Signs and Symptoms of Severe Hyponatremia
Severe hyponatremia presents with a spectrum of neurological symptoms ranging from headache and confusion to seizures and coma, with symptom severity depending on the rapidity of onset, duration, and degree of sodium depletion. 1, 2
Definition and Classification
- Severe hyponatremia is generally defined as serum sodium <125 mEq/L 3
- Hyponatremia can be classified based on:
Neurological Manifestations
Mild to Moderate Symptoms
- Headache
- Nausea and vomiting
- Weakness
- Muscle cramps
- Lethargy
- Confusion
- Irritability
- Mild neurocognitive deficits
- Gait disturbances (increasing fall risk) 2
Severe Symptoms (Medical Emergency)
- Delirium
- Obtundation
- Impaired consciousness
- Ataxia
- Seizures
- Coma
- Cardiorespiratory distress
- Brain herniation (rare but fatal) 2, 3
Risk Factors for Symptomatic Hyponatremia
- Acute onset (<48 hours) - less time for brain adaptation 5, 1
- Extreme sodium depletion (<115-120 mEq/L) 6
- Female gender
- Children (larger brain-to-skull size ratio increases risk) 5
- Elderly patients
- Patients with liver cirrhosis 5
- Postoperative state 7
- Medications that stimulate ADH secretion 4
Associated Clinical Findings
- Increased risk of falls and fractures (23.8% vs 16.4% in normonatremic patients) 2
- Higher rates of new fractures over long-term follow-up (23.3% vs 17.3%) 2
- Secondary osteoporosis 2
- Increased hospital length of stay 2
- Higher mortality rates (12.4% in patients with severe hyponatremia) 6
Complications of Severe Hyponatremia
- Hyponatremic encephalopathy
- Permanent neurological damage if left untreated 8
- Death in severe cases 2, 6
Warning Signs of Osmotic Demyelination Syndrome
This is a complication of overly rapid correction of chronic hyponatremia (>12 mEq/L/24 hours) 7:
- Dysarthria
- Mutism
- Dysphagia
- Lethargy
- Affective changes
- Spastic quadriparesis
- Seizures
- Parkinsonism
- Coma
- Death 1, 7, 2
Clinical Pearls
- Even mild chronic hyponatremia can cause cognitive impairment and increased fall risk 2
- Symptoms may be nonspecific in chronic cases, making diagnosis challenging 5
- Symptom severity correlates with both the absolute sodium level and the rapidity of development 2
- Patients with liver disease, alcoholism, or malnutrition are at higher risk for osmotic demyelination syndrome if sodium is corrected too rapidly 1
- Inflammation and IL-6 may play a role in non-osmotic ADH release, making hyponatremia a potential marker of inflammation 4
The recognition of these signs and symptoms is crucial for prompt diagnosis and appropriate management, as severe symptomatic hyponatremia represents a medical emergency requiring immediate intervention to prevent permanent neurological damage or death.