Ulf Schött

Tranexamic acid reduces blood loss in total hip replacement surgery.

Intraoperatively administered, tranexamic acid (TA) does not reduce bleeding in total hip replacement (THR). Therefore, its prophylactic use was attempted in the present study because this has been shown to be more effective in cardiac surgery. We investigated 40 patients undergoing THR in a prospective, randomized, double-blinded study. Twenty patients received TA given in two bolus doses of 10 mg/kg each, the first just before surgical incision and the second 3 h later. In addition, a continuous infusion of TA, 1.0 mg · kg−1 · h−1 for 10 h, was given after the first bolus dose. The remaining 20 patients formed a control group. Both groups used preoperative autologous blood donation and intraoperative autotransfusion. Intraoperative bleeding was significantly less (P = 0.001) in the TA group compared with the control group (630 ± 220 mL vs 850 ± 260 mL). Postoperative drainage bleeding was correspondingly less (P = 0.001) (520 ± 280 vs 920 ± 410 mL). Up to 10 h postoperatively, plasma D-dimer concentration was halved in the TA group compared with the control group. One patient in each group had an ultrasound-verified late deep vein thrombosis. In conclusion, we found TA, administrated before surgical incision, to be efficient in reducing bleeding during THR. Implications In a prospective, double-blinded study of 40 patients undergoing total hip replacement, the preoperative administration of tranexamic acid reduced bleeding by 35%, probably by decreasing induced fibrinolysis. Whether tranexamic acid therapy can replace predonation of autologous blood or intraoperative autotransfusion requires further study.

Desmopressin acetate does not reduce blood loss during total hip replacement in patients receiving dextran

The blood loss‐reducing effect of desmopressin during dextran therapy was studied in a double‐blind fashion in 79 elderly but otherwise healthy patients with preoperative normal bleeding time undergoing total hip replacement for primary coxarthrosis. An infusion of desmopressin (0.3 μg/kg body weight) or placebo was randomly administered immediately after administration of spinal anaesthesia and six hours later. Haemostasis was evaluated on the basis of vWF: ristocetin cofactor activity, FVIII: C activity, human tissue plasminogen activator (tPA), plasminogen activator inhibitor type (PAI), ß‐thromboglobuline (ßTG) and a clot impedance test (Sonoclot). There were no statistically significant differences (P>0.05) in mean blood loss or transfusion requirements between the placebo and the desmopressin group. There was a significantly increase (P<0.01) both in vWF: ristocetin cofactor and in FVIII: C activity after both infusions of desmopressin compared with placebo. There was no significant difference in ßTG, tPA, PAI or Sonoclot analysis between the groups. In conclusion, desmopressin did not reduce blood loss in patients undergoing total hip replacement.

The endothelial glycocalyx and its disruption, protection and regeneration: a narrative review

The glycocalyx is a carbohydrate-rich layer that lines the luminal side of the vascular endothelium. Its soluble components exist in a dynamic equilibrium with the bloodstream and play an important role in maintaining endothelial layer integrity. However, the glycocalyx can be easily damaged and is extremely vulnerable to insults from a variety of sources, including inflammation, trauma, haemorrhagic shock, hypovolemia and ischaemia-reperfusion. Damage to the glycocalyx commonly precedes further damage to the vascular endothelium. Preclinical research has identified a number of different factors capable of protecting or regenerating the glycocalyx. Initial investigations suggest that plasma may convey protective and regenerative effects. However, it remains unclear which exact components or properties of plasma are responsible for this protective effect. Studies have reported protective effects for several plasma proteins individually, including antithrombin, orosomucoid and albumin; the latter of which may be of particular interest, due to the high levels of albumin present in plasma. A further possibility is that plasma is simply a better intravascular volume expander than other resuscitation fluids. It has also been proposed that the protective effects are mediated indirectly via plasma resuscitation-induced changes in gene expression. Further work is needed to determine the importance of specific plasma proteins or other factors for glycocalyx protection, particularly in a clinical setting.

Monitoring of dabigatran anticoagulation and its reversal in vitro by thrombelastography.

BACKGROUND Dabigatran etexilate, a pro-drug of a direct thrombin inhibitor, was approved a few years ago for non-valvular atrial fibrillation and deep venous thrombosis. Rapid monitoring of the dabigatran level is essential in trauma and bleeding patients but the traditional plasma-based assays may not sufficiently display the effect. Furthermore, no antidote exists and reversal of the anticoagulant effect is impossible or difficult. The present study investigated the in vitro effect of dabigatran on whole blood thromboelastography (TEG) and its reversal by recombinant activated factor VII and prothrombin complex concentrate. METHODS Blood was collected from 10 healthy donors and spiked in vitro with therapeutic doses of dabigatran to a plasma concentration of 200 ng/ml, followed by therapeutic doses of recombinant activated factor VII (corresponding to 100 μg/kg) and prothrombin complex concentrate (corresponding to 50 IE/kg) and evaluated by TEG. RESULTS Compared to baseline, dabigatran changed all TEG parameters in a hypocoagulable direction corresponding to increased R time and time to maximum rate of thrombus generation, reduced angle, A5, A10, maximum amplitude and maximum rate of thrombin formation. Recombinant activated factor VII had a procoagulant effect on the majority of the investigated TEG parameters when added to dabigatran spiked samples. Prothrombin complex concentrate appeared not to have a procoagulant effect on TEG even when the heparin content in the formulation was neutralized by heparinase. CONCLUSIONS TEG displays the presence of dabigatran in whole blood in vitro and the anticoagulant effect of dabigatran is partly reversed by spiking with recombinant activated factor VII.

