title: Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery.
abstract: OBJECTIVE
  Acute normovolaemic haemodilution with subsequent autologous blood transfusion after surgery is widely used to reduce homologous blood requirements during cardiac surgery. The hypothesis tested was whether a low intraoperative haematocrit (Hct) resulting from haemodilution decreases gastric mucosal pH (pHi).
  
  
  METHODS
  Prospective clinical investigation.
  
  
  METHODS
  University Hospital of Vienna, Austria.
  
  
  METHODS
  16 consecutive patients scheduled for elective cardiac surgery.
  
  
  METHODS
  The patients were randomly assigned to one of two groups: In 10 patients (group 1), 500 ml of blood was withdrawn and stored after anaesthesia induction. An equal amount of 6% hydroxyethyl starch was simultaneously infused. After discontinuation of cardiopulmonary bypass (CPB), the autologous blood unit was transfused. Six patients (group 2), who were not subjected to haemodilution and autologous blood transfusion served as controls. In all patients, a gastric tonometry probe was inserted.
  
  
  RESULTS
  Measurements of pHi and Hct were performed before and after acute normovolaemic haemodilution, during pulsatile hypothermic (30-32 degrees C) CPB, after rewarming, and 30 min after autologous blood transfusion in group 1, and at corresponding time intervals in group 2. Repeated measures analysis of variance and the Mann-Whitney U test were used for statistical analysis. Data are presented as means +/- standard error of the mean. Haemodilution in group 1 caused a significant and persistent decrease in Hct (after haemodilution in group 1 34 +/- 1 vs 40 +/- 1% in group 2). In both groups, pHi decreased during rewarming and after termination of CPB. However, in group 1, pHi was better preserved than in group 2 (rewarming: 7.44 +/- 0.02 vs 7.34 +/- 0.04; after CPB: 7.38 +/- 0.03 vs 7.28 +/- 0.02; p < 0.05).
  
  
  CONCLUSIONS
  Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery.
authors.affiliation: Department of Anaesthesiology and General Intensive Care, University of Vienna, Austria. andreas.bacher@univie.ac.at
authors.forename: A
authors.initials: A
authors.lastname: Bacher
authors.forename: N
authors.initials: N
authors.lastname: Mayer
authors.forename: A M
authors.initials: AM
authors.lastname: Rajek
authors.forename: W
authors.initials: W
authors.lastname: Haider
mesh_terms: D000138:Acidosis / Q000209:etiology* / Q000378:metabolism; D000368:Aged; D000704:Analysis of Variance; D001784:Blood Gas Analysis; D002315:Cardiopulmonary Bypass; D005260:Female; D005753:Gastric Mucosa / Q000737:chemistry; D006400:Hematocrit; D006438:Hemodilution / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007431:Intraoperative Complications / Q000209:etiology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011446:Prospective Studies; D013152:Splanchnic Circulation; D018709:Statistics, Nonparametric