In normal individuals, increased serum sodium levels and blood volume suppress aldosterone secretion. In primary aldosteronism, however, this response is not seen. Serum sodium levels may be elevated through ingestion of a high-sodium diet for approximately 4 days or by infusing 2 L of normal saline intravenously. If appropriate control of aldosterone levels is managed through negative feedback systems and the renin-angiotensin system, plasma aldosterone levels will be low normal or decreased in response to the increased sodium load. Fludrocortisone acetate (Florinef), a synthetic mineralocorticoid, produces the same effect after 3 days of administration. Aldosterone challenges are used to differentiate between primary and secondary hyperaldosteronism.⁵⁴

• Upright body posture (see "Nursing Care Before the Procedure" section), stress, and late pregnancy may lead to increased levels.
• Therapy with diuretics, hydralazine (Apresoline), diazoxide (Hyperstat), and nitroprusside may lead to elevated levels.
• Excessive licorice ingestion may produce decreased levels, as may therapy with propranolol and fludrocortisone (Florinef).
• Altered serum electrolyte levels affect aldosterone secretion.
• Decreased serum sodium and elevated serum potassium increase aldosterone secretion.
• Elevated serum sodium and decreased serum potassium suppress aldosterone secretion.

• Suspected hyperaldosteronism as indicated by elevated levels:
  • Primary aldosteronism (e.g., resulting from benign adenomas or bilateral hyperplasia of the aldosterone-secreting zona glomerulosa cells) is indicated by elevated aldosterone and low plasma renin levels.
  • Secondary hyperaldosteronism (e.g., resulting from changes in blood volume and serum electrolytes, CHF, cirrhosis, nephrotic syndrome, chronic obstructive pulmonary disease [COPD], and renal artery stenosis) is indicated by elevated aldosterone and plasma renin levels.
• Suspected hypoaldosteronism (e.g., as seen in diabetes mellitus and toxemia of pregnancy) as indicated by decreased levels
• Evaluation of hypertension of unknown etiology

Nursing Care Before the Procedure

General client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• The client should not have ingested licorice for 2 weeks before the test. Medications that alter plasma aldosterone levels also may be withheld for up to 2 weeks before the test, although this practice should be confirmed with the person ordering the study.
• If hospitalized, the client should be told not to get out of bed in the morning until the sample has been obtained and that it may be necessary to obtain a second sample after he or she has been up for about 2 to 4 hours.
• Nonhospitalized individuals should be instructed on when to report to the laboratory in relation to the length of time to be upright before the test.

A venipuncture is performed and the sample is collected in a red-, green-, or lavender-topped tube, depending on laboratory procedures. The client's position and length of time the position was held should be noted on the laboratory request form. The sample(s) should be handled gently to avoid hemolysis and sent to the laboratory immediately. A sample for plasma renin also may be obtained in conjunction with the test.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Resume any medications withheld before the test.
• Increased levels: Note and report increased levels related to urinary aldosterone levels. Assess for fluid volume excess caused by sodium and fluid retention, and administer ordered diuretics.
• Decreased levels: Note and report decreased levels related to sodium levels. Assess for fluid volume deficit. Instruct in sodium and corticosteroid replacement regimen.