Activation of the Hemostatic System During Cardiopulmonary Bypass

Ultrafiltration in cardiac surgery: Results of a systematic review and meta-analysis

Background: Ultrafiltration is used with cardiopulmonary bypass to reduce the effects of hemodilution and restore electrolyte balance. We performed a systematic review and meta-analysis to analyze the effect of conventional and modified ultrafiltration on intraoperative blood transfusion.Methods: Utilizing the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement, we systematically searched MEDLINE, EMBASE, Web of Science, and Cochrane Library to perform a meta-analysis of studies of randomized controlled trials (RCTs) and observational studies evaluating conventional ultrafiltration (CUF) and modified ultrafiltration (MUF) on the primary outcome of intraoperative red cell transfusions.Results: A total of 7 RCTs (n = 928) were included, comparing modified ultrafiltration (n = 473 patients) to controls (n = 455 patients) and 2 observational studies (n = 47,007), comparing conventional ultrafiltration (n = 21,748) to controls (n = 25,427). Overall, MUF was associated with transfusion of fewer intraoperative red cell units per patient (n = 7); MD -0.73 units; 95% CI -1.12 to -0.35 p = 0.04; p for heterogeneity = 0.0001, I2 = 55%) compared to controls. CUF was no difference in intraoperative red cell transfusions compared to controls (n = 2); OR 3.09; 95% CI 0.26-36.59; p = 0.37; p for heterogeneity = 0.94, I2 = 0%. Review of the included observational studies revealed an association between larger volumes (>2.2 L in a 70 kg patient) of CUF and risk of acute kidney injury (AKI).Conclusion: The results of this systematic review and meta-analysis suggest that MUF is associated with fewer intraoperative red cell transfusions. Based on limited studies, CUF does not appear to be associated with a difference in intraoperative red cell transfusion.

Effect of Retrograde Autologous Priming on Coagulation Assessed by Rotation Thromboelastometry in Patients Undergoing Valvular Cardiac Surgery

OBJECTIVES

To investigate the effect of retrograde autologous priming (RAP) on coagulation function using rotation thromboelastometry (ROTEM) in patients undergoing valvular cardiac surgery.

DESIGN

A prospective, randomized, patient- and outcome assessor-blinded study.

SETTING

At a single-center university hospital.

PARTICIPANTS

Patients aged 20 years or older undergoing valvular cardiac surgery.

INTERVENTIONS

A total of 104 patients were allocated to the RAP or control group (1:1 ratio). In the RAP group, the prime was displaced into the collection bag before bypass initiation. ROTEM was performed at the induction of anesthesia, at the beginning of rewarming, and after the reversal of heparinization. Allogeneic plasma products and platelet concentrates were transfused according to ROTEM-based algorithms.

MEASUREMENTS AND MAIN RESULTS

An average volume of 635 ± 114 mL was removed using RAP (from the 1,600 mL initial prime volume). The hematocrit 10 minutes after cardiopulmonary bypass (CPB) was 24.7 ± 3.5% in the control group, and 26.1 ± 4.1% in the RAP group (p = 0.330). ROTEM, including EXTEM, INTEM, and FIBTEM, showed prolonged clotting time and decreased maximal clot firmness after CPB in both groups without intergroup differences. The number of patients who received intraoperative erythrocytes (27% v 25%, control versus RAP, p = 0.823), fresh frozen plasma (14% v 8%, control versus RAP, p = 0.339), cryoprecipitate (21% v 12%, control versus RAP, p = 0.185), or platelet concentrate transfusion (19% v 12%, control versus RAP, p = 0.277) did not differ between the groups.

CONCLUSIONS

Cardiopulmonary bypass induced impaired coagulation function on ROTEM. However, RAP did not improve coagulation function when compared with conventional priming in patients undergoing valvular cardiac surgery.

Assessing the impact of different heparin dosing regimens for cardiopulmonary bypass on anticoagulation: the HepDOSE pilot study

PURPOSE

It has been suggested that a larger heparin dose during cardiopulmonary bypass (CPB) is associated with reduced perioperative coagulopathy and thromboembolic complications. We investigated the effect of different heparin doses during routine elective cardiac surgery. Our primary outcomes include blood loss and transfusion and secondary outcomes investigate the effects on coagulation biomarkers.

METHODS

In this prospective pilot trial, we allocated 60 patients undergoing cardiac surgery on CPB in a single tertiary cardiac centre into three groups to receive an initial dose of 300, 400, or 500 units (U) per kilogram of intravenous heparin prior to the commencement of CPB. Blood was sampled after induction of anesthesia, at 30 and 60 min of CPB, and three minutes after heparin reversal with protamine. Samples were analyzed for fibrinopeptide A (FPA), fibrinopeptide B (FPB), D-dimer, and thrombin-antithrombin (TAT) complexes. Postoperative blood loss and transfusion was measured for the first 24-hr period after surgery.

RESULTS

The total mean (95% CI) administered heparin dose in the 300 U·kg-1, 400 U·kg-1, and 500 U·kg-1 groups were 39,975 (36,528 to 43,421) U, 43,195 (36,940 to 49,449) U and 47,900 (44,807 to 50,992) U, respectively. There were no statistically significant differences in FPA, FPB or D-dimer levels at the measured time intervals. There was a trend towards lower TAT levels while on CPB with greater heparin dosing, which was statistically significant after the administration of protamine. The clinical significance appears to be negligible, as there is no difference in overall blood loss and amount of packed red blood cell transfusion or other blood product transfusion.

CONCLUSION

This pilot study indicates that, while larger heparin dosing for routine cardiac surgery results in subtle biochemical changes in coagulation, there is no demonstrable benefit in postoperative blood loss or transfusion requirements.

Amplitude at 10 min in thromboelastography predicts maximum amplitude: a single-center observational study

Thromboelastography is a quantitative test widely used to measure the efficiency of blood clotting. However, awaiting the results of maximum amplitude (MA) is necessary for determining the need for platelet- and fibrinogen-containing products. A more rapid prediction of MA could facilitate faster preparation and administration of blood transfusion products, thereby resulting in coagulation improvement. In this retrospective study, we hypothesized that early amplitude at 10 min (A10) could be a predictor of MA. Therefore, we investigated whether MA can be rapidly inferred from thromboelastographic 6 s (TEG6s) measurements and evaluated its correlation with A10. We extracted TEG6s measurements obtained in operating rooms and intensive care units of our hospital between January 2018 and December 2022. The correlation of MA with display items of TEG6s results, including reaction time, kinetics, α angle, activated clotting time, and A10, was evaluated. The relationship between citrated rapid TEG (CRT)-A10 and CRT-MA, as well as between citrated functional fibrinogen (CFF)-A10 and CFF-MA, were evaluated if A10 and MA showed a good correlation. The results showed good correlations between CRT-A10 and CRT-MA, as well as between CFF-A10 and CFF-MA. Therefore, evaluating A10 using TEG6s could predict MA.

Titanium is a potent inducer of contact activation: implications for intravascular devices

BACKGROUND

Titanium (Ti) and its alloys are widely used in manufacturing medical devices because of their strength and resistance to corrosion. Although Ti compounds are considered compatible with blood, they appear to support plasma contact activation and may be thrombogenic.

OBJECTIVES

The objective of this study was to compare Ti and titanium nitride (TiN) with known activators of contact activation (kaolin and silica) in plasma-clotting assays and to assess binding and activation of factor XII, (FXII), factor XI (FXI), prekallikrein, and high-molecular-weight kininogen (HK) with Ti/TiN.

METHODS

Ti-based nanospheres and foils were compared with kaolin, silica, and aluminum in plasma-clotting assays. Binding and activation of FXII, prekallikrein, HK, and FXI to surfaces was assessed with western blots and chromogenic assays.

