BioMed Research International

Volume 2014 (2014), Article ID 583794, 7 pages

http://dx.doi.org/10.1155/2014/583794

Review Article

Management of the Bleeding Patient Receiving New Oral Anticoagulants: A Role for Prothrombin Complex Concentrates

Lisa M. Baumann Kreuziger,¹ Joseph C. Keenan,¹ Colleen T. Morton,² and David J. Dries²

¹University of Minnesota, 420 Delaware Street SE, Minneapolis, MN 55455, USA

²Regions Hospital, University of Minnesota, 640 Jackson Street, No. 11503C, Saint Paul, MN 55101, USA

Received 12 May 2014; Accepted 25 June 2014; Published 20 July 2014

Academic Editor: Jonathan Douxfils

Copyright © 2014 Lisa M. Baumann Kreuziger et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Ease of dosing and simplicity of monitoring make new oral anticoagulants an attractive therapy in a growing range of clinical conditions. However, newer oral anticoagulants interact with the coagulation cascade in different ways than traditional warfarin therapy. Replacement of clotting factors will not reverse the effects of dabigatran, rivaroxaban, or apixaban. Currently, antidotes for these drugs are not widely available. Fortunately, withholding the anticoagulant and dialysis are freqnently effective treatments, particularly with rivaroxaban and dabigatran. Emergent bleeding, however, requires utilization of Prothrombin Complex Concentrates (PCCs). PCCs, in addition to recombinant factor VIIa, are used to activate the clotting system to reverse the effects of the new oral anticoagulants. In cases of refractory or emergent bleeding, the recommended factor concentrate in our protocols differs between the new oral anticoagulants. In patients taking dabigatran, we administer an activated PCC (aPCC) [FELBA] due to reported benefit in human in vitro studies. Based on human clinical trial evidence, the 4-factor PCC (Kcentra) is suggested for patients with refractory rivaroxaban- or apixaban-associated hemorrhage. If bleeding continues, recombinant factor VIIa may be employed. With all of these new procoagulant agents, the risk of thrombosis associated with administration of factor concentrates must be weighed against the relative risk of hemorrhage.

1. Introduction

Hemorrhage is the major cause of early mortality after injury and a leading risk in any operative procedure. Recently developed target-specific oral anticoagulants defy traditional reversal protocols previously used with warfarin. In the face of new oral anticoagulants, we have developed additional approaches to management of bleeding. Patients with life threatening hemorrhage may benefit from use of a new 4-factor prothrombin complex concentrate (PCC) (Kcentra, CSL Behring Gmbh, Marburg, Germany). Recent data suggest that there may be a role for factor concentrates including PCCs, activated PCCs (aPCC), and recombinant factor VIIa (rfVIIa, NovoSeven, Novo Nordisk, Bagsvaerd, Denmark) in dabigatran, rivaroxaban, and apixaban-associated bleeding. This report will briefly review the mechanism of action of the oral anticoagulants, present our bleeding management protocols, and discuss the rationale for our use of prothrombin complex concentrates and rfVIIa in refractory hemorrhage.

2. Mechanism of Action

Understanding the mechanism of action of oral anticoagulants provides a biologic foundation for use of PCCs, aPCCs, and rfVIIa in treatment of uncontrolled bleeding. Warfarin creates a deficiency of factors II, VII, IX, and X through inhibition of vitamin K-dependent carboxylation of the clotting proteins [1]. Replacement of functional coagulation factors can reverse the anticoagulant effect of warfarin. The newer oral anticoagulants interact with the coagulation cascade in different ways. Dabigatran directly inhibits thrombin (activated factor II), which limits the formation of fibrin [2]. Rivaroxaban and apixaban directly inhibit activated factor X [3, 4]. Replacement of clotting factors will not reverse the effects of dabigatran, rivaroxaban, and apixaban and we currently do not have antidotes for these drugs.

Rates of bleeding seen with the new oral anticoagulants in real world patients treated with dabigatran are consistent with those seen in clinical trials and less than those seen with warfarin. Most of the data available at this time comes from clinical trials. Gastrointestinal and intracranial hemorrhage are the two most important bleeding complications reported with the new oral anticoagulants. In postmarketing surveillance, there did not appear to be higher bleeding rates associated with dabigatran as opposed to warfarin. Some of the largest trials are in patients with atrial fibrillation. In these studies, reduced rates of intracranial hemorrhage are seen with dabigatran in comparison to warfarin as well as a reduced death rate. The rate of gastrointestinal hemorrhage is similar between dabigatran and warfarin-treated patients. Factor Xa inhibitors are also associated with reduced risk of mortality and intracranial hemorrhage compared to warfarin in trials conducted in patients with atrial fibrillation and may be used in ablation procedures [5–8].

