Chronic deep vein thrombosis.

Deep vein thrombosis (DVT) is an important cause of short-term mortality and long-term morbidity. Although acute DVT is often well managed, there is uncertainty in the management of chronic DVT which is increasingly being noted among patients presenting with similar symptoms to their initial DVT. The presence of a residual venous clot can be a problem for both physicians and patients fearing the risk of emboli to the same extent as the acute DVT. There are also issues in the accurate diagnosis and appropriate management of chronic DVT, which is the focus of the second part of this review.

Iliofemoral deep vein thrombosis and the problem of post-thrombotic syndrome.

Deep vein thrombosis (DVT) is an important cause of short-term mortality and long-term morbidity. Among the different presentations of DVT, thrombus in the iliofemoral veins may be considered the severest form. Although anticoagulation is the mainstay of the management of iliofemoral thrombosis, despite adequate anticoagulant treatment, complications including post-thrombotic syndrome is not uncommon. The latter is often overlooked but can cause considerable morbidity to the affected individuals. Preventing this condition remains a challenge but recent clinical trials of catheter directed thrombolysis and elasticated compression stockings provide some advance in this context. In this article, with the aid of a clinical case, we review the particular considerations to take into account when managing patients with an iliofemoral DVT.

Evaluation of the use of rotational thromboelastometry in the assessment of FXI deficency.

INTRODUCTION: The absence of a reliable clinical test to predict bleeding tendency leaves factor XI (FXI)-deficient individuals at risk of overtreatment or under treatment. AIM: To assess whether rotational thromboelastometry has value in detection of FXI deficiency and identification of bleeding tendency. METHODS: Thromboelastometry was measured in whole blood and platelet-rich plasma (PRP) samples containing corn trypsin inhibitor (CTI) from controls (n = 50) and FXI-deficient individuals (n = 93) at tissue factor (TF) 0.12 pm. The effect of tissue plasminogen activator was also assessed. For analysis, FXI-deficient individuals were divided into bleeders (n = 24) and non-bleeders (n = 44) based on experience of tonsillectomy and/or dental extraction prior to diagnosis. RESULTS: In whole blood, thromboelastometry distinguished those with major FXI deficiency (FXI:C ≤ 15 IU dL-1 ) but not partial deficiency from control populations, but did not identify bleeding phenotype. In PRP, bleeders had significantly longer clot formation time [CFT; 434 ± 179 s vs. 277 ± 70 s (mean ± SD); P < 0.05] and smaller α angle [43.8 ± 9.5° vs. 52.4 ± 5.8° (mean ± SD); P < 0.05] compared to non-bleeders. However, these parameters were found to depend on multiple additional variables and on an individual basis, ROC analysis showed test specificity for bleeding phenotype identification to be only 38.5% at 100% sensitivity: CFT (area under first derivative curve: AUC = 0.8091, P = 0.0014), α angle (AUC = 0.7804, P = 0.006). CONCLUSION: Thromboelastometry in PRP with CTI samples triggered with TF 0.12 pm was able to distinguish between bleeders and non-bleeders in FXI deficiency, but poor specificity restricts its clinical application as a test to identify bleeding phenotype. Further technical advances to the assay may allow better discrimination.

Evaluation of the use of global haemostasis assays to monitor treatment in factor XI deficiency.

INTRODUCTION: Previous guidelines recommend that FXI:C levels should be used to monitor FXI replacement in factor XI (FXI) deficiency. However, FXI:C levels do not correlate with bleeding tendency in this disorder and may not be the optimal test by which to monitor and determine further treatment in the postoperative period. AIM: To assess whether the thrombin generation assay (TGA) and rotational thromboelastometry can be used to monitor FXI replacement peri-operatively in FXI deficiency and to determine if changes in FXI:C levels correlate with changes in thrombin generation and clot formation parameters following treatment with solvent-detergent fresh frozen plasma (SD-FFP). METHODS: The TGA and rotational thromboelastometry were used to measure thrombin generation and clot formation in 11 adults with FXI deficiency who were treated with either SD-FFP (n = 8) or FXI concentrate (n = 3) as prophylaxis peri-operatively. Blood samples were taken pre- and 30 min post-treatment. RESULTS: Global haemostasis assays can be used to measure the effect of FXI replacement with SD-FFP or FXI concentrate in FXI deficiency. Both treatment types improved thrombin generation and clot formation. However, the remaining response to treatment at 24 h post SD-FFP was variable and changes in FXI:C levels were not predictive of changes in thrombin generation/thromboelastometry parameters after treatment with SD-FFP. CONCLUSION: Global haemostasis assays may provide a more reliable means of monitoring SD-FFP treatment with the potential to prevent individuals receiving unnecessary treatment, however, their clinical use in decision making needs to be tested in a larger prospective study.

