- Sodium is the most abundant cation and the chief base of the blood.
- Its primary functions in the body are to maintain osmotic pressure and acid-base balance chemically and to transmit nerve impulses.
- Mechanisms for maintaining a constant sodium level in the plasma and extracellular fluid include renal blood flow, carbonic anhydrase enzyme activity, aldosterone, and action of other steroids.
- Determinations of serum sodium balance detect changes in water balance rather than sodium balance.
- Sodium levels are used to determine electrolytes, acid-base balance, water balance, water intoxication and dehydration.
- Infants: 133 – 142 mEq/L
- Children (1 – 16 years old): 136 – 145 mEq/L
- Adults: 136 – 145 mEq/L
- This is done by obtaining 5 mL of venous blood serum sample.
- Heparinized blood can be used.
- Avoid hemolysis.
- Increased sodium / hypernatremia:
- dehydration and insufficient water intake
- Conn’s syndrome
- primary aldosteronism
- Cushing’s disease
- diabetes insipidus
- Decreased sodium / hyponatremia:
- severe burns
- congestive heart failure
- excessive fluid loss such as severe diarrhea, vomiting
- excessive IV induction of nonelectrolyte fluids such as glucose
- Addison’s disease
- severe nephritis
- pyloric obstruction
- malabsorption syndrome
- diabetic acidosis
- drugs such as diuretics
- large amounts of water per orem
- excessive ADH production
- Anabolic steroids, corticosteroids, calcium, fluorides, and iron can increase sodium levels.
- Heparin, laxatives, sulfates and diuretics can cause decreases in sodium levels.
- High triglycerides or low protein can cause artificially low sodium values.
Decreased serum sodium
- Assess for signs and symptoms of hyponatremia. (apprehension, anxiety, muscular, twitching, muscular weakness, headaches, tachycardia and hypotension)
- Be knowledgeable that hyponatremia after surgery is the result of SIADH. There is an increased reabsorption from the kidney and sodium dilution between one to two days before the surgery.
- Take vital signs to determine cardiac status during hyponatremia.
Increased serum sodium
- Check for signs and symptoms of hypernatremia. (restlessness, thirst, flushed skin, sticky mucous membrane, a rough dry tongue and tachycardia)
- Keep an accurate record of input and output of fluids.
- Observe for signs of edema and overhydration resulting from an elevated serum sodium level.