Hemostatic alterations during coronary artery bypass grafting

Cardiopulmonary bypass associated acute kidney injury: better understanding and better prevention

Cardiopulmonary bypass (CPB) is a common technique in cardiac surgery but is associated with acute kidney injury (AKI), which carries considerable morbidity and mortality. In this review, we explore the range and definition of CPB-associated AKI and discuss the possible impact of different disease recognition methods on research outcomes. Furthermore, we introduce the specialized equipment and procedural intricacies associated with CPB surgeries. Based on recent research, we discuss the potential pathogenesis of AKI that may result from CPB, including compromised perfusion and oxygenation, inflammatory activation, oxidative stress, coagulopathy, hemolysis, and endothelial damage. Finally, we explore current interventions aimed at preventing and attenuating renal impairment related to CPB, and presenting these measures from three perspectives: (1) avoiding CPB to eliminate the fundamental impact on renal function; (2) optimizing CPB by adjusting equipment parameters, optimizing surgical procedures, or using improved materials to mitigate kidney damage; (3) employing pharmacological or interventional measures targeting pathogenic factors.

Supplemental fibrinogen restores thrombus formation in cardiopulmonary bypass-induced platelet dysfunction ex vivo

BACKGROUND

Major cardiac surgery related blood loss is associated with increased postoperative morbidity and mortality. Platelet dysfunction is believed to contribute to post-cardiopulmonary bypass (CPB)-induced microvascular bleeding. We hypothesised that moderately hypothermic CPB induces platelet dysfunction and that supplemental fibrinogen can restore in vitro thrombus formation.

METHODS

Blood from 18 patients, undergoing first-time elective isolated aortic valve surgery was drawn before CPB, 30 min after initiation of CPB, and after CPB and protamine administration, respectively. Platelet aggregation was quantified by optical aggregometry, platelet activation by flow-cytometric detection of platelet surface expression of P-selectin, annexin V, and activated glycoprotein IIb/IIIa, thrombus formation under flow and effect of supplemental fibrinogen (4 mg ml-1) on in vitro thrombogenesis.

RESULTS

Post-CPB adenosine-diphosphate and TRAP-6-induced aggregation decreased by 40% and 10% of pre-CPB levels, respectively (P<0.0001). Although CPB did not change glycoprotein IIb/IIIa receptor expression, it increased the percentage of unstimulated P-selectin (1.2% vs 7%, P<0.01) positive cells and annexin V mean fluorescence intensity (15.5 vs 17.2, P<0.05), but decreased percentage of stimulated P-selectin (52% vs 26%, P<0.01) positive cells and annexin V mean fluorescence intensity (508 vs 325, P<0.05). Thrombus area decreased from 6820 before CPB to 5230 after CPB (P<0.05, arbitrary units [a.u.]). Supplemental fibrinogen increased thrombus formation to 20 324 and 11 367 a.u. before CPB and after CPB, respectively (P<0.001), thereby restoring post-CPB thrombus area to levels comparable with or higher than pre-CPB baseline.

CONCLUSIONS

Single valve surgery using moderately hypothermic CPB induces partial platelet dysfunction. Thrombus formation was restored in an experimental study design by ex vivo supplementation of fibrinogen.

Anti-factor X Activity Levels with Continuous Intravenous Infusion and Subcutaneous Administration of Enoxaparin after Coronary Artery Bypass Grafting: a Randomized Clinical Trial

BACKGROUND

Low-molecular-weight heparin enoxaparin is widely used in pharmacological thromboprophylaxis after coronary artery bypass grafting (CABG). The aim of this study was to compare anti-factor X activity (anti-Xa) levels when the thromboprophylactic dose of enoxaparin was provided after CABG, with two different administration routes: continuous intravenous infusion (CIV) and subcutaneous bolus (SCB) injection. We hypothesized that the current standard method of SCB administration might lead to lower anti-Xa levels than recommended in other patient groups, due to reduced bioavailability.

METHODS

In this prospective, randomized, controlled clinical trial, 40 patients scheduled for elective CABG were randomized to receive 40 mg of enoxaparin per day either as CIV or SCB for 72 h. Enoxaparin was initiated 6-10 h after CABG. Anti-Xa levels were measured 12-14 times during the study period. The primary outcome i.e. the maximum anti-Xa concentration over 0-24 h (C_max0-24h ), was calculated from these measured values. Secondary outcomes were C_max25-72h and the trough concentration of anti-Xa after 72 h of enoxaparin initiation (C_72h ).

