Epidemiology of Hyponatremia
Section snippets
Hospital-Associated Hyponatremia
Hospitalized patients are exposed to a number of anti-aquaretic influences, such as medications, pain, severe nausea, and organ failure. These influences combined with the intake of electrolyte-free water in amounts exceeding the water excretory capacity can result in both generation and aggravation of hyponatremia. In their 1968 report, Owen and Campbell4 observed the mean serum sodium concentration of hospitalized patients to be 5 to 6 mEq/L lower than that of healthy outpatients. Subsequent
Ambulatory Care and Hyponatremia
Limited work has been performed on the epidemiology of hyponatremia in the outpatient setting. Hawkins,7 in his report from Singapore, showed the frequency of hyponatremia (serum sodium level of <136 mEq/L) on initial presentation to be 21% in hospital-based ambulatory clinics and 7% in community-based clinics. Only about 1% of patients in hospital-based ambulatory clinics and 0.2% of patients in community-based clinics had serum sodium values of 126 mEq/L or less on initial presentation. A
Geriatric Population and Hyponatremia
The geriatric population is susceptible to hyponatremia because of the aging-related impaired water-excretory capacity, and an increased exposure to drugs and diseases associated with hyponatremia. Even mild hyponatremia recently has been linked to falls, unsteadiness, fractures, and cognitive problems in the elderly, which can have important long-term consequences.19, 20 Approximately 7% of home-dwelling people aged 65 or older were noted to have serum sodium concentrations of 137 mEq/L or
Drug-Induced Hyponatremia
Drug-induced hyponatremia is a common problem. Medications cause hyponatremia by several mechanisms, including volume depletion, inappropriate AVP secretion, potentiation of AVP effect, and change in hypothalamic osmolality threshold.26 Thiazide diuretics, antidepressants, antipsychotics, anticonvulsants, anticancer drugs, methamphetamines, and nonsteroidal anti-inflammatory agents are some of the common classes of drugs known to be associated with hyponatremia.26 Most of the literature on
Exercise-Associated Hyponatremia
Exercise-associated hyponatremia increasingly is being recognized as a potentially serious complication of endurance sports.41 Consumption of hypotonic fluids in excess of insensible and renal fluid losses along with the inability to maximally suppress AVP secretion during the prolonged endurance activities are thought to be the main etiologic mechanisms responsible for this condition.41, 42 The incidence of hyponatremia (serum sodium level of ≤135 mEq/L) was 13% in a prospective analysis of
Medical Cost and Hyponatremia
The information on the impact of hyponatremia on health care resource consumption is limited. Boscoe et al52 examined the medical cost of hyponatremia using a publicly available database of hospital discharges, published reports, and opinions from a panel of expert physicians. They concluded that the direct annual medical cost of treating hyponatremia (serum sodium level of <130 mEq/L) in the United States ranges from $1.6 to $3.6 billion. About 70% of the total cost was attributed to
Hyponatremia in Selected Conditions
A number of clinical conditions, such as congestive heart failure (CHF), cirrhosis, pneumonia, human-immunodeficiency virus infection, childhood diarrhea, chronic obstructive pulmonary disease, myocardial infarction, malignancies, and several neurologic disorders are known to be associated with hyponatremia. We address the frequency and prognostic implications of hyponatremia in CHF, cirrhosis, pneumonia, and human-immunodeficiency virus infection.
Conclusions
Hyponatremia is a common electrolyte abnormality with important prognostic implications in clinical practice. However, considerable more work is required to address epidemiologic aspects of hyponatremia in various clinical conditions and settings. Although even mild degrees of hyponatremia are associated with adverse consequences, hyponatremia continues to remain a largely underdiagnosed condition. Two recent studies have revealed that the ICD coding system is highly insensitive in detecting
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Supported by grants from the National Institutes of Health (DK065102 and DK07775 to B.L.J.).
Dr Madias has served as a consultant to and has received lecture fees from Astellas Pharma US, Inc. (manufacturer of Vaprisol–Conivaptan hydrochloride injection), and has served as a consultant to Sanofi-Aventis (manufacturer of Satavaptan).