In vitro comparison of the effect of two factor XI (FXI) concentrates on thrombin generation in major FXI deficiency.

INTRODUCTION: Bleeding risk in factor XI (FXI) deficiency following surgery may be reduced by treatment with either of two FXI concentrates, but indications for their use are unclear and treatment has been associated with thrombosis. AIM: To quantify and compare the effects of two different FXI concentrates on thrombin generation (TG) in major FXI deficiency (FXI:C < 15 IU dL(-1) ). METHODS: Thrombin generation was measured in controls (n = 50), FXI-deficient individuals pre and post in vitro spiking with FXI concentrates (n = 10), and in ex vivo samples following treatment with FXI concentrate (n = 3). RESULTS: Thrombin generation was significantly impaired in FXI deficiency but improved following FXI replacement in vitro and in vivo. LFB Hemoleven(®) had greater effect on TG than BPL FXI concentrate in vitro (equivalent in vivo doses 10, 20 and 30 U kg(-1) ): higher endogenous thrombin potential (ETP) (P < 0.0001), peak height (P < 0.01) velocity (P < 0.0002) and shorter lag time and time to peak (both P < 0.003). Some measurements with LFB Hemoleven(®) exceeded the reference range. At lower dose (5 U kg(-1) ), BPL FXI concentrate normalized all TG parameters and LFB Hemoleven(®) normalized the ETP but exceeded the reference range with other parameters. CONCLUSION: Both FXI concentrates improve TG in vitro in major FXI deficiency but differ in dose response, and for both products, doses lower than previously recommended normalized TG in vitro. Comparison of in vitro spiked and ex vivo samples suggest that in vitro results could be used to estimate an expected in vivo response to FXI replacement.

Perioperative management of patients on new oral anticoagulants.

BACKGROUND: New oral anticoagulants (NOACs) offer an alternative to warfarin for preventing stroke in patients with atrial fibrillation. NOACs are expected to replace warfarin and other vitamin K antagonists for most of their indications in the future. Knowledge of the use of NOACs in the perioperative period is important for optimal care. METHODS: Studies that reported on the use of NOACs were identified, focusing on evidence-based guidance relating to the perioperative period. PubMed was searched for relevant articles published between January 2000 and January 2014. RESULTS: The anticipated expanded clinical use of NOACs such as rivaroxaban (Xarelto™), apixaban (Eliquis™) and dabigatran (Pradaxa™) has the potential to simplify perioperative anticoagulant management because of fewer drug-drug interactions, rapid onset of action, predictable pharmacokinetics and relatively short half-lives. However, coagulation status cannot be monitored by international normalized ratio and no antidotes are currently available. In elective surgery, it is important to discontinue the use of NOACs, with special consideration of renal function as route of elimination. Guidelines for the management of bleeding complications in patients on NOACs are provided, and may be considered for trauma and emergency surgery. Haemodialysis could be considered for bleeding with use of dabigatran. Better options for reversal of the effects of NOACs when bleeding occurs may follow with novel drugs. CONCLUSION: Management of NOACs in elective and emergency conditions requires knowledge of time of last intake of drug, current renal function and the planned procedure in order to assess the overall risk of bleeding. Currently no antidote exists to reverse the effects of these drugs.

Emergency and out of hours care of patients with inherited bleeding disorders.