RESULTS

Twenty patients were randomized to the CIV-group and 19 to the SCB-group. The median anti-Xa C_max0-24h was significantly lower in the CIV-group than in the SCB-group: 0.15 [interquartile range (IQR) 0.13-0.19] IU/mL versus 0.25 (IQR 0.18-0.32) IU/mL, p < 0.005. The median anti-Xa C_max25-72h was 0.12 (IQR, 0.1-0.17) IU/mL versus 0.23 (IQR 0.19-0.31) IU/mL, respectively, p < 0.005. At 72 h, there was no difference between the groups in their anti-Xa levels.

CONCLUSIONS

In this low-risk CABG patient population, SCB administration of a thromboprophylactic dose of enoxaparin provided anti-Xa levels that are considered sufficient for thromboprophylaxis in other patient groups. CIV administration resulted in lower anti-Xa levels compared to the SCB route.

Tranexamic Acid Administered During Off-Pump Coronary Artery Bypass Graft Surgeries Achieves Good Safety Effects and Hemostasis

BACKGROUND

Tranexamic acid (TXA) administered during off-pump coronary artery bypass (OPCAB) surgeries has achieved good blood control in small cohorts. We aimed to investigate the safety issues and hemostasis associated with TXA administration during OPCAB in a large retrospective cohort study.

METHODS

This study included 19,687 patients with OPCAB from 2009 to 2019. A total of 1,307 patients were excluded because they were younger than 18 years or certain values were missing. Among the remaining 18,380 patients, 10,969 were in the TXA group and 7,411 patients were in the no-TXA group. There were 4,889 patients whose TXA dose was ≥50 mg/kg, and the remaining 6,080 patients had a TXA dose of <50 mg/kg. Propensity score matching (PSM) was performed between the TXA and no-TXA groups and between the high-dose and low-dose groups, and statistical analysis was performed.

RESULTS

Tranexamic acid administration did not increase the risk of hospital death or thromboembolic events. Patients who administered TXA had less blood loss at 24 h (478.32 ± 276.41 vs. 641.28 ± 295.09, p < 0.001) and 48 h (730.59 ± 358.55 vs. 915.24 ± 390.13, p < 0.001) and total blood loss (989.00 ± 680.43 vs. 1,220.01 ± 720.68, p < 0.001) after OPCAB than the patients with non-TXA. Therefore, the risk of total blood exposure [odds ratio (OR) = 0.50, 95% CI 0.47-0.54, p < 0.001] or blood component exposure (p < 0.001) was decreased significantly in the patients who administered TXA. The TXA dosage did not impact the patient survival, thromboembolic events, or blood management.

CONCLUSIONS

The application of TXA was safe and provided blood control in patients with OPCAB, and the dosage did not affect these parameters.

Tranexamic Acid Administered During Off-Pump Coronary Artery Bypass Graft Surgeries Achieves Good Safety Effects and Hemostasis

BACKGROUND

Tranexamic acid (TXA) administered during off-pump coronary artery bypass (OPCAB) surgeries has achieved good blood control in small cohorts. We aimed to investigate the safety issues and hemostasis associated with TXA administration during OPCAB in a large retrospective cohort study.

METHODS

This study included 19,687 patients with OPCAB from 2009 to 2019. A total of 1,307 patients were excluded because they were younger than 18 years or certain values were missing. Among the remaining 18,380 patients, 10,969 were in the TXA group and 7,411 patients were in the no-TXA group. There were 4,889 patients whose TXA dose was ≥50 mg/kg, and the remaining 6,080 patients had a TXA dose of <50 mg/kg. Propensity score matching (PSM) was performed between the TXA and no-TXA groups and between the high-dose and low-dose groups, and statistical analysis was performed.

RESULTS

Tranexamic acid administration did not increase the risk of hospital death or thromboembolic events. Patients who administered TXA had less blood loss at 24 h (478.32 ± 276.41 vs. 641.28 ± 295.09, p < 0.001) and 48 h (730.59 ± 358.55 vs. 915.24 ± 390.13, p < 0.001) and total blood loss (989.00 ± 680.43 vs. 1,220.01 ± 720.68, p < 0.001) after OPCAB than the patients with non-TXA. Therefore, the risk of total blood exposure [odds ratio (OR) = 0.50, 95% CI 0.47-0.54, p < 0.001] or blood component exposure (p < 0.001) was decreased significantly in the patients who administered TXA. The TXA dosage did not impact the patient survival, thromboembolic events, or blood management.

CONCLUSIONS

The application of TXA was safe and provided blood control in patients with OPCAB, and the dosage did not affect these parameters.

