Elizabeth M. Van Cott

Guidance on the emergent reversal of oral thrombin and factor Xa inhibitors

The new oral anticoagulants dabigatran, rivaroxaban and apixaban have advantages over warfarin which include no need for laboratory monitoring, less drug–drug interactions and less food‐drug interactions. However, there is no established antidote for patients who are bleeding or require emergent surgery and there is a paucity of evidence to guide the clinical care during these situations. Members of thrombosis and anticoagulation groups participating in the Thrombosis and Hemostasis Summit of North America formulated expert opinion guidance for reversing the anticoagulant effect of the new oral anticoagulants and suggest: routine supportive care, activated charcoal if drug ingestion was within a couple of hours, and hemodialysis if feasible for dabigatran. Also, the pros and cons of the possible use of four factor prothrombin complex concentrate are discussed. Am. J. Hematol. 2012.

Effect of Marathon Running on Hematologic and Biochemical Laboratory Parameters, Including Cardiac Markers

Participants in marathon races may require medical attention and the performance of laboratory assays. We report the changes in basic biochemical parameters, cardiac markers, CBC counts, and WBC differentials observed in participants in a marathon before, within 4 hours, and 24 hours after a race. The concentrations of glucose, total protein, albumin, uric acid, calcium, phosphorus, serum urea nitrogen, creatinine, bilirubin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, total creatine kinase, creatine kinase-MB, myoglobin, and the anion gap were increased after the race, consistent with the effects of exertional rhabdomyolysis and hemolysis. The increase in WBC counts was due mainly to neutrophilia and monocytosis, with a relative decrease in circulating lymphocytes, consistent with an inflammatory reaction to tissue injury. A significant percentage of laboratory results were outside the standard reference ranges, indicating that modified reference ranges derivedfrom marathon runners might be more appropriatefor this population. We provide a table of modified reference ranges (or expected ranges) for basic biochemical, cardiac, and hematologic laboratory parameters for marathon runners.

Effect of Marathon Running on Inflammatory and Hemostatic Markers

A lthough increasing levels of regular physical activity are incrementally cardioprotective, prolonged strenuous exercise such as marathon running may trigger acute myocardial infarction and sudden cardiac death. The mechanism of such events is not well understood but may be due to hemodynamic, vasoconstrictive, and prothrombotic effects with disruption of unstable coronary plaques leading to acute coronary thrombosis. Although several studies have demonstrated exercise-induced activation of fibrinolysis and coagulation, the effect of marathon running on hemostatic balance has not been well studied. We therefore measured changes in C-reactive protein (CRP), von Willebrand factor (vWF), D-dimer, fibrinogen, fibrinolytic activity, white blood cell (WBC) counts, and platelet activation in middle-aged runners before and after the Boston Marathon. An imbalance in prothrombotic and fibrinolytic factors after strenuous physical exertion may transiently increase the risk for intravascular—including coronary—thrombosis and trigger acute ischemic events. • • • Subjects were attendees at the prerace Scientific Symposia of the American Medical Athletic Association as entrants in the 100th to 105th Boston Athletic Association Marathons from 1966 to 2001 (mean age 47.6 years), who reported no smoking or known coronary heart disease by yearly questionnaire. Blood samples were drawn without stasis from an antecubital vein using a 21-gauge butterfly needle the morning before, within 4 hours after the race, and the next morning. Samples were drawn at the same time points for platelet studies in the year 2000 from subjects reporting no use of anti-inflammatory drugs in the prior 2 weeks and for complete blood counts in the year 2001. Whole blood was collected in 3.2% sodium citrate (9:1, vol/vol), and centrifuged at 2,500 g for 20 minutes at 4°C to obtain platelet-poor plasma for the measurement of CRP, vWF, D-dimer, fibrinolytic activity, and fibrinogen. Whole blood was similarly collected and processed in 15% (K3) ethylenediaminetetraacetic acid at a final concentration of 1 mg/ml for determination of vWF. CRP and D-dimer levels were determined using commercially available enzymelinked immunosorbant assays by TintEliza Biopool (Ventura, California) and Diagnostica Stago (Persippany, New Jersey), respectively. The vWF was determined by an enzyme-linked immunoassay procedure described by Penny et al, fibrinolytic activity by a fibrin plate assay as described by Brackman, and fibrinogen levels by the Clauss method. Whole blood for platelet aggregation studies was collected in 3.2% sodium citrate (9:1, vol/vol), and centrifuged within 1 hour of collection at 125 g for 10 minutes at room temperature to obtain platelet-rich plasma for testing after 30 minutes. Platelet aggregation testing was performed using a platelet aggregometer (PACKS-4 Platelet Aggregation Chromogenic Kinetic System, Helena Laboratories, Beaumont, Texas) in response to 10 ug/ml collagen, 10 uM adenosine diphosphate, 10 uM epinephrine, 500 ug/ml arachidonate, and 1.5 mg/ml ristocetin. Complete blood counts were performed in an ADVIA 120 automated hematology autoanalyzer (Bayer Diagnostics, Tarrytown, New York). Total and high-density lipoprotein cholesterol levels were measured using an Abbot Diagnostics ABA-200 biochromatic analyzer and Abbot A-Gent enzymatic reagents (Abbott Lab., Chicago, Illinois). Creatinine, blood urea nitrogen, and electrolytes were determined using a Hitachi 917 chemistry autoanalyzer (Roche Diagnostics, Indianapolis, Indiana). The Student paired t test was used to compare results from pooled data before and after the 1996 and 1997 marathons becausea there were no significant differences in baseline values between the 2 races. In comparing prerace values with those within 4 hours after the race in 55 finishers in 1996 to 1997, marathon running resulted in a twofold or greater increase in CRP (343 611 to 762 973 ng/ml [p 0.001]), vWF (109 47% to 233 65% [p 0.001]), D-dimer (177 137 to 529 279 ng/ml [p 0.001]), and fibrinolytic activity (75 48 to 213 95 mm [p 0.001]), whereas fibrinogen levels decreased (278 52 to 260 45 mg/dl [p 0.001]; Table 1). When comparing prerace specimens with those within 4 hours after the marathon in 32 runners in 2001, WBC and platelet counts increased (5.5 0.2 to 17.4 1.5 th/mm [p 0.005] and 226 25 to 253 27 th/mm [p 0.05]), respectively, whereas hematocrit and hemoglobin levels were unchanged. Platelet studies showed a shortened lag time to aggregation with collagen and an increase with epinephrine (n 5, year 2000). When comparing prerace values with those the morning after the race in 13 runners in 1997, vWF and From the Department of Medicine, McLean Hospital, Belmont; Institute for Prevention of Cardiovascular Disease; Massachusetts General Hospital and Brigham and Women’s Hospital, Boston, Massachusetts; Royal North Shore Hospital, Sydney, Australia; and Harvard Medical School, Boston, Massachusetts. Dr. Siegel’s address is: McLean Hospital, Department of Internal Medicine, 115 Mill Street, Belmont, Massachusetts 02478. E-mail: ajsiegel@mclean.harvard.edu. Manuscript received December 29, 2000; revised manuscript received and accepted May 23, 2001.

