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Introduction ⬇

Sodium (Na+) Level

A sodium level measures the amount of sodium in the blood. Sodium levels are measured in order to determine acid–base balance and fluid balance (water intoxication and dehydration).

Sodium is the most abundant cation (90% of the electrolyte fluid) and, as such, plays an important role in maintaining osmotic pressure and acid–base balance. Mechanisms for maintaining a constant sodium level in the plasma and extracellular fluid include renal blood flow, carbonic anhydrase enzyme activity, aldosterone, action of other steroids whose plasma level is controlled by the anterior pituitary gland, renin enzyme secretion, antidiuretic hormone (ADH), and vasopressin secretion.

Procedure ⬆ ⬇

  1. Obtain a 5-mL venous blood sample in an SST or red-topped tube. Heparinized blood can be used. Avoid hemolysis. Centrifuge for red-topped tube only and transfer serum to a plastic transport tube.

  2. Observe standard precautions.

Clinical Implications ⬆ ⬇

  1. Hyponatremia reflects a relative excess of body water rather than low total-body sodium and is associated with the following conditions:

    1. Severe burns

    2. Heart failure (predictor of cardiac mortality)

    3. Excessive fluid loss (e.g., severe diarrhea, vomiting, sweating)

    4. Excessive IV induction of nonelectrolyte fluids (e.g., glucose)

    5. Addison disease (impairs sodium reabsorption)

    6. Severe nephritis (nephrotic syndrome)

    7. Pyloric obstruction

    8. Malabsorption syndrome

    9. Diabetic acidosis

    10. Drugs such as diuretics

    11. Edema (dilutional hyponatremia)

    12. Large amounts of water by mouth (water intoxication)

    13. Stomach suction accompanied by water or ice chips by mouth

    14. Hypothyroidism

    15. Excessive ADH production; also known as vasopressin, ADH is secreted from the posterior pituitary gland

  2. Hypernatremia is uncommon, but when it does occur, it is associated with the following conditions:

    1. Dehydration and insufficient water intake

    2. Primary aldosteronism (Conn syndrome)

    3. Coma

    4. Cushing disease

    5. DI

    6. Tracheobronchitis

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedure.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Monitor for fluid and sodium imbalances.

  2. Remember that IV therapy considerations are as follows:

    1. Sodium balance is maintained in adults with an average dietary intake of 90–250 mEq/d (90–250 mmol/d). The maximal daily tolerance to an acute load is 400 mEq/d (400 mmol/d). A patient who is given 3 L of isotonic saline in 24 hours will receive 465 mEq (465 mmol) of sodium. This amount exceeds the average, healthy adult’s tolerance level. It will take a healthy person 24–48 hours to excrete the excess sodium.

    2. After surgery, trauma, or shock, there is a decrease in extracellular fluid volume. Replacement of extracellular fluid is essential if water and electrolyte balance is to be maintained. The ideal replacement IV solution should have a sodium concentration of 140 mEq/L (140 mmol/L).

  3. Monitor for signs of edema or hypertension and record and report these if present.

  4. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆ ⬇

  1. Many drugs affect levels of blood sodium.

    1. Anabolic steroids, corticosteroids, calcium, fluorides, and iron can cause increases in sodium level.

    2. Heparin, laxatives, sulfates, and diuretics can cause decreases in sodium level.

  2. High triglycerides or low protein causes artificially low sodium values.

Reference Values ⬆

Normal

Clinical Alert

Critical Values

  1. Hyponatremia (low Na+ level):

    1. <125 mEq/L (<125 mmol/L) causes weakness and dehydration.

    2. 90–105 mEq/L (90–105 mmol/L) causes severe neurologic symptoms and vascular problems.

  2. Hypernatremia (high Na+ level):

    1. >152 mEq/L (>152 mmol/L) results in cardiovascular and kidney symptoms.

    2. >160 mEq/L (>160 mmol/L) can cause heart failure.