Klaus Görlinger

Point-of-care testing: a prospective, randomized clinical trial of efficacy in coagulopathic cardiac surgery patients.

Introduction: The current investigation aimed to study the efficacy of hemostatic therapy guided either by conventional coagulation analyses or point-of-care (POC) testing in coagulopathic cardiac surgery patients. Methods: Patients undergoing complex cardiac surgery were assessed for eligibility. Those patients in whom diffuse bleeding was diagnosed after heparin reversal or increased blood loss during the first 24 postoperative hours were enrolled and randomized to the conventional or POC group. Thromboelastometry and whole blood impedance aggregometry have been performed in the POC group. The primary outcome variable was the number of transfused units of packed erythrocytes during the first 24 h after inclusion. Secondary outcome variables included postoperative blood loss, use and costs of hemostatic therapy, and clinical outcome parameters. Sample size analysis revealed a sample size of at least 100 patients per group. Results: There were 152 patients who were screened for eligibility and 100 patients were enrolled in the study. After randomization of 50 patients to each group, a planned interim analysis revealed a significant difference in erythrocyte transfusion rate in the conventional compared with the POC group [5 (4;9) versus 3 (2;6) units [median (25th and 75th percentile)], P < 0.001]. The study was terminated early. The secondary outcome parameters of fresh frozen plasma and platelet transfusion rates, postoperative mechanical ventilation time, length of intensive care unit stay, composite adverse events rate, costs of hemostatic therapy, and 6-month mortality were lower in the POC group. Conclusions: Hemostatic therapy based on POC testing reduced patient exposure to allogenic blood products and provided significant benefits with respect to clinical outcomes.

Pathophysiology and Treatment of Coagulopathy in Massive Hemorrhage and Hemodilution

Fluid resuscitation after massive hemorrhage in major surgery and trauma may result in extensive hemodilution and coagulopathy, which is of a multifactorial nature. Although coagulopathy is often perceived as hemorrhagic, extensive hemodilution affects procoagulants as well as anticoagulant, profibrinolytic, and antifibrinolytic elements, leading to a complex coagulation disorder. Reduced thrombin activation is partially compensated by lower inhibitory activities of antithrombin and other protease inhibitors, whereas plasma fibrinogen is rapidly decreased proportional to the extent of hemodilution. Adequate fibrinogen levels are essential in managing dilutional coagulopathy. After extensive hemodilution, fibrin clots are more prone to fibrinolysis because major antifibrinolytic proteins are decreased. Fresh frozen plasma, platelet concentrate, and cryoprecipitate are considered the mainstay hemostatic therapies. Purified factor concentrates of plasma origin and from recombinant synthesis are increasingly used for a rapid restoration of targeted factors. Future clinical studies are necessary to establish the specific indication, dosing, and safety of novel hemostatic interventions.

Early and individualized goal-directed therapy for trauma-induced coagulopathy

Severe trauma-related bleeding is associated with high mortality. Standard coagulation tests provide limited information on the underlying coagulation disorder. Whole-blood viscoelastic tests such as rotational thromboelastometry or thrombelastography offer a more comprehensive insight into the coagulation process in trauma. The results are available within minutes and they provide information about the initiation of coagulation, the speed of clot formation, and the quality and stability of the clot. Viscoelastic tests have the potential to guide coagulation therapy according to the actual needs of each patient, reducing the risks of over- or under-transfusion. The concept of early, individualized and goal-directed therapy is explored in this review and the AUVA Trauma Hospital algorithm for managing trauma-induced coagulopathy is presented.

Hypothermia and acidosis synergistically impair coagulation in human whole blood.

