Coagulation Variables Research Articles

The effects of automated plasmapheresis on clinical, haematological, biochemical and coagulation variables in horses

The goal of this study was to determine the effects of plasmapheresis on the behaviour, general condition, haematological, biochemical and coagulation variables of donor horses for 32 days following the procedure. Twenty millilitres of plasma/kg body weight were collected via plasmapheresis in six clinically healthy horses. The general behaviour and condition of the horses was not affected by the procedure. During plasmapheresis, there was a mild increase in the haematocrit, haemoglobin concentration and total erythrocyte and leucocyte counts ( P<0.01). The mean concentrations of total protein and albumin decreased significantly ( P<0.01) and total protein did not normalise for about three weeks. Several other biochemical variables also decreased significantly during plasmapheresis, but mostly remained within reference ranges. After plasmapheresis, the mean value of the activated partial thromboplastin time and the thrombin time were mildly but significantly increased ( P<0.01), and the mean activities of factor V, factor VIII and antithrombin decreased significantly ( P<0.01), although all coagulation values remained within reference ranges. Our results indicate that, in horses, the collection of 20 mL of plasma/kg body weight via plasmapheresis results in mild changes in several haematological, biochemical and coagulation variables, although these were of no clinical relevance for the donors.

Blood flow reductions during continuous renal replacement therapy and circuit life.

Reductions in blood flow rate may occur undetected during peristaltic pumping of blood through continuous renal replacement therapy circuits. We investigated whether undetected reductions in blood flow rate occur during continuous veno-venous haemofiltration, and whether they are correlated with filter life. Twelve patients receiving continuous veno-venous haemofiltration in the intensive care unit of a tertiary hospital. Extracorporeal circuit blood flow during haemofiltration was continuously monitored utilizing a miniature ultrasound Doppler device. Otherwise undetected blood flow reductions were identified at severity levels of between 20% and 100% less than the set diastolic flow rate (83 ml/min). Information on anticoagulation status was simultaneously obtained. The frequency and severity of blood flow reductions were recorded, and the correlation with filter life was determined. The duration of filter life ranged from 1.5 to 53 h, with a mean functional life of 19.62+/-16.32 h. There were 314 episodes of blood flow reduction during the 525 h of monitoring (0.59 episodes/h). There was a significant inverse relationship between the number of medium-level blood flow reductions and filter life. This correlation was much stronger than that between APTT and filter life. Undetected blood flow reductions occur during continuous veno-venous haemofiltration. Such reductions are frequent, and when sufficiently severe appear to be correlated with filter life more strongly than the blood coagulation variables typically used to monitor adequacy of anticoagulation and promote filter longevity.

Biochemical changes after trauma and skeletal surgery of the lower extremity: Quantification of the operative burden

Pape, Hans-Christoph MD; Schmidt, Reinhold E. MD; Rice, John FRCS; van Griensven, Martijn PhD; das Gupta, Ronjan; Krettek, Christian MD; Tscherne, Harald MD Author Information

Inhibition of coagulation and inflammation by activated protein C or antithrombin reduces intestinal ischemia/reperfusion injury in rats.

