Perioperative management of patients on chronic antithrombotic therapy

Perioperative Management of Antiplatelet and Anticoagulation in Brain Tumor Surgery: A Survey of International Practices

BACKGROUND

Perioperative management of antithrombotic therapy is a necessary preprocedural consideration for patients prescribed direct oral anticoagulants (DOACs), vitamin K antagonists, or antiplatelet medications. There is a lack of evidence-based guidelines to help inform decision-making in managing antiplatelet and anticoagulation medications in the perioperative period around brain tumor resection. The objective of this study was to provide an example of the heterogeneity in practice and raise awareness for the need to create standardized guidelines for managing these medications.

METHODS

A survey was sent to a list of over 800 international neurosurgeons who are members of the Neurosurgery Research Listserv. The survey comprised 70 questions assessing individual practices for managing thromboprophylaxis, antiplatelet medications, and anticoagulation in the perioperative period. The survey was sent via e-mail invitation between March 2021 and June 2021.

RESULTS

A total of 72 surgeons responded to the survey. There was no difference in medication management preoperatively or postoperatively when comparing intra- and extra-axial tumor resections. Cessation of antiplatelet medications varied between 3 and 11 days while restart varied between 1 and 14 days. Preoperative management of vitamin K antagonists varied between indication for use (P < 0.001) while DOAC management did not. In our group of respondents, 90% started heparin products within 5 days of surgery, while the same fraction restarted DOAC within 14 days.

CONCLUSIONS

Respondents demonstrated significant heterogeneity in their perioperative management of antiplatelet and anticoagulation medication in brain tumor resection. This may lead to an unacceptable level of heterogeneity in practice that has the potential to cause patient harm due to errors in medication management.

Restarting Antithrombotic Therapies After Endoscopic Sinus Surgery: A Systematic Review

OBJECTIVES

Antithrombotic therapies, comprised of both anticoagulant and antiplatelet agents, are routinely paused prior to endoscopic sinus surgery (ESS) to reduce the risk of perioperative hemorrhage. At present, no clear guidelines exist to guide otolaryngologists on when to resume these agents after ESS. Our goal was to systematically review the existing literature related to this topic.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically queried the PubMed, Embase, Ovid, Web of Science, Cochrane, and CINAHL databases to identify publications reporting on antithrombotic and antiplatelet therapy in the context of ESS. The primary outcomes we sought were recommendations on the timing of antithrombotic therapy resumption after ESS.

RESULTS

Of the 104 unique articles identified, all were screened for relevance by 2 independent reviewers based on title and abstract, 20 underwent full-text review, and 6 met inclusion criteria for analysis. Of these, 3 were literature reviews, 2 were case-control studies, and 1 was a cohort study. All publications discussed when to pause antithrombotic therapy prior to surgery while only 3 articles discussed resumption of these agents. Recommendations were mixed.

CONCLUSION

A paucity of literature exists on the resumption of antithrombotic therapies after ESS. As a major determining factor in patient morbidity, guideline-based resumption of these therapies is needed.

The Impact of Preoperative Antithrombotic Therapy on the Risks for Thrombo-ischemic Events and Bleeding among Patients Undergoing Elective Spine Surgery

STUDY DESIGN

Retrospective matched analysis.

PURPOSE

To evaluate the effect of antithrombotic drug therapy on the rates of thrombo-ischemic or bleeding events 90 days following elective spine surgery.

OVERVIEW OF LITERATURE

Thrombo-ischemic and bleeding complications in patients undergoing spine surgery are major causes of morbidity. Many patients who pursue elective spine surgery are concurrently receiving antithrombotic therapy for unrelated conditions; however, at this time, the effects of preoperative antithrombotic use on postoperative bleeding and thrombosis are unclear.

METHODS

Using an all-payer claims database, patients who underwent elective cervical and lumbar spine interventions between January 1, 2010, and June 30, 2018, were identified. Individuals were categorized into groups taking and not taking antithrombotics. A 1:1 analysis was constructed based on comorbidities found to be independently associated with bleeding or ischemic complications using logistic regression models. The primary outcomes were the rates of thrombo-ischemic events and bleeding complications.

