Other causes, such as SIADH and endocrine deficiencies, usually require further evaluation before identification and appropriate treatment. The initial rate of sodium correction with hypertonic saline should not exceed 1 to 2 mmol per L per hour. Overzealous correction of chronic hyponatremia can lead to central pontine myelinolysis. Demeclocycline Declomycin in a dosage of to 1, mg daily is effective in patients with refractory hyponatremia.
Arginine vasopressin receptor antagonists may be useful in patients with chronic hyponatremia. Already a member or subscriber? Log in. Interested in AAFP membership? Learn more. Address correspondence to Kian Peng Goh, M. Reprints are not available from the author. The author indicates that he does not have any conflicts of interest. Sources of funding: none reported. The author thanks Evelyn Koay, S.
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Hypervolemic hyponatremia is characterized by an increase in both total body sodium and thus ECF volume and total body water with a relatively greater increase in TBW. Cirrhosis is characterized by regenerative nodules surrounded by dense It is more common among children and has both primary and secondary In each of these disorders, a decrease in effective circulating volume results in the release of vasopressin and angiotensin II.
The following factors contribute to hyponatremia:. The antidiuretic effect of vasopressin on the kidneys. The syndrome of inappropriate ADH vasopressin secretion is attributed to excessive vasopressin release. It is defined as less-than-maximally-dilute urine in the presence of plasma hypo-osmolality hyponatremia without volume depletion or overload, emotional stress, pain, diuretics, or other drugs that stimulate vasopressin secretion eg, chlorpropamide , carbamazepine , vincristine , clofibrate, antipsychotic drugs, aspirin , ibuprofen in patients with normal cardiac, hepatic, renal, adrenal, and thyroid function.
Among the many potential contributing factors are. Nonosmotic vasopressin release due to intravascular volume depletion. In addition, adrenal insufficiency has become increasingly common among AIDS patients as the result of cytomegalovirus adrenalitis, mycobacterial infection, or interference with adrenal glucocorticoid and mineralocorticoid synthesis by ketoconazole.
SIADH may be present because of coexistent pulmonary or central nervous system infections. Hyponatremia frequently occurs in patients with brain pathology, including concussion, intracranial hemorrhage, encephalitis, meningitis, and CNS tumors. However, cerebral salt wasting has been recognized by some as a separate entity affecting a small group of these patients, especially those with subarachnoid hemorrhage Subarachnoid Hemorrhage SAH Subarachnoid hemorrhage is sudden bleeding into the subarachnoid space.
The most common cause of spontaneous bleeding is a ruptured aneurysm. Symptoms include sudden, severe headache, usually Cerebral salt wasting is thought to be due to either decreased sympathetic nervous system function or secretion of a circulating factor that decreases renal sodium reabsorption. Symptoms mainly involve central nervous system dysfunction. However, when hyponatremia is accompanied by disturbances in total body sodium content, signs of ECF volume depletion Volume Depletion Volume depletion, or extracellular fluid ECF volume contraction, occurs as a result of loss of total body sodium.
ECF volume expansion typically occurs in heart failure, kidney failure, nephrotic syndrome, and cirrhosis In general, older chronically ill patients with hyponatremia develop more symptoms than younger otherwise healthy patients.
Symptoms are also more severe with faster-onset hyponatremia. Sequelae include hypothalamic and posterior pituitary infarction and occasionally osmotic demyelination syndrome or brain stem herniation. Hyponatremia is occasionally suspected in patients who have neurologic abnormalities and are at risk. However, because findings are nonspecific, hyponatremia is often recognized only after serum electrolyte measurement. Serum sodium may be low when severe hyperglycemia or exogenously administered mannitol or glycerol increases osmolality and water moves out of cells into the ECF.
Serum sodium concentration falls about 1. This condition is often called translocational hyponatremia because it is caused by translocation of water across cell membranes. Pseudohyponatremia with normal serum osmolality may occur in severe hyperlipidemia Dyslipidemia Dyslipidemia is elevation of plasma cholesterol, triglycerides TGs , or both, or a low high-density lipoprotein cholesterol level that contributes to the development of atherosclerosis.
Autoanalyzers in many clinical laboratories are affected by this artifact. Methods of measuring serum electrolytes with direct ion-selective electrodes circumvent this problem. Such direct ion-selective electrodes are available in some hospital laboratories by special request, but are also used by most point-of-care bedside analyzers.
These analyzers can be used to exclude pseudohyponatremia. Formulas exist to estimate the effect these abnormalities have on sodium measurement. Identifying the cause of hyponatremia can be complex. The history sometimes suggests a cause eg, significant fluid loss due to vomiting or diarrhea, renal disease, compulsive fluid ingestion, intake of drugs that stimulate vasopressin release or enhance vasopressin action.
