Platelet-Emboli from Arterial Filter and Oxygenator: Major Source of Embolic Complications During Cardiopulmonary Bypass (CPB)

Abstract

We developed a direct technique for the estimation of parameters related to half-life (T1/2) and rate constants of embolization (RCE) and quantitation of amount of emboli of three size (small, medium and large) shed from the oxygenator and of arterial filter during cardiopulmonary bypass (CPB). CPB was performed in 16 Yorkshire pigs, systemic heparin group (SHG:6); systemic heparin/heparinized circuit group (SH/HCG:5) and Iloprost (2ng/kg/min)/heparinized circuit group (IHCG:5) with 111In labeled autologous platelets. The anesthetized pigs underwent CPB at 2.5-3.0 L/min for 3 hours. Pigs were injected with 111In platelets (300-420 μCi), 24 hours prior to CPB. During CPB, thrombosis and embolization on oxygenator and filter were monitored by a calibrated Geiger probe. The radioactivity in the oxygenator and filter reached a peak value at 25–45 min. post-CPB; the radioactivity then declined for oxygenator, but remained at steady state for filter suggesting continous embolization at the same rate of trapping. The curve-stripping technique of the normalized radioactivity-time curve of the oxygenator was used for the RCE-estimation of different size of emboli shed from the oxygenator; 42% of thrombus embolized from oxygenator in SHG with 3 rate constants with a T1/2 of 12 min, 42 min and 13 hr; SH/HCG embolized 35% with T1/2 of 78 min and IHCG embolized 30% with a T1/2 of 22 min, indicating that there is less embolization in the IHCG. By direct continuous monitoring, we developed a sensitive technique for quantitation of rate of embolus-shedding during CPB.