RESULTS

A total of 660,866 patients were eligible for inclusion. Following the matching procedure, 56,476 patient records were analyzed, with 28,238 in each group. The antithrombotic agent group had significantly greater odds of developing any 90-day thromboischemic event after surgery: deep vein thrombosis (odds ratio [OR], 3.61; 95% confidence interval [CI], 3.06-4.25), pulmonary embolism (OR, 3.93; 95% CI, 3.34-4.62), myocardial infarction (OR, 6.20; 95% CI, 5.69-6.76), and ischemic stroke (OR, 3.76; 95% CI, 3.31-4.27). In addition, the antithrombotic agent group had an increased likelihood of experiencing hematoma (OR, 1.54; 95% CI, 1.35-1.76) and need for transfusion (OR, 2.61; 95% CI, 2.29-2.96).

CONCLUSIONS

Patients taking antithrombotic medications before elective surgery of the cervical and lumbar spine had increased risks of both ischemic and bleeding events. Spine surgeons should carefully consider these implications when appraising patients for surgery, given the lack of guidelines on perioperative management of antithrombotic agents.

Proactive Risk Assessment through Failure Mode and Effect Analysis (FMEA) for Perioperative Management Model of Oral Anticoagulant Therapy: A Pilot Project

INTRODUCTION

Correct perioperative management of anticoagulant therapy is essential to prevent thromboembolic events and reduce the risk of bleeding. The lack of universally accepted guidelines makes perioperative anticoagulant therapy management difficult. The present study aims to identify the perioperative risks of oral anticoagulant therapy and to reduce adverse events through Failure Mode and Effect Analysis (FMEA).

MATERIALS AND METHODS

A multidisciplinary working group was set up, and four main phases of the process were identified. Each of these phases was divided into micro-activities to identify the related possible failure modes and their potential consequences. The Risk Priority Number was calculated for each failure mode.

RESULTS AND DISCUSSION

Seventeen failure modes were identified in the entire perioperative period; those with a higher priority of intervention concern the incorrect timing between therapy suspension and surgery, and the incorrect assessment of the bleeding risk related to the invasive procedure.

CONCLUSION

The FMEA method can help identify anticoagulant therapy perioperative failures and implement the management and patient safety of surgical procedures.

Symptomatic Postoperative Epidural Hematoma in the Lumbar Spine

A symptomatic postoperative epidural hematoma (SPEH) in the lumbar spine is a complication with variable presentation and the potential to rapidly cause an irrecoverable neurological injury. Significant heterogeneity exists among current case series reporting SPEH in the literature. This review attempts to clarify the known incidence, risk factors, and management pearls. Currently, literature does not support the efficacy of subfascial drains in reducing the incidence of SPEHs and possibly suggests that medication for thromboembolism prophylaxis may increase risk. Acute back pain and progressing lower extremity motor weakness are the most common presenting symptoms of SPEH. Magnetic resonance imaging is the mainstay of diagnostic imaging necessary to confirm the diagnosis, but if not acutely available, an immediate return to the operative theater for exploration without advanced imaging is justified. Treatment of a SPEH consists of emergent hematoma evacuation as a delay in repeat surgery has a deleterious effect on neurological recovery. Outcomes are poorly defined, though a significant portion of patients will have lasting neurological impairments even when appropriately recognized and managed.

[Perioperative management of coagulation in otorhinolaryngologic surgery]

Considering the increasing number of patients suffering from drug-induced coagulation disorders caused by antiplatelet or anticoagulant therapy, the right balance between minimizing the risk of bleeding and the risk of a venous thrombosis or embolism during otorhinolaryngologic (ORL) surgery is becoming increasingly important. According to a recent study, the highest risk of intraoperative bleeding in ORL surgery is associated with transoral tumor surgery, tonsillectomy, thyroidectomy, and glomus tumor surgery. The risk of venous thrombosis or embolism during ORL surgery is estimated to be 1%, and increases to 6% among tumor patients. Currently, there is no general recommendation for perioperative hemostatic management because of the limited available data. In the majority of patients who continue antiplatelet therapy with acetylsalicylic acid (ASS) to prevent thromboembolic events, the perioperative bleeding risk is considered to be acceptable. For patients with dual antiplatelet therapy, surgical procedures should be only performed after adaption of the medication.

