title: Acid-base changes caused by 5% albumin versus 6% hydroxyethyl starch solution in patients undergoing acute normovolemic hemodilution: a randomized prospective study.
abstract: BACKGROUND
  Preoperative acute normovolemic hemodilution (ANH) is an excellent model for evaluating the effects of different colloid solutions that are free of bicarbonate but have large chloride concentrations on acid-base equilibrium.
  
  
  METHODS
  In 20 patients undergoing gynecologic surgery, ANH to a hematocrit of 22% was performed. Two groups of 10 patients each were randomly assigned to receive either 5% albumin or 6% hydroxyethyl starch solutions containing chloride concentrations of 150 and 154 mm, respectively, during ANH. Blood volume (double label measurement of plasma and red cell volumes), pH, Paco2, and serum concentrations of sodium, potassium, chloride, lactate, ionized calcium, phosphate, albumin, and total protein were measured before and 20 min after completion of ANH. Strong ion difference was calculated as serum sodium plus serum potassium minus serum chloride minus serum lactate. The amount of weak plasma acid was calculated using a computer program.
  
  
  RESULTS
  After ANH, blood volume was well maintained in both groups. ANH caused slight metabolic acidosis with hyperchloremia and a concomitant decrease in strong ion difference. Plasma albumin concentration decreased after hemodilution with 6% hydroxyethyl starch solution and increased after hemodilution with 5% albumin solution. Despite a three-times larger decrease in strong ion difference after ANH with 6% hydroxyethyl starch solution, the decrease in pH was nearly the same in both groups.
  
  
  CONCLUSIONS
  ANH with 5% albumin or 6% hydroxyethyl starch solutions led to metabolic acidosis. A dilution of extracellular bicarbonate or changes in strong ion difference and albumin concentration offer explanations for this type of acidosis.
authors.affiliation: Clinic of Anesthesiology, Ludwig-Maximilians-University, Klinikum Grosshadern, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Rehm
authors.forename: V
authors.initials: V
authors.lastname: Orth
authors.forename: S
authors.initials: S
authors.lastname: Scheingraber
authors.forename: U
authors.initials: U
authors.lastname: Kreimeier
authors.forename: H
authors.initials: H
authors.lastname: Brechtelsbauer
authors.forename: U
authors.initials: U
authors.lastname: Finsterer
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects; D000138:Acidosis / Q000097:blood / Q000139:chemically induced* / Q000503:physiopathology; D000328:Adult; D000418:Albumins / Q000008:administration & dosage / Q000009:adverse effects*; D001810:Blood Volume / Q000187:drug effects / Q000502:physiology; D002712:Chlorides / Q000097:blood; D004573:Electrolytes / Q000097:blood; D004911:Erythrocyte Volume; D005260:Female; D006400:Hematocrit; D006438:Hemodilution / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006895:Hydroxyethyl Starch Derivatives / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D010952:Plasma Substitutes / Q000008:administration & dosage / Q000009:adverse effects*; D011446:Prospective Studies; D012996:Solutions; D002583:Uterine Cervical Neoplasms / Q000601:surgery
chemical_list: D000418:Albumins; D002712:Chlorides; D004573:Electrolytes; D006895:Hydroxyethyl Starch Derivatives; D010952:Plasma Substitutes; D012996:Solutions