Fluid and electrolyte considerations in diuretic therapy for hypertensive patients with chronic obstructive pulmonary disease.

When a patient with chronic obstructive pulmonary disease (COPD) requires medical therapy for systemic hypertension, a number of special considerations may affect the choice of antihypertensive drug and subsequent management. Thiazide diuretics have no adverse effect on airway function and are the agents of choice for initial therapy. beta-Antagonists are usually considered first-line agents in antihypertensive therapy, but even relatively cardioselective ones may increase airway resistance in patients with obstructive lung diseases, and they should be used with caution, if at all, in such patients. Although potassium-wasting diuretics are the preferred agents for treating hypertension in patients with COPD, they may worsen carbon dioxide retention in hypoventilating patients and potentiate hypokalemia in those receiving corticosteroids. In addition, beta-agonists may substantially lower serum potassium levels in patients already rendered hypokalemic by diuretics. Patients with COPD receiving potassium-wasting diuretics who have chronic respiratory acidosis or are receiving corticosteroids or beta-agonists should undergo close monitoring of electrolyte levels and be considered for therapy with potassium supplements or, preferably, potassium-sparing agents.