RESULTS

Using equivalent surface amounts, Ti and TiN were comparable with kaolin and superior to silica, for inducing coagulation and FXII autoactivation. Similar to many inducers of contact activation, Ti and TiN are negatively charged; however, their effects on FXII are not neutralized by the polycation polybrene. Antibodies to FXII, prekallikrein, or FXI or coating Ti with poly-L-arginine blocked Ti-induced coagulation. An antibody to FXII reduced FXII and PK binding to Ti, kallikrein generation, and HK cleavage.

CONCLUSION

Titanium compounds induce contact activation with a potency comparable with that of kaolin. Binding of FXII with Ti shares some features with FXII binding to soluble polyanions but may have unique features. Inhibitors targeting FXII or FXI may be useful in mitigating Ti-induced contact activation in patients with titanium-based implants that are exposed to blood.

Validity and Utility of Early Parameters in TEG6s Platelet Mapping to Assess the Coagulation Status During Cardiovascular Surgery With Cardiopulmonary Bypass

Background The aim of this retrospective observational study was to explore the early predictive parameters for maximum amplitudein the kaolin with heparinase (HKH) assay (MA_HKH) of TEG6s Platelet Mapping in cardiovascular surgery including cardiopulmonary bypass (CPB) period. The relationship between each parameter of the assay and laboratory data was also assessed. Methods We included the patients who underwent TEG6s Platelet Mapping during cardiovascular surgery under CPB between November 2021 and May 2022. The correlation between MA_HKH and the early parameters was assessed. The association between each parameter of Platelet Mapping and a combination of fibrinogen concentration > 150 mg/dL and platelet count > 100,000µL was also evaluated by the receiver operating characteristic (ROC) curve. Results In 23 patients who underwent TEG6s Platelet Mapping during the study period, 62 HKH assay data including 59 pairs of data (HKH assay and laboratory data) were analyzed. K and angle, but not R, were significantly correlated with MA_HKH (r [95% CI]: -0.90 [-0.94, -0.83], p < 0.0001 for K, and 0.87 [0.79, 0.92], p < 0.0001 for angle). Furthermore, ROC curves suggested that these parameters predicted a combination of fibrinogen concentration > 150 mg/dL and platelet count > 100,000/µL with high accuracy. Similar results were confirmed in the heparinized blood samples obtained during CPB. Conclusion These findings suggest that not only MA_KHK but also K and angle, which are early parameters in the HKH assay, provide clinically significant information that will facilitate rapid decision-making regarding coagulation strategies during cardiovascular surgery including the CPB period.

Platelet Function is Preserved After Moderate Cardiopulmonary Bypass Times But Transiently Impaired After Protamine

OBJECTIVES

Previous studies have described impaired platelet function after cardiopulmonary bypass (CPB). Whether this is still valid in contemporary cardiac surgery is unclear. This study aimed to quantify changes in function and number of platelets during CPB in a present-day cardiac surgery cohort.

DESIGN

Prospective, controlled clinical study.

SETTING

A single-center university hospital.

PARTICIPANTS

Thirty-nine patients scheduled for coronary artery bypass graft surgery with CPB.

INTERVENTIONS

Platelet function and numbers were measured at 6 timepoints in 39 patients during and after coronary artery bypass graft surgery; at baseline before anesthesia, at the end of CPB, after protamine administration, at intensive care unit (ICU) arrival, 3 hours after ICU arrival, and on the morning after surgery.

MEASUREMENTS AND MAIN RESULTS

Platelet function was assessed with impedance aggregometry and flow cytometry. Platelet numbers are expressed as actual concentration and as numbers corrected for dilution using hemoglobin as a reference marker. There was no consistent impairment of platelet function during CPB with either impedance aggregometry or flow cytometry. After protamine administration, a decrease in platelet function was seen with impedance aggregometry and for some markers of activation with flow cytometry. Platelet function was restored 3 hours after arrival in the ICU. During CPB (85.0 ± 21 min), the number of circulating platelets corrected for dilution increased from 1.73 ± 0.42 × 10⁹/g to 1.91 ± 0.51 × 10⁹/g (p < 0.001).

CONCLUSIONS

During cardiac surgery with moderate CPB times, platelet function was not impaired, and no consumption of circulating platelets could be detected. Administration of protamine transiently affected platelet function.

Annexin A2 Loss After Cardiopulmonary Bypass and Development of Acute Postoperative Respiratory Dysfunction in Children

The primary objective of this study was to determine whether expression of the multifunctional and adherens junction-regulating protein, annexin A2 (A2), is altered following cardiopulmonary bypass (CPB). A secondary objective was to determine whether depletion of A2 is associated with post-CPB organ dysfunction in children.

DESIGN

In a prospective, observational study conducted over a 1-year period in children undergoing cardiac surgery requiring CPB, we analyzed A2 expression in peripheral blood mononuclear cells at different time points. We then assessed the relationship of A2 expression with organ function at each time point in the early postoperative period.

SETTING

Twenty-three-bed mixed PICU in a tertiary academic center.

PARTICIPANTS

Patients 1 month to 18 years old undergoing cardiac surgery requiring CPB.

MEAN OUTCOME MEASUREMENTS AND RESULTS

We analyzed A2 expression in 22 enrolled subjects (n = 9, 1-23 mo old; n = 13, 2-18 yr old) and found a proteolysis-mediated decline in intact A2 immediately after bypass (p = 0.0009), reaching a median of 4% of baseline at 6 hours after bypass (p < 0.0001), and recovery by postoperative day 1. The degree of A2 depletion immediately after bypass in 1-23-month-olds correlated strongly with the extent of organ dysfunction, as measured by PICU admission Vasoactive-Ventilation-Renal (p = 0.004) and PEdiatric Logistic Organ Dysfunction-2 (p = 0.039) scores on postoperative day 1. A2 depletion immediately after bypass also correlated with more protracted requirement for both respiratory support (p = 0.007) and invasive ventilation (p = 0.013) in the 1-23-month-olds.

CONCLUSIONS AND RELEVANCE

The degree of depletion of A2 following CPB correlates with more severe organ dysfunction, especially acute respiratory compromise in children under 2 years. These findings suggest that loss of A2 may contribute to pulmonary microvascular leak in young children following CPB.

Heparin Resistance During Cardiopulmonary Bypass in Adult Cardiac Surgery

The use of heparin for anticoagulation has changed the face of cardiac surgery by allowing a bloodless and motionless surgical field throughout the introduction of cardiopulmonary bypass (CPB). However, heparin is a drug with complex pharmacologic properties that can cause significant interpatient differences in terms of responsiveness. Heparin resistance during CPB is a weighty issue due to the catastrophic consequences stemming from inadequate anticoagulation, and the treatment of it necessitates a rationalized stepwise approach due to the multifactorial contributions toward this entity. The widespread use of activated clotting time (ACT) as a measurement of anticoagulation during CPB is examined, as it may be a false indicator of heparin resistance. Heparin resistance also has been repeatedly reported in patients infected with COVID-19, which deserves further exploration in this pandemic era. This review aims to examine the variability in heparin potency, underlying mechanisms, and limitations of using ACT for monitoring, as well as provide a framework towards the current management of heparin resistance.

Dysregulated Hemostasis and Immunothrombosis in Cerebral Cavernous Malformations

Cerebral cavernous malformation (CCM) is a neurovascular disease that affects 0.5% of the general population. For a long time, CCM research focused on genetic mutations, endothelial junctions and proliferation, but recently, transcriptome and proteome studies have revealed that the hemostatic system and neuroinflammation play a crucial role in the development and severity of cavernomas, with some of these publications coming from our group. The aim of this review is to give an overview of the latest molecular insights into the interaction between CCM-deficient endothelial cells with blood components and the neurovascular unit. Specifically, we underscore how endothelial dysfunction can result in dysregulated hemostasis, bleeding, hypoxia and neurological symptoms. We conducted a thorough review of the literature and found a field that is increasingly poised to regard CCM as a hemostatic disease, which may have implications for therapy.

