Serum potassium and outcomes in CKD: insights from the RRI-CKD cohort study.
OBJECTIVE
The relationship between serum potassium (S(K)) and mortality in chronic kidney disease (CKD) has not been systematically investigated.


METHODS
We examined the predictors and mortality association of S(K) in the Renal Research Institute CKD Study cohort, wherein 820 patients with CKD were prospectively followed at four US centers for an average of 2.6 years. Predictors of S(K) were investigated using linear and repeated measures regression models. Associations between S(K) and mortality, the outcomes of ESRD, and cardiovascular events in time-dependent Cox models were examined.


RESULTS
The mean age was 60.5 years, 80% were white, 90% had hypertension, 36% had diabetes, the average estimated GFR was 25.4 ml/min per 1.73 m(2), and mean baseline S(K) was 4.6 mmol/L. Higher S(K) was associated with male gender, lower estimated GFR and serum bicarbonate, absence of diuretic and calcium channel blocker use, diabetes, and use of angiotensin-converting enzyme inhibitors and/or statins. A U-shaped relationship between S(K) and mortality was observed, with mortality risk significantly greater at S(K) < or = 4.0 mmol/L compared with 4.0 to 5.5 mmol/L. Risk for ESRD was elevated at S(K) < or = 4 mmol/L in S(K) categorical models. Only the composite of cardiovascular events or death as an outcome was associated with higher S(K) (> or = 5.5).


CONCLUSIONS
Although clinical practice usually emphasizes greater attention to elevated S(K) in the setting of CKD, our results suggest that patients who have CKD and low or even low-normal S(K) are at higher risk for dying than those with mild to moderate hyperkalemia.
Korgaonkar
Sonal
S
Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48103, USA.
Tilea
Anca
A
Gillespie
Brenda W
BW
Kiser
Margaret
M
Eisele
George
G
Finkelstein
Fredric
F
Kotanko
Peter
P
Pitt
Bertram
B
Saran
Rajiv
R
D000368:Aged; D015415:Biomarkers / Q000097:blood; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology* / Q000401:mortality; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006947:Hyperkalemia / Q000097:blood* / Q000150:complications / Q000401:mortality; D007008:Hypokalemia / Q000097:blood* / Q000150:complications / Q000401:mortality; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000150:complications / Q000401:mortality; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood*; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014481:United States
D015415:Biomarkers; D011188:Potassium