To examine whether administration of activated protein C or antithrombin reduces local splanchnic derangement of coagulation and inflammation and attenuates intestinal dysfunction and injury following intestinal ischemia/reperfusion. Randomized prospective animal study. University research institute. Adult male Wistar rats, weighing 300-325 g (n = 72). Rats were subjected to superior mesenteric artery occlusion consisting of 20 or 40 mins of ischemia and 3 hrs of reperfusion. A randomized intravenous administration of vehicle (0.9% NaCl), heparin, antithrombin, or activated protein C was performed during ischemia, 15 mins before reperfusion. Coagulation and fibrinolysis variables obtained from portal blood were correlated with mucosal fibrin deposition (determined by anti-rat fibrin antibody staining), intestinal function (glucose/water clearance), and intestinal injury (histologic evaluation by Park/Chiu score). Activated protein C- or antithrombin-treated animals demonstrated less ischemia/reperfusion-induced intestinal dysfunction and histologic changes compared with control animals, whereas intravenous administration of heparin only showed less histologic derangement. Activated protein C- or antithrombin-treated animals showed less thrombin generation, fibrin degradation products, and fibrin deposition compared with control animals, as confirmed by histologic examination, whereas heparin administration showed only a limited reduction of portal fibrin degradation product concentrations. Furthermore, activated protein C or antithrombin administration markedly inhibited the inflammatory response, as reflected by reduced interleukin-6 plasma concentrations to baseline values, whereas heparin had no effect. Administration of activated protein C or antithrombin inhibited local and systemic derangement of coagulation and inflammation following intestinal ischemia/reperfusion, diminished mucosal fibrin deposition, and attenuated ischemia/reperfusion-induced intestinal injury. These observations suggest that activated protein C or antithrombin reduces ischemia/reperfusion-induced intestinal injury, both through their anticoagulant and anti-inflammatory effects.

Heparinase-Modified Thrombelastography in Term and Preterm Neonates

Thrombelastography (TEG) appears to be a promising test to assess coagulation in infants and children. TEG enables a rapid assessment of hemostatic function with only 300 microL of whole blood and provides information about plasmatic coagulation, platelet function, and fibrinolysis. In this study, we used TEG to assess the coagulation system of preterm and term neonates to determine the effects of their deficient coagulation factor levels on global hemostatic function. Heparinase-modified TEG, platelet and red blood cell count, plasma fibrinogen, and prothrombin time were assessed in four groups of clinically stable infants: severely preterm (gestational age [GA], 27-31 wk), moderately preterm (GA, 32-36 wk), term (GA, 36-40 wk), and former preterm (corrected GA, 34-40 wk). Healthy adult volunteers served as a control group. When compared with the adult group, thromboelastography revealed no defects in coagulation from groups of clinically stable infants, documenting the functional integrity of coagulation despite, in part, decreased conventional coagulation variables. Because clinically stable preterm and term infants show a relatively small incidence of bleeding, despite prolonged conventional coagulation tests, TEG may better reflect the hemostatic potential of these patients compared with conventional coagulation tests. This study assessed the coagulation of preterm and term infants by thrombelastography and found functional integrity of coagulation despite, in part, decreased conventional coagulation variables.

Factor V Leiden polymorphism modifies sepsis outcome: evidence from animal studies.

The high prevalence of the factor V Leiden mutation in certain populations has prompted speculation that the mutation may have been subject to positive selection during evolution, either by providing a survival benefit or by directly enhancing reproductive performance. We investigated the hypothesis that heterozygous factor V Leiden carrier status might protect against the lethal consequences of severe inflammatory disease. Two mouse models (thrombomodulin-deficient TMPro mice and factor V Leiden mice), in which the endogenous protein C anticoagulant pathway is disrupted either at the level of protein C activation (TMPro mice) or at the level of factor V proteolysis by activated protein C (factor V Leiden mice), were employed. The mutant mouse strains were subjected to lethal doses of bacterial lipopolysaccharide. The effects of these two mutations on coagulation activation and inflammatory cytokine elaboration were observed and compared with those in wild-type mice. As has already been shown, heterozygous factor V Leiden carrier status improves the survival of mice subjected to endotoxemia induced by bacterial lipopolysaccharide. The survival of homozygous factor V Leiden mice did not differ from that of normal mice. The survival benefit derived from heterozygous factor V Leiden carrier status was only evident at doses of lipopolysaccharide producing death in approximately 50% of wild-type animals. At higher (LD90) or lower (LD10) doses of lipopolysaccharide, the survival of heterozygous factor V Leiden mice did not differ from that of wild-type mice. Concomitant administration of an LD90 dose of lipopolysaccharide and therapeutic heparin abolished the relative survival advantage of heterozygous factor V Leiden mice. Analysis of systemic coagulation and cytokine variables failed to provide conclusive evidence for altered coagulation activation or inflammatory cytokine production as the basis for the survival advantage associated with heterozygous factor V Leiden carrier status. The improved survival of mice heterozygous for the factor V Leiden mutation complements results from the analysis of the factor V Leiden subgroup of patients enrolled in the PROWESS trial. Such convergent findings in two different species strongly suggest that the factor V Leiden mutation is indeed a potent modifier of the response to severe inflammatory disease. The striking magnitude of the factor V Leiden survival benefit in the initial PROWESS population, and in mice, suggests that the as-yet unknown mechanism conferring this benefit is a rather potent endogenous modifier of the pathogenic pathways engaged in sepsis. Delineation of this pathway will be important for understanding the therapeutic mechanisms, or absence thereof, of agents designed to act at the interface of coagulation and inflammation.