Citrate does not change viscoelastic haemostatic assays after cardiopulmonary bypass

CONTEXT

Viscoelastic hemostatic assays (VHA) are commonly used to identify specific cellular and humoral causes for bleeding in cardiac surgery patients. Cardiopulmonary bypass (CPB) alterations to coagulation are observable on VHA. Citrated VHA can approximate fresh whole blood VHA when kaolin is used as the activator in healthy volunteers. Some have suggested that noncitrated blood is more optimal than citrated blood for point-of-care analysis in some populations.

AIMS

To determine if storage of blood samples in citrate after CPB alters kaolin activated VHA results.

SETTINGS AND DESIGN

This was a prospective observational cohort study at a single tertiary care teaching hospital.

METHODS AND MATERIAL

Blood samples were subjected to VHA immediately after collection and compared to samples drawn at the same time and stored in citrate for 30, 90, and 150 min prior to kaolin activated VHA both before and after CPB.

STATISTICAL ANALYSIS USED

VHA results were compared using paired T-tests and Bland-Altman analysis.

RESULTS

Maximum clot strength and time to clot initiation were not considerably different before or after CPB using paired T-tests or Bland-Altman Analysis.

CONCLUSIONS

Citrated samples appear to be a clinically reliable substitute for fresh samples for maximum clot strength and time to VHA clot initiation after CPB. Concerns about the role of citrate in altering the validity of the VHA samples in the cardiac surgery population seem unfounded.

Use of a recombinant positive control in the diagnostic of canine Ehrlichiosis from 16sRNA gen of Ehrlichia canis in Mexico City

Ehrlichia canis has gained importance over the years as a zoonotic bacterium, nevertheless in Mexico is unknown the extent of the problem in animals and public health. The country had a few studies carried out locally using serology and molecular tests as diagnostic methods. Ehrlichiosis is not considered endemic in the central valley of Mexico, because the climatic conditions in the region have not allowed the vector (Rhipicephalus sanguineus) to establish itself adequately, therefore, diagnosis is not used in clinical practice in this area. A nested PCR (nPCR) offers rapid results with high sensitivity and specificity regardless of cost. The use of a recombinant positive control provides the advantage of timely diagnosis, follow-up treatment and allows the clinician to decide. In this work, the nPCR reported by Wen et al. (J Clin Microbiol 35(7):1852-2185, 1997) was used for the diagnosis of E. canis by modifying the reaction conditions to improve the detection of the test. We constructed a recombinant positive control to nPCR as diagnostic technique for E. canis, also we modified the reaction conditions to improve detection of the test which allowed the diagnosis of E. canis in dogs in the Mexican Republic using 53 samples from dogs with positive serological diagnosis of Ehrlichiosis, some of them from the valley of Mexico. Currently, this nPCR is offered to public at the Faculty of Veterinary Medicine and Zootechnics of the National Autonomous University of Mexico at an accessible cost and allows to begin to generate epidemiological information to know distribution of the bacterium.

Recent advancements in pediatric cardiopulmonary bypass technology for better outcomes of pediatric cardiac surgery

Background

Pediatric cardiac surgery is in itself very enigmatic and individualized. Presently, there has been a slew of new developments aimed primarily toward pediatric cardiopulmonary bypass for safer, patient-centered pediatric cardiac surgery. Still, lot of technological challenges need to be resolved, and their safer application in pediatric and neonate patients requires further refinement.

Main body of the abstract

Considering various significant yet unresolved issues of pediatric cardiac bypass, an exhaustive literature search was done on various internet databases with standard keywords. There are various new recent improvements; as the first oxygenator explicitly designed for neonatal patients; pediatric oxygenators with low prime volumes and surface areas that allow flows up to 2 L/min; pediatric oxygenators with integrated arterial filters; and miniature ultrafiltration devices that allow for high rates of ultrafiltrate removal. These advancements can significantly reduce cardiopulmonary bypass circuit surface areas and prime volumes. These advancements could reduce or eliminate the requirement for homologous red blood cells during or after surgery with reduction or eliminate bypass-related hemodilution, and inflammation. Because of the immaturity of the neonatal hemostatic system, conventional coagulation tests alone are insufficient to guide neonatal hemostatic therapy. Myocardial preservation techniques, safe temperature with duration are still debatable and yet to be fully explored.

Short conclusion

This review is based on Standards for Quality Improvement Reporting Excellence guidelines to provide a framework for reporting new knowledge to find better management strategy for pediatric cardiac cases.

Relationship between predisposing and facilitating factors: Does it influence the risk of developing peri-operative pressure injuries?

This study examined the relationship between the personal predisposing factors of patients and the severity of pressure injuries (PIs) developed during surgery. This retrospective cohort study collected 439 cases of peri-operative PIs. Using binary logistic regression to identify the variables associated with PI severity, the effects of interactions between associated variables were then tested. The results of this study revealed that among the personal predisposing factors, only higher patient age (P = .001) and higher body mass index (P < .001) posed a greater risk of stage 2 PIs or higher. Among the surgery-related facilitating factors, only patients who were placed in the prone position during surgery and patients who lost ≥1000 mL of blood during surgery were at greater risk of stage 2 PIs or higher, compared, respectively, to those placed in the supine position and those who lost ≤100 mL of blood. Furthermore, the amount of blood lost during surgery moderated the influence of age on PI severity. For elderly patients who are expected to lose a large blood volume during surgery or lose an immeasurable amount of blood due to the use of cardiopulmonary bypass, taking more precautionary measures to prevent PIs is recommended.

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.

Enhancement of the anticoagulant capacity of polyvinyl chloride tubing for cardiopulmonary bypass circuit using aluminum oxide nanoscale coating applied through atomic layer deposition

For cardiopulmonary bypass, the polyvinyl chloride (PVC) circuit which can initiate the activation of platelets and the coagulation cascade after blood cell contacting is the possible detrimental effect. Surface coating of the PVC tubing system can be an effective approach to enhance circuit's hemocompatibility. In this study, aluminum oxide (Al₂ O₃ ) thin films were deposited through thermal atomic layer deposition (T-ALD) or plasma-enhanced ALD (PE-ALD) on PVC samples, and the anticoagulation of the Al₂ O₃ -coated PVC samples was demonstrated. The results revealed that Al₂ O₃ deposition through ALD increased surface roughness, whereas T-ALD had a relative hydrophilicity compared with blank PVC and PE-ALD. Whole blood immersion tests showed that blood clots formed on blank PVC and that a large amount of red blood cells was found on PE-ALD substrates, whereas less blood cells were noted in T-ALD samples. Both T-ALD and PE-ALD Al₂ O₃ films did not cause activation of blood cells, as evidenced in CD3⁺ /CD4⁺ /CD8⁺ , CD61⁺ /CD62P⁺ , and CD45⁺ /CD42b⁺ populations. Analysis of serum coagulation factors showed that a lower amount of prothrombin was absorbed on T-ALD Al₂ O₃ samples than that on blank PVC. For albumin and fibrinogen immersion tests, immunostaining and scanning electron microscopy further revealed that a thin albumin layer was absorbed on T-ALD Al₂ O₃ substrates but not on PVC samples. This study revealed that deposition of Al₂ O₃ films by T-ALD can improve anticoagulation of the PVC tubing system.

