Comparison of Blood Activation in the Wound, Active Vent, and Cardiopulmonary Bypass Circuit

Extracellular vesicles: biomarkers and regulators of vascular function during extracorporeal circulation

Extracellular vesicles (EVs) are generated at increased rates from parenchymal and circulating blood cells during exposure of the circulation to abnormal flow conditions and foreign materials associated with extracorporeal circuits (ExCors). This review describes types of EVs produced in different ExCors and extracorporeal life support (ECLS) systems including cardiopulmonary bypass circuits, extracorporeal membrane oxygenation (ECMO), extracorporeal carbon dioxide removal (ECCO₂R), apheresis, dialysis and ventricular assist devices. Roles of EVs not only as biomarkers of adverse events during ExCor/ECLS use, but also as mediators of vascular dysfunction are explored. Manipulation of the number or subtypes of circulating EVs may prove a means of improving vascular function for individuals requiring ExCor/ECLS support. Strategies for therapeutic manipulation of EVs during ExCor/ECLS use are discussed such as accelerating their clearance, preventing their genesis or pharmacologic options to reduce or select which and how many EVs circulate. Strategies to reduce or select for specific types of EVs may prove beneficial in preventing or treating other EV-related diseases such as cancer.

Cerebral oxygen saturation during pulsatile and non-pulsatile cardiopulmonary bypass in patients with carotid stenosis

Pulsatile and non-pulsatile cardiopulmonary bypass (CPB) flows may have different impact on cerebral oxygen saturation in patients with restricted cerebral arterial blood supply. Twenty patients, ten diagnosed with carotid stenosis (CS, n = 10) and ten without known carotid disease (Controls, n = 10), were subjected to one period of pulsatile and one period of non-pulsatile flow (6-8 min each) during CPB at 32°C. Cerebral oxygen saturation was registered by near-infrared light spectroscopy (NIRS).The mean arterial pressure (MAP) was significantly lowered by pulsatile CPB flow. The NIRS tissue oxygenation index (TOI) tended to decrease in the CS group and increase in the Controls during pulsatile flow compared with non-pulsatile; however, the changes were not statistically significant.No significant correlations were seen between the changes in MAP and TOI across the observation periods.In conclusion, pulsatile CPB flow caused slightly decreased mean arterial pressure while the effect on cerebral oxygenation was unclear. Pulsatile flow was not found superior to non-pulsatile flow in patients with or without carotid stenosis.

Is elimination of cardiotomy suction preferable in aortic valve replacement? Assessment of perioperative coagulation, fibrinolysis and inflammation

OBJECTIVES

Guidelines recommend the avoidance of direct return of pericardial blood based on evidence from coronary surgery. A continuous auto-transfusion system (CATS) can be a good alternative to cardiotomy suction by reinfusing aspirated pericardial blood without the necessity of intermittent collection. To clarify the effects of direct return of pericardial blood in aortic valve replacement (AVR), we compared the effects of cardiotomy suction and an alternative CATS on perioperative coagulofibrinolysis and inflammation systems, and clinical outcomes.

METHODS

In 40 AVR operations between April 2009 and April 2011, the retransfusion method of pericardial blood during cardiopulmonary bypass (CPB) was allocated to the use of cardiotomy suction (non-Cell-Saver group, n = 20) or CATS (Cell-Saver group, n = 20) under identical protocols of anticoagulation and transfusion. The blood from the left ventricular vent was returned to the venous reservoir. We obtained blood samples at nine points up to the morning after surgery.

RESULTS

Perioperative values for coagulofibrinolysis markers, such as thrombin-antithrombin III complex, fibrinogen degeneration products, D-dimer and plasmin-α2 plasmin inhibitor complex, were significantly lower in the Cell-Saver group than those in the non-Cell-Saver group from 1 h after the initiation of cardiopulmonary bypass to 3 or 6 h after termination of cardiopulmonary bypass (P < 0.05 for all markers). A fibrinolysis inhibition marker of plasminogen activator inhibitor-1 and the inflammation markers of interleukin-6, 8 and 10 as well as tumour necrosis factor-α were not significantly different. The amount of packed red blood cells required after the termination of CPB was significantly less in the Cell-Saver group compared with that in the non-Cell-Saver group (P = 0.004). There were no significant differences in the other clinical outcomes between the two groups.

CONCLUSIONS

In AVR, the avoidance of direct return of pericardial blood induced considerable suppressions of coagulofibrinolysis responses. A CATS is a favourable alternative for managing pericardial blood during cardiopulmonary bypass. Our results support the published guidelines and could help to establish ideal strategies for eliminating the use of cardiotomy suction, thus facilitating less-invasive valve surgeries with marked suppression of coagulofibrinolysis responses.