PCCs are plasma-derived products containing factors II, VII, IX, and X. The 3-factor PCCs contain a minimal amount of factor VII. Table 1 shows the PCCs available in the United States. FEIBA (Baxter AG, Vienna, Austria) is unique because it contains factor VII primarily in the activated form (activated PCC (aPCC)) [9]. Kcentra contains all of the vitamin K-dependent proteins (factors II, VII, IX, and X and proteins C and S) [10]. Kcentra and Bebulin (Baxter AG, Vienna, Austria) contain small amounts of heparin which is insufficient to cause anticoagulation but contraindicates use of these products in patients with a history of heparin-induced thrombocytopenia. Recombinant factor VIIa initiates coagulation independent of tissue factor, factor VIII and factor IX, and is approved for use in patients with factor VII deficiency and hemophilia with factor inhibitors [11]. PCCs provide replacement of functional vitamin K-dependent proteins to more rapidly reverse the anticoagulant effect of warfarin [12]. In contrast, for patients with uncontrolled bleeding while taking dabigatran, rivaroxaban, or apixaban, PCCs, aPCCs, and rVIIa can be used to activate the coagulation system.

Table 1: Prothrombin complex concentrates (PCC) available in the United States.

Product
Coagulation factors in product
FDA approved indications to manage hemorrhage
Heparin in product?

Nonactivated

    3-factor PCC

        Profilnine
Nonactivated II, IX, X, and small amounts of VII
Hemophilia B
No

        Bebulin
Nonactivated II, IX, X, and small amounts of VII
Hemophilia B
Yes

    4-factor PCC

        Kcentra
Nonactivated II, VII, IX, X, protein C, and protein S
Warfarin
Yes

Activated PCC

        Feiba
Activated VII,

nonactivated II, IX, and X
Hemophilia A & B with inhibitors
No

3. Animal and Human Data for Management of Dabigatran, Rivaroxaban, and Apixaban-Associated Hemorrhage

The PCC selection in our protocols for dabigatran, rivaroxaban, and apixaban-associated hemorrhage is based upon the available human and animal data presented in detail in Table 2 and summarized in Table 3. Human in vitro and animal studies have shown improved thrombin generation after administration of aPCCs in dabigatran treated animals [13, 14]. In a prospective crossover study, 4-factor PCCs failed to correct coagulation times or thrombin generation in humans taking dabigatran [15] suggesting that 4-factor PCCs are not useful for dabigatran-associated hemorrhage. rfVIIa could be considered in dabigatran-associated bleeding based on corrected time to thrombin generation from in vitro studies and decreased bleeding time in rats [13, 14, 16]. However, one case report suggested decreased bleeding after administration of rfVIIa in a patient taking dabigatran [17] and two reports noted continued bleeding [18–20]. Due to the mixed efficacy reported in case reports of rfVIIa, we use the aPCC (Feiba) prior to rfVIIa in refractory bleeding associated with dabigatran [21, 22]. In contrast to dabigatran, 4-factor PCCs improved rivaroxaban-induced coagulation testing abnormalities in a prospective crossover study in healthy volunteers [15], informing our decision to use a 4-factor PCC (Kcentra) in the setting of rivaroxaban-associated refractory bleeding. Given the mechanistic similarity and positive in vitro data, we also use a 4-factor PCC (Kcentra) in patients with refractory apixaban-associated bleeding [23]. Animal studies suggest that correction of coagulation testing does not always correlate to improvement in bleeding outcomes [14]. Outcomes of patients receiving factor concentrates via these protocols must be closely monitored.

Table 2: Animal and human studies using factor concentrates to reverse anticoagulant effect of dabigatran, rivaroxaban, and apixaban.

