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.
Normal Values
Infants: 133 – 142 mEq/L
Children (1 – 16 years old): 136 – 145 mEq/L
Adults: 136 – 145 mEq/L
Procedure
This is done by obtaining 5 mL of venous blood serum sample.
Heparinized blood can be used.
Avoid hemolysis.
Clinical Implications
Increased sodium / hypernatremia:
dehydration and insufficient water intake
Conn’s syndrome
primary aldosteronism
coma
Cushing’s disease
diabetes insipidus
tracheobronchitis
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
edema
large amounts of water per orem
hypothyroidism
excessive ADH production
Interfering Factors
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.