title: Impact of chloride balance in acidosis control: the Stewart approach in hemodialysis critically ill patients.
abstract: 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.
authors.affiliation: Department of Nephrology, University of São Paulo School of Medicine, Hospital das Clínicas, São Paulo 01246-903, Brazil.
authors.forename: Alexandre Braga
authors.initials: AB
authors.lastname: Libório
authors.forename: Cristianne
authors.initials: C
authors.lastname: da Silva Alexandre
authors.forename: Danilo Teixeira
authors.initials: DT
authors.lastname: Noritomi
authors.forename: Lúcia
authors.initials: L
authors.lastname: Andrade
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Seguro
mesh_terms: 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
chemical_list: D002712:Chlorides