Author
Reversal agent
Test system
Coagulation test effect
Bleeding outcome effect

Dabigatran

    Van Ryn et al. [16]
aPCC
Rat
aPTT unchanged
Decreased bleeding time

rfVIIa
Rat
aPTT decreased
Decreased bleeding time

    Van Ryn et al. [14]
4-Factor PCC
Rat
PT decreased, aPTT unchanged
Decreased bleeding time

aPCC
Rat
PT decreased, aPTT unchanged, increased thrombin generation
Decreased bleeding time

rfVIIa

PT and aPTT decreased
Decreased bleeding time

    Lambourne et al. [38]
4-Factor PCC
Mouse
No effect
No effect

rfVIIa
Mouse
aPTT decreased
No effect

4-Factor PCC + rfVIIa
Mouse
TT and aPTT decreased
No effect

aPCC
Mouse
No effect
No effect

    Pragst et al. [39]
4-Factor PCC
Rabbit
PT decreased, aPTT unchanged
Normalized blood loss

    Zhou et al. [40]
4-Factor PCC
Mouse ICH

Prevented hematoma expansion; control level mortality

rfVIIa
Mouse ICH

Ineffective control of hematoma expansion

    Marlu et al. [13]
4-Factor PCC
Human in vitro
Increased amount of thrombin generation

rfVIIa
Human in vitro
Corrected time to thrombin generation

aPCC
Human in vitro
Corrected time to thrombin generation

    Eerenberg et al. [15]
4-Factor PCC
Human
No effect on aPTT, TT, or ECT

    Khoo et al. [41]
aPCC
Human in vitro
Increased thrombin generation and corrected time to thrombin generation

    Warkentin et al. [17]
rfVIIa
Human case report
Decreased aPTT and PT
Decreased blood loss

    Garber et al. [18]
rfVIIa
Human case report

Worsening ICH

    Truumees et al. [19]
rfVIIa
Human case report

Continued blood loss

    Lillo-Le Louët et al. [20]
4-Factor PCC + rfVIIa
Human case report
PT and aPTT unchanged
Continued bleeding

4-Factor PCC + rfVIIa
Human case report
PT and aPTT unchanged
Bleeding stopped with dialysis

    Wychowski and Kouides [42]
3-Factor PCC
Human case report
TT and aPTT unchanged, PT decreased
No further bleeding

    Dumkow et al. [43]
3-Factor PCC
Human case report

Clinical bleeding and hemoglobin stabilized

Rivaroxaban

    Perzborn and Tinel [44]
4-factor PCC
Rat
PT decreased
Bleeding time decreased

    Godier et al. [45]
4-factor PCC
Rabbit
aPTT normalized, PT decreased
No effect on blood loss

rfVIIa
Rabbit
aPTT normalized, PT decreased
Decreased bleeding time, no effect on blood loss

    Perzborn et al. [46]
4-Factor PCC
Rat
Decreased PT, normalized TAT concentration
Reduced bleeding time

aPCC
Rat
Decreased PT
Reduced bleeding time

Primate
Reduced PT
Normalized bleeding time

rVIIa
Rat
Decreased PT
Reduced bleeding time

Primate
Decreased PT
Bleeding time unchanged

    Marlu et al. [13]
4-Factor PCC
Human in vitro
Increased amount of thrombin generation

rfVIIa
Human in vitro
Corrected time to thrombin generation

aPCC
Human in vitro
Corrected all thrombin generation parameters

    Eerenberg et al. [15]
4-Factor PCC
Human in vivo
Normalized PT and thrombin generation

    Dinkelaar et al. [47]
4-Factor PCC
Human in vitro
No effect on PT or time to thrombin generation Normalized amount of thrombin generation

    Körber et al. [48]
4-Factor PCC
Human in vitro
No effect on aPTT, PT

rfVIIa
Human in vitro
Decreased clotting time, no effect on aPTT, PT

Apixaban

    Escolar et al. [23]
PCC
Human in vitro
Increased thrombin generation

rfVIIa
Human in vitro
Increased thrombin generation

aPCC
Human in vitro
Increased thrombin generation

aPCC: activated prothrombin complex concentrate; rfVIIa: recombinant factor VIIa.

Table 3: Summary of animal and human data for reversal of dabigatran, rivaroxaban, and apixaban using factor concentrates.

Dabigatran
Rivaroxaban
Apixaban

Animal
Human
Animal
Human
Animal
Human

3-factor PCC

Case report +/−

4-factor PCC
Rats +/−

Rabbits +

Mice −

Mice ICH +
In vitro +

In vivo −

Case report −
Rats +

Rabbits +/−
In vitro +/−

In vivo +

In vitro +

aPCC
Rats +/−

Mice −
In vitro +
Rat +

Primate +
In vitro +

In vitro +

rfVIIa
Rats +/−

Mice +/−

Mice ICH −
In vitro +

Case report +/−
Rat +

Rabbits +/−

Primate +/−
In vitro +/−

In vitro +

+: effective; −: ineffective; +/−: mixed results between studies or between coagulation testing and bleeding outcomes; PCC: prothrombin complex concentrate; aPCC: activated prothrombin complex concentrate; rfVIIa: recombinant factor VIIa.

