EMBOLI FROM AN EXTRALUMINAL BLOOD-FLOW HOLLOW-FIBER OXYGENATOR WITH AND WITHOUT AN ARTERIAL FILTER DURING CARDIOPULMONARY BYPASS IN A PIG MODEL

The effect of an arterial filter on visceral emboli was quantified wit h autologous indium-111 labeled platelets (INPLT) during cardiopulmona ry bypass (CPB) in Yorkshire pigs. Biodistribution of INPLT was determ ined in 12 control pigs (30-35 kg, unoperated control [n = 6] and sham operated control [n = 6]). CPB was carried out with (n = 6) and witho ut (n = 6) an arterial filter in 12 pigs at a flow rate of 2.5-3.5 L/m in. Platelets labeled with In-111 tropolone (650-780 mu Ci) were injec ted intravenously 24 hr before CPB. All pigs were systemically heparin ized (activated coagulation time > 400 sec); CPB was instituted with a roller pump, an extraluminal blood flow oxygenator (Bentley Univox, 1 .8 m(2)), and an arterial filter (0.25 m(2)) and continued for 3 hr. P latelet kinetics, pooling, and counts were monitored by a Geiger probe and a Coulter counter. The thrombi in the oxygenator and arterial fil ter and emboli in viscera and brain were imaged with a gamma camera an d measured with an ion chamber and gamma counter. Percentage of INPLT (mean +/- SD) in organs, tissues, and components of the circuit in fou r groups of pigs was calculated. Flow cytometry with antibodies to CD6 1. (GPIIIa) and CD62P (GMP-140: control) of porcine platelets was carr ied out with blood samples taken before, during, and after CPB for est imation of circulating platelet aggregates and platelet microparticles . Pulmonary, renal, cardiac, and cerebral emboli in pigs undergoing CP B with and without a filter were similar (p < 0.1). The amount of filt er adherent thrombi was small (0.04 +/- 0.01%); oxygenator adherent th rombus in both groups was similar (p < (0.1). Emboli were found in the cerebral medulla, hippocampus, and posterior cerebral cortex in both groups. During CPB, the arterial filter functioned minimally as a frap for platelet thrombi detached from the oxygenator and circulating emb oli. Plow cytometry of blood demonstrated the shift of equilibria from single platelets to platelet aggregates and microparticles during CPB and their gradual reversal to single platelets after CPB; the loosely adherent emboli disaggregated and further shifted these equilibria to single platelets and smaller aggregates, probably through the action of endogenous nitric oxide and prostacyclin. The emboli were trapped i n organs and tissues and microparticles were sequestered by the reticu loendothelial system.