Use of Thromboelastography and Rotational Thromboelastometry in Otolaryngology: A Narrative Review

In the field of otolaryngology—head and neck surgery (ENT), coagulopathies present unique diagnostic and therapeutic challenges. In both hyper- and hypocoagulable patients, management of coagulopathies requires intricate attention to the nature of hemostatic competence. Common coagulation tests (CCTs) offer only a snapshot of hemostatic competence and do not provide a clear insight into the patient’s real-time hemostatic condition. Viscoelastic tests (VETs) offer a holistic and concurrent picture of the coagulation process. Although VETs have found prominent utilization in hepatic transplants, obstetrics, and emergent surgical settings, they have not been fully adopted in the realm of otolaryngology. The objective of this manuscript is to provide an overview of the literature evaluating the current utilization and possible future uses of VETs in the field of otolaryngology. The authors performed a comprehensive literature search of the utilization of VETs in otolaryngology and identified applicable studies that included descriptions of viscoelastic testing. Twenty-five studies were identified in this search, spanning topics from head and neck oncology, microvascular free flap reconstruction, obstructive sleep apnea, adenotonsillectomy, facial trauma, and epistaxis. The applicability of VETs has been demonstrated in head and neck oncology and microvascular free flap management, although their pervasiveness in practice is limited. Underutilization of VETs in the field of otolaryngology may be due to a lack of familiarity of the tests amongst practitioners. Instead, most otolaryngologists continue to rely on CCTs, including PT, PTT, INR, CBC, fibrinogen levels, and thrombin time. Learning to perform, interpret, and skillfully employ VETs in clinical and operative practice can greatly improve the management of coagulopathic patients who are at increased risk of bleeding or thrombosis.

Antithrombotic therapy and digestive endoscopy

Antithrombotic therapy and digestive endoscopy Antithrombotic therapy comprises anticoagulation and antiplatelet treatment. The number of patients treated with various forms of antithrombotic therapy is growing. Procedures of digestive endoscopy are very frequently indicated by general practitioners and doctors of various specialisations. Interdisciplinary cooperation and mutual understanding are required in order for digestive endoscopy to be effective and safe. Hence, we present an overview based on recent European, British (1), and North American guidelines (2) for endoscopic procedures, with respect to guidelines for perioperative care in general (3). Antithrombotic therapy management in patients undergoing digestive endoscopy procedures is based on individual consideration of postprocedural bleeding (particularly a delayed one) on one hand, and thromboembolic risk on the other hand, ideally in cooperation with the physician prescribing antithrombotic therapy. Despite all efforts, patients taking antithrombotic medication are at a higher risk of postprocedural bleeding in comparison with those without this risk; this fact should be accepted by attending physicians and patients should be informed of it. Postprocedural bleeding is mostly manageable with a subsequent endoscopic procedure. By contrast, cerebral and cardiovascular thromboembolic complications are often life-threatening and not uncommonly disabling. One should always consider postponing an elective procedure in a patient with temporary antithrombotic therapy (after pulmonary embolism or after coronary stent insertion). Basic principles of administration of antithrombotic therapy in the context of an endoscopic procedure are described in Table 1. Digestive endoscopy procedures can be categorized according to postprocedural bleeding risk (Table 2). Postprocedural bleeding risk can be specifically reduced in some procedures (ERCP with papillary balloon dilation instead of sphincterotomy, mechanical securing of polypectomy base, etc.). Acetylsalicylic acid administered as secondary prevention (primary preventive indications are very narrow nowadays) should not be discontinued perioperatively (discontinuation is associated with an approximately threefold increase in thrombotic complications!). The riskiest procedures are the only exception in which discontinuation is explicitly requested by the digestive endoscopist. Reduction of dual antiplatelet therapy is better abandoned in high-risk patients - particularly those with recently implanted coronary stents (Table 3) - and postponement of an elective procedure should always be considered. Bridging of warfarin with low-molecular-weight heparin (LMWH) is not indicated routinely (in some cases, this practice increases the bleeding risk). Bridging with LMWH is appropriate in patients with high (or moderate) thromboembolic risk (Table 5). Furthermore, LMWH therapy carries specific risks, particularly in patients with renal function impairment (Table 4). In patients with a high thromboembolic risk, a statement of the physician indicating anticoagulation is always appropriate before an elective procedure (Table 6). Direct oral anticoagulants (DOACs) should not be administered on the day of the procedure, not even in one with a low risk (e.g., biopsy); a longer withdrawal is recommended in high-risk procedures (this cessation should not be bridged with LMWH given the rapid onset and elimination half-time) (Table 7). Recommencement of antithrombotic therapy after a high-risk endoscopic procedure should always be determined by the endoscopist and the recommended intervals should be considered minimal: 1-2 days after the procedure in the case of P2Y12 inhibitors; 2-3 days after the procedure in the case of DOACs; in the evening of the day of the procedure for warfarin with a maintenance (not saturation) dose; and 48 hours after the procedure in the case of LMWH at a therapeutic dose. Earlier administration of a lower-than-therapeutic dose of LMWH (twice a day per weight) can be considered in this context: prophylactic (once a day) or higher prophylactic (once a day per weight) doses. In general, a full anticoagulation effect should not be achieved earlier than approximately 48 hours after the procedure. The patient should be properly informed of the course of antithrombotic therapy before and after the endoscopic procedure, including a written form (a calendar can be downloaded online for this purpose).