4. Protocols

Our institution has created protocols to help direct the use of factor concentrates in the treatment of life threatening bleeding in patients taking new oral anticoagulants (Figure 1). The initial measures are the same for any bleeding patient, with local intervention and supportive care. In addition, confirmation of medication, dosing, and duration since the last dose guides further therapy. Renal and hepatic function are evaluated to determine patient metabolism of medication. Transfusion of packed RBCs and a transfusion protocol featuring a balance of packed red blood cells, plasma, and platelets may be utilized depending on the severity of hemorrhage. Based largely on retrospective data, the optimal ratio of plasma to packed RBCs administered is thought to be 1 : 1 or 1 : 2 [24]. The effects of antiplatelet agents are reversed by transfusion of 2 apheresis units of platelet concentrates if needed (see below) [25, 26].

Figure 1: Management protocol for hemorrhage in patients taking dabigatran, rivaroxaban, or apixaban.

Our management protocols in the setting of life threatening bleeding in the patient taking dabigatran, rivaroxaban, or apixaban are summarized in Figure 1. Activated charcoal may be administered if the last dose of anticoagulant was ingested less than 2 hours (dabigatran [2] or rivaroxaban [27]) or 3 hours (apixaban [28]) before presentation. Hemodialysis removes dabigatran and should be considered based on clinical status and need for surgical intervention. In a survey of nonmalignant hematologists, withholding the anticoagulant and dialysis were the most effective treatment used in 80% of bleeding episodes associated with rivaroxaban and dabigatran, respectively [29]. Thus, the use of specialized resuscitation protocols is often not required.

After transfusion of 4 units of PRBCs, we transfuse PRBCs, plasma, and platelets in a 1 : 1 : 1 ratio with a goal of hemoglobin of 9-10 g/dL [24]. We employ this transfusion strategy to avoid additional mechanisms of coagulopathy as the new oral anticoagulants prolong the PTT and INR and, thus, interfere with laboratory monitoring of other coagulation abnormalities. For patients on antiplatelet drugs we consider administration of two apheresis units of platelets.

In cases of refractory bleeding, the recommended factor concentrate in our protocols differs between the new oral anticoagulants. In patients taking dabigatran, we administer 50 units/kg IV of aPCC (Feiba) due to suggested benefit in human in vitro studies [13]. Based on human clinical trial evidence, 50 units/kg IV of the 4-factor PCC (Kcentra) is suggested for patients with refractory rivaroxaban or apixaban-associated hemorrhage. If bleeding continues, rfVIIa may be employed. Thrombosis has been reported with administration of all of the factor concentrates and the relative risk of hemorrhage and thrombosis must be considered.

Platelets are an essential but poorly understood component of hemostasis after injury. Previous evidence identifies admission platelet counts as inversely correlated with early mortality and supports transfusion of platelets with critical injury and trauma, even for platelet counts in the normal reference range. Quantitative platelet deficits have predicted progression of intracranial hemorrhage and mortality after traumatic brain injury. Study of platelet dysfunction has been hindered by technical complexity of existing platelet assays [30, 31].

Given the controversy which continues in the trauma and acute surgery literature, a number of observations can be made [30, 32–37]. Patients receiving antiplatelet agents have an increased number of comorbidities. While recent retrospective work suggests limited impact of antiplatelet medications on outcome with trauma, limited prospective work suggests that the elderly and patients with intracranial hemorrhage are at greater risk for poor outcomes if taking antiplatelet agents. A normal platelet count is not reassuring in this setting. Normal clotting studies also do not predict good outcome. Despite this, a specific role for empiric platelet therapy has not been identified. Finally, while a variety of assays for platelet function have been reported, consensus regarding the optimal assay and the standard for acute management of injury has not been reached. Of assays which can be performed at the bedside, thromboelastography is the most promising bedside assay [31]. Our recommendation favoring consideration of platelet administration in the setting of life threatening bleeding must be understood in the context of the quality of studies which are available.