Imaging the dynamics and microstructure of fibrin clot polymerization in cardiac surgical patients using spectrally encoded confocal microscopy

During cardiac surgery with cardiopulmonary bypass (CPB), altered hemostatic balance may disrupt fibrin assembly, predisposing patients to perioperative hemorrhage. We investigated the utility of a novel device termed spectrally-encoded confocal microscopy (SECM) for assessing fibrin clot polymerization following heparin and protamine administration in CPB patients. SECM is a novel, high-speed optical approach to visualize and quantify fibrin clot formation in three dimensions with high spatial resolution (1.0 μm) over a volumetric field-of-view (165 × 4000 × 36 μm). The measurement sensitivity of SECM was first determined using plasma samples from normal subjects spiked with heparin and protamine. Next, SECM was performed in plasma samples from patients on CPB to quantify the extent to which fibrin clot dynamics and microstructure were altered by CPB exposure. In spiked samples, prolonged fibrin time (4.4 ± 1.8 to 49.3 ± 16.8 min, p < 0.001) and diminished fibrin network density (0.079 ± 0.010 to 0.001 ± 0.002 A.U, p < 0.001) with increasing heparin concentration were reported by SECM. Furthermore, fibrin network density was not restored to baseline levels in protamine-treated samples. In CPB patients, SECM reported lower fibrin network density in protaminized samples (0.055 ± 0.01 A.U. [Arbitrary units]) vs baseline values (0.066 ± 0.009 A.U.) (p = 0.03) despite comparable fibrin time (baseline = 6.0 ± 1.3, protamine = 6.4 ± 1.6 min, p = 0.5). In these patients, additional metrics including fibrin heterogeneity, length and straightness were quantified. Note, SECM revealed that following protamine administration with CPB exposure, fibrin clots were more heterogeneous (baseline = 0.11 ± 0.02 A.U, protamine = 0.08 ± 0.01 A.U, p = 0.008) with straighter fibers (baseline = 0.918 ± 0.003A.U, protamine = 0.928 ± 0.0006A.U. p < 0.001). By providing the capability to rapidly visualize and quantify fibrin clot microstructure, SECM could furnish a new approach for assessing clot stability and hemostasis in cardiac surgical patients.

Pro-Con Debate: Fibrinogen Concentrate or Cryoprecipitate for Treatment of Acquired Hypofibrinogenemia in Cardiac Surgical Patients

Cryoprecipitate has been the gold standard for treating acquired hypofibrinogenemia in cardiac surgery for nearly 50 years. More recently, fibrinogen concentrate has been used off-label in the United States and is the standard in European countries and Canada to treat the acquired hypofibrinogenemia during cardiac surgery. Fibrinogen concentrate has multiple potential advantages including rapid reconstitution, greater dose predictability, viral inactivation during processing, and reduced transfusion-related adverse events. However, because fibrinogen concentrate lacks the other components contained in the cryoprecipitate, it may not be the "ideal" product for replacing fibrinogen in all cardiac surgical patients, particularly those with longer cardiopulmonary bypass duration. In this Pro-Con commentary article, we discuss the advantages and disadvantages of using fibrinogen concentrate and cryoprecipitate to treat acquired hypofibrinogenemia in cardiac surgical patients.

Synthetic Material Abdominal Swabs Reduce Activation of Platelets and Leukocytes Compared to Cotton Materials

During surgical procedures, cotton abdominal swabs with their high absorptive capacity and malleability are used to retain organs and absorb blood or other body fluids. Such properties of the natural material cotton are advantageous for most operations, but in cardiopulmonary bypass (CPB) surgery, a high blood volume can accumulate in the thoracic cavity that is quickly retransfused via the heart-lung machine (HLM). This common practice is supposed to be safe due to the high anticoagulation. However, in vitro analyses showed that blood cells and plasma proteins were activated despite a high anticoagulation, which can propagate especially an inflammatory response in the patient. Thus, we investigated patients' blood during CPB surgery for inflammatory and coagulation-associated activation after contact to the HLM and either cotton or synthetic abdominal swabs. Contact with cotton significantly increased thrombocyte and neutrophil activation measured as β-thromboglobulin and PMN-elastase secretion, respectively, compared to synthetic abdominal swabs. Both inflammatory cytokines, interleukin (IL) 1β and IL6, were also significantly increased in the cotton over the synthetic patient group, while SDF-1α was significantly lower in the synthetic group. Our data show for the first time that cotton materials can activate platelets and leukocytes despite a high anticoagulation and that this activation is lower with synthetic materials. This additional activation due to the material on top of the activation exerted by the tissue contact that blood is exposed to during CPB surgery can propagate further reactions in patients after surgery, which poses a risk for this already vulnerable patient group.

Tranexamic acid rapidly inhibits fibrinolysis, yet transiently enhances plasmin generation in vivo

Tranexamic acid (TXA) is a lysine analogue that inhibits plasmin generation and has been used for decades as an antifibrinolytic agent to reduce bleeding. Recent reports have indicated that TXA can paradoxically promote plasmin generation. Blood was obtained from 41 cardiac surgical patients randomly assigned to TXA or placebo before start of surgery (preOP), at the end of surgery (EOS), then again on postoperative day 1 (POD-1) as well as POD-3. Plasma levels of tissue-type plasminogen activator (t-PA), urokinase (u-PA), the plasmin-antiplasmin (PAP) complex, as well as t-PA and u-PA-induced clot lysis assays were then determined. Clot lysis and PAP complex levels were also assessed in healthy volunteers before and at various time points after taking 1 g TXA orally. Surgery induced an increase in circulating t-PA, yet not u-PA at EOS. t-PA levels were unaffected by TXA; however, u-PA levels were significantly reduced in patients on POD-3. t-PA and u-PA-induced clot lysis were both inhibited in plasma from TXA-treated patients. In contrast, PAP complex formation, representing plasmin generation, was unexpectedly enhanced in the plasma of patients administered TXA at the EOS time point. In healthy volunteers, oral TXA effectively blocked fibrinolysis within 30 min and blockade was sustained for 8 h. However, TXA also increased PAP levels in volunteers 4 h after administration. Our findings demonstrate that TXA can actually augment PAP complex formation, consistent with an increase in plasmin generation in vivo despite the fact that it blocks fibrinolysis within 30 min. This may have unanticipated consequences in vivo.

Safety and efficacy of tranexamic acid in minimizing perioperative bleeding in extrahepatic abdominal surgery: meta-analysis

BACKGROUND

Perioperative bleeding is associated with increased morbidity and mortality in patients undergoing elective abdominal surgery. The antifibrinolytic agent tranexamic acid (TXA) has been shown to reduce perioperative bleeding and mortality risk in patients with traumatic injuries, but there is a lack of evidence for its use in elective abdominal and pelvic surgery. This meta-analysis of RCTs evaluated the effectiveness and safety of TXA in elective extrahepatic abdominopelvic surgery.

METHODS

PubMed, Embase, and ClinicalTrial.gov databases were searched to identify relevant RCTs from January 1947 to May 2020. The primary outcome, intraoperative blood loss, and secondary outcomes, need for perioperative blood transfusion, units of blood transfused, thromboembolic events, and mortality, were extracted from included studies. Quantitative pooling of data was based on a random-effects model.

RESULTS

Some 19 studies reporting on 2205 patients who underwent abdominal, pelvic, gynaecological or urological surgery were included. TXA reduced intraoperative blood loss (mean difference -188.35 (95 per cent c.i. -254.98 to -121.72) ml) and the need for perioperative blood transfusion (odds ratio (OR) 0.43, 95 per cent c.i. 0.28 to 0.65). TXA had no impact on the incidence of thromboembolic events (OR 0.49, 0.18 to 1.35). No adverse drug reactions or in-hospital deaths were reported.

CONCLUSION

TXA reduces intraoperative blood loss during elective extrahepatic abdominal and pelvic surgery without an increase in complications.

The rebirth of the contact pathway: a new therapeutic target

PURPOSE OF REVIEW

Anticoagulation with vitamin-K antagonists or direct oral anticoagulants is associated with a significant risk of bleeding. There is a major effort underway to develop antithrombotic drugs that have a smaller impact on hemostasis. The plasma contact proteins factor XI (FXI) and factor XII (FXII) have drawn considerable interest because they contribute to thrombosis but have limited roles in hemostasis. Here, we discuss results of preclinical and clinical trials supporting the hypothesis that the contact system contributes to thromboembolic disease.