BACKGROUND:Hypothermia and acidosis were reported to influence coagulopathy in different clinical settings. We evaluated whole blood coagulation to determine the effects of hypothermia and/or acidosis on hemostasis. METHODS:Whole blood samples (3.000 &mgr;L) from 10 healthy volunteers (2 female, 8 male) were acidified by adding 40 &mgr;L of hydrochloric acid of increasing molarity to achieve a blood pH (&agr;-stat) between 7.0 and 7.37, and coagulation was analyzed by rotational thromboelastometry after an incubation period of 30 min using both intrinsically (InTEM ™) and extrinsically (ExTEM ™) activated assays. To assess temperature-dependent effects, all tests were performed at blood/thromboelastometer temperatures of 30, 33, 36, and 39°C, respectively. An additional extrinsically activated test with addition of cytochalasin D was performed to examine clot formation without platelet contribution. RESULTS:Hypothermia at a normal pH produced an increased coagulation time [ExTEM: 65 s ± 3.6 (36°C) vs 85 ± 4 (30°C), P < 0.001; coagulation time, InTEM: 181 s ± 10 (36°C) vs 226 ± 9, P < 0.001] and clot formation time [ExTEM: 105 s ± 5 (36°C) vs 187 ± 6 (30°C), P < 0.001]; clot formation time [InTEM: 101 s ± 5 (36°C) vs 175 ± 7, P < 0.001], as well as decreased &agr; angle [ExTEM: 65.6 ± 1.8 (36°C) vs 58 ± 1.1, P < 0.01, P < 0.01; InTEM: 70.5 ± 1.8 (36°C) vs 60.2 ± 1.5, P < 0.001]. Maximum clot firmness was significantly impaired only in InTEM assays [56.9 mm ± 0.9 (36°C) vs 52.7 ± 0.9, P < 0.05]. In contrast, acidosis per se had no significant effects during normothermia. Acidosis amplified the effects of hypothermia, and synergistically impaired clotting times, &agr; angle, and decreased maximum clot firmness, again in both extrinsically and intrinsically activated assays. Formation of a fibrin clot tested after abolition of platelet function by cytochalasin D was not impaired. Clot lysis decreased under hypothermic and/or acidotic conditions, but increased with hyperthermia. CONCLUSIONS:In this in vitro study, hypothermia produced coagulation changes that were worsened by acidosis whereas acidosis without hypothermia has no significant effect on coagulation, as studied by thromboelastometry. This effect was mediated by the inhibition of coagulation factors and platelet function. Thus, thromboelastometry performed at 37°C overestimated integrity of coagulation during hypothermia in particular in combination with acidosis.

Reduction of Fresh Frozen Plasma Requirements by Perioperative Point-of-Care Coagulation Management with Early Calculated Goal-Directed Therapy

Background: Massive bleeding and transfusion of packed red blood cells (PRBC), fresh frozen plasma (FFP) and platelets are associated with increased morbidity, mortality and costs. Patients and Methods: We analysed the transfusion requirements after implementation of point-of-care (POC) coagulation management algorithms based on early, calculated, goal-directed therapy with fibrinogen concentrate and prothrombin complex concentrate (PCC) in different perioperative settings (trauma surgery, visceral and transplant surgery (VTS), cardiovascular surgery (CVS) and general and surgical intensive care medicine) at 3 different hospitals (AUVA Trauma Centre Salzburg, University Hospital Innsbruck and University Hospital Essen) in 2 different countries (Austria and Germany). Results: In all institutions, the implementation of POC coagulation management algorithms was associated with a reduction in the transfusion requirements for FFP by about 90% (Salzburg 94%, Innsbruck 88% and Essen 93%). Furthermore, PRBC transfusion was reduced by 8.4–62%. The incidence of intraoperative massive transfusion (≧10 U PRBC) could be more than halved in VTS and CVS (2.56 vs. 0.88%; p < 0.0001 and 2.50 vs. 1.06%; p = 0.0007, respectively). Platelet transfusion could be reduced by 21–72%, except in CVS where it increased by 115% due to a 5-fold increase in patients with dual antiplatelet therapy (2.7 vs. 13.7%; p < 0.0001). Conclusions: The implementation of perioperative POC coagulation management algorithms based on early, calculated, goaldirected therapy with fibrinogen concentrate and PCC is associated with a reduction in the transfusion requirements for FFP, PRBC and platelets as well as with a reduced incidence of massive transfusion. Thus, the limited blood resources can be used more efficiently.