5. Conclusion

Our institution developed management protocols in an effort to standardize treatment of severe bleeding associated with use of new oral anticoagulants and approval of new factor concentrates. These protocols are based on limited human data but serve as a tool to guide therapy as providers gain experience with these anticoagulants and PCCs. Standardizing therapy allows the collection of clinical data, which can guide further trials. We anticipate continued modification of these protocols as laboratory and clinical experience expand. In particular, thrombosis risk with powerful newer agents designed to enhance coagulation must be monitored. At this time, data related to thrombosis risk is limited to anecdotes [5].

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Authors’ Contribution

Lisa Baumann Kreuziger and Joseph Keenan completed a literature search, primary paper writing, and revisions. Colleen Morton assisted with literature search, content review, and revisions and developed protocols. David Dries, MSE, MD, initiated the project, developed protocols, and completed content review and revisions.

References

F. Kazmier, J. A. Spittel, J. J. Thompson, and C. A. Owen, “Effect of oral anticoagulation on factors VII, IX, X, and II,” Archives of Internal Medicine, vol. 115, pp. 667–673, 1965.

J. van Ryn, J. Stangier, S. Haertter et al., “Dabigatran etexilate—a novel, reversible, oral direct thrombin inhibitor: interpretation of coagulation assays and reversal of anticoagulant activity,” Thrombosis & Haemostasis, vol. 103, no. 6, pp. 1116–1127, 2010.

B. I. Eriksson, D. J. Quinlan, and J. I. Weitz, “Comparative pharmacodynamics and pharmacokinetics of oral direct thrombin and factor xa inhibitors in development,” Clinical Pharmacokinetics, vol. 48, pp. 1–22, 2009.

P. C. Wong, D. J. P. Pinto, and D. Zhang, “Preclinical discovery of apixaban, a direct and orally bioavailable factor Xa inhibitor,” Journal of Thrombosis and Thrombolysis, vol. 31, no. 4, pp. 478–492, 2011.

D. M. Siegal, D. A. Garcia, and M. A. Crowther, “How I treat target-specific oral anticoagulant-associated homorrhage,” Blood, vol. 123, pp. 1152–1158, 2014.

M. R. Southworth, M. E. Reichman, and E. F. Unger, “Dabigatran and postmarketing reports of bleeding,” The New England Journal of Medicine, vol. 368, no. 14, pp. 1272–1274, 2013.

K. M. Bruins Slot and E. Berge, “Factor Xa inhibitors vs warfarin for preventing stroke and thromboembolism in pateints with atrial fibrillation,” JAMA, vol. 311, pp. 1150–1151, 2014.

G. Stepanyan, N. Badhwar, R. J. Lee et al., “Safety of new oral anticoagulants for patients undergoing atrial fibrillation ablation,” Journal of Interventional Cardiac Electrophysiology, vol. 40, pp. 33–38, 2014.

Baxter, “FEIBA prescribing information,” 2011.

CSL Behring GmbH, “Kcentra prescribing information,” http://labeling.cslbehring.com/PI/US/Kcentra/EN/Kcentra-Prescribing-Information.pdf

Novo Nordisk Inc, NovoSeven RT Coagulation Factor VIIa Prescribing Information, 1999.

R. Meehan, M. Tavares, and J. Sweeney, “Clinical experience with oral versus intravenous vitamin K for warfarin reversal (CME),” Transfusion, vol. 53, no. 3, pp. 491–498, 2013.

R. Marlu, E. Hodaj, A. Paris, P. Albaladejo, J. L. Cracowski, and G. Pernod, “Effect of non-specific reversal agents on anticoagulant activity of dabigatran and rivaroxaban: a randomised crossover ex vivo study in healthy volunteers,” Thrombosis and Haemostasis, vol. 108, no. 2, pp. 217–224, 2012.

J. van Ryn, J. Schurer, M. Kink-Eiband, and A. Clemens, “The successful reversal of dabigatran-induced bleeding by coagulation factor concentrates in a rat tail bleeding model do not correlate with ex vivo markers of anticoagulation,” Blood, vol. 118, p. 2316, 2011.

E. S. Eerenberg, P. W. Kamphuisen, M. K. Sijpkens, J. C. Meijers, H. R. Buller, and M. Levi, “Reversal of rivaroxaban and dabigatran by prothrombin complex concentrate: a randomized, placebo-controlled, crossover study in healthy subjects,” Circulation, vol. 124, no. 14, pp. 1573–1579, 2011.