Monitoring Low Molecular Weight Heparins at Therapeutic Levels: Dose-Responses of, and Correlations and Differences between aPTT, Anti-Factor Xa and Thrombin Generation Assays

Background Low molecular weight heparins (LMWH’s) are used to prevent and treat thrombosis. Tests for monitoring LMWH’s include anti-factor Xa (anti-FXa), activated partial thromboplastin time (aPTT) and thrombin generation. Anti-FXa is the current gold standard despite LMWH’s varying affinities for FXa and thrombin. Aim To examine the effects of two different LMWH’s on the results of 4 different aPTT-tests, anti-FXa activity and thrombin generation and to assess the tests’ concordance. Method Enoxaparin and tinzaparin were added ex-vivo in concentrations of 0.0, 0.5, 1.0 and 1.5 anti-FXa international units (IU)/mL, to blood from 10 volunteers. aPTT was measured using two whole blood methods (Free oscillation rheometry (FOR) and Hemochron Jr (HCJ)) and an optical plasma method using two different reagents (ActinFSL and PTT-Automat). Anti-FXa activity was quantified using a chromogenic assay. Thrombin generation (Endogenous Thrombin Potential, ETP) was measured on a Ceveron Alpha instrument using the TGA RB and more tissue-factor rich TGA RC reagents. Results Methods’ mean aPTT at 1.0 IU/mL LMWH varied between 54s (SD 11) and 69s (SD 14) for enoxaparin and between 101s (SD 21) and 140s (SD 28) for tinzaparin. ActinFSL gave significantly shorter aPTT results. aPTT and anti-FXa generally correlated well. ETP as measured with the TGA RC reagent but not the TGA RB reagent showed an inverse exponential relationship to the concentration of LMWH. The HCJ-aPTT results had the weakest correlation to anti-FXa and thrombin generation (Rs0.62–0.87), whereas the other aPTT methods had similar correlation coefficients (Rs0.80–0.92). Conclusions aPTT displays a linear dose-respone to LMWH. There is variation between aPTT assays. Tinzaparin increases aPTT and decreases thrombin generation more than enoxaparin at any given level of anti-FXa activity, casting doubt on anti-FXa’s present gold standard status. Thrombin generation with tissue factor-rich activator is a promising method for monitoring LMWH’s.

Increased Lactate Levels Impair the Coagulation System-A Potential Contributing Factor to Progressive Hemorrhage After Traumatic Brain Injury.

Progressive intracerebral contusions are a major problem in the management of patients with severe traumatic brain injury that is also linked to worse outcome. Microdialysis studies have revealed that lactate levels are very high inside contusions, corresponding to significant acidosis. The current study was performed in an effort to investigate whether the lactate accumulation inside cerebral contusions may be a contributing factor to the prolonged bleeding inside contusions. We have investigated the effects of lactic acidosis on the coagulation system with rotational thromboelastometry. It was a laboratory study involving 6 healthy volunteers. Blood was drawn and the pH was adjusted by addition of lactic acid in vitro. The pH levels studied were 7.4, 7.2, 7.0, and 6.8. The pH was also readjusted to 7.4 by addition the buffer THAM to blood initially adjusted to a pH of 6.8 to study the reversibility of potential adverse effects induced by the lactic acidosis. We found the coagulation to be significantly impaired by lactic acidosis (P=0.000l). The impairment found was reversible after correction of the acidosis by a buffer. In conclusion, we found that lactic acidosis impaired the coagulation system. The impairment caused by lactic acidosis may be one factor causing the progressive hemorrhage in posttraumatic cerebral contusions, known to have high levels of lactate and correspondingly low pH. It may also be important to consider in bleeding trauma patients.

An evaluation of monitoring possibilities of argatroban using rotational thromboelastometry and activated partial thromboplastin time

Background: Rotational thrombelastometry/thrombelastography with ROTEM® and TEG® is becoming available bedside in an increasing number of intensive care units, where many patients with heparin‐induced thrombocytopenia (HIT) are treated. The study has been performed in an effort to find out whether ROTEM® could be an alternative to activated partial thromboplastin time (aPTT) when argatroban is used for anticoagulation.