Mannose-binding lectin and its associated proteases (MASPs) mediate coagulation and its deficiency is a risk factor in developing complications from infection, including disseminated intravascular coagulation.

The first line of host defense is the innate immune system that includes coagulation factors and pattern recognition molecules, one of which is mannose-binding lectin (MBL). Previous studies have demonstrated that MBL deficiency increases susceptibility to infection. Several mechanisms are associated with increased susceptibility to infection, including reduced opsonophagocytic killing and reduced lectin complement pathway activation. In this study, we demonstrate that MBL and MBL-associated serine protease (MASP)-1/3 together mediate coagulation factor-like activities, including thrombin-like activity. MBL and/or MASP-1/3 deficient hosts demonstrate in vivo evidence that MBL and MASP-1/3 are involved with hemostasis following injury. Staphylococcus aureus infected MBL null mice developed disseminated intravascular coagulation (DIC), which was associated with elevated blood IL-6 levels (but not TNF-α and multi-organ inflammatory responses). Infected MBL null mice also develop liver injury. These findings suggest that MBL deficiency may manifest into DIC and organ failure during infectious diseases.

Warfarin-induced skin necrosis

Warfarin-induced skin necrosis is a rare complication of anticoagulant therapy with a high associated morbidity and mortality requiring immediate drug cessation. Cutaneous findings include petechiae that progress to ecchymoses and hemorrhagic bullae. Characteristic dermatopathological findings are diffuse dermal microthrombi with endothelial cell damage and red cell extravasation with progression to full-thickness coagulative necrosis. The lesions of warfarin-induced skin necrosis may be difficult to differentiate from mimickers, but skin biopsy in conjunction with careful consideration of the clinical history, including time of onset, cutaneous distribution of the lesions, and laboratory findings, are essential for prompt diagnosis and patient treatment. Herein, we review the clinical and histologic features helpful for differentiating warfarin-induced skin necrosis and report a case illustrative of the diagnostic difficulty that may at times be encountered in clinical practice.

Physician Survey of a Laboratory Medicine Interpretive Service and Evaluation of the Influence of Interpretations on Laboratory Test Ordering

CONTEXT Complex coagulation test panels ordered by clinicians are typically reported to clinicians without a patient-specific interpretive paragraph. OBJECTIVES To survey clinicians regarding pathologist-generated interpretations of complex laboratory testing panels and to assess the ability of the interpretations to educate test orderers. DESIGN Surveys were conducted of physicians ordering complex coagulation laboratory testing that included narrative interpretation. Evaluation of order requisitions was performed to assess the interpretations influence on ordering practices. SETTING Physicians ordering coagulation testing at a large academic medical center hospital in Boston, Mass, and physicians from outside hospitals using the academic medical center as a reference laboratory for coagulation testing. OUTCOME MEASURES Physician surveys and evaluation of laboratory requisition slips. RESULTS In nearly 80% of responses, the ordering clinicians perceived that the interpretive comments saved them time and improved the diagnostic process. Moreover, the interpretations were perceived by ordering clinicians to help prevent a misdiagnosis or otherwise impact the differential diagnosis in approximately 70% of responses. In addition, interpretations appeared to be able to train the ordering clinicians as to the standard ordering practices. CONCLUSIONS The results demonstrate physician satisfaction with an innovative information delivery approach that provides laboratory diagnostic interpretation and test-ordering education to clinicians in the context of their daily workflow.

