Hyponatremia in Older Adults: Diagnosis

21Jan

Hyponatremia, defined as serum sodium level less than 135mEq/L, is one of the most common electrolyte abnormalities seen in older adults. In one study, more than 50% of patients in acute geriatric wards were found to have hyponatremia. Chronic hyponatremia has been reported in 18% of nursing home residents.

TIPS ABOUT HYPONATREMIA IN OLDER ADULTS

Hyponatremia, one of the most common electrolyte abnormalities in older adults, is associated with falls, cognitive decline, osteoporosis, fractures, and increased hospital stays and mortality rates. Acute changes are associated with more severe symptoms; severe acute hyponatremia can cause cerebral edema and brainstem herniation.
Be sure to ask about whether the patient is taking medications associated with hyponatremia (see Table 1).
Key factors determining the cause of hyponatremia are a patient’s volume status (hypovolemia, euvolemia, or hypervolemia) and measurements of serum osmolality and urine osmolality (see algorithm).

Contents

1 Why is the Prevalence Increased in Older Adults?
2 Why is Hyponatremia Important?
3 What Causes Hyponatremia?
4 Author

Why is the Prevalence Increased in Older Adults?

A number of factors contribute to the high prevalence of hyponatremia in older adults (Table 1.)

Table 1. Factors Contributing to the Increased Prevalence of Hyponatremia in Older Adults

Decreased total body water content
Decreased urinary concentrating and diluting ability
Decreased aldosterone levels
Higher rates of dehydration and malnutrition
Increased levels of arginine vasopressin
Lower sensitivity of thirst mechanisms
Use of medications associated with hyponatremia (some common medications are listed here)
- Thiazide diuretics
- Selective serotonin reuptake inhibitors (SSRIs)
- Neuroleptics (antipsychotic drugs)
- Carbamazepine
- Amiodarone

Why is Hyponatremia Important?

Long-standing or slowly developing chronic hyponatremia may be asymptomatic but is associated with increased osteoclastic activity leading to bone demineralization and fractures. Symptoms of acute hyponatremia vary depending on the degree of hyponatremia and rapidity with which it develops (Table 2). Those with severe acute hyponatremia can develop cerebral edema. Less severe cases are associated with confusion, functional and cognitive decline, and gait disturbances that can lead to falls. Patients with hyponatremia also have increased mortality rates and longer hospitalizations.

Table 2. Common Clinical Manifestations of Acute Hyponatremia
Mild (Sodium Level 130-134 mEq/L)	Moderate (Sodium Level 125-129 mEq/L)	Severe (Sodium Level <125 mEq/L)
Anorexia Cramping Nausea Vomiting Headache Irritability	Disorientation Confusion Weakness Lethargy	Seizures Coma Respiratory arrest Brainstem herniation Permanent brain damage

What Causes Hyponatremia?

Depending on a patient’s volume status, hyponatremia is classified hypovolemic (low fluid volume status), euvolemic (normal volume status) or hypervolemic (increased volume status). Common causes of each of these forms of hyponatremia are shown in Table 3, but in older adults, the cause is often multifactorial. The algorithm and the items in Table 4 show the general approach to identifying the cause.

Table 3. Common Causes of Hyponatremia
Hypovolemic	Euvolemic	Hypervolemic
Inadequate fluid intake or replacement Diarrhea Vomiting Renal salt wasting Burns, with skin loss of fluid Mineralocorticoid deficiency	Syndrome of inappropriate anti-diuretic hormone secretion Medications Hypothyroidism Fluid loss with inappropriate salt replacement Glucocorticoid deficiency	Cardiac failure Nephrotic syndrome Chronic kidney disease Acute kidney injury Cirrhosis

Table 4. Components of the History and Physical in Older Adults with Hyponatremia to Aid in Identifying the Cause
Review Hospital Records	Use of hypotonic fluids, medications, surgical history, pain assessment, recent interventions (transurethral resection of prostate, use of hypertonic fluids)
Medical History	Vomiting, diarrhea, heart failure, pulmonary disease, liver disease, renal failure, thyroid, neurological disorders, falls, cognitive impairment, adrenal disorders
Medication Use	Diuretics, SSRIs, neuroleptics (anti-psychotics), carbamazepine, and amiodarone are common causes. But, check prescribing information for all medication a patient is taking to determine potential to cause hyponatremia.
Social History	Living conditions, diet, alcohol
Psychiatric History	Abnormal water intake
Assessment of Volume Status	Signs of hypervolemia = peripheral edema, pulmonary rales Signs of hypovolemia = orthostatic hypotension, tachycardia, dry axillae

References and Resources

Al Zahrani, Sinnerty R, Gernsheimer J. . Acute kidney Injury, sodium disorders, and hypercalcemia in the aging kidney: diagnostic and therapeutic management strategies in emergency medicine Clin Geriatr Med, 2013; 29:275-319.
Choudhury D, Levi M. Aging and Kidney Disease. In: Skorecki K, Chertow GM, et al . Eds. Brenner and Rector’s The Kidney, 24, 727-751. 2
Murugapandian S, Thajudeen B. Hyponatremia in Older Adults – Therapeutic Considerations. Elder Care, 2017.
Soiza RL, Cumming K, Clarke JM, Wood KM, Myint PK. Hyponatremia: special considerations in older patients. J Clin Med. 2014;3(3):944-958.

National Editorial Board: Theodore M Johnson II, MD, MPH, Emory University; Jenny Jordan, PT, DPT, Sacred Heart Hospital, Spokane, WA; Jane Marks, RN, MS, FNGNA, Johns Hopkins University; Josette Rivera, MD, University of California San Francisco; Jean Yudin, CRNP, University of Pennsylvania

Interprofessional Associate Editors: Carleigh High, PT, DPT; David Coon, PhD; Marilyn Gilbert, MS, CHES; Jeannie Lee, PharmD, BCPS; Marisa Menchola, PhD; Francisco Moreno, MD; Linnea Nagel, PA-C, MPAS; Lisa O’Neill, DBH, MPH; Floribella Redondo; Laura Vitkus, MPH, CHES

Author

Melissa Ford

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