Association of predialysis serum bicarbonate levels with risk of mortality and hospitalization in the Dialysis Outcomes and Practice Patterns Study (DOPPS).
BACKGROUND
Experimental and some clinical data suggest that metabolic acidosis contributes to poor nutritional status, a strong predictor for mortality in hemodialysis patients. However, recent cross-sectional studies indicate that severe predialysis metabolic acidosis is associated with a greater normalized protein catabolic rate (nPCR) and greater serum albumin levels. Given this controversy, we analyzed data from the Dialysis Outcomes and Practice Pattern Study (DOPPS) for associations between predialysis serum bicarbonate and albumin concentrations, nPCR, and patient risk for mortality and hospitalization.


METHODS
Data from more than 7,000 representative and randomly selected hemodialysis DOPPS patients from France, Germany, Italy, Japan, Spain, the United Kingdom, and the United States were analyzed. Serum bicarbonate (total CO2 ) levels predialysis were corrected to the midweek interdialytic interval.


RESULTS
The midweek predialysis serum bicarbonate level averaged 21.9 mEq/L (mmol/L) and correlated inversely with nPCR, serum albumin, and serum phosphorus values. Before and after adjusting for 15 comorbidities, nutrition, and equilibrated Kt/V, a U-curve best represented the association between predialysis serum bicarbonate level and risk for mortality or hospitalization. Patients with midweek predialysis serum bicarbonate levels of 20.1 to 21.0 mEq/L (mmol/L) faced the lowest risk for mortality, whereas those with bicarbonate levels of 21.1 to 22.0 mEq/L faced the lowest risk for hospitalization. Both high (>27 mEq/L) and low (< or =17 mEq/L) serum bicarbonate levels were associated with increased risk for mortality and hospitalization.


CONCLUSIONS
Moderate predialysis acidosis seems to be associated with better nutritional status and lower relative risk for mortality or hospitalization than is observed in patients with normal ranges of midweek predialysis serum bicarbonate concentration (approximately 24 mEq/L) or severe acidosis (<16 mEq/L).
Bommer
Jürgen
J
Medizinische Universitätsklinik, Heidelberg, Germany.
Locatelli
Francesco
F
Satayathum
Sudtida
S
Keen
Marcia L
ML
Goodkin
David A
DA
Saito
Akira
A
Akiba
Takashi
T
Port
Friedrich K
FK
Young
Eric W
EW
D000138:Acidosis; D001639:Bicarbonates / Q000097:blood*; D006760:Hospitalization; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000401:mortality* / Q000628:therapy*; D009752:Nutritional Status; D016016:Proportional Hazards Models; D006435:Renal Dialysis; D012306:Risk; D012709:Serum Albumin; D016896:Treatment Outcome
D001639:Bicarbonates; D012709:Serum Albumin