Strategies to reduce hemostatic activation during cardiopulmonary bypass

The association between platelet dysfunction and adverse outcomes in cardiac surgical patients

Haemostatic activation during cardiopulmonary bypass is associated with prothrombotic complications. Although it is not possible to detect and quantify haemostatic activation directly, platelet dysfunction, as measured with point-of-care-assays, may be a useful surrogate. In this study, we assessed the association between cardiopulmonary bypass-associated platelet dysfunction and adverse outcomes in 3010 cardiac surgical patients. Platelet dysfunction, as measured near the end of the rewarming phase of cardiopulmonary bypass, was calculated as the proportion of non-functional platelets after activation with collagen. Logistic regression and multivariable analyses were applied to assess the relationship between platelet dysfunction and a composite of in-hospital death; myocardial infarction; stroke; deep vein thrombosis or pulmonary embolism; and acute kidney injury (greater than a two-fold increase in creatinine). The outcome occurred in 251 (8%) of 3010 patients. The median (IQR [range]) percentage platelet dysfunction was less for those without the outcome as compared with those with the outcome; 14% (8-28% [1-99%]) vs. 19% (11-45% [2-98%]), p < 0.001. After risk adjustment, platelet dysfunction was independently associated with the composite outcome (p < 0.001), such that for each 1% increase in platelet dysfunction there was an approximately 1% increase in the composite outcome (OR 1.012; 95%CI 1.006-1.018). This exploratory study suggests that cardiopulmonary bypass-associated platelet dysfunction has prognostic value and may be a useful clinical measure of haemostatic activation in cardiac surgery.

[Postoperative excessive blood loss after cardiac surgery can be predicted with International Society on Thrombosis and Hemostasis scoring system]

BACKGROUND AND OBJECTIVE

Prediction of postoperative excessive blood loss is useful for management of Intensive Care Unit after cardiac surgery. The aim of present study was to examine the effectiveness of International Society on Thrombosis and Hemostasis scoring system in patients with cardiac surgery.

METHOD

After obtaining approval from the institutional review board, the medical records of patients undergoing elective cardiac surgery using Cardio-Pulmonary Bypass between March 2010 and February 2014 were retrospectively reviewed. International Society on Thrombosis and Hemostasis score was calculated in intensive care unit and patients were divided with overt disseminated intravascular coagulation group and non-overt disseminated intravascular coagulation group. To evaluate correlation with estimated blood loss, student t-test and correlation analyses were used.

RESULTS

Among 384 patients with cardiac surgery, 70 patients with overt disseminated intravascular coagulation group (n=20) or non-overt disseminated intravascular coagulation group (n=50) were enrolled. Mean disseminated intravascular coagulation scores at intensive care unit admission was 5.35±0.59 (overt disseminated intravascular coagulation group) and 2.66±1.29 (non-overt disseminated intravascular coagulation group) and overt disseminated intravascular coagulation was induced in 29% (20/70). Overt disseminated intravascular coagulation group had much more EBL for 24h (p=0.006) and maintained longer time of intubation time (p=0.005).

CONCLUSION

In spite of limitation of retrospective design, management using International Society on Thrombosis and Hemostasis score in patients after cardiac surgery seems to be helpful for prediction of the post- cardio-pulmonary bypass excessive blood loss and prolonged tracheal intubation duration.

Tranexamic acid leads to paradoxical coagulation changes during cardiac surgery: a pilot rotational thromboelastometry study

BACKGROUND

Tranexamic acid (TXA) is increasingly used during major surgery with the goal to reduce excessive bleeding, transfusion requirements, and reexploration. Our aim was to examine the effect of TXA on coagulation at different times during cardiac surgery using rotational thromboelastometry.

MATERIALS AND METHODS

Nineteen adult males (EuroSCORE 4-5) were recruited consecutively for first-time cardiopulmonary bypass (CPB) surgery. Ten patients received TXA at anesthesia and nine received no TXA. Rotational thromboelastometry analysis occurred before anesthesia (baseline), after sternotomy, after CPB-heparinization and surgery, and after protamine administration-sternal closure.

RESULTS

A median sternotomy had no effect on clot time (CT), formation, amplitude, or lysis in non-TXA patients. In contrast, TXA patients had twofold prolonged clotting time (all-tests) and ∼30% reduced FIBTEM (A5-30) and maximum clot firmness, indicating reduced thrombin generation and lower clot fibrinogen. After CPB, CTs in both groups were prolonged, possibly linked to overheparinization. In addition, TXA patients had significantly decreased EXTEM (A5-30), suggesting lower clot strength. After protamine-sternal closure, clotting time remained prolonged in both groups, and TXA patients had a persistently 25%-33% lower FIBTEM (A5-30) and maximum clot firmness. TXA patients also had significantly reduced platelet numbers (37% from baseline), which continued Days 1 and 2. Maximum clot lysis was <10% indicating little or no hyperfibrinolysis during cardiac surgery.

CONCLUSIONS

In this nonrandomized, nonblinded, observational trial, patients in the TXA group displayed prolonged CTs and clot fibrinogen (FIBTEM A5-30) after sternotomy, decreased clot strength (EXTEM) after CPB/surgery, and acute thrombocytopenia after protamine-sternal closure. There was no significant decrease in clot lysis, questioning the need for TXA in this medium-risk group.

