hyponatremia
HYPONATREMIA

Hyponatremia is serum sodium concentration <135 mEq/L due to failure of normal water excretion.

Most common causes are medication effects, fluid retention and syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Volume status should be assessed to help determine the underlying cause.

Commonly, patients with hyponatremia are asymptomatic and it is only an incidental finding.

 

Hyponatremia Signs and Symptoms

Definition

  • Serum sodium concentration <135 mEq/L due to failure of normal water excretion
    • Severe hyponatremia is when there is <120 mEq/L serum sodium concentration

Etiology

  • Most common causes are medication effects, fluid retention and syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Signs and Symptoms

  • Commonly, patients with hyponatremia are asymptomatic and it is only an incidental finding
  • Gradual decrease in sodium usually shows minimal symptoms whereas rapid decreases manifest severe symptoms
    • Severe symptoms are due to brain edema and increased intracranial pressure
  • Mild to moderate symptoms that are relatively nonspecific and occur most commonly in patients with severe chronic hyponatremia are the following:
    • Headache
    • Fatigue
    • Lethargy
    • Nausea and vomiting
    • Dizziness
    • Gait disturbances
    • Forgetfulness
    • Confusion
    • Muscle cramps
  • Severe symptoms include seizures, obtundation, coma and respiratory arrest
  • Acute intervention is needed if the following symptoms occur:
    • Polydipsia
    • Muscle cramps
    • Headaches
    • Falls
    • Confusion
    • Altered mental status
    • Obtundation
    • Coma
    • Status epilepticus

Epidemiology

  • Hyponatremia is the most common body fluid disorder and electrolyte imbalance encountered in clinical practice
    • Accounts for 15-30% of emergency admissions in hospital and associated with increased morbidity, mortality and length of hospital stay in patients presenting with a range of conditions
    • Increases risk of falls and osteoporosis and in severe cases it can be associated with mental state changes, including risk of coma and seizures

Pathophysiology

  • Osmolality (total concentration of solutes in water) of plasma plays a role in the pathophysiology of hyponatremia
  • Arginine vasopressin [antidiuretic hormone (ADH)] system and thirst strict regulation help maintain plasma osmolality
  • Increase in plasma osmolality leads to ADH secretion and water retention which decreases serum osmolality
  • Decrease in plasma osmolality decreases ADH that will result in diuresis of free water and a return to homeostasis
  • Hyponatremia is a disorder of water imbalance where there is a relative excess of body water compared to total body sodium and potassium content due to impaired renal water excretion
    • Usually associated with disturbance in the ADH that governs water balance
Digital Edition
Asia's trusted medical magazine for healthcare professionals. Get your MIMS Endocrinology - Malaysia digital copy today!
Sign In To Download
Editor's Recommendations
Most Read Articles
11 May 2020
This second issue revisits the impact EMPA-REG OUTCOME had on clinical practice and helps readers discover how it gives life back to patients through its cardiovascular indication. Learn how it was approved and the possible mechanisms for its cardiovascular benefits.
Stephen Padilla, 22 Jul 2019
Zinc supplementation significantly lowers key glycaemic indicators, particularly fasting glucose (FG) in individuals with diabetes and in those who received an inorganic supplement, results of a systematic review and meta-analysis have shown.
Elaine Soliven, 15 Oct 2020

Higher levels of exercise appear to be associated with a lower risk of all-cause mortality in adults with type 2 diabetes (T2D) compared with no exercise at all, according to a study presented at EASD 2020.

Elvira Manzano, 07 Oct 2020
Exendin-4 imaging targeting GLP-1* receptor (GLP-1R) ably detects residual, dysfunctional pancreatic beta cells in individuals with long-standing type 1 diabetes (T1D), according to a study presented at EASD 2020. This breakthrough brings research closer to the possibility of restoring insulin-producing cells depleted in T1D.