Clot Growth Research Articles

Crotalus atrox Venom Exposed to Carbon Monoxide Has Decreased Fibrinogenolytic Activity In Vivo in Rabbits.

Envenomation by haemotoxic enzymes remains a significant source of human morbidity and mortality worldwide, with administration of long-acting or multiple doses of antivenom first-line therapy. However, coagulopathy can still occur and recur. Of interest, it has been recently demonstrated that direct, isolated exposure of snake venom enzymes with fibrinogenolytic activity to carbon monoxide (CO) abrogates venom-mediated loss of coagulation in human plasma. These observations of CO inhibition of venom fibrinogenolytic activity were subsequently repeated in rabbit whole blood. This study sought to translate these findings in an in vivo rabbit model of envenomation with fibrinogenolytic Crotalus atrox venom. Sedated rabbits were intravenously administered C. atrox venom (400 μg/kg) pre-exposed to 0 or 1000 μM carbon monoxide-releasing molecule-2 (CORM-2) in vitro. Arterial whole-blood samples demonstrated that compared to pre-envenomation values, the CORM-2-naïve venom significantly prolonged the onset of coagulation, decreased the velocity of clot growth and decreased clot strength as determined by thromboelastography an hour after venom injection. In contrast, CORM-2 pre-exposure prevented or attenuated C. atrox venom effects on coagulation kinetics. Future studies to determine whether rabbits injected with such venom subcutaneously/intramuscularly can have consequent coagulopathy abrogated by injection of carbon monoxide-releasing molecules into the 'bite site' are justified.

Moderate plasma dilution using artificial plasma expanders shifts the haemostatic balance to hypercoagulation

Artificial plasma expanders (PEs) are widely used in modern transfusion medicine. PEs do not contain components of the coagulation system, so their infusion in large volumes causes haemodilution and affects haemostasis. However, the existing information on this effect is contradictory. We studied the effect of the very process of plasma dilution on coagulation and tested the hypothesis that moderate dilution with a PE should accelerate clotting owing to a decrease in concentration of coagulation inhibitors. The standard clotting times, a thrombin generation test, and the spatial rate of clot growth (test of thrombodynamics) were used to assess donor plasma diluted in vitro with various PEs. The pH value and Ca+2 concentration were maintained strictly constant in all samples. The effect of thrombin inhibitors on dilution-induced hypercoagulation was also examined. It was shown that coagulation was enhanced in plasma diluted up to 2.0–2.5-fold with any PE. This enhancement was due to the dilution of coagulation inhibitors in plasma. Their addition to plasma or PE could partially prevent the hypercoagulation shift.

Reaction-diffusion waves of blood coagulation

One of the main characteristics of blood coagulation is the speed of clot growth. In the current work we consider a mathematical model of the coagulation cascade and study existence, stability and speed of propagation of the reaction-diffusion waves of blood coagulation. We also develop a simplified one-equation model that reflects the main features of the thrombin wave propagation. For this equation we estimate the wave speed analytically. The resulting formulas provide a good approximation for the speed of wave propagation in a more complex model as well as for the experimental data.

A mathematical model for in vitro coagulation of blood: role of platelet count and inhibition

A mechanistic model including the role of platelets is proposed for clot formation and growth in plasma in vitro. Initiation of clot formation is by the addition of tissue factor, and initiation via the intrinsic pathway is neglected. Activation of zymogens follows the extrinsic pathway cascade and reactions on platelet membranes are included. Platelet activation occurs due to thrombin and also due to other activated platelets. Inhibition of the active clotting factors is by ATIII and TFPI, whereas inhibition due to APC is not relevant in the conditions modeled. The model predictions matched existing data for thrombin production in synthetic plasma. The model predicts that inhibition of platelet-driven activation of platelets has a major effect on concentration of activated platelets in PRP, normal plasma and PPP. Inhibition of platelet activation by (other activated) platelets significantly delays thrombin production in PRP and normal plasma as compared to that by thrombin. Further, sensitivity analysis shows that the model is most sensitive to the activation of platelet membrane-bound factor X by the intrinsic tenase complex.

Conditions of microvessel occlusion for blood coagulation in flow.