Preclinical characterization of a new liquid “immune globulin intravenous (human), 10% triple virally reduced solution” (IGIV, 10%TVR)

Rationale In preclinical testing the efficacy, safety, pharmacokinetics, and toxicity of a new liquid 10% intravenous immunoglobulin preparation (IGIV, 10%TVR) was compared with Gammagard® S/D, a licensed lyophilized immunoglobulin for intravenous infusion. Methods Efficacy is proved in vivo by mouse protection testing and in vitro by opsonization and affinity chromatography using protein A Sepharose. The blood-pressure-lowering effect in spontaneously hypertensive rats and the bronchospastic effect in guinea pigs are used as indicators of the anaphylactoid potential. Pharmacokinetics in rats is evaluated by the variables “in vivo recovery” and “half-life” after a single intravenous dose of 1000 mg/kg. Thrombogenicity is assessed in a rabbit model and the influence of the products on vital functions like cardiovascular, respiratory and blood coagulation variables is tested in dogs. Acute toxicity studies are carried out in mice and rats. Results The mouse protection test showed that the protective activity against systemic bacterial infections of IGIV, 10%TVR is at least as good as the reference Gammagard S/D. This result is supported by the broad spectrum of antibodies in high titers against bacteria and viruses and the high functional integrity of the IgG molecule (≥90% functional intact IgG) in IGIV, 10%TVR. In safety and thrombogenicity studies, no adverse effects of IGIV, 10%TVR were observed. Pharmacokinetic studies showed no statistically significant differences between the two products. In the acute toxicity animal studies, IGIV, 10%TVR was better tolerated than the reference Gammagard S/D. Conclusions Liquid IGIV, 10%TVR combines excellent qualities of efficacy, safety and tolerability.

Changes in Blood Viscosity With Mucopolysaccharide Polysulfate

We examined the dose-dependent effects of mucopolysaccharide polysulfate (MPS) on coagulation variables and whole-blood viscosity in human blood. Both 0.01% and 0.1% MPS significantly reduced levels of both fibrin monomer and thrombin-antithrombin III complex in a manner similar to that of 2.0 IU/ml heparin sodium. Furthermore, MPS dose-dependently decreased whole-blood viscosity, as measured with an oscillation viscometer. Because MPS can be applied in creams and gels, percutaneous application of MPS may effectively reduce whole-blood viscosity in local veins.