The Effect and Duration of Prophylactic Platelet Transfusions Before Insertion of a Central Venous Catheter in Patients with Bone Marrow Failure Evaluated with Point-of-Care Methods and Flow Cytometry

BACKGROUND:Patients with bone marrow failure and severe thrombocytopenia are frequently given prophylactic platelet transfusion before interventions. The clinical effects of such transfusions, however, are poorly defined. We performed a prospective observational study on patients with bone marrow failure scheduled for prophylactic platelet transfusion before the insertion of a central venous catheter. The objectives were to evaluate the effect and duration of prophylactic platelet transfusions on central venous catheter insertion in thrombocytopenic patients with bone marrow failure. METHODS:Thirty-nine adult patients with bone marrow failure and platelet counts below 50 × 109/L were consecutively enrolled before prophylactic platelet transfusion for subclavian central venous catheter insertion. Blood samples were drawn from the patients before platelet transfusion, 1 hour, and 4 hours after completion of the transfusion. The coagulation profile was assessed by conventional hematological tests, thromboelastometry (ROTEM®) assays (EXTEM® and FIBTEM®), multiple electrode aggregometry (Multiplate®) assays including adenosine diphosphate, collagen, and thrombin receptor agonist peptide, and by flow cytometry for the platelet expression of P-selectin (CD62P) and activated glycoprotein IIb–IIIa (PAC-1). Bleeding complications were classified with a 5-grade scale, according to the Common Terminology Criteria for Adverse Events. RESULTS:Seventeen women and 22 men were included in the study. Platelet count was increased from 24 × 109/L (18–32) before to 42 × 109/L (31–50) 1 hour after transfusion (P < 0.0001) and was not significantly different 4 hours after transfusion (40 × 109/L (29–50), P = 0.047). Maximal clot firmness EXTEM was increased from 38 mm (32–45) before to 46 mm (41–52) 1 hour after transfusion (P < 0.0001) and did not change 4 hours after transfusion. Clotting time EXTEM was decreased from 58.5 seconds (50–78) beforehand to 53 seconds (45–61) 1 hour after transfusion (P = 0.0006) and was not significantly different 4 hours after transfusion (57 seconds (52–70, P = 0.025). FIBTEM results were all unchanged after transfusion. All Multiplate analyses were significantly increased after 1 hour and were not diminished 4 hours after transfusion. Four grade 1 bleeding episodes occurred, but no grade 2 to 5 bleeding could be detected. Flow cytometry analyses showed mixed results with no overall trend. CONCLUSIONS:Prophylactic platelet transfusions in thrombocytopenic patients with bone marrow failure improve hemostatic parameters on ROTEM and Multiplate by increasing the number of platelets, and not through enhancement of platelet function. Improved clotting parameters on ROTEM and platelet aggregation on Multiplate appear to persist between 1 and 4 hours after transfusion.

Free oscillation rheometry monitoring of haemodilution and hypothermia and correction with fibrinogen and factor XIII concentrates.

BackgroundHaemodilution and hypothermia induce coagulopathy separately, but their combined effect on coagulation has not been widely studied. Fibrinogen concentrate can correct dilutional coagulopathy and has an additional effect when combined with factor XIII concentrate. However, their effect on dilutional coagulopathy concomitant with hypothermia has not been studied previously. Free oscillation rheometry – FOR (Reorox®) – is a novel viscoelastic haemostatic assay that has not been studied in this context before.MethodsBlood from 10 healthy volunteers was diluted by 33% with hydroxyethyl starch or Ringer’s acetate solutions. Effects of fibrinogen added in vitro with and without factor XIII were studied at 33°C and 37°C. Coagulation velocity (coagulation time) and clot strength (elasticity) were assessed with FOR. Coagulation was initiated in vitro with thromboplastin alone, or thromboplastin plus a platelet inhibitor.ResultsHydroxyethyl starch increased the coagulation time and decreased clot strength significantly more than Ringer’s acetate solution, both in the presence and absence of a platelet inhibitor. There was a significant interaction between haemodilution with hydroxyethyl starch and hypothermia, resulting in increased coagulation time. After addition of fibrinogen, coagulation time shortened and elasticity increased, with the exception of fibrinogen-dependent clot strength (i.e., elasticity in the presence of a platelet inhibitor) after hydroxyethyl starch haemodilution. Factor XIII had an additional effect with fibrinogen on fibrinogen-dependent clot strength in blood diluted with Ringer’s acetate solution. Hypothermia did not influence any of the coagulation factor effects.ConclusionsBoth haemodilution and mild hypothermia impaired coagulation. Coagulopathy was more pronounced after haemodilution with hydroxyethyl starch than with Ringer’s acetate. Addition of fibrinogen with factor XIII was unable to reverse hydroxyethyl starch induced clot instability, but improved coagulation in blood diluted with Ringer’s acetate solution. Fibrinogen improved coagulation irrespective of hypothermia.

Bleeding complications after central line insertions: relevance of pre‐procedure coagulation tests and institutional transfusion policy

The aim of this study was to map pre‐procedural variables for insertion of a central venous catheter, prophylactic blood component use and to investigate whether any independent variable could be identified as an independent risk factor for associated bleeding complications in patients outside the intensive care unit.