical Presentation by Severity
Mild Hypernatremia
- Thirst (if thirst mechanism is intact)
- Anorexia
- Muscle weakness
- Restlessness
Moderate Hypernatremia
- Nausea and vomiting
- Altered mental status
- Irritability
- Lethargy
Severe Hypernatremia (Na >158-160 mmol/L)
- Stupor
- Coma
- Seizures 2
Diagnostic Considerations
The clinical presentation of hypernatremia is often characterized by:
- Central nervous system dysfunction (confusion progressing to coma)
- Pronounced thirst (in awake patients with intact thirst mechanism) 3
Important Pitfalls to Avoid
Failure to recognize hypernatremia in patients with altered mental status: These patients may not report thirst, masking a key symptom.
Overly rapid correction: Correction of chronic hypernatremia (>48 hours) should not exceed 8-10 mmol/L/day to prevent cerebral edema 3.
Missing the underlying cause: Hypernatremia is rarely due to excessive sodium intake but more commonly results from free water loss relative to sodium excretion 3.
Overlooking hypernatremia in neurosurgical patients: These patients are at particular risk for developing central diabetes insipidus and subsequent hypernatremia 1.
Ignoring volume status: Assessment of extracellular volume status is crucial for proper diagnosis and management 4.
By recognizing these signs and symptoms early, clinicians can initiate appropriate treatment to prevent the serious neurological sequelae associated with severe hypernatremia.