Fibrinogen and Bleeding in Adult Cardiac Surgery: A Review of the Literature

Background: Fibrinogen is a substrate for blood clots formation. In cardiac surgery, a number of different mechanisms lead to a decrease in fibrinogen levels and consequent impaired haemostasis. Patients undergoing cardiac surgery are therefore frequently exposed to blood loss and allogeneic blood transfusion, which are risk factors associated with morbidity and mortality. Thus, particular efforts in fibrinogen management should be made to decrease bleeding and the need for blood transfusion. Therefore, fibrinogen remains an active focus of investigations from basic science to clinical practice. This review aims to summarise the latest evidence regarding the role of fibrinogen and current practices in fibrinogen management in adult cardiac surgery. Methods: The PubMed database was systematically searched for literature investigating the role and disorders of fibrinogen in cardiac surgery and diagnostic and therapeutic procedures related to fibrinogen deficiency aimed at reducing blood loss and transfusion requirements. Clinical trials and reviews from the last 10 years were included. Results: In total, 146 articles were analysed. Conclusion: The early diagnosis and treatment of fibrinogen deficiency is crucial in maintaining haemostasis in bleeding patients. Further studies are needed to better understand the association between fibrinogen levels, bleeding, and fibrinogen supplementation and their impacts on patient outcomes in different clinical settings.

Local IGF Bioactivity Associates with High PAPP-A Activity in the Pericardial Cavity of Cardiovascular Disease Patients

OBJECTIVE

Pregnancy-associated plasma protein-A (PAPP-A) has been suggested as a proatherogenic enzyme by its ability to locally increase insulin-like growth factor (IGF) activity through proteolytic cleavage of IGF binding protein-4 (IGFBP-4). Recently, stanniocalcin-2 (STC2) was discovered as an inhibitor of PAPP-A. This study aimed to investigate IGFBP-4, PAPP-A, and STC2 as local regulators of IGF bioactivity in the cardiac microenvironment by comparing levels in the pericardial fluid with those in the circulation of patients with cardiovascular disease.

METHODS

Plasma and pericardial fluid were obtained from 39 patients undergoing elective cardiothoracic surgery, hereof 15 patients with type 2 diabetes. Concentrations of IGF-I, intact and fragmented IGFBP-4, PAPP-A, and STC2 were determined by immunoassays and IGF bioactivity by a cell-based assay.

RESULTS

In pericardial fluid, the concentrations of total IGF-I, intact IGFBP-4, and STC2 were 72 ± 10%, 91 ± 5%, and 40 ± 24% lower than in plasma, while PAPP-A was 15 times more concentrated. The levels of the 2 IGFBP-4 fragments generated by PAPP-A and reflecting PAPP-A activity were elevated by more than 25%. IGF bioactivity was 62 ± 81% higher in the pericardial fluid than plasma. Moreover, pericardial fluid levels of both IGFBP-4 fragments correlated with the concentration of PAPP-A and with the bioactivity of IGF. All protein levels were similar in pericardial fluid from nondiabetic and diabetic subjects.

CONCLUSIONS

PAPP-A increases IGF bioactivity by cleavage of IGFBP-4 in the pericardial cavity of cardiovascular disease patients. This study provides evidence for a distinct local activity of the IGF system, which may promote cardiac dysfunction and coronary atherosclerosis.

Society of Cardiovascular Anesthesiologists Clinical Practice Improvement Advisory for Management of Perioperative Bleeding and Hemostasis in Cardiac Surgery Patients

Bleeding after cardiac surgery is a common and serious complication leading to transfusion of multiple blood products and resulting in increased morbidity and mortality. Despite the publication of numerous guidelines and consensus statements for patient blood management in cardiac surgery, research has revealed that adherence to these guidelines is poor, and as a result, a significant variability in patient transfusion practices among practitioners still remains. In addition, although utilization of point-of-care (POC) coagulation monitors and the use of novel therapeutic strategies for perioperative hemostasis, such as the use of coagulation factor concentrates, have increased significantly over the last decade, they are still not widely available in every institution. Therefore, despite continuous efforts, blood transfusion in cardiac surgery has only modestly declined over the last decade, remaining at ≥50% in high-risk patients. Given these limitations, and in response to new regulatory and legislature requirements, the Society of Cardiovascular Anesthesiologists (SCA) has formed the Blood Conservation in Cardiac Surgery Working Group to organize, summarize, and disseminate the available best-practice knowledge in patient blood management in cardiac surgery. The current publication includes the summary statements and algorithms designed by the working group, after collection and review of the existing guidelines, consensus statements, and recommendations for patient blood management practices in cardiac surgery patients. The overall goal is creating a dynamic resource of easily accessible educational material that will help to increase and improve compliance with the existing evidence-based best practices of patient blood management by cardiac surgery care teams.

