Lecture on Fluids and Electrolytes: Sodium

Importance of Sodium

• Sodium is a crucial electrolyte in the body.
• It is vital for the proper functioning of:
  • Muscles
  • Brain
  • Heart
  • Kidneys
• Sodium constitutes 90-95% of the osmolarity or concentration of the extracellular fluid (ECF).

Daily Sodium Requirements

• Adults generally require about 0.5 grams of sodium daily.
• The typical American diet contains high sodium levels, approximately 3-7 grams per day.

Regulation of Sodium

• Sodium levels are regulated by multiple mechanisms:
  • Aldosterone
    • Secreted by the adrenal gland.
    • Promotes sodium retention in kidneys.
    • Triggered by hormonal stimulation and low plasma sodium.
    • The renin-angiotensin system enhances aldosterone secretion due to low blood pressure.
  • Anti-Diuretic Hormone (ADH)
    • Affects sodium concentration but not the total amount in the body.
    • Secreted by the posterior pituitary gland in response to increased osmolarity or blood solute concentration.
    • Encourages water retention in kidneys, reducing plasma osmolarity.
  • Atrial Natriuretic Peptide (ANP)
    • Hormone secreted by the heart.
    • Responds to atrial stretch due to increased blood volume.
    • Inhibits sodium reabsorption in kidneys.

Sodium Imbalances

• Hypernatremia (High Sodium Concentration)
  • Plasma sodium concentration > 145 mEq/L.
  • Can result in:
    • Water retention
    • Hypertension
    • Edema
• Hyponatremia (Low Sodium Concentration)
  • Plasma sodium concentration < 135 mEq/L.
  • Can lead to:
    • Nausea and vomiting
    • Muscle problems
    • Seizures
    • Coma

Conclusion

• Sodium is essential for numerous bodily functions and is tightly regulated by several hormonal mechanisms.
• Imbalances can have significant health implications, such as hypertension or neurological symptoms.