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Introduction ⬇

Sodium is a primary regulator for retaining or excreting water and maintaining acid–base balance. The body has a strong tendency to maintain a total base content; on a relative scale, only small shifts are found even under pathologic conditions. As the predominant base substance in the blood, sodium helps to regulate acid–base balance because of its ability to combine with chloride and bicarbonate. Sodium also promotes the normal balance of electrolytes in the intracellular and extracellular fluids by acting in conjunction with potassium under the effect of aldosterone. This hormone promotes the 1:1 exchange of sodium for potassium or the hydrogen ion.

This test measures one aspect of electrolyte balance by determining the amount of sodium excreted in a 24-hour period. It is done for diagnosis of kidney, adrenal, water, and acid–base imbalances.

Normal Findings ⬆ ⬇

Adult: 40–220 mEq/24 hr or 40–220 mmol/d

Child: 41–115 mEq/24 hr or 41–115 mmol/d

Values are diet dependent.

Procedure ⬆ ⬇

  1. Properly label a 24-hour urine container with the patient’s name, date and time of collection, and test(s) ordered.

  2. The urine container must be refrigerated or kept on ice.

  3. Follow general instructions for 24-hour urine collections (see Long-Term, Timed Urine Specimen [2-Hour, 24-Hour]).

  4. Record exact starting and ending times on the specimen container and in the patient’s healthcare record.

  5. Transfer the specimen to the laboratory for proper storage when the test is completed.

Clinical Implications ⬆ ⬇

  1. Increased urine sodium occurs in:

    1. Adrenal failure (Addison disease) (primary and secondary)

    2. Salt-losing nephritis

    3. Renal tubular acidosis

    4. SIADH

    5. Diabetic acidosis

    6. Aldosterone defect (AIDS-related hypoadrenalism)

    7. Tubulointerstitial disease

    8. Bartter syndrome

  2. Decreased urine sodium occurs in:

    1. Excessive sweating, diarrhea

    2. Heart failure

    3. Adrenocortical hyperfunction

    4. Nephrotic syndromes with acute oliguria

    5. Prerenal azotemia

    6. Cushing disease

    7. Primary aldosteronism

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain purpose of test, procedure for urine collection (including the need to refrigerate or place specimen on ice), and interfering factors. Written instructions can be helpful.

  2. Encourage food and fluids.

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

Clinical Alert

Because electrolytes and water balance are so closely related, determine the patient’s state of hydration by checking and recording daily weights, accurate intake and output of fluids, and observations about skin turgor, the appearance of the tongue and mucous membranes, and the appearance of the urine

Posttest Patient Care

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

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

Interfering Factors ⬆

  1. Increased sodium levels are associated with caffeine intake, diuretic therapy, dehydration, dopamine, postmenstrual diuresis, increased sodium intake, and vomiting (see Appendix E).

  2. Decreased sodium levels are associated with intake of corticosteroids and propranolol, low sodium intake, premenstrual water retention, overhydration, and stress diuresis (see Appendix E).