The association of preoperative atrial fibrillation with post-cardiopulmonary bypass hyperfibrinolysis in rheumatic valvular heart disease patients

OBJECTIVE

The purpose of this study was to assess the fibrinolytic status after cardiopulmonary bypass in rheumatic valvular heart disease patients, and detect the associated factors of post-cardiopulmonary bypass hyperfibrinolysis.

METHODS

According to the fibrinolytic status after cardiopulmonary bypass, 203 rheumatic valvular heart disease patients were divided into two groups: hyperfibrinolysis group (H group, n = 78) and non-hyperfibrinolysis group (NH group, n = 125). The demographic characteristics, operative variables, and postoperative follow-ups were compared between these two groups.

RESULTS

The incidence of hyperfibrinolysis was 38.4% after cardiopulmonary bypass. Patients in the H group had a significant higher incidence of preoperative atrial fibrillation than patients in the NH group (92.3% vs. 55.2%, P < 0.01). Furthermore, postoperative daily drainage (655.3 ± 131.5 ml vs. 535.4 ± 161.4 ml, P < 0.01), transfusion volume of fresh frozen plasma (621.8 ± 220.2 ml vs. 455.2 ± 208.5 ml, P < 0.01), and red blood cells (5.9 ± 2.2 u vs. 4.7 ± 2.8 u, P < 0.01) was greater in the H group than in the NH group. Moreover, the logistic regression analysis revealed that preoperative atrial fibrillation was associated with post-cardiopulmonary bypass hyperfibrinolysis (OR = 19.691, 95% CI = 6.849-56.612; P < 0.05).

CONCLUSION

Preoperative artial fibrillation is associated with post-cardiopulmonary bypass hyperfibrinolysis in rheumatic valvular heart disease patients.

Postoperative thrombotic effects of tranexamic acid in open heart surgery

BACKGROUND

Following the administration of tranexamic acid, the occurrence of thromboembolic events is a controversial issue.

AIMS

In this retrospective cohort study, we aimed to determine the possible thromboembolic complications due to tranexamic acid as a prophylactic method in patients undergoing open heart surgery.

METHODS

The data of 172 adult patients undergoing open heart surgery were analyzed. All patients received tranexamic acid at a dose of 50 mg/kg. The patients were divided into 3 groups as multiple-valve surgery (group 1), coronary bypass alone (group 2), and coronary bypass with valve surgery (group 3). The amount of blood transfusion, bleeding in intra- and postoperative period, and the presence of thromboembolic events including myocardial infarction, stroke, pulmonary embolism, and deep vein thrombosis were investigated.

RESULTS

Patient demographics and duration of surgery were not significantly different in groups (p > 0.05). Hb, Htc, INR, and platelet levels of all groups did not differ significantly (p > 0.05). In total, 7 patients underwent reexploration. Postoperative DVT, stroke, and seizure were not seen at all. There was no statistically significant difference between groups in terms of the amount of blood transfusion, drainage, or peritoneal hematoma. The length of hospital stay and the mortality rate did not differ (p > 0.05).

CONCLUSIONS

In patients receiving tranexamic acid infusion at 50 mg/kg dose, reexploration rates remained at 4.1% even after major cardiac surgeries. No thrombosis, stroke, or seizure were reported. Our findings support that tranexamic acid is a safe drug which has positive effect on reducing perioperative bleeding.

Short-term recovery pattern of plasma fibrinogen after cardiac surgery: A prospective observational study