Effects of Intravascular Volume Therapy with a Hydroxyethyl Starch (HES 130/0.4) on Blood Coagulation in Children Undergoing Cardiac Surgery

Background: Hydroxyethyl starch (HES) is used for intravascular volume expansion in cardiac surgery. Studies have produced conflicting data on the effects of intraoperative HES administration on postoperative bleeding. We evaluated the effects of intraoperative HES infusion, shortly after the termination of cardiopulmonary bypass (CPB), on hemostasis following a cardiac operation. Methods: According to a prospective, random sequence, 30 children undergoing cardiac surgery received one of the following; fresh frozen plasma (FFP)(n = 10), HES 130/0.4 (n = 10), or HES 200/0.5 (n = 10) shortly after CPB termination. Standard coagulation variables were measured using arterial blood samples Results: While the use of allogenic blood/ blood products and aPTT did not differ significantly among the groups, blood loss during the 24 hours following surgery increased significantly in the HES 200 group and PT after fluid infusion increased in both HES groups. Conclusions: Our study shows that the administration of moderate dose of HES (130/0.4) in children undergoing cardiac surgery did not cause more bleeding than FFP administration. Thus, this HES (130/0.4) solution appears to be a safe alternative plasma substitute for intravascular volume replacement in this patient population.

Disturbances of haemostasis in diabetes mellitus.

Diabetes mellitus is associated with disturbances in haemostasis that could contribute to the development of thrombotic complications.The present study was undertaken to determine the behavior of coagulation variables and fibrinolytic system in diabetes mellitus. Forty five diabetic patients and forty five matched controls were evaluated by doing the following haemostatic parameter, prothrombin time, partial thromboplastin time, thrombin time, coagulation factors assay II, VII, IX, & plasma fibrinogen, ADP-induced platelet aggregation, protein C, a2- antiplasmin, PAI and FDPs. Generally diabetic patients have high levels of fibrinogen, a2- antiplasmin, & PAI and lower level of protein C. Other haemostatic parameters did not show statistically significant difference between diabetic patients and control group. Significantally elevated levels of PAI, a2- antiplasmin together with low protein C level in diabetic patients may result in the disturbance of haemostatic balance favoring thrombotic events. Conclusion: High levels of plasma fibrinogen, a2A- antiplasmin with low plasma protein C activity could lead to a prothrombotic tendency in insulin dependent diabetic patients. Moreover, in non-insulin dependent diabetic patients, the above mentioned parameters together with high levels of ADP-induced platelet aggregation and plasminogen activator inhibitor may increase the risk of thrombotic complications. Obesity can be considered as an additional risk factor for development of thrombosis in diabetic patients.

Fluid Therapy and Coagulation

SUMMARYThis article reviews the influence of commonly used resuscitation solutions on both laboratory and clinical coagulation variables. Contrary to the common view, crystalloid solutions enhance coagulation over a range of hemodilution between 10–40%, and do not impair coagulation until hemodilution approaches 70%, provided that ionized calcium concentrations are maintained. By contrast, all of the colloid solutions exert some inhibitory effect on coagulation that appears to exceed the effects of simple hemodilution. The gelatin preparations appear to have the least adverse effect, while dextran preparations impair coagulation to the greatest extent. There is a range of effects exerted by the hydroxyethyl starches that is determined by the in vivo molecular weight of the starch product, with the medium‐to‐low molecular weight solutions (&lt; 200 kD) with a low degree of substitution (&lt; 0.5) exhibiting effects on coagulation that are not significantly different from those of either albumin or the gelatins.