Anticoagulation With the Oral Direct Thrombin Inhibitor Dabigatran Does Not Enlarge Hematoma Volume in Experimental Intracerebral Hemorrhage

Background— The direct thrombin inhibitor dabigatran etexilate (DE) may constitute a future replacement of vitamin K antagonists for long-term anticoagulation. Whereas warfarin pretreatment is associated with greater hematoma expansion after intracerebral hemorrhage (ICH), it remains unclear what effect direct thrombin inhibitors would have. Using different experimental models of ICH, this study compared hematoma volume among DE-treated mice, warfarin-treated mice, and controls. Methods and Results— CD-1 mice were fed with DE or warfarin. Sham-treated mice served as controls. At the time point of ICH induction, DE mice revealed an increased activated partial thromboplastin time compared with controls (mean±SD 46.1±5.0 versus 18.0±1.5 seconds; P=0.022), whereas warfarin pretreatment resulted in a prothrombin time prolongation (51.4±17.9 versus 10.4±0.3 seconds; P<0.001). Twenty-four hours after collagenase-induced ICH formation, hematoma volume was 3.8±2.9 &mgr;L in controls, 4.8±2.7 &mgr;L in DE mice, and 14.5±11.8 &mgr;L in warfarin mice (n=16; Welch ANOVA between-group differences P=0.007; posthoc analysis with the Dunnett method: DE versus controls, P=0.899; warfarin versus controls, P<0.001; DE versus warfarin, P=0.001). In addition, a model of laser-induced cerebral microhemorrhage was applied, and the distances that red blood cells and blood plasma were pushed into the brain were quantified. Warfarin mice showed enlarged red blood cell and blood plasma diameters compared to controls, but no difference was found between DE mice and controls. Conclusions— In contrast with warfarin, pretreatment with DE did not increase hematoma volume in 2 different experimental models of ICH. In terms of safety, this observation may represent a potential advantage of anticoagulation with DE over warfarin.

Laboratory tests for antithrombin deficiency

Hereditary antithrombin deficiency is a hypercoagulable state associated with an increased risk for venous thrombosis. The recommended initial test for antithrombin is an activity (functional) assay. The advantages and disadvantages of the various testing options are presented. The causes of acquired antithrombin deficiency are much more common than hereditary deficiency. Therefore, this article describes the appropriate steps to take when antithrombin activity is low, in order to confirm or exclude a hereditary deficiency. The causes of falsely normal results are also described, including direct thrombin inhibitors. Am. J. Hematol. 85:947–950, 2010.

Laboratory monitoring of new anticoagulants.

Maintaining a balance between bleeding and clotting has always been a challenge in treating coagulation disorders. A perturbation in that balance can be associated with substantial morbidity and mortality. As a result, anticoagulant monitoring is extremely important, and inappropriate testing may lead to complications. There are now a variety of new anticoagulant drugs in clinical use including several direct thrombin inhibitors (DTIs), such as argatroban, bivalirudin, and hirudin, as well as a Factor Xa inhibitor, fondaparinux. There are pitfalls associated with some of the currently used laboratory monitoring tests, and newer alternative laboratory monitoring tests have been investigated (Walenga and Hoppensteadt, Semin Thromb Hemost 2004;30:683–695). In addition, laboratory testing can assist with transitioning patients from DTI to warfarin therapy. Am. J. Hematol. 2010.

Laboratory evaluation of hypercoagulability with venous or arterial thrombosis.

OBJECTIVE To provide recommendations for hypercoagulation testing for patients with venous, arterial, or neurovascular thrombosis, as reflected in the medical literature and the consensus opinion of recognized experts in the field. DATA SOURCES, EXTRACTION, AND SYNTHESIS The authors extensively examined the literature and current practices, and prepared a draft manuscript with preliminary recommendations. The draft manuscript was circulated to each of the expert participants (n = 30) in the consensus conference prior to the convening of the conference. The manuscript and recommendations were then presented at the conference for discussion. Recommendations were accepted if a consensus of the 28 experts attending the conference was reached. The discussions were also used to revise the manuscript into its final form. CONCLUSIONS The resulting article provides 17 recommendations for hypercoagulation testing in the setting of venous, arterial, or neurovascular thrombosis. The supporting evidence for test selection is analyzed and cited, and consensus recommendations for test selection are presented. Issues for which a consensus was not reached at the conference are also discussed.