Low plasma fibrinogen level is common after cardiopulmonary bypass (CPB). Current substitution practice with fibrinogen concentrate generally follows a single measurement and cut-off values from the literature, whereas early postoperative endogenous fibrinogen kinetics is incompletely described and widely disregarded. The aim of this study was to determine the short-term recovery pattern of plasma fibrinogen after CPB weaning. Our hypothesis was that in the absence of surgical bleeding, CPB-induced hypofibrinogenemia would resolve spontaneously and predictably within a few hours. In a prospective, observational study of 26 patients undergoing conventional CPB (cCPB) or minimally invasive extracorporeal circulation (MiECC), Clauss fibrinogen level (C-FIB) was determined at 10 closely spaced time points after protamine administration. Primary endpoint was the time to recovery of post-CPB fibrinogen levels to ≥1.5 g/L. C-FIB reached its nadir after protamine administration corresponding to 62 ± 5% (mean ± SD) of the baseline level after cCPB and 68 ± 7% after MiECC (p = 0.027 vs. cCPB). C-FIB recovered spontaneously at a nearly constant rate of approximately 0.08 g/L per hour. In all patients, C-FIB was ≥1.5 g/L at 4 hours and ≥2.0 g/L at 13 hours after CPB weaning. Following cardiac surgery with CPB and in the absence of surgical bleeding, spontaneous recovery of normal endogenous fibrinogen levels can be expected at a rate of 0.08 g/L per hour. Administration of fibrinogen concentrate triggered solely by a single-point measurement of low plasma fibrinogen some time after CPB is not justified.

Fibrinogen levels compensation of thrombocytopenia-induced bleeding following cardiac surgery

BACKGROUND

After cardiopulmonary bypass (CPB) thrombocytopenia is a relatively common pattern which may trigger postoperative bleeding. The purpose of this study is to verify if the endogenous fibrinogen levels are independent determinants of chest drain blood loss and need for allogeneic blood products transfusions in a clinical model of post-CPB thrombocytopenia.

METHODS

Retrospective analysis on 445 consecutive patients having a platelet count <100×1000cells/μL after CPB. Based on the fibrinogen levels the patients were divided into three groups with similar platelet count and low (LF, median 170mg/dL), intermediate (IF, median 215mg/dL), and high (HF, median 280mg/dL), fibrinogen levels. Chest drain blood loss (mL/12h), transfusion rate of red blood cells (RBC), fresh frozen plasma (FFP) and platelet concentrates were assessed and compared between groups.

RESULTS

There was a significant (P=0.001) difference in chest drain blood loss with higher values in the LF group (487mL/12h, IQR 300-600mL/12h) than in the IF group (350mL/12h, IQR 200-500mL/12h) and the HF group (300mL/12h, IQR 200-475mL/12h). Transfusion rates of FFP significantly (P=0.014) differed between groups (LF: 18.4%, IF: 7.9%, HF: 9.2%) and platelet concentrate transfusions significantly (P=0.020) differed between groups (LF: 23.5%, IF: 16.5%, HF: 10.7%). In multivariable models, these differences were confirmed. Thromboelastography parameters showed an effective compensation of clot firmness in group HF vs. IF and LF.

CONCLUSIONS

Levels of fibrinogen >240mg/dL compensate the decrease in clot firmness observed in thrombocytopenic patients following CPB, and reduce bleeding and transfusion needs.

Sepsis prediction in critically ill patients by platelet activation markers on ICU admission: a prospective pilot study

Background

Platelets have been involved in both immune surveillance and host defense against severe infection. To date, whether platelet phenotype or other hemostasis components could be associated with predisposition to sepsis in critical illness remains unknown. The aim of this work was to identify platelet markers that could predict sepsis occurrence in critically ill injured patients.

Methods

This single-center, prospective, observational, 7-month study was based on a cohort of 99 non-infected adult patients admitted to ICUs for elective cardiac surgery, trauma, acute brain injury, and post-operative prolonged ventilation and followed up during ICU stay. Clinical characteristics and severity score (SOFA) were recorded on admission. Platelet activation markers, including fibrinogen binding to platelets, platelet membrane P-selectin expression, plasma soluble CD40L, and platelet-leukocytes aggregates were assayed by flow cytometry at admission and 48 h later, and then at the time of sepsis diagnosis (Sepsis-3 criteria) and 7 days later for sepsis patients. Hospitalization data and outcomes were also recorded.

Methods

Of the 99 patients, 19 developed sepsis after a median time of 5 days. These patients had a higher SOFA score at admission; levels of fibrinogen binding to platelets (platelet-Fg) and of D-dimers were also significantly increased compared to the other patients. Levels 48 h after ICU admission no longer differed between the two patient groups. Platelet-Fg % was an independent predictor of sepsis (P = 0.0031). By ROC curve analysis, cutoff point for Platelet-Fg (AUC = 0.75) was 50%. In patients with a SOFA cutoff of 8, the risk of sepsis reached 87% when Platelet-Fg levels were above 50%. Patients with sepsis had longer ICU and hospital stays and higher death rate.

Conclusions

Platelet-bound fibrinogen levels assayed by flow cytometry within 24 h of ICU admission help identifying critically ill patients at risk of developing sepsis.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-017-0145-2) contains supplementary material, which is available to authorized users.