title: The effects of hyperoxaemia on tissue oxygenation in patients with a nadir haematocrit lower than 20% during cardiopulmonary bypass.
abstract: Excessive haemodilution and the resulting anaemia during CPB is accompanied by a decrease in the total arterial oxygen content, which may impair tissue oxygen delivery. Hyperoxic ventilation has been proven to improve tissue oxygenation in different pathophysiological states of anaemic tissue hypoxia. The aim of this study was to examine the influence of arterial hyperoxaemia on tissue oxygenation during CPB. Records of patients undergoing isolated CABG with CPB were retrospectively reviewed. Patients with nadir haematocrit levels below 20% during CPB were included in the study. Tissue hypoxia was defined as hyperlactataemia (lactate >2.2 mmol/L) coupled with low ScVO2 (ScVO2 <70%) during CPB. One hundred patients with normoxaemia and 100 patients with hyperoxaemia were included in the study. Patients with hyperoxaemia had lower tissue hypoxia incidence than patients with normoxaemia (p<0.001). Compared with patients without tissue hypoxia, patients with tissue hypoxia had significantly lower PaO2 values (p<0.001) and nadir haematocrit levels (p<0.001). Nadir haematocrit levels <18% (OR: 5.3; 95% CI: 2.67-10.6; p<0.001) and hyperoxaemia (OR: 0.28; 95% CI: 0.14-0.56; p<0.001) were independently associated with tissue hypoxia.
  
  
  CONCLUSIONS
  Hyperoxaemia during CPB may be protective against tissue hypoxia in patients with nadir haematocrit levels <20%.
authors.affiliation: Department of Cardiovascular Surgery, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey utkansevuk@gmail.com.
authors.forename: Utkan
authors.initials: U
authors.lastname: Sevuk
authors.affiliation: Department of Cardiology, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey.
authors.forename: Rojhat
authors.initials: R
authors.lastname: Altindag
authors.affiliation: Department of Cardiology, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey.
authors.forename: Erkan
authors.initials: E
authors.lastname: Baysal
authors.affiliation: Department of Cardiology, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey.
authors.forename: Baris
authors.initials: B
authors.lastname: Yaylak
authors.affiliation: Department of Cardiology, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey.
authors.forename: Mehmet Sahin
authors.initials: MS
authors.lastname: Adiyaman
authors.affiliation: Department of Cardiology, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey.
authors.forename: Suleyman
authors.initials: S
authors.lastname: Akkaya
authors.affiliation: Department of General Surgery, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey.
authors.forename: Nurettin
authors.initials: N
authors.lastname: Ay
authors.affiliation: Department of General Surgery, Diyarbakir Gazi Yasargil Education and Research Hospital, Diyarbakir, Turkey.
authors.forename: Vahhac
authors.initials: V
authors.lastname: Alp
mesh_terms: D000368:Aged; D002315:Cardiopulmonary Bypass / Q000379:methods*; D005260:Female; D006400:Hematocrit; D006801:Humans; D018496:Hyperoxia / Q000097:blood* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000379:methods
keywords: cardiac surgery; cardiopulmonary bypass; hyperoxemia; nadir hematocrit; tissue hypoxia