J. van Ryn, D. Ruehl, H. Priepke, H. Hauel, and W. Wienan, “Reversibility of the anticoagulant effect of high doses of the direct thrombin inhibitor dabigatran, by recombinant factor VIIa or activated prothrombin complex concentrate,” Haematologica, vol. 93, p. 148, 2008.

T. Warkentin, P. Margetts, S. Connolly, A. Lamy, C. Ricci, and J. Eikelboom, “Recombinant factor VIIa (rFVIIa) and hemodialysis to manage massive dabigatran-associated postcardiac surgery bleeding,” Blood, vol. 119, pp. 2172–2174, 2012.

S. T. Garber, W. Sivakumar, and R. H. Schmidt, “Neurosurgical complications of direct thrombin inhibitors—catastrophic hemorrhage after mild traumatic brain injury in a patient receiving dabigatran,” Journal of Neurosurgery, vol. 116, no. 5, pp. 1093–1096, 2012.

E. Truumees, T. Gaudu, C. Dieterichs, M. Geck, and J. Stokes, “Epidural hematoma and intraoperative hemorrhage in a spine trauma patient on pradaxa (dabigatran),” Spine, vol. 37, pp. E863–E865, 2012.

A. Lillo-Le Louët, M. Wolf, L. Soufir et al., “Life-threatening bleeding in four patients with an unusual excessive response to dabigatran: implications for emergency surgery and resuscitation,” Thrombosis and Haemostasis, vol. 108, no. 3, pp. 583–585, 2012.

S. Schulman, B. Ritchie, J. K. Goy, S. Nahirniak, M. Almutawa, and S. Ghanny, “Activated prothrombin complex concentrate for dabigatran-associated bleeding,” British Journal of Haematology, vol. 164, pp. 296–310, 2013.

G. Dickneite and M. Hoffman, “Reversing the new oral anticoagulants with prothrombin comlpex concentrates (PCCs): what is the evidence?” Thrombosis and Haemostasis, vol. 111, no. 2, pp. 189–198, 2014.

G. Escolar, J. Reverter, J. Villalta, V. Sanz, P. Molina, and M. Diaz-Ricart, “Reversal of apixaban induced alterations of hemostasis by different coagulation factor concentrates: Studies in vitro with circulating human blood,” Circulation, vol. 126, p. 521, 2012.

D. J. Dries, “The contemporary role of blood products and components used in trauma resuscitation,” Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine, vol. 18, no. 1, article 63, 2010.

C. Li, J. Hirsh, C. Xie, M. A. Johnston, and J. W. Eikelboom, “Reversal of the anti-platelet effects of aspirin and clopidogrel,” Journal of Thrombosis and Haemostasis, vol. 10, no. 4, pp. 521–528, 2012.

T. Thiele, A. Sümnig, G. Hron et al., “Platelet transfusion for reversal of dual antiplatelet therapy in patients requiring urgent surgery: a pilot study,” Journal of Thrombosis and Haemostasis, vol. 10, pp. 968–971, 2012.

Janssen Pharmaceuticals Inc, “Xarelto prescribing information,” 2011

Bristol-Myers Squibb, “Eliquis (apixiban) prescribing information,” 2012, http://packageinserts.bms.com/pi/pi_eliquis.pdf

L. M. Baumann Kreuziger and M. T. Reding, “Management of bleeding associated with dabigatran and rivaroxaban: a survey of current practices,” Thrombosis Research, vol. 132, no. 2, pp. e161–e163, 2013.

M. E. Kutcher, B. J. Redick, R. C. McCreery, et al., “Characterization of platelet dysfunction after trauma,” Journal of Trauma and Acute Care Surgery, vol. 73, pp. 13–19, 2012.

D. Bolliger, M. D. Seeberger, and K. A. Tanaka, “Principles and practice of thromboelastography in Clinical Coagulation Management and Transfusion Practice,” Transfusion Medicine Reviews, vol. 26, no. 1, pp. 1–13, 2012.

V. A. Ferraris, A. C. Bernard, B. Hyde, and P. A. Kearney, “The impact of antiplatelet drugs on trauma outcomes,” Journal of Trauma and Acute Care Surgery, vol. 73, no. 2, pp. 492–497, 2012.

B. Joseph, V. Pandit, M. Sadoun, et al., “A prospective evaluation of platelet function in patients on antiplatelet therapy with traumatic intracranial hemorrhage,” Journal of Trauma and Acute Care Surgery, vol. 75, pp. 900–994, 2013.