Effects of oxypolygelatin and dextran 70 on hemostatic variables in dogs

ObjectiveTo evaluate and compare coagulation variables following the administration of oxypolygelatin and dextran 70 to clinically healthy dogs. Study designRandomized cross–over experimental study. AnimalsA total of eight healthy adult female Beagles aged 2–4 years old and weighing 11.8 ± 2.7 kg. MethodsThe dogs received a 15–minute intravenous (IV) infusion of 5 mL kg−1 oxypolygelatin or 10 mL kg−1 6% dextran 70. Before (PRE) and at 2, 5, and 24 hours after administration, packed cell volume (PCV), total solids concentration (TS), prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration (FIB), platelet numbers (Plat), factor VIII coagulant activity (VIII:C), von Willebrand factor antigen concentration (vWf:Ag) and platelet function and buccal mucosal bleeding time (BMBT) were measured. Platelet function was assessed using aggregation and by measuring ATP release from aggregating platelets over 6 minutes, with 20, 10, and 5 μm ADP and 5 and 10 μg of collagen mL−1 as platelet activation agonists. ResultsAll baseline values were within our normal ranges, except for one dog that had low vWf:Ag PRE values prior to both dextran and oxypolygelatin administration. Following dextran and oxypolygelatin administration, the PCV and TP were significantly (p < 0.05) decreased. Plat, FIB, and vWf:Ag decreased, while BMBT and VIII:C increased following dextran administration. Dextran also caused a significant decrease in platelet aggregation in response to ADP. Oxypolygelatin caused a significant decrease in vWf:Ag, Plat, and FIB compared to PRE values. The total amount of ATP released, standardized to platelet number, did not vary significantly for either group at any sampling time from PRE values. No significant changes from PRE values were noted at any time in either group for PT or APTT. ConclusionAt the doses administered, both dextran and oxypolygelatin can interfere with hemostatic variables in healthy dogs, but dextran's effect is more profound and prolonged when compared to oxypolygelatin. Clinical relevanceOxypolygelatin causes fewer hemostatic abnormalities when compared to dextran, making it a superior colloid for administration at the doses tested.

Ecarin Chromogenic Assay – A New Method for Quantitative Determination of Direct Thrombin Inhibitors Like Hirudin

A new sensitive and precise method for quantitative determination of direct thrombin inhibitors is described, the ecarin chromogenic assay (ECA). Ecarin is used as the specific prothrombin-activating principle. The cleavage of a chromogenic substrate by meizothrombin is inhibited in a concentration-dependent fashion by direct thrombin inhibitors. For the ECA, the linear measuring range is about 0.1–3.0 µg hirudin/ml plasma. Coefficients of variations between 2.3 and 4% over the whole concentration range were achieved. The ECA has proved to be more sensitive than the compared tests (ecarin clotting time and a thrombin-based chromogenic assay); a detection limit of 0.011 µg hirudin/ml and a quantitation limit of 0.032 µg hirudin/ml were calculated. The ECA is independent of the variations of the coagulation variables fibrinogen and prothrombin. Neither heparin nor oral anticoagulants interfere with the ECA.

The Influence of Crystalloid and Colloid Replacement Solutions in Acute Normovolemic Hemodilution: A Preliminary Survey of Hemostatic Markers

Acute normovolemic hemodilution (ANH), in which blood for autologous use is collected immediately before the onset of surgical blood loss, is a recommended autologous blood procurement technique for blood conservation. Both crystalloid and colloid replacement fluids have been used to maintain normovolemia during ANH, but few data are available to justify the use of a particular replacement fluid. Therefore, we designed a prospective, randomized study to determine if the replacement fluid choice affects various coagulation variables and perioperative blood loss. Forty adult patients, ASA physical status 1–3, scheduled for ANH during radical prostatectomy were randomly assigned to one of four replacement fluid groups: (a) Ringer’s lactate, (b) 5% albumin, (c) 6% dextran 70 (DEX), or (d) 6% hetastarch (HES). After the induction of a standardized general anesthetic, all patients underwent ANH to a final hemoglobin level of 9 g/dL. Complete blood count, prothrombin time, partial thromboplastin time, fibrinogen, factors V and VIII levels, bleeding time, and thromboelastography (TEG®) measurements were obtained at similar time points in the procedure. When compared with baseline, activated partial thromboplastin time decreased and factor VIII levels increased in the postanesthesia care unit in both the Ringer’s lactate and 5% albumin groups. The DEX and HES groups demonstrated a decrease in TEG® maximum amplitude between preoperative and postanesthesia care unit measurements and TEG® α (angle) was decreased from baseline in the DEX group. The changes in factor VIII, activated partial thromboplastin time, and TEG® measurements indicate that HES and DEX may attenuate the hypercoagulability related to surgery.