The topical application of tranexamic acid to control bleeding in inguinal hernia surgery candidate patients: A randomized controlled trial

Background and objectives

Inguinal hernia surgery is a common procedure, especially for the elderly, who usually use anticoagulants and antiplatelet drugs. In this study, we evaluated the effectiveness of tranexamic acid (TXA) on the complications of inguinal hernia repair in patients using antiplatelets.

Patients and methods

This study is a randomized controlled trial that was performed during the 2018-2019 years. Forty patients with inguinal hernia and antiplatelet use were enrolled randomly into the two groups. In the intervention group, the patients received two injectable form (500mg/5 mL) of TXA, totally 10 mL as a topical application at the surgical site, and then the patient's surgical site was seen every 8 h for 48 h, and the patient was examined daily for one week.

Results

The mean length of hospitalization, seroma, hematoma and infection in the two groups were not statistically significant (P > 0.05). However, the duration of surgery in the TXA group was significantly shorter than in the control group (54.85 vs. 68.72 min) (P < 0.001). The mean bleeding during surgery was significantly lower in the TXA group than in the control group (P < 0.001).

Conclusion

The findings of present study indicate that topical TXA has a high ability to control bleeding. As a result, TXA is beneficial in terms of reducing bleeding and increasing the surgeon's satisfaction. Therefore, it is recommended that TXA be prescribed for patients requiring inguinal hernia surgery with a high risk of bleeding.

Society of Family Planning clinical recommendations: Management of individuals with bleeding or thrombotic disorders undergoing abortion

Individuals who have bleeding disorders, thrombophilias, a history of venous thromboembolism (VTE), or who are taking anticoagulation medication for other reasons may present for abortion. Clinicians should be aware of risk factors and histories concerning for excessive bleeding and thrombotic disorders around the time of abortion. This document will focus on how to approach abortion planning in these individuals. For first-trimester abortion, procedural abortion (sometimes called surgical abortion) is generally preferred over medical management for individuals with bleeding disorders or who are on anticoagulation. First-trimester procedural abortion in an individual on anticoagulation can generally be done without interruption of anticoagulation. The decision to interrupt anticoagulation for a second-trimester procedure should be individualized. Individuals at high risk for VTE can be offered anticoagulation post-procedure. Individuals with bleeding disorders or who are anticoagulated can safely be offered progestin intrauterine devices. Future research is needed to better assess quantitative blood loss and complications rates with abortion in these populations.

Perception of dental professionals towards dental management of patients using antithrombotic medications in Saudi Arabia: A cross-sectional survey

Objectives:

To assess dental professionals' perception and knowledge about dental management of patients on antithrombotics and determine if the treatment approach is according to the international guidelines.

Methods:

This cross-sectional survey was conducted in Saudi Arabia during January 2014-December 2015 and included licensed dentists and hygienists from different dental institutions and Saudi's annual dental conference attendees. Data were collected by using a self-administered questionnaire, with questions about dental management of patients on antithrombotics. Data analysis was done using Statistical Package for Social Sciences statistical software, version 22.

Results:

Of the 305 participants, 302 completed the survey (dentists: 94.7% and dental hygienists: 5.3%). For traditional antithrombotics, familiarity was higher for Warfarin and Aspirin compared to Clopidogrel. However, for new oral anticoagulants (NOACs), familiarity was significantly less for Rivaroxaban (P = 0.042). A significant number of participants responded that they were unsure as to how to treat patients [Enoxaparin (P < 0.001), Rivaroxaban (P < 0.037), and Dabigatran (P < 0.027)]. Furthermore, the management of patients on traditional or NOACs was not under guidelines (ranging: 8.2%-42.2%).