Vessel occlusion is a perturbation of blood flow inside a blood vessel because of the fibrin clot formation. As a result, blood circulation in the vessel can be slowed down or even stopped. This can provoke the risk of cardiovascular events. In order to explore this phenomenon, we used a previously developed mathematical model of blood clotting to describe the concentrations of blood factors with a reaction-diffusion system of equations. The Navier-Stokes equations were used to model blood flow, and we treated the clot as a porous medium. We identify the conditions of partial or complete occlusion in a small vessel depending on various physical and physiological parameters. In particular, we were interested in the conditions on blood flow and diameter of the wounded area. The existence of a critical flow velocity separating the regimes of partial and complete occlusion was demonstrated through the mathematical investigation of a simplified model of thrombin wave propagation in Poiseuille flow. We observed different regimes of vessel occlusion depending on the model parameters both for the numerical simulations and in the theoretical study. Then, we compared the rate of clot growth in flow obtained in the simulations with experimental data. Both of them showed the existence of different regimes of clot growth depending on the velocity of blood flow.

Risk assessment of thrombotic events in patients with schizophrenia and schizoaffective disorder in the acute state: the 'fibrinodynamics' technology

To assess the risk of thrombotic events in patients with schizophrenia and schizoaffective disorder based on 'fibrinodynamics' technology. A group of 76 women, including 38 with paranoid schizophrenia (F20.0), 18 with schizoaffective disorder (F25.1) in the acute stage, and 20 healthy controls, participated in the study. The technology includes the study of coagulation and fibrinolysis, Karmin author software, and calculation of peak time and hemostasis potential of spontaneous clots. Growth and lysis of fibrin clots were studied in plasma purified from platelets. All preanalytic procedures were conducted within 30 minutes after blood sampling. Blood serum was studied separately using the neuroimmunological test. Dynamic of brightness profiles of the clots was determined and a number of parameters (peak time and hemostasis potential of spontaneous clots) were calculated using the Karmin software. In patients with schizophrenia, the dynamic brightness profile of the clots has two peaks: the first peak is formed as a result of the growth and lysis of the clot initiated by the activator, the second peak is due to the growth and lysis of spontaneous clots in the volume of the measuring cuvette far from the activator. In healthy donors, the second peak under experimental conditions is absent. In the group of schizophrenic patients, a strong negative correlation is observed between the peak time of the second peak and the activity of leukocyte elastase (Spearman R = -0.75, p<0.0001), i.e. the greater the activity of elastase, the earlier the maximum of the second peak is formed and vice versa. In the control group, there is no such correlation. Evaluation of the potential of hemostasis of spontaneous clots showed that in 42% of schizophrenic patients this parameter is shifted above the norm, which indicates an increased risk of thrombosis of small brain arteries in these patients. The developed technology of 'fibrinodynamics' has a good potential for introduction into personalized medicine to identify increased risks of thrombosis of small cerebral vessels in patients with acute schizophrenia leading to the development of cognitive disorders and to control the normalization of hemostasis with antiplatelet or anticoagulant drugs.

Coagulation way of hemostasis in pregnant women and puerperae with pre-eclampsia in whom caesarean section was performed

Aim. To evaluate clinical value of trombodynamics in diagnosing the state of coagulation way of hemostasis in patients with pre-eclampsia in whom caesarean section was performed.Methods. The study included 66 pregnant women. The study group included 34 of them with moderate to severe pre-eclampsia. During the postoperative period all puerperae received low molecular weight heparin (Dalteparin 2500 IU subcutaneously once a day for 7 days). The comparison group consisted of 32 pregnant women. All of them had scheduled Caesarean section. LMWH was not administered in this group. Thrombodynamics assay was performed in both groups. Blood samples were taken 1-2 hours before cesarean section, 6-12 hours after the surgery before the first injection of anticoagulant if administered, and on day 5 after delivery not less than 24 hours after the injection of anticoagulant.Results. In the group of patients with pre-eclampsia changes in trombodynamics characteristic for hypercoagulation were revealed: increase of clot growth velocity (V), clot size (CS), its relative density (D) and development of spontaneous clots (Tsp). These numbers become normal slower than in pregnant women and puerperae without pre-eclampsia and with delivery performed surgically.Conclusion. According to trombodynamics assay, in pregnant women and puerperae with pre-eclampsia, severe hypercoagulation with increased reaction kinetics of clot formation and its physical characteristics were revealed, as well as increase of blood procoagulant potential.