Aprotinin and preservation of myocardial function after ischemia-reperfusion injury

Ischemia-reperfusion injury, a complex process involving the generation and release of inflammatory cytokines, accumulation and infiltration of neutrophils and macrophages, release of oxygen free radicals, activation of proteases, and generation of nitric oxide (NO), may result in myocardial dysfunction and possible injury to other major organs. Aprotinin, a nonspecific serine protease inhibitor used to reduce the blood loss and transfusion requirements accompanying cardiac surgery, has dose-dependent effects on coagulation, fibrinolytic, and inflammatory variables. Data indicate that aprotinin may provide protection from ischemia-reperfusion injury. In myocardial tissue models of ischemia and reperfusion, aprotinin has been shown to reduce uptake of tumor necrosis factor-α (TNF-α), generation of NO, and accumulation of leukocytes. Improved myocardial function has been observed with aprotinin treatment in animal models of ischemia-reperfusion injury. In humans, data indicate that integrin expression associated with leukocyte transmigration as well as markers of myocardial damage are reduced in patients receiving aprotinin. Further, data suggest that patients who receive aprotinin may have a reduced need for inotropic support and a decreased incidence of postoperative atrial fibrillation. In all, review of this topic indicates that aprotinin may reduce aspects of ischemia-reperfusion injury and prospective clinical studies are needed to evaluate the impact of aprotinin on associated patient outcomes.

The role of the initial state in the response of the hemostasis system to repeated exercise

Changes in the hemostasis system were studied in males with a high working capacity when they performed the same dosed double stress exercise test with moderate ( N 1 = 1.4 W/kg, t 1 = 6.93 min) and high ( N 2 = 2.96 W/kg, t 2 = 3.15 min) intensity with a 1-h interval between. The direction and the magnitude of changes in the main variables of blood coagulation, anticoagulants, and blood and plasma fibrinolytic activity under the influence of exercise were shown to correlate with the initial state of the system. At high values of the variables before the beginning of muscular activity, work results in their decrease, and at low values, in their increase. Previous work increases the dependence of changes in blood coagulation on its initial value upon repeat exercise, without influencing the relationship between alterations in the fibrinolytic activity of whole blood and its value before exercise. Double loading reveals closer relations between the initial values of blood coagulation, anticoagulants, and fibrinolysis and their changes due to work. It was concluded that, on the basis of the correlations presented, it is possible to predict with high probability the direction and the magnitude of hemocoagulant and fibrinolytic response to physical activity in the group of subjects studied.

Conventional coagulation and thromboelastograph parameters and longevity of continuous renal replacement circuits.

To determine the relationship between conventional and thromboelastograph (TEG) coagulation parameters and continuous renal replacement therapy (CRRT) circuit longevity. Conventional coagulation and TEG parameters were measured at the commencement of and during CRRT. Time to circuit cessation was measured and only circuits reaching a predetermined rise from baseline in the pressure gradient across the haemofilter were diagnosed as failing due to clotting. All other circuits were excluded from analysis. A general critical care unit of a metropolitan tertiary hospital. Fourteen consecutive patients requiring CRRT were studied. The CRRT technique used was continuous veno-venous haemodialysis. Thromboelastograph measurements were made prior to the commencement of CRRT and daily thereafter for each circuit. The international normalised ratio (INR), activated partial thromboplastin time (APTT) and platelet numbers were measured at commencement and 8 hourly thereafter. Heparin was used for anticoagulation unless considered contraindicated. Forty-seven circuits with a mean (SD) circuit life of 33.0 (30.2) h were entered. Twenty-five circuits fulfilled circuit clotting criteria; the mean circuit life was 30.8 (22.1) h. Heparin anticoagulation was found to prolong circuit life significantly despite adequate mean circuit life, 33.2 (35.7) h, in heparin-free circuits. The starting APTT and the TEG variables reaction time (R) and coagulation time (RK) were significantly correlated. The starting APTT, starting RK and mean time taken for the amplitude to increase from 2 to 20 mm (K) were predictive of circuit life. None of these variables predicted which patients would need heparin. While TEG variables more closely predicted circuit longevity than conventional coagulation variables, the clinical benefit of TEG monitoring of anticoagulation for CRRT would appear to be minimal.

