ASSOCIATION BETWEEN OXYGEN DELIVERY AND CONSUMPTION IN PATIENTS UNDERGOING CARDIAC-SURGERY - IS THERE SUPPLY DEPENDENCE

We studied the relationship between oxygen delivery (DO2) and consumpt ion (VO2) in twenty patients undergoing cardiac surgery, in order to d etermine if VO2 was dependent on DO2 (pathological oxygen supply depen dence). We measured VO2 from expired gas analysis (VO2G) and compared this to that calculated using the reverse Fick method (VO2F). Both VO2 G and VO2F increased after cardiopulmonary bypass (P<0.001), without c hange in DO2 (i.e. oxygen extraction ratio increased). There was a sig nificant relationship between changes in DO2 and VO2F, both before byp ass (r=0.74, P<0.001) and after bypass (r=0.69, P<0.001), while change s in DO2 and VO2G had no such relationship (pre-bypass: r=0.38, P=0.09 4; post-bypass: r=0.10, P=0.68). There was poor agreement between VO2F and VO2G perioperatively. We could not demonstrate supply dependence in elective cardiac surgical patients.