Multiscale simulation of thrombus growth and vessel occlusion triggered by collagen/tissue factor using a data-driven model of combinatorial platelet signalling.

During clotting under flow, platelets bind and activate on collagen and release autocrinic factors such as ADP and thromboxane, while tissue factor (TF) on the damaged wall leads to localized thrombin generation. Towards patient-specific simulation of thrombosis, a multiscale approach was developed to account for: platelet signalling [neural network (NN) trained by pairwise agonist scanning (PAS), PAS-NN], platelet positions (lattice kinetic Monte Carlo, LKMC), wall-generated thrombin and platelet-released ADP/thromboxane convection–diffusion (partial differential equation, PDE) and flow over a growing clot (lattice Boltzmann). LKMC included shear-driven platelet aggregate restructuring. The PDEs for thrombin, ADP and thromboxane were solved by finite element method using cell activation-driven adaptive triangular meshing. At all times, intracellular calcium was known for each platelet by PAS-NN in response to its unique exposure to local collagen, ADP, thromboxane and thrombin. When compared with microfluidic experiments of human blood clotting on collagen/TF driven by constant pressure drop, the model accurately predicted clot morphology and growth with time. In experiments and simulations at TF at 0.1 and 10 molecule-TF/n}{}mumn}{}^{2} and initial wall shear rate of 200 sn}{}^{-1}, the occlusive blockade of flow for a 60-n}{}mum channel occurred relatively abruptly at 600 and 400 s, respectively (with no occlusion at zero TF). Prior to occlusion, intrathrombus concentrations reached 50 nM thrombin, ~ 1 n}{}muM thromboxane and ~ 10 n}{}muM ADP, while the wall shear rate on the rough clot peaked at ~ 1000–2000 sn}{}^{-1}. Additionally, clotting on TF/collagen was accurately simulated for modulators of platelet cyclooxygenase-1, P2Yn}{}_{1} and IP-receptor. This multiscale approach facilitates patient-specific simulation of thrombosis under hemodynamic and pharmacological conditions.

Clinical correlates of thrombodynamics in men with metabolic syndrome: the impact of insulin resistance

Background. Hypercoagulation is one of the cardiovascular risk factors in patients with metabolic syndrome (MS). It results from various factors including hyperhomocysteinemia, endothelial dysfunction, non-enzymatic glycation of proteins etc.The aim of this study was to assess clinical correlates of thrombodynamics in insulin resistant and non insulin resistant men with metabolic syndrome.Methods. We investigated 79 patients with MS diagnosed in accordance with IDF criteria (2009). The main group consisted of 44 men with MS including insulin resistance. The control group consisted of 35 men with MS not including insulin resistance. In addition to routine clinical tests we performed thrombodynamics assay and measured serum levels of asymmetric dimethylarginine (ADMA) and homocysteine. Mann-Whitney U-test and Spearmen’s correlation coefficient (rs) were used for statistical analysis.Results. There was no significant difference between thrombodynamics parameters, ADMA and homocysteine levels between the two groups. In both groups thrombodynamics parameters had no correlations with body mass index, hemoglobin level, platelet count and serum ADMA level. In patients with insulin resistance clot density correlated positively with serum level of C-reactive protein (rs=0.621, p=0.007); average and initial rates of clot growth correlated positively with homocysteine level (rs=0.539, p=0.017, and rs=0.554, p=0.014, respectively). In patients with insulin resistance clot density and rates of clot growth were not interrelated with the above mentioned parameters.Conclusions. The results of the study suggest that insulin resistant men with MS are characterized by clinical correlates between thrombodynamics parameters, homocysteine and C-reactive protein levels while patients without insulin resistance have other, unestablished determinants of clot density and rates of clot growth.

