Insulin and mineralocorticoids influence on extrarenal potassium metabolism in chronic hemodialysis patients

Effect of mineralocorticoids on interdialytic weight gain in hemodialysis patients with perdialytic hypotension

Fludrocortisone is recommended in patients with orthostatic hypotension and a benefit has been suggested in hemodialysis patients with severe hypokaliemia. We report 2 patients who suffered from chronic severe perdialytic hypotension resistant to midodrine and who were treated in a long-term period with fludrocortisone. A rise of post-dialytic BP was observed with a decrease of the interdialytic weight gain (IWG). We suggest that the IWG decrease is induced by a lessening of the renin angiotensin aldosterone system that could be less stimulated at the end of the dialysis session because of a better-preserved arterial pressure. The decrease of angiotensin could lessen the feeling of thirst.

Effect of spironolactone on K(+) homeostasis and ENaC expression in lymphocytes from chronic hemodialysis patients

BACKGROUND

Cardiac disease is the major cause of death in hemodialysis patients (HD). It is now clear that aldosterone has deleterious effects in the cardiovascular system. In the present study, we evaluated the effects of an aldosterone-antagonist, spironolactone, on the extrarenal regulation of potassium in HD patients. Furthermore, to validate the effectiveness of the spironolactone dose-design, we measured the expression of Na(+)-channel (ENaC alpha subunit) in peripheral blood mononuclear cells (PBMC), before and after a two-week course of spironolactone.

METHODS

The study design included a two-week baseline period, followed by spironolactone treatment (50 mg three times weekly for 15 days), and by a two-week washout period and then a two-week placebo period. An oral K(+) load (0.3 mEq/K(+) kg body weight plus carbohydrates) was administered at the end of each period, and time-course of plasma potassium was evaluated. ENaC expression in PBMC was assessed before and after spironolactone.

RESULTS

The maximal increase in plasma potassium after the K(+) carbohydrate load was: control 5.33 +/- 0.88 mEq K(+)/L; spironolactone 5.23 +/- 0.68 mEq K(+)/L; placebo 5.38 +/- 0.61 mEq K(+)/L (N= 9). No patients developed hyperkalemia during the spironolactone treatment period. ENaC expression was significantly higher in all six HD patients studied, compared to control subjects (P < 0.05). Treatment with spironolactone in HD patients reduced alpha subunit mRNA expression to values similar to those of normal subjects.

CONCLUSION

Spironolactone may be considered for the treatment of selected chronic HD patients. The effect of the drug on a known target of aldosterone, the ENaC, demonstrates the effectiveness of the drug to block aldosterone effects in nonepithelial tissues.

Aldosterone-receptor antagonism and end-stage renal disease

Blockade of aldosterone effect with either spironolactone or eplerenone is an approach that is being used more frequently in the treatment of hypertension and congestive heart failure; however, sparse information exists pertaining to efficacy or side-effects of this line of treatment for patients with chronic kidney disease and/or end-stage renal disease (ESRD). Hyperkalemia is, by far, the most worrisome complication of therapy with either of these compounds and, not surprisingly, hinders their use in moderate-to-advanced renal failure. However, patients with anuric ESRD should theoretically not be at risk for hyperkalemia. To this end, pilot safety studies with aldosterone-receptor antagonists in ESRD patients have begun. These studies imply that spironolactone can be safely used in carefully selected and closely monitored patients. Eplerenone has not been studied in ESRD in a therapeutic or safety capacity. Additional studies are needed with these compounds in the ESRD population before their use can be considered safe.