Argatroban Anticoagulation in Critically Ill Patients

Background: Despite long-term use of argatroban in clinical practice, no dosing recommendations exist for critically ill patients with multiple organ dysfunction (MODS) and suspected or proven heparin-induced thrombocytopenia (HIT). Objective: To determine the suitability of argatroban use in critically ill patients with MODS and HIT. Methods: We conducted prospective observation of 24 consecutive patients with suspected HIT who were being anticoagulated with argatroban (target activated partial thromboplastin time [aPTT] 1.5–2 times normal or 50–60 sec) using 2 μg/kg/min in the first 5 patients and 0.2 μg/kg/min in the subsequent 19 patients. Results: Infusion of argatroban 2 μg/kg/min over 4 hours caused bleeding complications in 3 patients as aPTT increased from 51 ± 18 to 86 ± 34 seconds (p = 0.02), prothrombin time (PT) decreased from 76 ± 27% to 33 ± 12% of normal reference values, and international normalized ratio (INR) increased from 1.4 ± 0.4 to 2.5 ± 0.9 (p = 0.007). Infusion of argatroban 0.2 μg/kg/min over 4 hours provided sufficient anticoagulation without bleeding complications. The aPTT in this population increased from 44 ± 9 to 59 ± 13 seconds (p < 0.001), and PT and INR remained unchanged (76 ± 22% and 69 ± 23% of normal reference values, 1.3 ± 0.3 and after 1.3 ± 0.3, respectively [p = 0.4]). Coagulation variables (aPTT, PT, INR) were significantly different between both dosing regimens after 4 hours of infusion (p = 0.042 and p = 0.003, respectively). The maintenance dose for target aPTT averaged 0.22 ± 0.15 μg/kg/min in both groups. Conclusions: In critically ill patients with MODS, argatroban 2 μg/kg/min, as recommended by the manufacturer, resulted in extensive anticoagulation. A tenfold lower starting dose is sufficient and safe for effective anticoagulation in this specific patient population.

Perioperative Coagulation Management and Control of Platelet Transfusion by Point-of-Care Platelet Function Analysis

About one third of all blood components transfused intraoperatively is used in cardiac surgery, whereas mortality of cardiosurgical patients correlates nearly linear with the number of transfused units of packed red blood cells. Acquired platelet function disorders play a major role in perioperative bleeding in cardiac surgery. Therefore, the use of point-of-care-suitable platelet function analyzers seems to be reasonable in this field. Methods: Platelet function analyzer PFA-100®, rotational thrombelastometry (ROTEM®), and multiple platelet function analyzer (Multiplate®) are in principle applicable for point-of-care testing. Since these three analyzers monitor different aspects of platelet function and have different limitations, the selection of the right test system depends on the right question. Results: Perioperative use of platelet function analyzers is helpful in prediction of blood loss in cardiac surgery. Perioperative usage of blood components and their respective costs can be reduced by an appropriate coagulation management. Conclusion: Algorithms for perioperative coagulation management based on point-of-care testing permit a fast diagnostic and goal-directed therapy of coagulation and functional platelet disorders. The possibility to reduce the mortality of patients and the overall cost for hospital stay is subject of further studies.

Potential value of transfusion protocols in cardiac surgery

Purpose of review On the one hand, cardiac and aortic surgery is associated with a high rate of allogeneic blood transfusion. On the other hand, both bleeding and allogeneic blood transfusion is associated with increased morbidity, mortality, and hospital costs in cardiac and aortic surgery. This article reviews the current literature between 1995 and 2012 dealing with transfusion protocols in cardiovascular surgery. The 16 studies fitting these search criteria have evaluated the impact of the implementation of ROTEM/TEG based coagulation management algorithms on transfusion requirement and outcome in overall 8507 cardiovascular surgical patients. Recent findings The use of point-of-care (POC) transfusion and coagulation management algorithms based on viscoelastic tests such as thromboelastometry (ROTEM) and thrombelastography (TEG) in combination with POC platelet function tests such as whole blood impedance aggregometry (Multiplate) have been shown to be associated with reduced allogeneic blood transfusion requirements, reduced incidence of thrombotic/thromboembolic and transfusion-related adverse events, and improved outcomes in cardiac surgery. Summary Implementation of POC algorithms including a comprehensive bundle of POC diagnostics (thromboelastometry and whole blood impedance aggregometry) in combination with first-line therapy using immediately available specific coagulation factor concentrates (fibrinogen and prothrombin complex concentrate) and defining strict indications, calculated dosages, and clear sequences for each haemostatic intervention seems to be complex but most effective in reducing perioperative transfusion requirements and has been shown to be associated with a decreased incidence of thrombotic/thromboembolic events, transfusion-related adverse events, as well as with improved patients’ outcomes including 6-month mortality.