Clinical correlates of thrombodynamics in men with metabolic syndrome: the impact of insulin resistance

Background. Hypercoagulation is one of the cardiovascular risk factors in patients with metabolic syndrome (MS). It results from various factors including hyperhomocysteinemia, endothelial dysfunction, non-enzymatic glycation of proteins etc.The aim of this study was to assess clinical correlates of thrombodynamics in insulin resistant and non insulin resistant men with metabolic syndrome.Methods. We investigated 79 patients with MS diagnosed in accordance with IDF criteria (2009). The main group consisted of 44 men with MS including insulin resistance. The control group consisted of 35 men with MS not including insulin resistance. In addition to routine clinical tests we performed thrombodynamics assay and measured serum levels of asymmetric dimethylarginine (ADMA) and homocysteine. Mann-Whitney U-test and Spearmen’s correlation coefficient (rs) were used for statistical analysis.Results. There was no significant difference between thrombodynamics parameters, ADMA and homocysteine levels between the two groups. In both groups thrombodynamics parameters had no correlations with body mass index, hemoglobin level, platelet count and serum ADMA level. In patients with insulin resistance clot density correlated positively with serum level of C-reactive protein (rs=0.621, p=0.007); average and initial rates of clot growth correlated positively with homocysteine level (rs=0.539, p=0.017, and rs=0.554, p=0.014, respectively). In patients with insulin resistance clot density and rates of clot growth were not interrelated with the above mentioned parameters.Conclusions. The results of the study suggest that insulin resistant men with MS are characterized by clinical correlates between thrombodynamics parameters, homocysteine and C-reactive protein levels while patients without insulin resistance have other, unestablished determinants of clot density and rates of clot growth.

Optimization of Approaches to the Prevention of Thromboembolic Complications after Total Hip Arthroplasty

To choose the optimum scheme of anticoagulant therapy for the prevention of thromboembolic complications after total hip arthroplasty 86 patients were examined. The patients were randomly divided into 3 groups. In group 1 (n=29) prevention of thromboembolic complications was performed by subcutaneous injection of enoxaparin (40 mg) started 12 hours before the surgery. In group 2 (n=28) enoxaparin (40 mg) was started 12 hours after surgical intervention. In those groups thromboprophylaxis with enoxaparin was continued during hospitalization period and at discharge the patients were given recommendations to take dabigatran etexilate up to 35 days. In group 3 (n=29) patients received oral dabigatran etexilate, 110 mg 1 - 4 hours after surgery, followed by 220 mg once-daily both at hospital and out-patient stage of treatment. The average duration of hospitalization made up 8.9±1.2 days. Minimum fibrinogen and D-dimer levels as well as maximum APTT values were observed in patients from group 3 on the 5th postoperative day. Thromboelastogram showed that on day 5 both plasma and platelet hypocoagulation were most expressed in 3rd group. Preoperative thrombodynamics showed high rate of clot growth and high percentage of spontaneous clots formation in all three groups that assumed initial hypercoagulation with maximum decrease of the frequency of spontaneous clots formation against the background of dabigatran prophylaxis. The lowest number (3,4%) of thromboembolic complications, i.e. distal thromboses, were observed in patients from dabigatran etexilate group. Assessment of anticoagulant prophylaxis costs showed a clear advantage of the 3rd group.

Iron and carbon monoxide prevent degradation of plasmatic coagulation by thrombin-like activity in rattlesnake venom.

Thousands suffer poisonous snake bite, often from defibrinogenating species annually. Three rattlesnake species in particular, the timber rattlesnake, Eastern diamondback rattlesnake, and Southern Pacific rattlesnake, cause clinically relevant hypofibrinogenemia via thrombin-like activity in their venom. It has been demonstrated that iron (Fe) and carbon monoxide (CO) change the ultrastructure of plasma thrombi and improve coagulation kinetics. Thus, the present investigation sought to determine if pretreatment of plasma with Fe and CO could attenuate venom-mediated catalysis of fibrinogen via thrombin-like activity. Human plasma was pretreated with ferric chloride (0-10 μM) and CO-releasing molecule-2 (0-100 μM) prior to exposure to 2.5-10 μg/ml of venom obtained from the aforementioned three species of rattlesnake. Coagulation kinetics were determined with thrombelastography. All three snake venoms degraded plasmatic coagulation kinetics to a significant extent, especially diminishing the speed of clot growth and strength. Pretreatment of plasma with Fe and CO completely abrogated the effects of all three venoms on coagulation kinetics. Further in vitro investigation of other pit viper venoms that possess thrombin-like activity is indicated to see if there is significant conservation of venom enzymatic target recognition of specific amino acid sequences such that Fe and CO can reliably attenuate venom-mediated catalysis of fibrinogen. These data also serve as a rationale for future preclinical investigation.