RECENT FINDINGS

Numerous compounds targeting FXI or FXII have shown antithrombotic properties in preclinical studies. In phase 2 studies, drugs-targeting FXI or its protease form FXIa compared favorably with standard care for venous thrombosis prophylaxis in patients undergoing knee replacement. While less work has been done with FXII inhibitors, they may be particularly useful for limiting thrombosis in situations where blood comes into contact with artificial surfaces of medical devices.

SUMMARY

Inhibitors of contact activation, and particularly of FXI, are showing promise for prevention of thromboembolic disease. Larger studies are required to establish their efficacy, and to establish that they are safer than current therapy from a bleeding standpoint.

The impact of CYP2C9 and VKORC1 genetic polymorphisms in anticoagulant therapy management after cardiac surgery with extracorporeal circulation

Extracorporeal circulation during cardiac surgery is characterized with increased risk for hypercoagulation because blood is exposed to foreign, nonendothelial cell surfaces. Thus, the usage of extracorporeal circulation is essentially not possible without anticoagulation. Open-heart surgery as well as many perioperative factors, such as acidosis, hypocalcemia, hypothermia, and hemodilution, might affect hemostasis and lead to coagulopathy and bleeding. A new insight into the effectiveness of anticoagulant therapy is applied to modify the dosing regimen with respect to the genetic CYP2C9 and VKORC1allelic variants. A systematic literature search was performed for VKORC1 and CYP2C9 and their association with coumarin anticoagulant therapy and bleeding risk in postoperative period of cardiac surgery with extracorporeal circulation.

Perioperative Management of Severe Acquired Coagulopathy in Patients with Left Ventricular Assist Device—a Literature Review and Expert Recommendations

Purpose of This Review

The implantation of a left ventricular assist device (LVAD) is associated with high hemorrhage-related re-exploration rates. Improved management of coagulopathy may improve patient outcome. The optimal management of acquired coagulopathy in LVAD patients needing urgent non-cardiac surgery needs to be defined. We aim to review risk factors for perioperative bleeding and diagnosis and management of LVAD-associated coagulopathy and to provide expert recommendations for clinical practice.

Recent Findings

In patients undergoing LVAD implantation, the severity of coagulopathy is directly related to the severity of the cardiac failure. The evidence from current literature for optimal management of acquired coagulopathy during and after LVAD implantation is sparse. The traditional transfusion strategy of replacing coagulation factors with fresh frozen plasma involves the risk of transfusion-associated circulatory overload. Current recommendations for targeted replacement of coagulation factors with 4-factor prothrombin concentrate and fibrinogen concentrate in cardiac surgery may be translated in this special setting.

Summary

The targeted, point-of-care use of concentrated coagulation factors may improve treatment of severe acquired coagulopathy during LVAD implantation and in LVAD patients needing urgent non-cardiac surgery.

Blood cell adhesion to arterial filters analysis by scanning electron microscopy and real-time PCR assay: observational clinical study in cardiac surgery patients

INTRODUCTION

Arterial filter is the part of the cardiopulmonary bypass circuit where blood cells are exposed to high mechanical stress and where cellular aggregates may fasten in large quantities. The aim of this study was to analyse blood cell adhesiveness in the arterial filter through scanning electron microscopy and real-time PCR assay.

METHODS

Prospective, clinical and observational study performed on 28 patients undergoing cardiac surgery with cardiopulmonary bypass. Arterial filters were analysed by scanning electron microscopy. Real-time PCR assay was performed in extracted material from the arterial filters for analysis of platelet GPIb and CD45 leucocyte gene expression. Blood coagulation was analysed during cardiopulmonary bypass. Patients were followed until hospital discharge or 28 days after surgery.

RESULTS

All studied arterial filters used in the subject patients showed a degree of adhesion from blood elements at scanning electron microscopy. All studied filters were positive for platelets GPIb gene expression and 15% had CD45 leucocyte gene expression. The GPIb platelet gene expression in blood lowered at the end of cardiopulmonary bypass (p = 0.019). There was negative correlation between blood GPIb platelet gene expression and Clot SR (HEPSCREEN2 ReoRox^®) (rho = 0.635; p = 0.027). The filter fields count was correlated to the D-dimer dosage (rho = 0.828; p < 0.001).

CONCLUSION

There was adhesion of blood elements, especially nucleated platelets, on all arterial filters studied. Although the arterial filter worked as a safety device, that possibly prevented arterial embolisation, it may also have caused greater hyperfibrinolysis during cardiopulmonary bypass.

Comparison of the in-vivo effect of two tranexamic acid doses on fibrinolysis parameters in adults undergoing valvular cardiac surgery with cardiopulmonary bypass - a pilot investigation

Background

The blood saving efficacy of TXA in cardiac surgery has been proved in several studies, but TXA dosing regimens were varied in those studies. Therefore, we performed this study to investigate if there is a dose dependent in-vivo effect of TXA on fibrinolysis parameters by measurement of fibrinolysis markers in adults undergoing cardiac surgery with CPB.

Methods

A double-blind, randomized, controlled prospective trial was conducted from February 11, 2017 to May 05, 2017. Thirty patients undergoing cardiac valve surgery were identified and randomly divided into a placebo group, low-dose group and high-dose group by 1: 1: 1. Fibrinolysis parameters were measured by plasma levels of D-Dimers, plasminogen activator inhibitor-1 (PAI-1), thrombin activatable fibrinolysis inhibitor (TAFI), plasmin-antiplasmin complex (PAP), tissue plasminogen activator (tPA) and thrombomodulin (TM). Those proteins were measured at five different sample times: preoperatively before the TXA injection (T₁), 5 min after the TXA bolus (T₂), 5 min after the initiation of CPB (T₃), 5 min before the end of CPB (T₄) and 5 min after the protamine administration (T₅). A Thrombelastography (TEG) and standard coagulation test were also performed.

Results

Compared with the control group, the level of the D-Dimers decreased in the low-dose and high-dose groups when the patients arrived at the ICU and on the first postoperative morning. Over time, the concentrations of PAI-1, TAFI, and TM, but not PAP and tPA, showed significant differences between the three groups (P <  0.05). Compared with the placebo group, the plasma concentrations of PAI-1 and TAFI decreased significantly at the T3 and T4 (P <  0.05); TAFI concentrations also decreased at the T5 in low-dose group (P < 0.05). Compared with the low-dose group, the concentration of TM increased significantly at the T4 in high-dose group.

Conclusions

The in-vivo effect of low dose TXA is equivalent to high dose TXA on fibrinolysis parameters in adults with a low bleeding risk undergoing valvular cardiac surgery with cardiopulmonary bypass, and a low dose TXA regimen might be equivalent to high dose TXA for those patients.

Trial registration

ChiCTR-IPR-17010303, Principal investigator: Zhen-feng ZHOU, Date of registration: January 1, 2017.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01234-8.

Fibrin clot susceptibility to lysis is impaired after on-pump coronary artery by-pass grafting with tranexamic acid: clinical implications

Coronary artery bypass grafting (CABG) done on-pump may cause a significant blood loss. Low fibrinogen is associated with perioperative bleeding. The influence of cardiopulmonary bypass on fibrin clot properties is poorly investigated. We studied 55 patients with isolated coronary artery disease on aspirin undergoing on-pump CABG with tranexamic acid. Fibrinogen levels, fibrinolytic capacity expressed as clot lysis time (CLT), thrombin generation potential and platelet count were assessed before and after the surgery (prior to admission to the intensive care unit). A postoperative drop in haemoglobin (-30% from baseline), haematocrit (-31% from baseline) and platelet count (-42% from baseline) was observed (all, P < 0.0001). Postoperative fibrinogen level was lower by 57%, compared with preoperative value (1.5 [1.3-1.8] vs. 3.5 [2.8-3.9] g/l, P < 0.0001). Postoperative CLT was longer by 48 min, compared with preoperative (182 [170-218] vs. 134 [122-165] min, P < 0.0001). Thrombin generation was impaired postoperatively: both lag time and time to peak thrombin were prolonged by 44 and 45%, respectively, whereas endogenous thrombin potential and peak thrombin generation decreased by 45 and 78%, respectively (all P < 0.0001). Median postoperative drainage at 12 h was 400 [290-570] ml. Predictors of blood loss at 12 h identified in multivariable linear regression model adjusted for sex and preoperative fibrinogen level were: BMI (b = -23.4, P = 0.048) and postoperative CLT (b = -2.4, P = 0.042). Despite decreased fibrinogen levels after on-pump CABG with tranexamic acid, fibrin clot susceptibility to lysis is impaired, as reflected by prolonged CLT. Postoperative CLT is associated with mediastinal drainage at 12 h.

