The use of amiloride in potassium depletion before cardiac surgery

Potassium depletion in heart failure and its relation to long-term treatment with diuretics: a review of the literature

There have been many studies which suggest that patients with heart failure were potassium depleted. This depletion has been attributed to the use of potent diuretics, and these are now given with either potassium supplements or potassium-retaining diuretics. A detailed examination of the studies suggests that the reported decrease in body potassium compared with the results in healthy persons is not due to the diuretics. It can be partly explained by a failure to match patients and controls in terms of age, and the remaining difference can be explained by muscle wasting. There is therefore no evidence of a potassium depletion in these patients with heart failure.

Effect of long-term diuretic treatment on body-potassium in heart-disease

Plasma and total body potassium have been measured in 151 patients with chronic heart-disease, 83 of whom were taking diuretics and potassium supplements. After allowance for age and body-size, the deficit in total body-potassium was only 3-5% (100-150 mmol) in the diuretic group. 13 of the 83 patients taking diuretic had hypokalaemia (less than 3-5 mmol/1) but the potassium deficit was no greater than in the patients with normal plasma-potassium. There was no relation between the dose of potassium supplements and either the plasma-potassium or the total body-potasium. It is suggested that potassium depletion is not a major problem in patients with heart-failure treated with diuretics. The dose of potassium supplements should therefore be determined entirely by the plasma-potassium.

Effect of potassium-sparing diuretics on the renin-angiotensin-aldosterone system and potassium retention in heart failure

The renin-angiotensin-aldosterone system and electrolyte levels in 11 patients with heart failure controlled on digoxin and frusemide were investigated after separate periods of Slow K, spironolactone, and amiloride therapy. When spironolactone or amiloride replaced Slow K, distinct parallel increments in the levels of renin, angiotensin II, and aldosterone resulted. Though plasma potassium was generally higher after spironolactone and amiloride than after Slow K, exchangeable potassium was similar with the three regimens. There was no significant relation between plasma potassium and concurrent exchangeable potassium.

Potassium-sparing effect of amiloride in a diuretic factorial study in man

1. The effects of amiloride (M, 20 mg/day), chlorothiazide (C, 1000 mg/day), ethacrynic acid (E, 100 MG/day) and frusemide (F, furosemide 80 mg/day, given alone and in combination, were investigated in eight patients in a 2(4) factorial study. Effects between blocks of four treatments in each sixteen-treatment replicate were confounded with higher interactions to allow for differences between early and late diuresis. 2. All patients exhibited marked diuresis, with significant mean increases in daily urinary sodium excretion (P smaller than 0.05) and urinary volume (P smaller than 0.01) induced by chlorothiazide, frusemide and ethacrynic acid (68, 69 and 38%; and 35, 40 and 34%, respectively). Amiloride appeared to be half to one-third as potent as the other diuretics. 3. Amiloride produced a significant potassium-sparing effect (P smaller than 0.01), reducing urinary potassium excretion by 30%, compared to significant urinary potassium wasting with frusemide (increase of 33%, P smaller than 0.01) and chlorothiazide (increase of 31%, P smaller than 0.05). 4. No adverse reactions occurred, but serum potassium levels twice rose to 6 mmol/l and subsided without additional therapy, and on one occasion fell to 2.5 mmol/l, requiring a potassium supplement for 4 days. 5. It was concluded from these factorial studies that amiloride is a mild diuretic and potent potassium-sparing agent acting independently and additively in combination with chlorothiazide, ethacrynic acid or frusemide. For the three latter diuretics, all two-drug interactions were simply additive also, without evidence of synergism or antagonism between drugs.