Flow and delta-P dictate where thrombin, fibrin, and von Willebrand Factor will be found

Hemostasis occurs in two different topological scenarios: complete severing of a vessel or disruption of the vessel wall. Either to meet the daily rigors of active life or during an acute trauma, hemostasis involves the regulated and self-limiting production of thrombin to stop bleeding. In contrast, arterial and venous thrombosis typically involves the unregulated, intraluminal growth of a clot, in the absence of bleeding. For either hemostasis or thrombosis, the presence of flow and pressure gradients (delta-P, ΔP) dictates when and where thrombin and fibrin are located and in what quantity. For hemostatic clots, fibrin formation helped limit clot growth. We found that γ'-fibrinogen had a role in limiting clot growth via anti-thrombin activity at venous, but not arterial conditions. For hemophilic blood, severe factor deficiency (<1% healthy) led to a defect in both platelet and fibrin deposition under flow. However, moderate deficiency, which is associated with a less severe bleeding phenotype, had normalized platelet function but still lacked fibrin production. We conclude signaling levels of thrombin can be generated during moderate hemophilia to sufficiently activate platelets to achieve primary hemostasis, even if fibrin formation remains defective. Finally, as a clot grows, shear stresses can become sufficiently extreme in diseased arteries to drive von Willebrand Factor self-association into massive fibers, potentially the final burst of clot growth towards full thrombotic occlusion.

Systems Analysis of Thrombus Formation.

The systems analysis of thrombosis seeks to quantitatively predict blood function in a given vascular wall and hemodynamic context. Relevant to both venous and arterial thrombosis, a Blood Systems Biology approach should provide metrics for rate and molecular mechanisms of clot growth, thrombotic risk, pharmacological response, and utility of new therapeutic targets. As a rapidly created multicellular aggregate with a polymerized fibrin matrix, blood clots result from hundreds of unique reactions within and around platelets propagating in space and time under hemodynamic conditions. Coronary artery thrombosis is dominated by atherosclerotic plaque rupture, complex pulsatile flows through stenotic regions producing high wall shear stresses, and plaque-derived tissue factor driving thrombin production. In contrast, venous thrombosis is dominated by stasis or depressed flows, endothelial inflammation, white blood cell-derived tissue factor, and ample red blood cell incorporation. By imaging vessels, patient-specific assessment using computational fluid dynamics provides an estimate of local hemodynamics and fractional flow reserve. High-dimensional ex vivo phenotyping of platelet and coagulation can now power multiscale computer simulations at the subcellular to cellular to whole vessel scale of heart attacks or strokes. In addition, an integrated systems biology approach can rank safety and efficacy metrics of various pharmacological interventions or clinical trial designs.

PO-22 - Thrombodynamics test for analysis of hemostasis in patients with malignant tumors and predicting thrombotic complications

Close correlation between oncologic diseases and blood coagulation disturbances dictates a necessity of prognosis of the main disease course and contemporary prevention of the thrombotic complications revealed. For this purpose, the global test for the hemostasis system assessment was used to reveal bleeding and thrombogenesis risks - "Thrombodynamics" (TD) allowing analysis in the real time of the thrombogenesis parameters in conditions the most resembling the natural functioning of the blood coagulation system. Parameters of TD test which enable differentiation between hyper-, normo- and hypocoagulation include the speed of the blood clot growth (the time of growth delay, initial and stationary blood clot growth) as well as the physical features of the clot (size and density). The aim of the present study was to access the capability of global hemostasis test Thrombodynamics in the evaluation of risk thrombotic complications in patients with cancer. Prospective investigation of hemostasis parameters was carried out in 23 patients with malignant tumors of the oral cavity, 25 patients with oropharynx cancer of I-II and III-IV stage, 23 patients - with brain metastasis, 21 patients - with glioblastoma aged 42-75 years (mean age 63.8±7.0). Standard coagulation test (activated partial thromboplastin time (APTT), thrombin time (TT), prothrombin (by Quick), international normalized ratio (INR), and fibrinogen concentration are used to estimate hemostasis. The spatial growth of the fibrin clot was estimated in all patients using "Thrombodynamics T-2 Registrator." It was established that TD allowed registration of all types of plasma hypercoagulation manifestations: acceleration of the main clot growth, formation of the spontaneous clots and their different combinations. Sensitivity of international normalized ratio (INR) and thrombodynamics test, while revealing patient group with higher fibrin level, was 43% and 86%, accordingly. Reliable dynamic changes were found for all parameters of TD test during patients follow-up (p<0.05). The results of regression analysis showed that the time of clot growth delay, initial and stationary clot growth speed, and clot size were reliable thrombosis predictors. The study showed that TD test might be effective in revealing oncologic patients with high risk of thrombotic complications and for monitoring of efficiency/safety of the anticoagulant therapy.