Tranexamic acid partially improves platelet function in patients treated with dual antiplatelet therapy.

Background Although the impact of tranexamic acid on platelet function remains controversial, tranexamic acid is part of clinical algorithms for the management of platelet dysfunction. The goal of our prospective, observational study was to examine the effects of tranexamic acid on platelet function in patients treated with dual antiplatelet therapy compared to those who ceased antiplatelet therapy for at least 7 days. Methods Forty patients scheduled for cardiac surgery were enrolled in this study. Group 1 consisted of 20 patients who ceased antiplatelet therapy with aspirin and clopidogrel at least 7 days before surgery. Group 2 consisted of 20 patients who were treated with aspirin and clopidogrel until the day before surgery. Using the Multiplate device (Dynabyte, Munich, Germany), multiple electrode aggregometry (MEA) was performed following platelet stimulation with thrombin receptor activating peptide-6 (TRAP-6), arachidonic acid or ADP on blood collected 20 min before and after application of 2 g tranexamic acid. Results Compared with group 1, platelet aggregation was statistically significantly reduced in ASPItest and ADPtest in group 2, whereas there were no significant differences in the TRAPtest. In group 1, platelet aggregation did not differ significantly before and after tranexamic acid treatment. In contrast, in group 2, we observed a significant increase in arachidonic acid-induced [295 (280/470) arbitrary aggregation units × min [AU*min; median (25th/75th percentile) vs. 214 (83/409) AU*min, P = 0.01] and ADP-induced platelet aggregation [560 AU*min (400/760 AU*min) vs. 470 AU*min (282/550 AU*min), P = 0.013], whereas platelet aggregation following stimulation with TRAP-6 did not change significantly [980 (877/1009) AU*min, median (25th/75th percentile) after tranexamic acid vs. 867 (835/961) AU*min before tranexamic acid, P = 0.464]. Conclusion The results of this study indicate that tranexamic acid potentially corrects defects in arachidonic acid-induced and ADP-induced platelet aggregation imposed by dual antiplatelet therapy. However, platelet aggregation in response to arachidonic acid or ADP in the blood of patients who have not received aspirin and clopidogrel is unaffected by tranexamic acid. These results support the use of tranexamic acid to partially reverse platelet aggregation dysfunction due to antiplatelet therapy.

Blood-transfusion requirements and blood salvage in donors undergoing right hepatectomy for living related liver transplantation.

Living related liver donation for liver transplantation in adults including its risks is receiving increased attention. We present data from 44 liver donors focusing on transfusion requirements and avoidance of heterologous transfusion. The volume of blood transfused (both autologous from preoperative donation and heterologous) was assessed including that derived from intraoperative isovolemic hemodilution, cell-saver salvaged, and retransfused blood. Hemoglobin concentration and central venous pressure were measured at specified time points before and during surgery. Intraoperative blood loss was calculated and correlated to the duration of parenchymal transsection, liver volume resected, and central venous pressure. There were no specific anesthesia-evoked complications. In 4 donors, major bleeding (>2000 mL) occurred. Blood loss averaged 902 ± 564 mL (sd), yielding a minimal mean hemoglobin concentration of 8.1 ± 1.2 g/dL. One donor received 3 U of heterologous blood and 30 donors received autologous blood from their preoperative donation. An average of 592 ± 112 mL of blood derived from perioperative acute isovolemic hemodilution was retransfused as was 421 ± 333 mL of washed red cells from the cell-saving system. Avoidance of heterologous blood transfusion, application of blood-saving techniques, and efficient pain management are crucial for adult living liver donors. Transfusion of banked blood can be avoided in most patients when intraoperative cell salvage, preoperative autologous blood donation, and intraoperative hemodilution are combined.