Impact of chloride balance in acidosis control: the Stewart approach in hemodialysis critically ill patients.
BACKGROUND
Metabolic acidosis is highly prevalent in critically ill patients with acute renal failure. Little is known about the mechanisms by which renal replacement therapy intervenes in such cases. The objective of this study is to analyze the role of hemodialysis in acidosis correction in intensive care unit patients, with an emphasis on chloride levels in plasma and dialysate.


METHODS
We studied 19 intermittent hemodialysis procedures in 17 acidotic patients. The patients were grouped by procedure type (conventional or sustained low-efficiency dialysis) and by predialysis plasma chloride level (higher or lower than the dialysate chloride concentration). Immediately before and after each procedure, blood samples were collected for biochemical analysis. The Stewart method was used to calculate the strong ion difference and strong ion gap.


RESULTS
The patients presented acidosis related to hyperchloremia, hyperphosphatemia, and high unmeasured anions. Hypoalbuminemia had an alkalinizing effect. Hemodialysis corrected acidosis mainly by reducing phosphate and unmeasured anions. In the group as a whole, chloride levels did not change after dialysis. However, when analyzed according to predialysis plasma chloride, the high-chloride group presented a reduction in plasma chloride, resulting in better base excess improvement (Delta standard base excess) than in the low-chloride group. Among the determinants of acid-base status, the only factors correlating with Delta SBE were Delta strong ion gap and Delta chloride.


CONCLUSIONS
The serum chloride/dialysate chloride relationship during hemodialysis has an important impact on acidosis control.
Libório
Alexandre Braga
AB
Department of Nephrology, University of São Paulo School of Medicine, Hospital das Clínicas, São Paulo 01246-903, Brazil.
da Silva Alexandre
Cristianne
C
Noritomi
Danilo Teixeira
DT
Andrade
Lúcia
L
Seguro
Antonio Carlos
AC
D000138:Acidosis / Q000150:complications / Q000378:metabolism* / Q000628:therapy*; D000368:Aged; D002712:Chlorides / Q000378:metabolism*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D006435:Renal Dialysis; D051437:Renal Insufficiency / Q000209:etiology / Q000628:therapy
D002712:Chlorides