Impact of retransfusion of blood processed in cell-saver on coagulation versus cardiopulmonary bypass: a prospective observational study using thromboelastography

AIMS

To compare an impact of retransfusion of blood processed in cell-saver (CS) with that of cardiopulmonary bypass (CPB) on blood coagulation in patients undergoing cardiac surgery.

METHODS

Prospective observational study using thromboelastography (TEG).

RESULTS

TEG samples from 170 patients were analyzed. Cardiopulmonary bypass was used in 100 patients while 70 patients were operated off-pump. In 20 off-pump patients collected blood was processed by cell-saver and returned. In all patients clot formation after heparin neutralization by protamine was unimpaired. However, there was a significant increase in fibrinolysis defined by the TEG parameter Lysis time 30 min after the maximum amplitude of the clot was reached (Ly30) in groups with CPB or CS but this increase still did not exceed the threshold for clinical fibrinolysis (Ly30 > 7.5%). In the group without CPB there was no significant impact on coagulation.

CONCLUSION

Surgery that avoids CPB and/or CS is the gentlest method for inducing blood coagulation.

Simultaneous use of argatroban and heparin during cardiopulmonary bypass

Heparin is the routine anticoagulant for cardiopulmonary bypass, but complications due to heparin are often reported. This study assessed argatroban as an alternative to heparin. Normothermic cardiopulmonary bypass with hemodilution was performed for 2 h in 15 dogs (mean weight, 9.8 kg) randomly assigned to 3 groups of 5 each. The controls were given heparin 200 IU x kg(-1) before cardiopulmonary bypass; group A had argatroban infused continuously at a rate of 20 microg x kg(-1) x min(-1); group H/A had half doses of both heparin (100 IU x kg(-1)) and argatroban (10 microg x kg(-1) x min(-1)). Blood samples were collected at 5 time points during the experiment. Activated clotting time, hemoglobin level, platelet counts, and serum concentrations of fibrinogen, antithrombin III, and thrombin-antithrombin III complex were measured. The platelet count was reduced significantly, and the production of thrombin-antithrombin III complex was inhibited in group H/A. Activated clotting time remained <300 sec at all time points in group A, but it was maintained at approximately 400 sec in group H/A. Fibrinogen and antithrombin III levels were reduced to half in all groups after initiation of cardiopulmonary bypass. The simultaneous use of heparin and argatroban infusion might be useful for cardiopulmonary bypass with hemodilution.

The relationships between air exposure, negative pressure, and hemolysis

The purpose of this study was to describe the hemolytic effects of both negative pressure and an air-blood interface independently and in combination in an in vitro static blood model. Samples of fresh ovine or human blood (5 ml) were subjected to a bubbling air interface (0-100 ml/min) or negative pressure (0-600 mm Hg) separately, or in combination, for controlled periods of time and analyzed for hemolysis. Neither negative pressure nor an air interface alone increased hemolysis. However, when air and negative pressure were combined, hemolysis increased as a function of negative pressure, the air interface, and time. Moreover, when blood samples were exposed to air before initiating the test, hemolysis was four to five times greater than samples not preexposed to air. When these experiments were repeated using freshly drawn human blood, the same phenomena were observed, but the hemolysis was significantly higher than that observed in sheep blood. In this model, hemolysis is caused by combined air and negative pressure and is unrelated to either factor alone.

Optimal Versus Suboptimal Perfusion During Cardiopulmonary Bypass and the Inflammatory Response

Despite major improvements in perfusion techniques over the past 50 years, it is still not possible to formulate a clear definition of what is meant by optimal perfusion. In part this is due to the lack of sufficient evidence-based data and in part because of the complex pathophysiology that takes place during cardiac surgery with cardiopulmonary bypass. To find an answer we need to understand the exact mechanism of the inflammatory reaction triggered by the cardiopulmonary bypass. However, it is clear that further improvement of the cardiopulmonary bypass components alone will be sufficient. Only a combined strategy can further improve cardiopulmonary bypass—related morbidity and mortality. Such a combined strategy will embrace perfusion techniques as well as a pharmacological approach. It will also require a continuous monitoring of the microcirculation. The latter will not only allow to rapidly sense changes in the quality of perfusion but, even more important, also make it possible to intervene at the moment of deterioration. Recent research shows that such an approach has positive an impact on cardiopulmonary bypass—related morbidity postoperatively.