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Published on: June 16, 2014
Renal potassium handling in chronic kidney disease: Differences between patients with or wihtout hyperkalemia
Fernando Caravaca-Fontán1, Julián Valladares1, Rosa Díaz-Campillejo1
1Servicio Nefrología, Hospital Infanta Cristina, Badajoz, España.
Insights
Hyperkalemia in advanced chronic kidney disease (CKD) is linked to increased potassium load and reduced renal excretion. Lower fractional excretion of potassium (FEK) is a key indicator of this limitation in CKD patients.
Area of Science:
- Nephrology
- Internal Medicine
- Clinical Biochemistry
Background:
- Hyperkalemia (HK) is a frequent complication in advanced chronic kidney disease (CKD).
- Reduced renal excretory capacity is the primary cause of positive potassium balance in CKD.
- Understanding the specific pathogenic factors is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate renal potassium handling in patients with stage 4-5 CKD before dialysis.
- To compare potassium handling differences between CKD patients with and without hyperkalemia.
Main Methods:
- Cross-sectional observational study of 212 adult patients with stage 4-5 CKD.
- Analysis of blood and urine biochemistry, including serum potassium and urinary electrolytes.
- Calculation of fractional excretion of potassium (FEK) and potassium load relative to glomerular filtration (Ku/GFR).
Main Results:
- 30% of CKD patients studied had hyperkalemia (serum K ≥5.5mmol/l).
- Hyperkalemic patients exhibited lower fractional excretion of potassium (FEK) and higher potassium load relative to glomerular filtration (Ku/GFR).
- FEK and Ku/GFR were identified as significant determinants of serum potassium levels and hyperkalemia in this cohort.
Conclusions:
- Potassium load relative to glomerular filtration (Ku/GFR) is a significant factor in hyperkalemia development in advanced CKD.
- A reduced compensatory urinary potassium excretion, indicated by lower FEK, is a primary characteristic of hyperkalemia in these patients.
Introduction:
Hyperkalemia (HK) is a common electrolyte disorder in chronic kidney disease (CKD), mainly in the advanced stages. A positive potassium balance due to reduced renal excretory capacity is likely the main pathogenic mechanism of HK. Research into the relative role of each pathogenic element in the development of HK in CKD may help to implement more suitable therapies.
Objective:
To investigate renal potassium handling in advanced CKD patients, and to determine the differences between patients with or without HK.
Material And Methods:
Cross-sectional observational study in adult patients with stage 4-5 CKD pre-dialysis. Selection criteria included clinically stable patients and the ability to collect a 24hour urine sample correctly. Blood and urinary biochemical parameters were analysed including sodium and potassium (K). Fractional excretion of K (FEK) and K load relative to glomerular filtration (Ku/GFR) were calculated. HK was defined as a serum K concentration ≥5.5mmol/l.
Results:
The study group consisted of 212 patients (mean age 65±14 years, 92 females) with a mean GFR of 15.0±4.2ml/min/1.73m2. 63 patients (30%) had HK. Patients with HK had lower mean bicarbonate levels with respect to patients with normal K levels (NK) (20.3±3.1 vs. 22.8±3.2 mEq/l, P<.0001), but no differences were noted in total urinary sodium and K excretion. While mean FEK values were lower in patients with HK (32.1±12.1% vs. 36.4±14.3%, P=.038), Ku/GFR values were significantly greater with respect to the NK subgroup (4.2±1.5 vs. 3.7±1.4 mmol/ml/min, P=0,049). FEK showed a strong linear correlation with Ku/GFR (R2=0.74), and partial linear regressions demonstrated that at a similar Ku/GFR level, the FEK of patients with HK was lower than that of NK patients. By multivariate linear and logistic regression analyses, both FEK and Ku/GFR were shown to be the main determinants of K serum levels and HK.
Conclusions:
Although the K load relative to glomerular filtration (Ku/GFR) is an important determinant of HK in advanced CKD, the most noteworthy characteristic associated with HK in these patients was the limitation of compensatory urinary K excretion, as indicated by lower FEK.
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