D. K. Nishijima, S. Zehtabchi, J. Berrong, and E. Legome, “Utility of platelet transfusion in adult patients with traumatic intracranial hemorrhage and preinjury antiplatelet use: a systematic review,” Journal of Trauma and Acute Care Surgery, vol. 72, pp. 1658–1663, 2012.

J. N. Harr, E. E. Moore, J. Johnson, et al., “Antiplatelet therapy is not associated with decreased transfusion-associated risk of lung dysfunction, multiple organ failure, and mortality in trauma patients,” Critical Care Medicine, vol. 41, pp. 399–404, 2013.

K. A. Peck, R. Y. Calvo, M. S. Schechter, et al., “The impact of preinjury anticoagulants and prescription antiplatelet agents on outcomes in older patients with traumatic brain injury,” Journal of Trauma and Acute Care Surgery, vol. 76, pp. 431–436, 2014.

J. L. Gordon, T. C. Fabian, M. D. Lee, and M. Dugdale, “Anticoagulant and antiplatelet medications encountered in emergency surgery patients: a review of reversal strategies,” The Journal of Trauma and Acute Care Surgery, vol. 75, no. 3, pp. 475–486, 2013.

M. D. Lambourne, L. J. Eltringham Smith, S. Gataiance, D. M. Arnold, M. A. Crowther, and W. P. Sheffield, “Prothrombin complex concentrates reduce blood loss in murine coagulopathy induced by warfarin, but not in that induced by dabigatran etexilate,” Journal of Thrombosis and Haemostasis, vol. 10, no. 9, pp. 1830–1840, 2012.

I. Pragst, S. H. Zeitler, B. Doerr et al., “Reversal of dabigatran anticoagulation by prothrombin complex concentrate (beriplex P/N) in a rabbit model,” Journal of Thrombosis and Haemostasis, vol. 10, no. 9, pp. 1841–1848, 2012.

W. Zhou, S. Schwarting, S. Illanes et al., “Hemostatic therapy in experimental intracerebral hemorrhage associated with the direct thrombin inhibitor dabigatran,” Stroke, vol. 42, pp. 3594–3599, 2011.

T.-L. Khoo, C. Weatherburn, G. Kershaw, C. J. Reddel, J. Curnow, and S. Dunkley, “The use of FEIBA in the correction of coagulation abnormalities induced by dabigatran,” International Journal of Laboratory Hematology, vol. 35, no. 2, pp. 222–224, 2013.

M. K. Wychowski and P. Kouides, “Dabigatran-induced gastrointestinal bleeding in an elderly patient with moderate renal impairment,” Annals of Pharmacotherapy, vol. 46, no. 4, article e10, 2012.

L. E. Dumkow, J. R. Voss, M. Peters, and D. L. Jennings, “Reversal of dabigatran-induced bleeding with a prothrombin complex concentrate and fresh frozen plasma,” American Journal of Health-System Pharmacy, vol. 69, no. 19, pp. 1646–1650, 2012.

E. Perzborn and H. Tinel, “Prothrombin complex concentrate reverses the effects of high-dose rivaroxaban in rats,” Journal of Thrombosis and Haemostasis, vol. 7, article 183, 2009.

A. Godier, A. Miclot, B. Le Bonniec et al., “Evaluation of prothrombin complex concentrate and recombinant activated factor VII to reverse rivaroxaban in a rabbit model,” Anesthesiology, vol. 116, pp. 94–102, 2012.

E. Perzborn, A. Gruber, H. Tinel et al., “Reversal of rivaroxaban anticoagulation by haemostatic agents in rats and primates,” Thrombosis and Haemostasis, vol. 110, no. 1, pp. 162–172, 2013.

J. Dinkelaar, P. J. Molenaar, M. Ninivaggi, B. de Laat, H. J. M. Brinkman, and A. Leyte, “In vitro assessment, using thrombin generation, of the applicability of prothrombin complex concentrate as an antidote for rivaroxaban,” Journal of Thrombosis and Haemostasis, vol. 11, no. 6, pp. 1111–1118, 2013.

M. Körber, E. Langer, S. Ziemer, E. Perzborn, C. Gericke, and C. von Heymann, “Measurement and reversal of prophylactic and therapeutic peak levels of rivaroxaban: an in vitro study,” Clinical and Applied Thrombosis/Hemostasis, 2013.