Effect of thoracotomy and cardiopulmonary bypass on activated platelet and neutrophil dynamics and platelet emboli in a pig model

Abstract

The effects of thoracotomy and components of extracorporeal circuits on dynamics of platelets and neutrophils were quantified with autologous In-111-labeled platelets (INPLT) and neutrophils (INN) during cardiopulmonary bypass (CPB) operations in Yorkshire pigs. Cardiopulmonary bypass was carried out with a hollow-fiber oxygenator and an arterial filter in 48 pigs (30-35 kg; 12 unoperated controls for platelets and neutrophils; 12 sham operated controls; 12 with 180 minutes of CPB with platelets and neutrophils; 12 with 90 minutes of CPB and 90 minutes of reperfusion at 2.5-3.5 one/min. Platelets and neutrophils were labeled with In-111 tropolone and were injected intravenously: platelets at 24 hours and neutrophils at 15 minutes before CPB. All pigs were systemically heparinized [activated coagulation time (ACT) > 400 seconds]; CPB was instituted with a roller pump, oxygenator (OX; Bentley Univox, 1.8 m2), and arterial filter (AF; 0.025 m2) for durations of 180 minutes and 90 minutes of bypass, followed by 90 minutes of reperfusion. The kinetics and pooling of platelets and neutrophils were monitored by a Geiger probe. The adherent thrombi and neutrophils in the OX, AF, viscera, and brain were imaged with a gamma camera and were measured with an ion chamber and a gamma counter. The percentile distribution of labeled platelets and neutrophils expressed as the mean +/- standard deviation of injected dose in eight groups was calculated and statistical analyses were performed (ANOVA and paired t-test). Sham operation alone increased platelet retention in the lung, heart, and brain significantly (p < 0.001) over that of unoperated pigs. Neutrophil margination to lung immediately after injection was high; CPB and reperfusion altered the distribution in blood, viscera, and connective tissues. During CPB, an equilibrium among single platelets, platelet thrombi, and emboli was reached in the blood, oxygenator, arterial filter, perfused organs, and tissues. After CPB, the pulmonary neutrophil retention increased significantly (p < 0.001). Reperfusion of 90 minutes following 90 minutes of CPB decreased the level of neutrophils and increased the level of platelets in the lung. Only a small amount of platelets and neutrophils was retained in the oxygenator and arterial filter. Neutrophil retention in the OX and AF was higher than that of platelets. The small amount of retained neutrophils in the heart, kidneys, and brain suggested that cytokines, rather than marginated neutrophils alone, may play a major role in inflammatory insult to these organs during and after CPB. OX thrombi increased with the time of CPB; AF thrombus in both groups was almost similar. During CPB, AF functioned minimally as a thrombus trap with a small percent of retained thrombi; reperfusion post-CPB did not change the amount. Thoracotomy alone has a significant effect on platelet and neutrophil kinetics, and on the subsequent effect of thrombus formation, embolization, and neutrophil margination in organs during the CPB procedure.

Do Surface-Modifying Additive Circuits Reduce the Rate of Cerebral Microemboli During Cardiopulmonary Bypass?

“…In this study, we did not find any differences between SMA and standard CPB circuits in the total or partial count of HITS measured in the MCAs at different time-points during CPB. Previous studies have found no differences in the rate of retinal emboli detected by fluorescein angiography (9) or in the counts of emboli trapped in brain and lungs (10,11) between heparin-coated and standard CPB circuits during CPB. Our findings suggest that improving the biocompatibility of CPB circuits may not necessarily decrease cerebral microemboli during CPB.…”

A kinetic model of bone marrow neutrophil production that characterizes late phenotypic maturation

“…Although the pulmonary marginal neutrophil reserve is excluded from the circulation during ECC, demargination of neutrophils from other organ-specific vascular beds can contribute to expansion of the circulating neutrophil pool. Because ECC is associated with limited demargination (15,16), it is likely that contributions from the marginal neutrophil pool are not likely to significantly confound our conclusions.…”

“…We anticipated that such an acute reduction in transit time may be quantifiable by determining the previously unknown rate of change in postmitotic maturation time during active neutrophil recruitment. Neutrophil postmitotic transit time was evaluated in terms of mean cellular age by modeling circulating neutrophil numbers during ECC, a stimulus that induces bone marrow neutrophil recruitment (38,41) in association with limited demargination (15,16) and which permits repeated and frequent sampling. Our model predicts the rate of change in the average age at which neutrophils exit the bone marrow during active neutrophil recruitment.…”

Platelet Storage Temperature – How Low Can We Go?

“…Dogs have been used to study fluorescently labeled rehydratedlyophilized platelet incorporation into wounds by fluorescent microscopy [82], and the use of porcine platelets has been proposed for studies of cold-induced activation of platelets [83]. However, few in vivo platelet studies are reported in pigs [84,85]. Murine transfusion models have been used to dissect platelet clearance mechanisms [17,56].…”