Conclusion:

Dental professionals have limited familiarity with antithrombotics, especially NOACs. Therefore, awareness about NOACs and their impact on dental procedures is needed among dentists in primary healthcare settings, to facilitate proper and timely management.

Evaluation of selected parameters of the coagulation system during the perioperative period in patients undergoing endoscopic surgery of the paranasal sinuses

INTRODUCTION

The aim of the study was to evaluate selected parameters of the coagulation system during the perioperative period in patients undergoing endoscopic sinus surgery.

MATERIAL AND METHODS

The study involved 121 patients: group I - 42 patients who did not receive anticoagulatory or antiplatelet medications, qualified for endoscopic sinus surgery under total intravenous anaesthesia (TIVA); group II - 40 patients who received in the perioperative period low-molecular-weight heparins, qualified for endoscopic sinus surgery under TIVA; group III - 39 patients diagnosed according to a schedule, due to vertigo or loss of hearing. All the patients received a full laryngological examination and detailed audiological and otoneurological diagnostics, and examination of selected haemostatic parameters before the surgery/diagnostics.

RESULTS

The analysis of concentrations of coagulation parameters in groups I and II revealed a statistically significantly higher international normalized ratio value before surgery (I - 1.11; II - 1.08) and 48 h following surgery (I - 1.15; II - 1.10) in group I. The concentration of coagulation factor VII in the study patients was considerably higher in group I for all three measurements (481.93; 443.13; 486.02). The concentration of fibrinogen (coagulation factor I) was significantly lower in group I before surgery (3.2) and at 6 h after surgery (2.84). A significantly lower level of von Willebrand factor was found in group I before surgery (2.94). Comparing test results of groups I and III, who did not receive antiaggregants, statistically significant differences were observed in both tests for factors VII and VIII.

CONCLUSIONS

Concentrations of von Willebrand factor and prothrombin revealed statistically significant differences in between groups.

Validation of an algorithm to predict decline in INR following warfarin cessation in patients undergoing invasive procedures

Patients on warfarin are required to withdraw from treatment for a fixed period (normally 5 days) prior to an invasive procedure. However, the anticoagulant effect of warfarin subsides at different rates among different patients, exposing some to increased risk of either thrombosis or bleeding. In a recent study in patients awaiting surgery, following warfarin cessation the INR declined slower over time in those with two CYP2C9 variant alleles, increasing age, weight and number of comorbidities and that INR decline was faster in those with higher maintenance INR value. Subsequently, we developed an algorithm which predicts INR decline in individual patients after 5 days of warfarin cessation. The current study validated the algorithm. An independent cohort of patients completing a short course of warfarin took part in the study. INR values for subsequent 9 days and CYP2C9 genotype were available. The predicted INR decline (INR_{day 1}–INR_{day 5}) was compared to the observed one (where an INR check on day 5 was unavailable, INR was estimated using a linear approximation model). There was a strong correlation between the decline in INR by day 5 and that predicted from the algorithm for the 117 patients (r = 0.949, p < 0.001). The algorithm was precise, with low degree of bias and variance of the prediction error. The algorithm can accurately predict the INR decline following warfarin cessation in individual adult patients. The use of this easily adoptable algorithm can reduce cancellation or delays of planned surgical procedures.

Image-Guided Percutaneous Gastrostomy Tube Placement is Safe in Patients Requiring Aspirin 325 mg

RATIONALE AND OBJECTIVES

Requests for gastrostomy tube placement in patients on aspirin (ASA) 325 mg are common, particularly in patients following reconstructive surgery for head and neck cancer, but periprocedural guidelines and recommendations regarding management of high dose aspirin are inconsistent. The purpose of this study was to assess the bleeding risk of percutaneous gastrostomy tube placement in patients on ASA 325 mg.

MATERIALS AND METHODS

This retrospective study of 213 patients who underwent image-guided "push" percutaneous gastrostomy tube placement compared rates of significant bleeding and other secondary outcomes (including all-cause mortality within 30 days, procedure-related mortality, bowel perforation, abdominal abscess, peritonitis, aspiration pneumonia, intraprocedural airway complications, and tube dislodgement) between patients maintained on ASA 325 mg and patients not on antiplatelet or anticoagulation therapy.