Perioperative hyperfibrinolysis - physiology and pathophysiology

Introduction and objectives

The role of the anesthesiologist in the perioperative management of hemostasis has attracted increasing attention. The fibrinolytic system participates in hemostasis, removing clots after repair of the vascular injury. Over the past two decades, several studies have assessed the efficacy and safety of antifibrinolytic agents in reducing perioperative bleeding and transfusion requirements. Some of the conditions that seem to benefit from antifibrinolytic drugs involve trauma, postpartum hemorrhage, cardiac surgery, spine surgery, knee or hip arthroplasty, urological and gynecological surgery, among others. However, there are currently few publications focusing on the perioperative features of fibrinolytic system, which will be the subject of the present review.

Content and conclusions

Fibrinolytic physiology, its relationship with the clot structure and its perioperative behavior are described. Pathophysiological mechanisms related to anesthesiology clinical practice and their possible perioperative scenarios are addressed according to a suggested classification. This article aims to provide anesthesiologists with a broader understanding of the normal functioning of fibrinolysis, the mechanisms of possible deviations from normality in the perioperative period, the pathophysiological rationale supporting the current indications of antifibrinolytics, and some recent outcomes obtained with their use.

"TEG talk": expanding clinical roles for thromboelastography and rotational thromboelastometry

Viscoelastic assays (VEAs) that include thromboelastography and rotational thromboelastometry add value to the investigation of coagulopathies and goal-directed management of bleeding by providing a complete picture of clot formation, strength, and lysis in whole blood that includes the contribution of platelets, fibrinogen, and coagulation factors. Conventional coagulation assays have several limitations, such as their lack of correlation with bleeding and hypercoagulability; their inability to reflect the contribution of platelets, factor XIII, and plasmin during clot formation and lysis; and their slow turnaround times. VEA-guided transfusion algorithms may reduce allogeneic blood exposure during and after cardiac surgery and in the emergency management of trauma-induced coagulopathy and hemorrhage. However, the popularity of VEAs for other indications is driven largely by extrapolation of evidence from cardiac surgery, by the drawbacks of conventional coagulation assays, and by institution-specific preferences. Robust diagnostic studies validating and standardizing diagnostic cutoffs for VEA parameters and randomized trials comparing VEA-guided algorithms with standard care on clinical outcomes are urgently needed. Lack of such studies represents the biggest barrier to defining the role and impact of VEA in clinical care.

Unstable Hemostasis and Specific Postoperative Complications (Literature Review)

Perioperative bleeding occupies a leading place among all surgical complications and, despite the rapid development of surgery, remains relevant to this day. In addition to an increase in mortality, bleeding can cause the development of other postoperative complications, which lead to disability of patients and to a decrease in the quality of life in all age groups. Most perioperative bleeding are caused by technical errors. This article reviews the problem of perioperative bleeding from the point of view of impaired coagulation capabilities of the body. The main etiopathogenetic features of hemostasis during the development of this complication are considered. The analysis of postoperative complications, which were directly or indirectly caused by bleeding during or after surgery, is presented. The prevalence of these complications in various areas of surgery has been demonstrated. More detailed study of the hemostasis system and the identification of predictors of hemostasis difficulties before the surgery may cause an improvement in the results of surgical treatment and reduce the number of postoperative complications and the duration of hospital stay. Accordingly, this will lead to a decrease in the cost of treatment and an increase in patient satisfaction with the medical care. In connection with the above, there is a great interest among surgeons and anesthesiologists in preventing the development of perioperative bleeding.

The ISTH DIC score predicts outcome in non-septic patients admitted to a cardiovascular intensive care unit

BACKGROUND

The International Society of Thrombosis and Haemostasis (ISTH) disseminated intravascular coagulation (DIC) score is widely used to predict mortality in critically ill - typically septic - patients. The objective of this study was to investigate whether the ISTH DIC-2001 and DIC-2018 score can be used to predict the 30-day mortality in non-septic patients in an intensive care unit (ICU).

METHODS

In this single-center, prospective observational study we included all patients ≥18 years of age who were admitted to a medical ICU with a focus on cardiovascular diseases between August 2012 and 2013. The DIC-2001 and DIC-2018 scores were calculated on admission (DIC-2001-0h and DIC-2018-0h) and 72 hours thereafter (DIC-2001-72h and DIC-2018-72h) and were classified as overt when ≥ 5 for DIC-2001 and ≥ 4 for DIC-2018.

RESULTS

A total of 233 patients were included in this study. Excluding septic patients and patients after routine surgery/procedures, we calculated the DIC score for 167 patients (32.4% female; median age 64.9 years). Overt DIC-2001-0h, DIC-2018-0h and overt DIC-2001-72h scores were associated with a significantly higher 30-day mortality rate (52.9% vs. 25.0%, 46.2% vs 21.2%, and 57.1% vs. 23.7%; p < 0.04). The DIC-2001 scores and the DIC-2018-0h score significantly predicted the 30-day mortality.

CONCLUSION

This study suggests that the DIC score may be applied to non-septic ICU populations, and indicates that it is a useful tool for mortality prediction, regardless of the underlying disease.

Cyclic peptide FXII inhibitor provides safe anticoagulation in a thrombosis model and in artificial lungs

Inhibiting thrombosis without generating bleeding risks is a major challenge in medicine. A promising solution may be the inhibition of coagulation factor XII (FXII), because its knock-out or inhibition in animals reduced thrombosis without causing abnormal bleeding. Herein, we have engineered a macrocyclic peptide inhibitor of activated FXII (FXIIa) with sub-nanomolar activity (K_i = 370 ± 40 pM) and a high stability (t_1/2 > 5 days in plasma), allowing for the preclinical evaluation of a first synthetic FXIIa inhibitor. This 1899 Da molecule, termed FXII900, efficiently blocks FXIIa in mice, rabbits, and pigs. We found that it reduces ferric-chloride-induced experimental thrombosis in mice and suppresses blood coagulation in an extracorporeal membrane oxygenation (ECMO) setting in rabbits, all without increasing the bleeding risk. This shows that FXIIa activity is controllable in vivo with a synthetic inhibitor, and that the inhibitor FXII900 is a promising candidate for safe thromboprotection in acute medical conditions.

High-dose IVIG plus cangrelor platelet "anesthesia" during urgent heparin-CPB in a patient with recent SRA-negative HIT-thrombosis with persisting platelet-activating antibodies

In a high-risk patient with subacute heparin-induced thrombocytopenia (HIT) type A (platelet count recovery following acute HIT but with persisting platelet-activating antibodies), in whom urgent cardiac surgery was required, a key clinical question arose: could intraoperative heparin be given safely with "platelet anesthesia" provided with high-dose intravenous immunoglobulin (IVIG) plus cangrelor (ultra-short-acting antiplatelet agent)? This approach proved successful, without unexpected postoperative thrombocytopenia or thromboembolism. In vitro studies confirmed that both IVIG and cangrelor contributed to perioperative inhibition of HIT antibody-induced platelet activation. Interestingly, despite the patient testing strongly positive in 4 HIT immunoassays (latex immunoturbidimetric assay and 3 enzyme-immunoassays), the serotonin-release assay (SRA) was consistently negative. Nevertheless, platelet-activating HIT antibodies were detectable using modified (platelet factor 4-enhanced) SRA. Our protocol of heparin rechallenge following IVIG/cangrelor provides both intraoperative and early postoperative inhibition of HIT antibody-induced platelet activation and is applicable to patients with circulating functional HIT antibodies requiring urgent heart surgery, including those with "SRA-negative HIT."