PO-59 - Hemorheologic disturbances as thrombosis risk factor in patients with some myeloproliferative neoplasms

In today's antithrombotic prevention we forget that hemorheologic abnormalities are part of Virchow's triad. Isn't this one of reasons that venous thromboembolism (VTE) including catheter-related thrombosis (CRT) retain high frequency despite of modern antithrombotic therapy? The aim was to investigate rheological behavior of blood in patients with some myeloproliferative neoplasms. The study included 16 adults with Polycythemia Vera (PV), 42 young with acute lymphoblastic leukemia (ALL), and 67 healthy donors as control group. Of patients 38% had thrombosis. We measured plasma viscosity, and whole blood viscosity (WBV) by shear rate from 300 to 5 s-1. Then indices were calculated for erythrocyte aggregation, and deformability, and non-Newtonian behavior of blood. Hematocrit, erythrocytes count, erythrocyte indices, leukocyte count, fibrinogen and B-type natriuretic peptide (BNP) were analyzed simultaneously. Increased WBV revealed totally in PV-patients but not by all shear rates in ALL-patients. Unlike donor, in patients WBV values had no equivalence under sequential one sample measurements with a decrease and then an increase of shear rates. We speculated this difference becomes diagnostic meaning like one and by its size. WBV dependent on leukocytes count, on MCH and mainly on MCV. Forty percent of patients had elevated BNP assuming subclinical cardiac dysfunction. The latter explains discoordinated changes in shear stress values required for fully reversible erythrocyte aggregation. As a result, residual units like "erythrocyte-erythrocyte" and/or "erythrocyte-leukocyte" interferes blood stream and violates mechanically blood flow in small vessels. Moreover in PV-patients but not in ALL-patients we found loss of non-Newtonian behavior of blood later than in control group. Both myeloproliferative neoplasms lead to increased erythrocyte aggregation but not impair deformability of red blood cells. In total these facts explains chronic hypoxia in these patients. Patients with some myeloproliferative neoplasms has abnormal blood flow properties. Revealed hemorheologic disturbances could be as a trigger to start of VTE or to growth of blood clot in the area of permanent venous catheter. These non-hemocoagulation conditions leaded for thrombus formation makes hemorheologic therapy looking attractive for antithrombotic management. The choice of targeted methods requires to continue this study.

Effect of iron and carbon monoxide on fibrinogenase-like degradation of plasmatic coagulation by venoms of four Crotalus species.

Annually, thousands suffer poisonous snake bite, often from defibrinogenating species. Iron and carbon monoxide (CO) improve coagulation kinetics by modulation of fibrinogen as demonstrated in various Agkistrodon species and Crotalus atrox. Thus, we sought to determine whether pretreatment of plasma with iron and CO could attenuate venom-mediated catalysis of fibrinogen obtained from four common Crotalus species with known fibrinogenase activity. Human plasma was pretreated with ferric chloride (0-10 μmol/l) and CO-releasing molecule-2 (0-100 μmol/l) prior to exposure to venom from a Northern Pacific rattlesnake, Arizona black rattlesnake, prairie rattlesnake, or red diamond rattlesnake. The concentration of venom used decreased coagulation function of one or more kinetic parameters by at least 50% of normal values. Coagulation kinetics were determined with thrombelastography.Three snake venoms significantly degraded plasmatic coagulation kinetics, prolonging the onset to clot formation, diminishing velocity of clot growth and decreasing clot strength. However, red diamond rattlesnake venom exposure resulted in mixed coagulation kinetics, significantly decreasing the time to onset of coagulation without decreasing the velocity of clot growth. Iron and CO attenuated these coagulation kinetic changes in a species-specific manner. Further in vitro investigation of other fibrinogenolytic venoms is indicated to determine if iron and CO can attenuate venom compromised coagulation.