Recently, the United Kingdom Haemophilia Centre Doctors Organisation published recommendations for the standard of care for assessment and treatment of patients with bleeding disorders in the emergency department (A&E). An audit was undertaken to compare the level of care to the acceptable standards in a tertiary hospital A&E, attached to a haemophilia comprehensive care centre. A&E attendances were found by cross referencing all patients with known bleeding disorders against the EDMS attendance system. Visits from the past 3 years were identified to produce sufficient data and electronic notes from these visits were then accessed, and marked against the proforma. Data were available from 45 of a total of 54 patients, who had a total of 75 emergency visits documented. In all aspects of care, the standards were not adequately met including the average length of time between booking and clinical assessment, early initiation of specific haemostatic treatment, seeking haematology advice and arrangement of follow-up. Also no specialist clotting investigations were done with only 9/11 patients admitted having their haematological diagnosis recorded. In addition, only very few patients had the severity of bleeding disorder noted and less than half their first line treatment documented. There were significant differences in the standard of care for haemophilia patients provided by the A&E department when compared with acceptable standards. Measures have been put in place and policies have been drafted to improve this situation and provide the best possible care to persons with haemophilia.

Biomarkers for the prediction of venous thromboembolism in critically ill COVID-19 patients.

BACKGROUND: Venous thromboembolism (VTE) is a frequent complication in critically ill patients with coronavirus disease 2019 (COVID-19) and is associated with mortality. Early diagnosis and treatment of VTE is warranted. OBJECTIVE: To develop a prediction model for VTE in critically ill COVID-19 patients. PATIENTS AND METHODS: In this retrospective cohort study, 127 adult patients with confirmed COVID-19 infection admitted to the intensive care unit of two teaching hospitals were included. VTE was diagnosed with either ultrasound or computed tomography scan. Univariate receiver operating characteristic (ROC) curves were constructed for Positive End Expiratory Pressure, PaO2/FiO2 ratio, platelet count, international normalized ratio, activated partial thromboplastin time as well as levels of fibrinogen, antithrombin, D-dimer and C-reactive protein (CRP). Multivariate analysis was done using binary linear regression. RESULTS: Variables associated with VTE in both univariate and multivariate analysis were D-dimer and CRP with an area under the curve (AUC) of 0.64, P = 0.023 and 0.75, P = 0.045, respectively. Variables indicating hypoxemia were not predictive. The ROC curve of D-dimer and CRP combined had an AUC of 0.83, P < 0.05. Categorized values of D-dimer and CRP were used to compute a mean absolute risk for the combination of these variables with a high positive predictive value. The predicted probability of VTE with a D-dimer > 15 in combination with a CRP > 280 was 98%. The negative predictive value of D-dimer was low. CONCLUSION: Elevated CRP and D-dimer have a high positive predictive value for VTE in critically ill COVID-19 patients. We developed a prediction table with these biomarkers that can aid clinicians in the timing of imaging in patients with suspected VTE.

Guidelines for the diagnosis and management of disseminated intravascular coagulation. British Committee for Standards in Haematology.

