ABSTRACT
Cardiopulmonaary bypass [CPB] with haemodilution is currently used as a common adjunctive measure in cardiac surgery. However, there is still much controversies as regards the effect of haemodilution on pulmonary gas exchange and tissue oxygenation after cardiac surgery with extracorporeal circulation. We have studied 60 adult patients, ASA II and III who were undergoing elective coronary artery bypass graft operation with CPB. Patients were allocated info three groups according to their final haematocrit after the end of extracorporeal circulation; group [I] haematocrit above 30%, group [2] haematocrit from 25%-30%, and group [3] with haematocrit between 21%-25%. Our study showed a significant impairment of pulmonary gas exchange after cardiopulmonary bypass as shown immediately after the end of bypass and continued all over the study period as shown by a decrease in the arterial oxygen partial pressure [PaO2] and arterial alveolar oxygen tension PaO2 /PAO2 and an increase in alveol-arterial oxygen tension gradient P [A-a] O2 and pulmonary shunt Qs /Qt. while no significant effect of the different haematocrit values was noted on the pulmonary gas exhange, in addition the tissue oxygenation parameters showed a stability in the oxygen consumption VO2 in spite of a marked decrease in the oxygen delivery DO2 this may be achieved through an increase in both oxygen extraction O2EX% and cardiac index CI