Human amniotic mesenchymal stem cells alleviate lung injury induced by ischemia and reperfusion after cardiopulmonary bypass in dogs

Transplantation of mesenchymal stem cells may inhibit pathological immune processes contributing to ischemia/reperfusion (I/R) injury. This study aimed to assess the capacity of human amniotic MSC (hAMSCs) to ameliorate I/R injury in a dog model of cardiopulmonary bypass (CPB). Dissociated hAMSCs were cultured ex vivo, and their immunophenotypes were assessed by flow cytometry and immunohistochemistry. A dog model of CPB was established by surgical blockage of the aorta for 1 h. Dogs either underwent mock surgery (Sham group), CPB (model group), or CPB, followed by femoral injection of 2 × 10(7) hAMSCs (n=6). Anti-human nuclei staining revealed hAMSCs in the lungs 3 h after surgery. Oxygen index (OI) and respiratory index (RI) of arterial blood were measured using a biochemical analyzer. Venous blood TNF-α, IL-8, MMP-9, and IL-10 concentrations were measured by ELISA. Pathological changes in the lung were assessed by light microscopy. Third-generation-cultured hAMSCs expressed high levels of CD29, CD44, CD49D, CD73, and CD166 levels, but low CD34 or CD45 amounts and their cytoplasm contained Vimentin. In CPB model animals, OI was elevated and RI reduced; TNF-α, IL-8, and MMP-9 levels were elevated, and IL-10 levels reduced within 3h (P<0.05), but hAMSC transplantation significantly ameliorated these changes (P<0.05). Pathological changes observed in the hAMSC group were significantly less severe than those in the CPB group. In conclusion, hAMSC transplantation can downregulate proinflammatory factors and reduce MMP-9 levels, whereas upregulating the anti-inflammatory molecule IL-10, thus reducing I/R lung injury in a dog model of CPB.

Cardiopulmonary bypass parameters and hemostatic response to cardiopulmonary bypass in infants versus children

OBJECTIVE

Because infants have relatively more blood loss (mL/kg) than older children during cardiac surgery involving cardiopulmonary bypass (CPB), the authors compared hemostatic activation between infants and older children undergoing cardiac surgery.

DESIGN

Observational study.

SETTING

University-affiliated children's hospital.

PARTICIPANTS

Twenty-eight children (18 infants <1 year and 10 children >1 year) undergoing cardiac surgery with CPB.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Markers of coagulation and fibrinolysis were evaluated at 9 sample points before, during, and after CPB in the 28 children. Infants had greater chest tube output, longer CPB times, and a larger drop in platelet counts during CPB than children. Active tissue plasminogen activator (tPA) increased during CPB in both groups, with infants showing lower levels than children (p < 0.001). In both groups, active plasminogen activator inhibitor type 1 (PAI-1) first decreased during CPB and then increased above baseline postoperatively. Infants had higher PAI-1 than children near the end of CPB (p = 0.01). Thrombin-antithrombin complex levels increased during and after CPB, with infants showing lower levels only during CPB (p = 0.01). D-dimer and prothrombin activation peptide (F1.2) levels increased in a similar pattern for both groups during and after CPB. The length of aortic cross-clamp time and the level of F1.2 after protamine administration correlated significantly and independently with 12-hour chest tube output.

CONCLUSIONS

Compared with children, infants had greater blood loss (mL/kg), greater drop in platelets during CPB, lower active tPA, and higher active PAI-1. Cumulative thrombin generation after CPB, indicated by F1.2 levels, correlated with early blood loss.

Perioperative blood transfusion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and The Society of Cardiovascular Anesthesiologists clinical practice guideline

BACKGROUND

A minority of patients having cardiac procedures (15% to 20%) consume more than 80% of the blood products transfused at operation. Blood must be viewed as a scarce resource that carries risks and benefits. A careful review of available evidence can provide guidelines to allocate this valuable resource and improve patient outcomes.

METHODS

We reviewed all available published evidence related to blood conservation during cardiac operations, including randomized controlled trials, published observational information, and case reports. Conventional methods identified the level of evidence available for each of the blood conservation interventions. After considering the level of evidence, recommendations were made regarding each intervention using the American Heart Association/American College of Cardiology classification scheme.

RESULTS

Review of published reports identified a high-risk profile associated with increased postoperative blood transfusion. Six variables stand out as important indicators of risk: (1) advanced age, (2) low preoperative red blood cell volume (preoperative anemia or small body size), (3) preoperative antiplatelet or antithrombotic drugs, (4) reoperative or complex procedures, (5) emergency operations, and (6) noncardiac patient comorbidities. Careful review revealed preoperative and perioperative interventions that are likely to reduce bleeding and postoperative blood transfusion. Preoperative interventions that are likely to reduce blood transfusion include identification of high-risk patients who should receive all available preoperative and perioperative blood conservation interventions and limitation of antithrombotic drugs. Perioperative blood conservation interventions include use of antifibrinolytic drugs, selective use of off-pump coronary artery bypass graft surgery, routine use of a cell-saving device, and implementation of appropriate transfusion indications. An important intervention is application of a multimodality blood conservation program that is institution based, accepted by all health care providers, and that involves well thought out transfusion algorithms to guide transfusion decisions.

CONCLUSIONS

Based on available evidence, institution-specific protocols should screen for high-risk patients, as blood conservation interventions are likely to be most productive for this high-risk subset. Available evidence-based blood conservation techniques include (1) drugs that increase preoperative blood volume (eg, erythropoietin) or decrease postoperative bleeding (eg, antifibrinolytics), (2) devices that conserve blood (eg, intraoperative blood salvage and blood sparing interventions), (3) interventions that protect the patient's own blood from the stress of operation (eg, autologous predonation and normovolemic hemodilution), (4) consensus, institution-specific blood transfusion algorithms supplemented with point-of-care testing, and most importantly, (5) a multimodality approach to blood conservation combining all of the above.