Impact of Albumin on Coagulation Competence and Hemorrhage During Major Surgery: A Randomized Controlled Trial.

For patients exposed to a massive blood loss during surgery, maintained coagulation competence is important. It is less obvious whether coagulation competence influences bleeding during elective surgery where patients are exposed to infusion of a crystalloid or a colloid.This randomized controlled trial evaluates whether administration of 5% human albumin (HA) or lactated Ringer solution (LR) affects coagulation competence and in turn blood loss during cystectomy due to bladder cancer.Forty patients undergoing radical cystectomy were included to receive either 5% HA (n = 20) or LR (n = 20). Nineteen patients were analyzed in the HA group and 20 patients in the lactated Ringer group.Blinded determination of the blood loss was similar in the 2 groups of patients: 1658 (800–3300) mL with the use of HA and 1472 (700–4330) mL in the lactated Ringer group (P = 0.45). Yet, by thrombelastography (TEG) evaluated coagulation competence, albumin affected clot growth (TEG-angle 69 ± 5 vs 74° ± 3°, P < 0.01) and strength (TEG-MA: 59 ± 6 vs 67 ± 6 mm, P < 0.001) more than LR. Furthermore, by multivariate linear regression analyses reduced TEG-MA was independently associated with the blood loss (P = 0.042) while administration of albumin was related to the changes in TEG-MA (P = 0.029), aPPT (P < 0.022), and INR (P < 0.033).This randomized controlled trial demonstrates that administration of HA does not affect the blood loss as compared to infusion of LR. Also the use of HA did not affect the need for blood transfusion, the incidence of postoperative complications, or the hospital in-stay. Yet, albumin decreases coagulation competence during major surgery and the blood loss is related to TEG-MA rather than to plasma coagulation variables.

In microfluidico: Recreating in vivo hemodynamics using miniaturized devices

Microfluidic devices create precisely controlled reactive blood flows and typically involve: (i) validated anticoagulation/pharmacology protocols, (ii) defined reactive surfaces, (iii) defined flow-transport regimes, and (iv) optical imaging. An 8-channel device can be run at constant flow rate or constant pressure drop for blood perfusion over a patterned collagen, collagen/kaolin, or collagen/tissue factor (TF) to measure platelet, thrombin, and fibrin dynamics during clot growth. A membrane-flow device delivers a constant flux of platelet agonists or coagulation enzymes into flowing blood. A trifurcated device sheaths a central blood flow on both sides with buffer, an ideal approach for on-chip recalcification of citrated blood or drug delivery. A side-view device allows clotting on a porous collagen/TF plug at constant pressure differential across the developing clot. The core-shell architecture of clots made in mouse models can be replicated in this device using human blood. For pathological flows, a stenosis device achieves shear rates of >100,000 s(-1) to drive plasma von Willebrand factor (VWF) to form thick long fibers on collagen. Similarly, a micropost-impingement device creates extreme elongational and shear flows for VWF fiber formation without collagen. Overall, microfluidics are ideal for studies of clotting, bleeding, fibrin polymerization/fibrinolysis, cell/clot mechanics, adhesion, mechanobiology, and reaction-transport dynamics.

Iron modulates the alpha chain of fibrinogen.

Iron-bound fibrinogen has been noted to accelerate plasmatic coagulation in patients with divergent conditions involving upregulation of heme oxygenase activity, including hemodialysis, Alzheimer's disease, sickle cell anemia, and chronic migraine. Our goal was to determine if a site of iron-fibrinogen interaction was on the alpha chain. Using thrombelastography, we compared the coagulation kinetic profiles of plasma exposed to 0-10 µM ferric chloride after activation of coagulation with thrombin generated by contact activation of plasma with the plastic sample cup or by exposure to 1 µg/ml of Calloselasma rhodostoma venom (rich in ancrod activity), which causes coagulation via polymerization of alpha chain monomers. Venom mediated coagulation always occurred before thrombin activated thrombus formation, and ferric chloride always diminished the time of onset of coagulation and increased the velocity of clot growth. Iron enhances plasmatic coagulation kinetics by modulating the alpha chain of fibrinogen.