Higher serum potassium level associated with late stage chronic kidney disease.

Background: The serum potassium (K+) level is kept in a narrow range to sustain normal physiology within the human body by the kidneys. The serum K+ level in different stages of chronic kidney disease (CKD) remains undefined.

Methods: We conducted a cross-sectional study to observe the serum K+ level in patients without clinical manifestations of hyperkalemia in the late stages of CKD (stages 3-5). A total of 531 patients with late stage CKD were included and followed up for at least 1 year, from March 2006 to May 2007. The patients were sub-grouped by stages of CKD, which were determined by a "Modification of Diet in Renal Disease" equation estimating the glomerular filtration rate (eGFR). The serum creatinine, eGFR and K+ levels were recorded at least twice during the study. We analyzed the average K+ level in these late-stage CKD patients.

Results: The average K+ level increased along with renal function deterioration in the late stages of CKD (stage 3: 4.36 ± 0.49; stage 4: 4.50 ± 0.55; stage 5: 4.69 ± 0.73 mEq/L, p < 0.05). Men and patients with diabetes mellitus, a low eGFR, and a low hemoglobin might have higher levels of serum K+. We also noticed that there was a linear increase in the standard deviation of the serum K+ level as renal function deteriorated. The use of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers was not associated with hyperkalemia in our patients.

Conclusion: Our results reflected that the serum K+ level increased in correlation with the decline in the eGFR in the late stages of CKD. Also, male gender, diabetes mellitus, and anemia might be risk factors for higher K+ levels in CKD patients. The variation in the serum K+ level became wider as renal failure progressed.