The functional state of the hemostasis system in traumatologic and orthopedic patients with atherosclerosis

Coagulopathy after sever injury predicts the requirements of blood products, organ failure and mortality in traumatic patients. The early onset and complexity of traumatic coagulopathy preclude the understanding the underlying mechanism. The aim of the study is to characterize the early coagulation alteration in a swine model with multi-trauma and shock.Twelve pigs were subjected to multi-trauma (femur fracture, laparotomy, 10 cm intestine resection and grade III injury of liver) and hemorrhaged to a mean arterial pressure (MAP) of 40 mmHg. Physiologic parameters and coagulation variables (prothrombin time (PT), international normalized ratio (INR), fibrinogen, antithrombin-III (AT-III) activity, D-dimer and thromboelastography (TEG)) were measured after instrumentation (baseline), 5 min after multi-trauma (after trauma), 10 min (early shock) and 40 min (late shock) after hemorrhage. A group of 6 instrumented pigs were used as control.Multi-trauma and hemorrhage caused significant increase of base excess (BE) and lactate (p < 0.05). PT shortened after multi-trauma but increased significantly at late shock (p < 0.05). Fibrinogen reduced greatly after trauma and at early shock (p < 0.05), while remained stable afterwards. AT-III activity decreased throughout the experiment. Reaction time (R) shortened after trauma and at early shock (both p < 0.05). Maximal amplitude (MA) decreased significantly during the shock period.After traumatic hemorrhagic shock, hypercoagulation turned into hypocoagulation in a short period, which was probably caused by hypoperfusion.

The Effects of Perioperatively Administered Colloids and Crystalloids on Primary Platelet-Mediated Hemostasis and Clot Formation

The Effects of Perioperatively Administered Colloids and Crystalloids on Primary Platelet-Mediated Hemostasis and Clot Formation

Tranexamic acid reduces bleeding and the need for blood transfusion in primary myocardial revascularization

Background. The objective of this study was to study the effect of low-dose tranexamic acid (TA) on postoperative bleeding and coagulation variables after coronary artery bypass grafting operation. Methods. Fifty patients undergoing primary coronary artery bypass grafting were randomly assigned to receive either placebo (0.9% NaCl; n = 25) or 10 mg/kg TA followed by infusion of 1 mg/kg per hour during the operation (n = 25). Data measured included blood loss, transfusion, reoperation, fibrinogen level, fibrinogen split products, platelet size, and platelet function. Measurements were made after induction of anesthesia, after heparin administration, during patient warming, after skin closure, and 24 hours after operation. Results. Patients in the TA study group weighed less. Other demographic characteristics were similar between groups. Postoperative bleeding was less in the TA group (194 ± 135 mL versus 488 ± 238 mL, p < 0.001), whereas blood requirement was higher in the control group (1.68 ± 1 versus 0.52 ± 0.9 U of packed cells per patient, p < 0.001). The percent of patients exposed to blood products was significantly less in the TA group (36% versus 100%, p < 0.001). Fibrinogen split products were lower in the TA group during bypass ( p < 0.001). Fibrinogen levels fell in both groups during cardiopulmonary bypass. Platelet number and function were reduced equally in both groups by cardiopulmonary bypass. Other test results were not different between groups. Conclusions. The use of low-dose TA during coronary artery bypass grafting significantly reduced the coagulopathy-induced postoperative bleeding and allogeneic blood products requirement. The low levels of fibrinogen split products during bypass in the study group reflect the inhibiting effect of TA in fibrinolysis. Tranexamic acid had no effect on platelet function during cardiopulmonary bypass.