The diagnosis of disseminated intravascular coagulation (DIC) should encompass both clinical and laboratory information. The International Society for Thrombosis and Haemostasis (ISTH) DIC scoring system provides objective measurement of DIC. Where DIC is present the scoring system correlates with key clinical observations and outcomes. It is important to repeat the tests to monitor the dynamically changing scenario based on laboratory results and clinical observations. The cornerstone of the treatment of DIC is treatment of the underlying condition. Transfusion of platelets or plasma (components) in patients with DIC should not primarily be based on laboratory results and should in general be reserved for patients who present with bleeding. In patients with DIC and bleeding or at high risk of bleeding (e.g. postoperative patients or patients due to undergo an invasive procedure) and a platelet count of <50 x 10(9)/l transfusion of platelets should be considered. In non-bleeding patients with DIC, prophylactic platelet transfusion is not given unless it is perceived that there is a high risk of bleeding. In bleeding patients with DIC and prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT), administration of fresh frozen plasma (FFP) may be useful. It should not be instituted based on laboratory tests alone but should be considered in those with active bleeding and in those requiring an invasive procedure. There is no evidence that infusion of plasma stimulates the ongoing activation of coagulation. If transfusion of FFP is not possible in patients with bleeding because of fluid overload, consider using factor concentrates such as prothrombin complex concentrate, recognising that these will only partially correct the defect because they contain only selected factors, whereas in DIC there is a global deficiency of coagulation factors. Severe hypofibrinogenaemia (<1 g/l) that persists despite FFP replacement may be treated with fibrinogen concentrate or cryoprecipitate. In cases of DIC where thrombosis predominates, such as arterial or venous thromboembolism, severe purpura fulminans associated with acral ischemia or vascular skin infarction, therapeutic doses of heparin should be considered. In these patients where there is perceived to be a co-existing high risk of bleeding there may be benefits in using continuous infusion unfractionated heparin (UFH) due to its short half-life and reversibility. Weight adjusted doses (e.g. 10 mu/kg/h) may be used without the intention of prolonging the APTT ratio to 1.5-2.5 times the control. Monitoring the APTT in these cases may be complicated and clinical observation for signs of bleeding is important. In critically ill, non-bleeding patients with DIC, prophylaxis for venous thromboembolism with prophylactic doses of heparin or low molecular weight heparin is recommended. Consider treating patients with severe sepsis and DIC with recombinant human activated protein C (continuous infusion, 24 microg/kg/h for 4 d). Patients at high risk of bleeding should not be given recombinant human activated protein C. Current manufacturers guidance advises against using this product in patients with platelet counts of <30 x 10(9)/l. In the event of invasive procedures, administration of recombinant human activated protein C should be discontinued shortly before the intervention (elimination half-life approximately 20 min) and may be resumed a few hours later, dependent on the clinical situation. In the absence of further prospective evidence from randomised controlled trials confirming a beneficial effect of antithrombin concentrate on clinically relevant endpoints in patients with DIC and not receiving heparin, administration of antithrombin cannot be recommended. In general, patients with DIC should not be treated with antifibrinolytic agents. Patients with DIC that is characterised by a primary hyperfibrinolytic state and who present with severe bleeding could be treated with lysine analogues, such as tranexamic acid (e.g. 1 g every 8 h).

Management of surgical patients receiving anticoagulation and antiplatelet agents.

BACKGROUND: Temporary interruption of long-term anticoagulation and antiplatelet therapy during surgical procedures exposes patients to thrombotic risk. Continuation of these agents, however, is associated with an increased risk of bleeding. Managing anticoagulation can be a particular challenge in the emergency setting. METHODS: A literature review of published articles sourced using the keywords heparin, warfarin, perioperative, antiplatelet, aspirin and surgery was undertaken. A management plan for all likely situations was developed. RESULTS AND CONCLUSION: Based on an individual assessment of risk factors for arterial or venous thromboembolism and the risk of perioperative bleeding, it is possible to form an anticoagulant and antiplatelet management plan likely to achieve a low incidence of bleeding and thrombosis. A multidisciplinary approach is desirable.

Nitric oxide and the clinical manifestations of acute porphyria.

The porphyrias comprise a clinically and genetically heterogenous group of diseases mostly arising from a genetically determined dysfunction of specific enzymes along the pathway of haeme biosynthesis. This leads to a pathological accumulation and measurable excretion of porphyrins and/or porphyrin precursors, which is considered the cause of the clinical features related to this group of diseases. However, acute porphyria can present with varied symptoms, which have some features in common with other diseases where nitric oxide has been shown to play a role. The article describes the possibility of nitric oxide depletion in porphyria contributing to its clinical manifestations.

Relevance of clotting tests in liver disease.

Liver disease is associated with impairment of the haemostatic function due to the abnormal and decreased synthesis of the clotting factors. It is thus only logical to have considered assessment of the clotting profile (to include prothrombin time (PT) and activated partial thromboplastin time (aPTT)) to be an integral part of the comprehensive assessment of a patient who presents with liver impairment. Laboratory abnormalities of coagulation are considered to be a predictive risk factor for bleeding, but patients with liver disease do not have bleeding pattern as those who have coagulation factor deficiencies. Recent experiments have cast doubts over the use of PT and aPTT as a marker of bleeding in liver disease and the use of such tests to decide the need for plasma replacement before interventions like liver biopsy. This article reviews the relevance of the clotting profile in liver disease, the other factors involved in the haemostatic failure associated with it, and the technical problems in the interpretation of these results. Most importantly, it stresses the need for more trials to help us guide the management of bleeding in patients with liver impairment.