Causes of Hyponatremia in the Elderly
Hyponatremia in elderly patients is primarily caused by medications, syndrome of inappropriate antidiuretic hormone secretion (SIADH), and age-related physiological changes that impair water homeostasis. 1 Understanding these causes is essential for proper management and prevention of associated morbidity and mortality.
Common Causes of Hyponatremia in the Elderly
Physiological Changes
- Reduced thirst perception and impaired urine concentration by the kidney increase dehydration risk in older adults 2
- Decreased total body water and more vulnerable water homeostasis lead to tendency for both hypo- and hypervolemia 2
- Age-related changes result in a shift toward increased extracellular and decreased intracellular water 2
Medication-Related Causes
- Diuretics (especially thiazides) are among the most common causes of hyponatremia in elderly patients 1
- Antidepressants frequently contribute to hyponatremia in the geriatric population 1
- Calcium channel blockers, though not traditionally associated with hyponatremia, can cause severe hyponatremia in elderly patients 3
- ACE inhibitors and other cardiovascular medications may require dosage adjustments in elderly patients due to altered pharmacokinetics 2
Disease States and Clinical Conditions
- Congestive heart failure contributes to hypervolemic hyponatremia in elderly patients 4
- Renal failure affects sodium balance and can lead to decreased renal gluconeogenesis, contributing to hyponatremia 2
- Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of euvolemic hyponatremia in the elderly 1
- Endocrinopathies must be excluded before diagnosing SIADH in elderly patients 1
- Malnutrition and the "tea and toast" syndrome (poor nutritional intake with excessive water consumption) contribute to hyponatremia 1
Classification of Hyponatremia in the Elderly
Based on Volume Status
- Hypovolemic hyponatremia: Caused by gastrointestinal losses, severe burns, and inadequate fluid intake 4
- Euvolemic hyponatremia: Often caused by SIADH, medications, endocrine disorders, and reset osmostat syndrome 4
- Hypervolemic hyponatremia: Associated with heart failure, liver cirrhosis, and renal disease 4
Clinical Implications and Complications
- Even mild hyponatremia is associated with increased hospital stay and mortality 5
- Chronic hyponatremia in elderly patients is linked to cognitive impairment, gait disturbances, and increased risk of falls and fractures 5
- Elderly patients with hyponatremia have higher rates of new fractures over time compared to those with normal sodium levels 5
- Hyponatremia is considered a secondary cause of osteoporosis 5
- Severe hyponatremia can lead to neurological symptoms including confusion, seizures, and coma 5
Special Considerations in the Elderly
- Hypoglycemia risk is increased in elderly patients with hyponatremia, especially those with renal failure, sepsis, and low albumin levels 2
- Orthostatic hypotension frequently coexists with hyponatremia in elderly patients, particularly those on diuretics 2
- Confusion and delirium are more common during somatic illness in geriatric patients with electrolyte disturbances 2
- Refeeding syndrome can cause severe electrolyte abnormalities including hyponatremia in malnourished elderly patients 2
- Hyponatremia is often multifactorial in the elderly population, requiring a comprehensive diagnostic approach 1
Diagnostic Approach
- Measurement of plasma osmolality helps differentiate between different types of hyponatremia 4
- Urinary sodium concentration is a useful diagnostic tool in patients with low plasma osmolality 4
- Careful medication review is essential as many commonly prescribed medications in the elderly can cause hyponatremia 3
- Special attention should be given to excluding endocrinopathies before establishing a diagnosis of SIADH 1
Recognizing these various causes of hyponatremia in the elderly is crucial for appropriate management and prevention of complications. The multifactorial nature of hyponatremia in this population requires careful clinical evaluation and targeted interventions.