Hyponatremia

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Última revisão: 17 Jul 2025

Última atualização: 28 Feb 2024

Hyponatremia is the most common electrolyte disorder encountered in clinical practice.

Can occur in settings of volume depletion, volume overload, or euvolemia.

Serum osmolality, urine osmolality, and urine sodium concentration help to determine the underlying cause.

Cerebral edema is a medical emergency and occurs more frequently when hyponatremia develops over <48 hours. Patients should be treated promptly with hypertonic 3% saline.

Other treatment depends on the underlying cause and may include fluid restriction and stopping causative medications.

Overly rapid correction of serum sodium concentration can lead to the life-threatening complication of myelinolysis and should be avoided.

Definição

Hyponatremia is defined as a serum sodium concentration of <135 mEq/L (normal serum sodium concentration is in the range of 135-145 mEq/L).[1] It is a disorder of water balance reflected by an excess of total body water relative to electrolytes (total body sodium and potassium) leading to low plasma osmolality (i.e., <275 mOsm/kg).[2] Hyponatremia is generally caused by an increase in renal water reabsorption due to release of vasopressin (arginine vasopressin also known as antidiuretic hormone) along with water intake, and can occur in situations of volume depletion, volume overload, or normal volume. It should be noted that loss of sodium is minor compared with gains in water in most types of hyponatremia.

This topic principally focuses on hypotonic (hypo-osmolar) hyponatremia, the most common type of hyponatremia.

História e exame físico

Principais fatores diagnósticos

high fluid intake
fluid losses
history of diabetes mellitus
history of cirrhosis, nephrosis, congestive heart failure
nausea/vomiting
mild cognitive symptoms
altered mental status, seizures, coma
low urine output
weight changes
orthostatic hypotension
abnormal jugular venous pressure
poor skin turgor
dry mucus membranes
absence of axillary sweat
edema
rales or crackles on lung auscultation
polyuria

Detalhes completos

Outros fatores diagnósticos

history of hyperlipidemia or paraproteinemia

Detalhes completos

Fatores de risco

older age
hospitalization
selective serotonin-reuptake inhibitor (SSRI) use
thiazide diuretic use
underlying medical conditions
severe hypothyroidism
adrenal insufficiency
malignancy
use of other medications
MDMA (ecstasy) use

Detalhes completos

Investigações diagnósticas

Primeiras investigações a serem solicitadas

serum sodium concentration
serum electrolytes, BUN, creatinine, and glucose
serum osmolality
urine sodium concentration
urine osmolality
urine electrolytes
urine flow rate
electrolyte-free water excretion
fractional excretion of sodium
thyroid-stimulating hormone
serum cortisol level and/or adrenocorticotropic hormone test
serum lipids and serum protein electrophoresis

Detalhes completos

Investigações a serem consideradas

CT brain, chest, abdomen/pelvis
other tests targeted at evaluating the underlying cause

Detalhes completos

Algoritmo de tratamento

AGUDA

acute onset (<48 hours) and/or symptomatic

CONTÍNUA

chronic onset (≥48 hours) or asymptomatic

overcorrection of serum sodium concentration

Colaboradores

Autores

Judith H. Veis, MD

Section Director

Nephrology

MedStar Washington Hospital Center

Washington

Declarações

JHV declares that she has no competing interests.

Revisores

Gregor Lindner, MD

Director

Department of Internal & Emergency Medicine

Hirslanden Klinik Im Park

Zurich

Switzerland

Declarações

GL is an author of a number of references cited in this topic.

Michael E. Ullian, MD

Professor of Medicine

Division of Nephrology

Department of Medicine

Medical University of South Carolina

Charleston

Declarações

MEU declares that he has no competing interests.

Referências

Nossas equipes internas de editoria e de evidências trabalham em conjunto com colaboradores internacionais especializados e pares revisores para garantir que forneçamos acesso às informações o mais clinicamente relevantes possível.

Principais artigos

Spasovski G, Vanholder R, Allolio B, et al; Hyponatraemia Guideline Development Group. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Eur J Endocrinol. 2014 Feb 25;170(3):G1-47.Texto completo Resumo

Adrogué HJ, Tucker BM, Madias NE. Diagnosis and management of hyponatremia: a review. JAMA. 2022 Jul 19;328(3):280-91. Resumo

Verbalis JG, Grossman A, Höybye C, et al. Review and analysis of differing regulatory indications and expert panel guidelines for the treatment of hyponatremia. Curr Med Res Opin. 2014 Jul;30(7):1201-7. Resumo

Hoorn EJ, Zietse R. Diagnosis and treatment of hyponatremia: compilation of the guidelines. J Am Soc Nephrol. 2017 May;28(5):1340-9.Texto completo Resumo

Artigos de referência

Uma lista completa das fontes referenciadas neste tópico está disponível para os usuários com acesso total ao BMJ Best Practice.

Diagnósticos diferenciais
- Hypertonic hyponatremia
- Pseudohyponatremia
- Evaluation of hyponatremia
Mais Diagnósticos diferenciais
Diretrizes
- Clinical practice guidelines for the management of exercise-associated hyponatremia: 2019 update
- Clinical practice guidelines for the management of exercise-associated hyponatremia: 2019 update
Mais Diretrizes
Folhetos informativos para os pacientes
Hyponatremia (low blood sodium)
Mais Folhetos informativos para os pacientes
Calculadoras
Sodium Correction in Hyperglycemia (Hillier 1999)
Osmolality Estimator (serum)
Mais Calculadoras
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Hyponatremia

Resumo

Definição

História e exame físico

Principais fatores diagnósticos

Outros fatores diagnósticos

Fatores de risco

Investigações diagnósticas

Primeiras investigações a serem solicitadas

Investigações a serem consideradas

Algoritmo de tratamento

acute onset (<48 hours) and/or symptomatic

chronic onset (≥48 hours) or asymptomatic

overcorrection of serum sodium concentration

Colaboradores

Autores

Judith H. Veis, MD

Declarações

Revisores

Gregor Lindner, MD

Declarações

Michael E. Ullian, MD

Declarações

Referências

Principais artigos

Artigos de referência

Uma lista completa das fontes referenciadas neste tópico está disponível para os usuários com acesso total ao BMJ Best Practice.

Diagnósticos diferenciais

Diretrizes

Folhetos informativos para os pacientes

Calculadoras

Conectar-se ou assinar para acessar todo o BMJ Best Practice

Conectar-se ou assinar para acessar todo o BMJ Best Practice

Conectar-se para acessar todo o BMJ Best Practice