RESULTS

No significant bleeding episodes occurred in patients on ASA 325 mg, compared to three episodes in patients not on ASA 325 mg (p = 0.37). A patient in each group had aspiration pneumonia possibly related to tube placement. There were no other notable secondary outcomes, including intraprocedural airway complications in this population with complex head and neck anatomy.

CONCLUSION

These findings suggest that holding ASA 325 mg in patients undergoing percutaneous gastrostomy tube placement is not necessary, especially in patients in whom holding ASA would pose considerable risk. Further multi-institutional longitudinal study is warranted to validate these results.

Interruption of long-term warfarin is not necessary in patients undergoing total hip arthroplasty

Introduction

The management of anticoagulation in patients undergoing arthroplasty remains a challenge. Guidelines for perioperative management of long-term warfarin recommend discontinuation of warfarin preoperatively in low risk patients. We hypothesised that patients who had their warfarin continued during the perioperative period would have shorter hospital stay and no significant increase risk of surgical complications compared to patients who had their warfarin interrupted.

Methods

This was a retrospective review of 20 consecutive patients receiving long-term warfarin who underwent total hip replacement without stopping warfarin. As a control group, we collected same data from 20 age and gender matched patients also on long term warfarin but their warfarin was stopped prior to surgery and restarted postoperatively.

Results

There was no significant difference in age, BMI or comorbidities between the 2 groups. There was a statistically significant difference between the two groups in postoperative INR (P < 0.0001) levels. The mean drop in Hb postoperatively was 25.95 g/L in the warfarin group and 35.7 g/L in the control group, which was statistically significant (P = 0.0066). Hospital stay was statistically significant with shorted stay observed in the warfarin group (P = 0.0447). The odds ratio for developing a postoperative complication was 1.5882 which was not statistically significant (P = 0.6346).

Conclusion

Our results support the hypothesis that it is safe to continue warfarin in patients on long term anticoagulation undergoing total hip replacement. Continuation of warfarin was associated with significantly shorter hospital stay and less INR fluctuations. There was no significant increase in the risk of complications or blood transfusion.

WACEM Consensus Paper on Deep Venous Thrombosis after Traumatic Spinal Cord Injury

The risk and outcome of deep vein thrombosis (DVT) in patients who sustained spinal cord injury (SCI) remain a challenge. We aimed to assess the incidence, risk, burden, and prophylaxis of DVT after SCI. Thirty-nine studies were identified from among 250 relevant articles based on firstly, broad criterion of DVT among SCI cases. secondly, "risk factors" impacting DVT, thirdly, published reports from apex bodies of global importance such as World Health Organization, Centre for disease control, Atlanta USA, and others were given due weightage for their authenticity. SCI is characterized by loss of motor, sensory, and autonomic function with partial or total damage of the anatomical structure leading to increased risk of thrombogenesis. SCIs present a higher risk of venous DVT constituting 9.7% of deaths in the 1st year of follow-up. Currently, prophylaxis with mechanical methods, vena cava filters and antithrombotic chemoprophylaxis in SCI are interventions for the management of DVT. DVT in SCI patients is not uncommon and needs a high index of suspicion and implementation of institutional prophylaxis protocol.

A road to bring Brij52 back to attention: Shear stress sensitive Brij52 niosomal carriers for targeted drug delivery to obstructed blood vessels

Thrombosis is a shared perpetrating event in the pathophysiology of several cardiovascular disorders such as ischemic stroke, venous thromboembolism, atherosclerosis, and myocardial infarction. Despite holding a wide range of ammunition in our arsenal to ameliorate such conditions, we are still facing with many stumbling blocks in the satisfactory pharmacotherapy of cardiovascular diseases among which the risk of hemorrhage and life threatening drug interactions can be highlighted. Our hypothesis focuses on mimicking the nature of platelet activation, to design a novel targeted delivery system based on the alterations of a physical parameter, the hemodynamic shear stress, to aim at the offending thrombi in an attempt to offer a noninvasive, rapid, and monitoring-free method that not only can prolong the circulation time of the cargo, but also deliver it locally and reduce both the undesirable adverse effects and drug interactions. Brij52 is our chosen candidate due to its unique non-spherical morphology after forming a niosomal vesicle. We surmised that thanks to its non-spherical shape, diverse shear rates may generate different shear stresses to its equators and axes which might result in the breakdown or at least distortion of niosomal structure under elevated shear stress. The vesicles have to be synthesized in the size of platelets or in the nano-sized scale. In order to prolong the time vesicles are circulating in the blood, PEGylation may help and to make such carriers highly selective to be only activated during pathophysiological clot formation, attachment of domain A1 von Willebrand factor can be of benefit to lead this proposed delivery system to the site of thrombus formation where shear rate exceeds those of 1000 s^-1. There is now an emerging fast growing universal research on shear activated carriers, and the present theory is an endeavor to reach a successful treatment strategy to combat cardiovascular diseases based on the hypothesis that a non-spherical nano-carrier such as Brij 52 niosomal vesicle can be of paramount benefit to deliver current antithrombotic agents in a targeted and controlled manner in the presence of elevated shear stress of the obstructed blood vessels. With more radical advanced drug delivery systems being developed and new strategies being pursued, there will be more options in our arsenal to represent a promising avenue for achieving preventive, well-tolerated, and intelligent drug carriers to circumvent the drawbacks of antithrombotic pharmacotherapy.

