Hyperoxia in extreme hemodilution

Intraoperative surgical blood loss is initially replaced by
infusion of red cell-free, cristalloidal or colloidal solutions.
When normovolemia is maintained the ensuing dilutional anemia is
compensated by an increase of cardiac output and of arterial oxygen
extraction. In the ideal case, a surgical blood loss can entirely
be `bridged' without transfusion by intraciperative normovolemic
hemodilution. However major blood loss results in extreme
hemodilution and the transfusion of red blood cells may finally
become necessary to increase arterial oxygen content and to
preserve tissue oxygenation. When transfusion has to be started
before surgical control of bleeding has been achieved, parts of the
red blood cells transfused will get lost, thereby increasing
intraoperative transfusion needs. Beside red blood cell
transfusion, arterial oxygen content can be rapidly increased by
ventilating the patient with 100% oxygen (hyperoxic ventilation),
thus enhancing the amount of physically dissolved oxygen in plasma
(hyperoxia). In experimental and clinical studies hyperoxic
ventilation has emerged as a simple, safe and effective
intervention to enlarge the margin of safety for hemodynamic
compensation and tissue oxygenation in hemodiluted subjects
experiencing major bleeding. The hyperoxia-associated
microcirculatory dysregulation and impaired tissue oxygenation
known to take place in the presence of a physiologic hemoglobin
concentration are not encountered in hemodiluted subjects.
Hyperoxic hemodilution i.e. the combination of intraoperative
extreme hemodilution and hyperoxic ventilation may therefore be
considered a cost-effective, safe and efficient supplement to
reduce allogeneic transfusion during surgical interventions
associated with high blood losses. The vast majority of the
experimental and clinical investigations this new concept is based
on was initiated and performed under the guidance of Prof. Konrad
Messmer. Copyright (C) 2002 S. Karger AG, Basel.