Multiple Electrode Aggregometry After Cardiopulmonary Bypass to Assess Platelet (Dys)-Function and Transfusion Threshold: A Concordance Study

OBJECTIVE

Cardiac surgery patients have a high risk of postoperative bleeding. Historically, the platelet count has been one of the main parameters used to establish the need for platelet transfusions, and the recent introduction of point-of-care tests for platelet function has allowed clinicians to rationalize platelet transfusion needs by assessing the platelet (dys-)function of the patient. For the present study, the authors evaluated how the introduction of one of these systems-the adenosine diphosphate (ADP) test, performed using a Multiplate electrode analyzer (Roche Diagnostics, Basel, Switzerland)-into their clinical practice had modified their platelet transfusion practice. The relationship between the platelet count and the functional evaluation of platelet aggregation (via the ADP test) also was examined.

DESIGN

This was a retrospective, single-center, observational study.

SETTING

Cardiac surgery department of a tertiary care center in North-east Italy.

PARTICIPANTS

Cardiac surgery patients requiring cardiac bypass in 2017 and 2019.

INTERVENTIONS

The primary outcome was to compare platelet transfusion practice before and after the implementation of a platelet function test (the ADP test) into the institution's transfusion algorithm, which replaced the platelet count as the trigger. Secondary outcomes were assessing whether the incorporation of the ADP test into their transfusion algorithm brought about a reduction in the frequency of platelet transfusions compared with previous rates (when only platelets counts were used); assessing patient blood loss in the first 12 postoperative hours; and ascertaining the percentage of patients requiring surgical reexplorations.

MEASUREMENTS AND MAIN RESULTS

The study comprised 110 patients undergoing cardiac surgery from the platelet count period (2017) and 110 patients from the ADP test period (2019). Agreement between platelet counts versus ADP tests in determining the need for platelet transfusion was moderate (κ = 0.483; 95% confidence interval [CI] 0.239-0.728), and the general linear regression relationship between platelet counts and the ADP test (Akaike information criterion = 2536; p < 0.001) was determined. Since the introduction of ADP testing, a highly significant reduction in platelet transfusions has occurred: 41.82% (platelet count period) versus 13.64% (ADP test period) (p < 0.001); average blood loss in the 12 hours postsurgery also was less in the ADP test period (p < 0.001) at 300 mL (95% CI 150-730) compared with 440 mL in the platelet count period (95% CI 135-900). Furthermore, a decreasing trend was observed in the number of patients requiring reexploration to optimize hemostasis in the first 12 hours postsurgery (6.36% v 2.73%); however, this trend did not achieve statistical significance (p = 0.195).

CONCLUSION

The application of new Multiplate analyzer technologies, like the ADP test, have the potential to reduce platelet transfusion rates in cardiac surgery patients compared with the use of platelet counts alone; this point-of-care test may constitute an important strategy to help spare the use of allogeneic blood products. Additional studies are needed to confirm this trend and establish the best cutoff values to apply.

A Novel C1-Esterase Inhibitor Oxygenator Coating Prevents FXII Activation in Human Blood

The limited hemocompatibility of currently used oxygenator membranes prevents long-term use of artificial lungs in patients with lung failure. To improve hemocompatibility, we developed a novel covalent C1-esterase inhibitor (C1-INH) coating. Besides complement inhibition, C1-INH also prevents FXII activation, a very early event of contact phase activation at the crossroads of coagulation and inflammation. Covalently coated heparin, as the current anticoagulation gold standard, served as control. Additionally, a combination of both coatings (C1-INH/heparin) was established. The coatings were tested for their hemocompatibility by dynamic incubation with freshly drawn human whole blood. The analysis of various blood and plasma parameters revealed that C1-INH-containing coatings were able to markedly reduce FXIIa activity compared to heparin coating. Combined C1-INH/heparin coatings yielded similarly low levels of thrombin-antithrombin III complex formation as heparin coating. In particular, adhesion of monocytes and platelets as well as the diminished formation of fibrin networks were observed for combined coatings. We could show for the first time that a covalent coating with complement inhibitor C1-INH was able to ameliorate hemocompatibility. Thus, the early inhibition of the coagulation cascade is likely to have far-reaching consequences for the other cross-reacting plasma protein pathways.

The effect of roller head pump on platelet deterioration during the simulated extracorporeal circulation

Roller pumping results in hemolysis and adverse effects on coagulation, but there are few reports on the influence of roller heads on platelets. Here, we evaluate the interaction between roller pumping and platelet function using a simulated extracorporeal circuit incorporating a vinyl chloride tube and roller head pump with 30 min recirculation. Platelet aggregation, platelet count, microparticle, P-selectin, Phosphatidylserine (PS) exposure and Ricinus Communis Agglutinin 1 (RCA-1) were measured before, 5, 10, 20, and 30 min after the recirculation using 100 ml of fresh human blood that had obtained from healthy volunteers (n = 9). Platelet aggregation and platelet count gradually decreased but microparticles significantly increased after the recirculation (P < 0.05). P-selectin, PS exposure and RCA-1 were measured using flow cytometry. There were no significant differences in the P-selectin and PS exposure expression during recirculation. RCA-1, a platelet apoptosis markers, significantly increased 30 min after recirculation (P < 0.05). We thus conclude that roller pumping induced platelet apoptosis and caused decreases in platelet count and aggregation after the recirculation.

U-shaped relationship between pre-operative plasma fibrinogen levels and severe peri-operative bleeding in cardiac surgery

BACKGROUND

An inverse linear relationship has been reported between pre-operative fibrinogen levels and postoperative blood loss in cardiac surgery. However, recently high pre-operative fibrinogen levels have also been reported to be associated with increased blood transfusion and re-operation.

OBJECTIVE

We tested the hypothesis that the relationship between pre-operative fibrinogen levels and severe peri-operative bleeding is not linear.

DESIGN

A large-scale (n = 3883) single-centre retrospective study.

SETTING

A tertiary care teaching hospital.

PATIENTS

We analysed data from our institutional database which includes all patients above 18 years who underwent on-pump cardiac surgery through a sternotomy between September 2010 and May 2014.

MAIN OUTCOME MEASURES

Peri-operative severe bleeding adapted from the Universal Definition of Peri-operative Bleeding, class 3 or 4. The relationship between pre-operative fibrinogen levels and peri-operative severe bleeding was analysed by binary logistic regression. A cubic B-spline transformation was used to estimate the relationship between pre-operative fibrinogen level associated with excessive peri-operative bleeding.

RESULTS

Severe peri-operative bleeding was observed in 957 (24.6%) patients. An L-shaped relationship was observed between pre-operative fibrinogen levels and 24-h postoperative blood loss. The relationship between pre-operative fibrinogen levels and severe peri-operative bleeding (i.e. Universal Definition of Peri-operative Bleeding class 3 or 4) was U-shaped: the risk of severe peri-operative bleeding bottomed at 3.3 g l when the upward sloping curve started at 5.8 g l with a steeper increase above 8.2 g l.

CONCLUSION

We reported a U-shaped relationship between severe peri-operative bleeding and pre-operative fibrinogen levels. While a low-level of fibrinogen appears to be associated with a high risk of bleeding, a high level does not necessarily protect the patient against such a risk and could even be a risk factor for peri-operative bleeding.

Anticoagulation management during pulmonary endarterectomy with cardiopulmonary bypass and deep hypothermic circulatory arrest

INTRODUCTION

Pulmonary endarterectomy requires cardiopulmonary bypass and deep hypothermic circulatory arrest, which may prolong the activated clotting time. We investigated whether activated clotting time-guided anticoagulation under these circumstances suppresses hemostatic activation.