Degarelix treatment is compatible with diabetes and antithrombotic therapy in patients with prostate cancer

Introduction

Therapeutically induced androgen deficiency (AD) is a standard treatment for patients with prostate cancer, but it is often associated with various adverse effects (AEs) that may lead to discontinuation. Some AEs may depend on the patient's health condition, while others may be due to complications of the drug delivery method. Degarelix is a gonadotropin-releasing hormone (GnRH) antagonist widely used for the treatment of androgen-dependent prostate cancer. This study aimed to ascertain the following: 1) the compatibility of degarelix treatment with diabetes and 2) any specific causal associations of degarelix injections with increased blood clotting and antithrombotic therapy requirements.

Patients and methods

The medical records of 162 patients with prostate cancer who had undergone degarelix treatment were retrospectively examined. The association of a medical history of diabetes and anticoagulant co-treatment with degarelix treatment discontinuation was analyzed statistically.

Results

Rapid and significant decreases in prostate-specific antigen (PSA) levels during the course of degarelix treatment were detected for patients with prostate cancer regardless of clinical state. During the 27 months of treatment, 68 subjects (48%) ceased degarelix treatment, owing to several reasons, mainly financial issues. Among these subjects, 19 had diabetes, while 35 were treated with antithrombotics. Extensive statistical analysis indicated that there were no causal associations between degarelix treatment discontinuation and preexisting diabetes or antithrombotic therapy.

Conclusion

Our study suggests that preexisting diabetes and antithrombotic therapy were not significant factors for the discontinuation of degarelix treatment in patients with prostate cancer.

Reversal of anticoagulants: an overview of current developments

Several new anticoagulants have entered the clinical arena or are under clinical development. These drugs include indirect (fondaparinux) and direct oral factor Xa inhibitors (rivaroxaban, apixaban, edoxaban, betrixaban), and the direct thrombin inhibitor dabigatran. Especially the oral direct FXa and FIIa inhibitors overcome many of the shortcomings of heparins and vitamin K antagonists (VKAs). They are administered orally at a fixed dose; regular monitoring is not necessary; interaction with other drugs or nutrition occur less than with VKAs and they are at least as effective as VKAs for most indications tested. They are associated with about 50 % less intracranial bleeding than VKAs. Nevertheless, they are still associated with bleeding complications. Bleeding can occur spontaneously or as a result of trauma or urgent surgery. In such situations rapid reversal of the anticoagulant effect is highly desirable. For unfractionated heparin protamine, and for VKAs prothrombin complex concentrates are available as specific antidotes. Under clinical development are: for the direct and indirect FXa inhibitors a modified recombinant FXa (andexanet alpha), which lacks enzymatic activity; and for dabigatran a Fab fragment of a monoclonal antibody (idarucizumab). In addition a small molecule (aripazine) has entered phase I clinical trials, which seems to inhibit nearly all anticoagulants but VKAs and argatroban. This review summarises the current options and strategies in development to antagonise anticoagulants with a focus on the status of the development of antidotes for the oral direct FXa and FIIa inhibitors.

