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Inadequate aldosterone response to hyperkalemia during angiotensin converting enzyme inhibition in chronic renal
Insights
Captopril treatment in chronic renal failure patients significantly raises potassium levels, indicating aldosterone
Area of Science:
- Nephrology
- Endocrinology
- Pharmacology
Background:
- Chronic renal failure (CRF) patients often experience electrolyte imbalances.
- Angiotensin-converting enzyme (ACE) inhibitors like captopril can affect potassium homeostasis.
Purpose of the Study:
- To investigate the mechanism of hyperkalemia during ACE inhibition with captopril in CRF patients.
- To assess the role of aldosterone and renin in captopril-induced hyperkalemia.
Main Methods:
- 16 hypertensive CRF patients received captopril (150 mg/day) for 4 weeks.
- Plasma potassium, creatinine, aldosterone excretion, and plasma renin activity were measured.
- Fractional excretion of potassium was calculated.
Main Results:
- Captopril increased plasma potassium levels significantly (3.9 to 5.5 mEq/L).
- In patients with higher creatinine levels, aldosterone excretion decreased while renin activity increased.
- Reduced fractional excretion of potassium correlated with lower aldosterone levels.
Conclusions:
- Adequate aldosterone production is crucial for maintaining potassium balance in CRF.
- Angiotensin II may be necessary for an appropriate aldosterone response to potassium stimulation during ACE inhibition.
Abstract:
To assess the mechanism involved in hyperkalemia during angiotensin converting enzyme inhibition with captopril in chronic renal failure, captopril, 150 mg/day, was administered to 16 patients with hypertension with plasma creatinine levels between 1.6 and 12.4 mg/dl. After 4 weeks of therapy, plasma potassium levels increased from 3.9 +/- 0.1 to 5.5 +/- 0.2 mEq/L (P less than 0.001) and the final plasma potassium levels correlated with plasma creatinine levels (r = 0.67; P less than 0.01). In six patients with plasma creatinine levels greater than or equal to 3 mg/dl, aldosterone excretion decreased after 4 weeks of captopril, from 7.5 +/- 3.1 to 1.8 +/- 0.5 micrograms/24 hr, whereas plasma renin activity increased from 0.6 +/- 0.2 to 4.4 +/- 1.1 ng/ml/hr (P less than 0.05). This was associated with increases in plasma potassium levels from 3.9 +/- 0.2 to 5.4 +/- 0.4 mEq/L (P less than 0.005) and a significant reduction in fractional excretion of potassium from an average of 34% to 25%. No significant changes in plasma creatinine levels were observed during therapy. There was a significant positive correlation between aldosterone excretion and the potassium excretion fraction (r = 0.53; P less than 0.01). Increases in plasma potassium levels were not able to increase aldosterone excretion, although the greater the plasma potassium level attained, the smaller the reduction in aldosterone excretion (r = 0.47; P less than 0.05). Our results indicate that adequate aldosterone production is essential to preserve potassium homeostasis in chronic renal failure. Moreover, angiotensin II appears necessary for an adequate aldosterone response to potassium stimulation.