METHODS

Individual heparin sensitivity was determined by the heparin dose-response test, and anticoagulation was monitored by the activated clotting time and heparin concentration. Perioperative hemostasis was evaluated by thromboelastometry, platelet aggregation, and several plasma coagulation markers.

RESULTS

Eighteen patients were included in this study. During cooling, tube-based activated clotting time increased from 719 (95% confidence interval = 566-872 seconds) to 1,273 (95% confidence interval = 1,136-1,410 seconds; p < 0.01) and the cartridge-based activated clotting time increased from 693 (95% confidence interval = 590-796 seconds) to 883 (95% confidence interval = 806-960 seconds; p < 0.01), while thrombin-antithrombin showed an eightfold increase. The heparin concentration showed a slightly declining trend during cardiopulmonary bypass. After protamine administration (protamine-to-heparin bolus ratio of 0.82 (0.71-0.90)), more than half of the patients showed an intrinsically activated coagulation test and intrinsically activated coagulation test without heparin effect clotting time >240 seconds. Platelet aggregation through activation of the P2Y12 (adenosine diphosphate test) and thrombin receptor (thrombin receptor activating peptide-6 test) decreased (both -33%) and PF4 levels almost doubled (from 48 (95% confidence interval = 42-53 ng/mL) to 77 (95% confidence interval = 71-82 ng/mL); p < 0.01) between weaning from cardiopulmonary bypass and 3 minutes after protamine administration.

CONCLUSION

This study shows a wide variation in individual heparin sensitivity in patients undergoing pulmonary endarterectomy with deep hypothermic circulatory arrest. Although activated clotting time-guided anticoagulation management may underestimate the level of anticoagulation and consequently result in a less profound inhibition of hemostatic activation, this study lacked power to detect adverse outcomes.

Extracorporeal membrane oxygenation without systemic anticoagulation: a case-series in challenging conditions

Background

Extracorporeal membrane oxygenation (ECMO) use in patients with active bleedings or traumatic injuries may be challenging because of the risk of refractory haemorrhage related to systemic anticoagulation (SA). Technological advancements, especially heparin coated circuits, allowed ECMO application with a mild or no anticoagulation regimen in some circumstances. We herein report a limited case-series of ECMO application without anticoagulation.

Methods

ECMO without SA was established in 6 patients. Four of them received veno-arterial mode. Full heparin antagonization with protamine was provided in 3 post-cardiotomy cases. Tip-to-tip heparin-coated ECMO circuit was used in 4 patients, whereas heparin-coated tubing and no heparin-coated cannulas were applied for the remaining subjects.

Results

Mean duration of support and pump flow were 10±4 hours and 3.0±0.7 litres respectively. No ECMO related complication or oxygenator failure occurred, nor was clotting of the circuit observed at inspection. All patients were weaned from ECMO and half of them survived and were discharged.

Conclusions

Short ECMO duration without anticoagulation was feasible and provided effective cardiopulmonary support in patients with active bleeding or high hemorrhagic risk. Further investigations are needed to evaluate its benefits or limitations for a protracted time, in a wider range of clinical conditions and in larger patient populations.

Platelets and extra-corporeal membrane oxygenation in adult patients: a systematic review and meta-analysis

Despite increasing improvement in extracorporeal membrane oxygenation (ECMO) technology and knowledge, thrombocytopenia and impaired platelet function are usual findings in ECMO patients and the underlying mechanisms are only partially elucidated. The purpose of this meta-analysis and systematic review was to thoroughly summarize and discuss the existing knowledge of platelet profile in adult ECMO population. All studies meeting the inclusion criteria (detailed data about platelet count and function) were selected, after screening literature from July 1975 to August 2019. Twenty-one studies from 1.742 abstracts were selected. The pooled prevalence of thrombocytopenia in ECMO patients was 21% (95% CI 12.9-29.0; 14 studies). Thrombocytopenia prevalence was 25.4% (95% CI 10.6-61.4; 4 studies) in veno-venous ECMO, whereas it was 23.2% (95% CI 11.8-34.5; 6 studies) in veno-arterial ECMO. Heparin-induced thrombocytopenia prevalence was 3.7% (95% CI 1.8-5.5; 12 studies). Meta-regression revealed no significant association between ECMO duration and thrombocytopenia. Platelet function impairment was described in 7 studies. Impaired aggregation was shown in 5 studies, whereas loss of platelet receptors was found in one trial, and platelet activation was described in 2 studies. Platelet transfusions were needed in up to 50% of the patients. Red blood cell transfusions were administered from 46 to 100% of the ECMO patients. Bleeding events varied from 16.6 to 50.7%, although the cause and type of haemorrhage was not consistently reported. Thrombocytopenia and platelet dysfunction are common in ECMO patients, regardless the type of ECMO mode. The underlying mechanisms are multifactorial, and understanding and management are still limited. Further research to design appropriate strategies and protocols for its monitoring, management, or prevention should be matter of thorough investigations.

Clinical application of a new ternary polymer, SEC-1 coat™, for pediatric cardiopulmonary bypass circuits: a prospective randomized pilot study

OBJECTIVE

The use of biocompatible materials to reduce the systemic activation of inflammation and coagulation pathways is expanding rapidly. However, there have been few clinical studies of biocompatible circuits for pediatric cardiopulmonary bypass. This pilot study aimed to preliminarily evaluate the biocompatibility of SEC-1 coat™ (SEC) for cardiopulmonary bypass circuits in pediatric cardiac surgery.

METHODS

Twenty infants undergoing cardiac surgery for isolated ventricular septal defects at Kobe Children's Hospital were assigned randomly to an SEC-coated (SEC group, n = 10) or heparin-coated (control group, n = 10) circuit. Perioperative data and the following markers were prospectively analyzed: platelet counts and interleukin-6, interleukin-8, C3a, β-thromboglobulin, and thrombin-antithrombin complex levels.

RESULTS

Neither patient characteristics nor postoperative clinical outcomes differed significantly between the SEC and control groups. Platelet counts markedly decreased during cardiopulmonary bypass in both groups, but were significantly better preserved in the SEC group. Fewer patients needed postoperative platelet transfusions in the SEC group. After cardiopulmonary bypass termination, serum levels of β-thromboglobulin and thrombin-antithrombin complex were significantly lower in the SEC than in the control group. Although the differences were not statistically significant, serum levels of interleukin-6, interleukin-8, and C3a had a tendency toward being lower in the SEC group, with good preservation of leukocyte counts, fibrinogen, and antithrombin III.

CONCLUSION

SEC-1 coat™ for cardiopulmonary bypass circuits have good biocompatibility with regard to platelet preservation and in terms of attenuating inflammatory reaction or coagulation activation during pediatric cardiac surgery. It can be beneficial in pediatric as well as adult cardiac surgery.

Thrombin generation and bleeding in cardiac surgery: a clinical narrative review

This narrative review discusses the role of thrombin generation in coagulation and bleeding in cardiac surgery, the laboratory methods for clinical detection of impaired thrombin generation, and the available hemostatic interventions that can be used to improve thrombin generation. Coagulopathy after cardiopulmonary bypass (CPB) is associated with excessive blood loss and adverse patient outcomes. Thrombin plays a crucial role in primary hemostasis, and impaired thrombin generation can be an important cause of post-CPB coagulopathy. Existing coagulation assays have significant limitations in assessing thrombin generation, but whole-blood assays designed to measure thrombin generation at the bed-side are under development. Until then, clinicians may need to institute therapy empirically for non-surgical bleeding in the setting of normal coagulation measures. Available therapies for impaired thrombin generation include administration of plasma, prothrombin complex concentrate, and bypassing agents (recombinant activated factor VII and factor eight inhibitor bypassing activity). In vitro experiments have explored the relative potency of these therapies, but clinical studies are lacking. The potential incorporation of thrombin generation assays into clinical practice and treatment algorithms for impaired thrombin generation must await further clinical development.