Hyponatremia - NYSORA

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Hyponatremia

Learning objectives

  • Defining, diagnosing, and managing hyponatremia

Definition

  • Hyponatremia is defined as: 
    • Mild: a serum sodium concentration between 130-135 mmol/l
    • Moderate: a serum sodium concentration between 125-129 mmol/l
    • Severe at a serum sodium concentration <125 mmol/l 
  • Hyponatremia is acute if it is documented to exist <48 hours and chronic if it is documented to exist for at least 48 hours
  • If unsure, consider chronic hyponatremia unless there is clinical or anamnestic evidence of the contrary

Signs and symptoms

  • Moderate symptoms
    • Nausea without vomiting
    • Confusion
    • Headache
  • Severe symptoms
    • Vomiting
    • Cardiorespiratory distress
    • Somnolence 
    • Seizures
    • Coma

Differential diagnosis

Hyponatremia, urine osmolality, urine sodium, diuretics, SIADH, adrenal insufficiency, hypothyroidism, diuretics, heart failure, liver cirrhosis, nephrotic syndrome

Management

Hyponatremia, hypertonic saline, SIAD, hypervolemic, hypovolemic

Suggested reading

  • Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia [published correction appears in Nephrol Dial Transplant. 2014 Jun;40(6):924]. Nephrol Dial Transplant. 2014;29 Suppl 2:i1-i39.
  • Hoorn EJ, Zietse R. Diagnosis and Treatment of Hyponatremia: Compilation of the Guidelines. J Am Soc Nephrol. 2017;28(5):1340-1349.

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