Complications of diuretic therapy: severe alkalosis and syndrome resembling inappropriate secretion of antidiuretic hormone

Diuretic-induced severe hyponatremia. Review and analysis of 129 reported patients

Thiazides were responsible for severe diuretic-induced hyponatremia (serum sodium level < 115 mEq/L) in 94 percent of 129 cases reported in the literature between 1962 and 1990. The hyponatremia developed within 14 days in most of the patients receiving thiazides but in none of the patients who were treated with furosemide. Diuretic-induced hyponatremia was four times more common in women than in men. Advanced age was not associated with a higher tendency for hyponatremia. In the majority of the patients who received thiazides, excess antidiuretic hormone activity, hypokalemia, and excess water intake were accompanying findings which, singly or together, appeared to contribute to the development of hyponatremia. In 12 patients, mortality was directly related to hyponatremia. Rapid average correction of hyponatremia and a relatively high total correction (over 20 mEq/L) in the first 24 h were significantly associated with higher mortality or demyelinating syndrome. The presence of neurologic signs is an indication for active sodium replacement. The onset of thiazide-induced hyponatremia may in some cases occur within 1 day and therefore needs to be corrected rapidly, but within a total elevation of 20 mEq/L in the first 24 h. Where the onset is judged to have been slow (over several days), the level should be corrected at a slow rate, up to a total of 12 to 15 mEq/L in 24 h.

Furosemide decreases ventilation in young rabbits

To test the hypothesis that furosemide would cause metabolic alkalosis and thus alveolar hypoventilation, normal rabbit pups were given either furosemide (4 mg/kg/day) or saline solution for the first 8 to 10 days of life. Pups given furosemide developed primary metabolic alkalosis and reduced ventilation, which resulted in secondary respiratory acidosis. Lung compliance was improved by furosemide, and the ventilatory response to CO2 was unaffected. KCl injection in alkalotic pups increased ventilation and decreased pH. The data show that conventional doses of furosemide can (1) cause metabolic alkalosis and reduce ventilation; (2) increase the PaCO2, which reflects changes in acid-base status and not changes in lung function; and (3) increase lung compliance, perhaps by decreasing lung water. When these effects occur in infants with chronic lung disease, the beneficial effect of furosemide may be obscured.

Effects of magnesium infusions in diuretic induced hyponatraemia

Eight hyponatraemic patients with severe congestive heart failure, long-term diuretic treatment, oedema, and increasing resistance to diuretic treatment, were studied with skeletal muscle biopsies and serum electrolytes before and after magnesium infusions. The infusions resulted in an increasing serum sodium level, a decrease in muscle sodium and chloride, and an increase in muscle potassium. The effect was probably mediated through the magnesium effect on membrane ATPase.

Diuretics: mechanism of action and clinical application

Despite the bewildering number of diuretics available to the physician, these drugs can be divided into 4 main groups, characterised by their site of action on sodium reabsorption in the kidney. Drugs acting on the ascending limb of the loop of Henle have a powerful but short acting diuretic effect; they include frusemide, ethacrynic acid and bumetanide. The benzothiadiazines and related compounds have a moderate diuretic action spread over a longer period, whilst the potassium-sparing diuretics, triamterene, amiloride and spironolactone, have only a weak diuretic effect but a marked ability to diminish urinary potassium excretion. The fourth group is made up of miscellaneous substances which function as vasodilator or osmotic agents. The pathogenesis of oedema formation in heart failure is outlined and a logical approach to treatment suggested. Duiretics are being increasingly used in the treatment of non-oedematous states, in particular hypertension, diabetes insipidus and hypercalciuria; their exact role in pregnancy and acute renal failure remains controversial. Side-effects can be related to their effect on electrolyte excretion and include hypokalaemia, hyponatraemia, hyperkalaemia and hyperuricaemia. The incidence of disturbed carbohydrate tolerance in previously normal individuals is low. Other less common side-effects are also discussed.

Case report: diuretics and non-respiratory alkalosis

A patient with chronic respiratory failure and cor pulmonale was admitted to hospital with an exacerbation of cardiac failure. In attempting to control cardiac failure, intensive diuretic therapy resulted in the development of dehydration, alkalosis, grand mal convulsions and signs of a left hemiparesis. Correction of the electrolyte and acid-base abnormalities resulted in complete neurological recovery.

Mechanisms of production by diuretics and the treatment of non-respiratory alkalosis is discussed.