Bleeding and multiorgan injury (ischemic injury by platelet-aggregates from arterial filter, oxidative injury by activated granulocytes) occur in patients undergoing cardiopulmonary bypass (CPB), specially in neonates and elderly patients. The sensitive tracer and morphometric techniques will be used for the mechanistic studies of cell pathology. We will quantify the embolization of platelet-aggregates, migration of activated granulocytes/aggregates from oxygenator/arterial filter in brain and internal organs, using the tracers for In-111 labeled platelets, I-125 labeled fibrinogen, In-111 labeled PMN granulocytes and Tc-99m tracer for brain blood-flow post-CPB. Considering the lack of suitable tracers, previous studies focussed only on plasma proteins and formed elements of blood. We have the data-base for platelet-thrombosis on hollow-fiber devices for oxygenation and hemodialysis for pin-pointing the site of thrombus formation, quantitation of emboli in viscera and quantification of platelet and granulocyte deposition on these devices in in vivo, ex vivo animal models and patients. The kinetics of platelets and granulocytes in the blood and viscera and dynamics of platelet/PMN granulocyte deposition on oxygenator/arterial filter during CPB will be determined in the anesthetized Yorkshire pig model. The oxygenators (Bentley CM-50, 5 meter2) and arterial filter (AF 1025) will be used in this study. The parameters of heparin anticoagulant, surface heparinization and Iloprost infusion, oxygenation time (3 and 6 hours), blood flow (2.5 L/min) and temperature (37oC, 28oC), will be evaluated in 4 groups of 140 pigs. The platelet-fragments will be determined by flow-cytometry with fluorescein-conjugated antibody to platelet-membrane glycoprotein Ib. The regional brain blood flow and thrombus on oxygenator/arterial filter will be imaged with a gamma camera interfaced with the computer. Statistical analyses of data will be performed with Bonferroni procedure. From the biodistribution studies, the platelet-aggregates and PMN granulocytes trapped in the lungs, brain, liver and kidneys will be determined. Understanding the mechanism of bleeding, multiorgan damage and development of pharmacological intervention will result in less post- operative bleeding, morbidity, mortality and early recovery reducing hospitalization cost in patients requiring CPB.