The volume status, particularly the presence of obvious volume depletion or volume overload, suggests certain causes see table Common Causes of Volume Depletion Common Causes of Volume Depletion Volume depletion, or extracellular fluid ECF volume contraction, occurs as a result of loss of total body sodium.
Overtly hypovolemic patients usually have an obvious source of fluid loss and typically have been treated with hypotonic fluid replacement. Overtly hypervolemic patients usually have a readily recognizable condition, such as heart failure or hepatic or renal disease. Euvolemic patients and patients with equivocal volume status require more laboratory testing to identify a cause. Laboratory tests should include serum and urine osmolality and electrolytes.
Euvolemic patients should also have thyroid and adrenal function tested. BUN blood urea nitrogen and creatinine values are normal, and serum uric acid is generally low.
Findings can be local eg, reflecting kidney inflammation or mass , result Hyperkalemia suggests adrenal insufficiency. When hypervolemic, fluid restriction, sometimes a diuretic, occasionally a vasopressin antagonist. Hyponatremia can be life threatening and requires prompt recognition and proper treatment. And, except during the first few hours of treatment of severe hyponatremia, sodium should be corrected no faster than 0. The degree of hyponatremia, the duration and rate of onset , and the patient's symptoms are used to determine which treatment is most appropriate.
In patients with hypovolemia and normal adrenal function, administration of 0. In hypervolemic patients, in whom hyponatremia is due to renal sodium retention eg, heart failure Heart Failure HF Heart failure HF is a syndrome of ventricular dysfunction. In patients with heart failure, an angiotensin-converting enzyme inhibitor, in conjunction with a loop diuretic, can correct refractory hyponatremia.
In other patients in whom simple fluid restriction is ineffective, a loop diuretic in escalating doses can be used, sometimes in conjunction with IV 0. Potassium and other electrolytes lost in the urine must be replaced. When hyponatremia is more severe and unresponsive to diuretics, intermittent or continuous hemofiltration Continuous Hemofiltration and Hemodialysis Continuous hemofiltration and hemodialysis procedures filter and dialyze blood without interruption.
See Overview of Renal Replacement Therapy for other renal replacement therapies. The principal Severe or resistant hyponatremia generally occurs only when heart or liver disease is near end-stage. In euvolemia, treatment is directed at the cause eg, hypothyroidism, adrenal insufficiency, diuretic use. Additionally, a loop diuretic may be combined with IV 0. Lasting correction depends on successful treatment of the underlying disorder.
When the underlying disorder is not correctable, as in metastatic cancer, and patients find severe water restriction unacceptable, demeclocycline to mg orally every 12 hours may be helpful by inducing a concentrating defect in the kidneys. However, demeclocycline is not widely used due to the possibility of drug-induced acute kidney injury Acute Kidney Injury AKI Acute kidney injury is a rapid decrease in renal function over days to weeks, causing an accumulation of nitrogenous products in the blood azotemia with or without reduction in amount of urine IV conivaptan , a vasopressin receptor antagonist, causes effective water diuresis without significant loss of electrolytes in the urine and can be used in hospitalized patients for treatment of resistant hyponatremia.
Oral tolvaptan is another vasopressin receptor antagonist with similar action to conivaptan. N Engl J Med ; 23 Copeptin in the diagnosis of vasopressin-dependent disorders of fluid homeostasis. Nat Rev Endocrinol ;12 3 Moderate hyponatremia is associated with increased risk of mortality: evidence from a meta-analysis. PLoS One ;8 12 :e Hyponatremia improvement is associated with a reduced risk of mortality: evidence from a meta-analysis. PLoS One ;10 4 :e Hyponatremia, falls and bone fractures: A systematic review and meta-analysis.
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A syndrome of renal sodium loss and hyponatremia probably resulting from inappropriate secretion of antidiuretic hormone.
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Am J Nephrol ;27 5 Contributors Authors. See Profile. Caitlin Clark MD Dr. Clark of Duke University has no relevant financial relationships to disclose. Heredity X-linked. Population groups selectively affected none selectively affected. Occupation groups selectively affected none selectively affected.
ICD Hypo-osmolality and hyponatremia: E This is an article preview. Start a Free Account to access the full version. Questions or Comment? Related Content. Associated Disorders. Acute asthmatic exacerbation Acute intermittent porphyria Adenocarcinoma of pancreas, duodenum, prostate Adult respiratory distress syndrome Brain abscesses Brain tumors Cerebral trauma Cystic fibrosis Diabetic insipidus Ewing sarcoma Guillain-Barre syndrome Hyponatremia Hypoosmolality Intracranial hemorrhage Lymphoma Meningitis Mesothelioma Pneumonitides Pneumothorax Postoperative state Pseudohyponatremia Psychogenic polydipsia Pulmonary abscess Small cell lung carcinoma Thymoma Tuberculosis.
Differential Diagnosis.
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