Intensive Care Med (1998) 24:313-321 © Springer-Verlag1998 A. Bacher N. Mayer A. M. Raj ek W. Haider Acute normovolaemic haemodUutiondoes not aggravate gastric mucosal acidosis during cardiac surgery Received: 4 September 1997 Accepted: 17 December 1997 This study was performed at the Depart- ment of Anaesthesiology and General Intensive Care, Universityof Vienna, Austria. The study was financedwith the department's own financialresources. The studywas presented in part at the 26th Educational & ScientificSymposium of the Societyof Critical Care Medicine, 6-10 February 1997, San Diego, California, USA A. Bacher ( ~ ) . N. Mayer. A. M. Rajek. W.Haider Department of Anaesthesiology and General IntensiveCare, University of Vienna, AKH, W~thringerGt~rte118-20, A-1090 Vienna, Austria Fax: + 43(1)40400/4104 email: andreas.bacher @ univie.ac.at Abstract Objective: Acute nor- movolaemic haemodilution with subsequent autologous blood trans- fusion after surgery is widely used to reduce homologous blood require- ments during cardiac surgery. The hypothesis tested was whether a low intraoperative haematocrit (Hct) resulting from haemodilution de- creases gastric mucosal pH (pHi). Design: Prospective clinical investi- gation. Setting: University Hospital of Vi- enna, Austria. Patients: 16 consecutive patients scheduled for elective cardiac sur- gery. Interventions: The patients were randomly assigned to one of two groups: In 10 patients (group 1), 500 ml of blood was withdrawn and stored after anaesthesia induction.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 % hydroxy- ethyl starch was simultaneously in- fused. After discontinuation of car- diopulmonary bypass (CPB), the autologous blood unit was trans- fused. Six patients (group 2), who were not subjected to haemodilu- tion and autologous blood transfu- sion served as controls. In all pati- ents, a gastric tonometry probe was inserted. Measurements and results: Measure- ments of pHi and Hct were per- formed before and after acute nor- movolaemic haemodilution, during pulsatile hypothermic (30-32 °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 pre- sented as means + standard error of the mean. Haemodilution in group 1 caused a significant and persistent decrease in Hct (after haemodilu- tion in group 1 34 _+ 1 vs 40 + 1% in group 2). In both groups, pHi de- creased 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 car- diac surgery. Key words Cardiopulmonary bypass. Hypothermic. Pulsatile - Heart, open heart surgery. Coronary artery bypass graft • Haematocrit • Haemoglobin, concentration • Oxygen, content • Perfusion, splanchnic • Tonometry, gastric. Gastric mucosal pH