Valvular heart disease and anaesthesia

Valvular heart disease presents as mixed spectrum lesion in healthcare settings in the third-world and developing countries. Rheumatic heart disease still forms the bulk of the aetiopathology of valve lesions. Mitral and aortic valve lesions top the list of valvular pathology. A thorough understanding of the pathophysiology of valvular heart disease is essential while planning anaesthesia and perioperative care for such patients. Meticulous use of optimal fluids, close monitoring of the changing haemodynamics and avoidance of situations that can cause major reduction of cardiac output and fluid shifts are mandatory to achieve good clinical outcome. We searched MEDLINE using combinations of the following: anaesthesia, aortic, mitral, regurgitation, stenosis and valvular heart disease. We also hand searched textbooks and articles on valvular heart disease and anaesthesia. This article mainly focuses on the understanding the pathophysiology of valvular heart disease in patients presenting for non-cardiac surgeries in secondary and tertiary care setting.

Unnecessary overuse. Study of "inadvisable practices" for patients with atrial fibrillation

OBJECTIVE

To identify overuse (diagnostic, therapeutic and self-care practices that represent risks that outweigh the potential benefits) in patients with atrial fibrillation.

METHOD

The study was based on qualitative research techniques. Using the "Metaplan" technique, we identified and ordered potentially inappropriate, ineffective and inefficient practices. By means of a consensus conference, we then established a number of "inadvisable practice" measures (relatively common practices that should be eliminated based on the scientific evidence or clinical experience). Professionals from the specialties of cardiology, haematology, neurology, internal medicine, family medicine and nursing participated in the consensus.

RESULTS

We developed a catalogue of 19 "inadvisable practices" related to the diagnosis, treatment and care of anticoagulated patients that were inappropriate, had questionable effectiveness or were ineffective, as well as 13 beliefs or behaviours for anticoagulated patients that could result in injury or were useless or inefficient.

CONCLUSION

The "inadvisable practices" approach helps identify practices that represent greater risks than benefits for patients. It seems appropriate to include algorithms in the clinical decision-making support systems that consider this information for the diagnosis, treatment and for home care. For this last case, recommendations have also been prepared that define specific contents for the healthcare education of these patients.

Deep Vein Thrombosis and Pulmonary Embolism Considerations in Orthopedic Surgery

Patients undergoing orthopedic surgery have an increased risk for deep venous thrombosis (DVT) and pulmonary embolism (PE). These complications are considered detrimental, as they cause major postoperative morbidity and mortality and lead to a substantial health care burden. Because of the high incidence and serious nature of these complications, it is essential for orthopedic surgeons to have a comprehensive knowledge of the risk factors, diagnosis, and treatment of acute DVT and PE. Perioperative management of orthopedic patients to prevent postoperative DVT and PE and optimize postoperative outcomes is also discussed in this review.

Generation of an anti-Dabigatran Monoclonal Antibody and Its Use in a Highly Sensitive and Specific Enzyme-Linked Immunosorbent Assay for Serum Dabigatran

BACKGROUND

Dabigatran (DT) is a direct thrombin inhibitor used to prevent venous and arterial thromboembolism due to atrial fibrillation. DT is the active form of the commercially available prodrug DT etexilate. Although DT has many clinical advantages over warfarin, it increases the incidence of bleeding in patients with renal dysfunction. Circulating levels of DT are increased in such patients because it is mainly eliminated by renal excretion. Therapeutic drug monitoring may therefore help to prevent adverse DT effects, but no method for measuring circulating DT levels has been reported, except for an analysis by liquid chromatography-tandem mass spectrometry. This study sought to develop a novel enzyme-linked immunosorbent assay (ELISA) to measure DT concentrations.

METHODS

Mice were immunized with a DT-keyhole limpet hemocyanin conjugate to generate an anti-DT antibody. Immunized mouse splenocytes and myeloma cells (SP2/0) were fused to obtain an anti-DT monoclonal antibody (DT-mAb). DT-mAb and DT solutions were added to microplate wells coated with a DT-human serum albumin conjugate. DT concentrations were determined based on the principles of ELISA.

RESULTS

DT-mAb was successfully purified from a hybridoma, and the competitive ELISA developed using this DT-mAb could evaluate DT concentrations ranging from 7.8 to 125 ng/mL. The ELISA signal was not linear using DT-spiked serum; however, it was linear when serum ultrafiltrate was used. Weak cross-reactivity with DT etexilate was detected, but no cross-reactivity was observed with other structurally related drugs or drugs commonly used for the treatment of atrial fibrillation.

CONCLUSIONS

The developed competitive ELISA is a valuable and specific tool to analyze free DT in serum ultrafiltrate for therapeutic drug monitoring and pharmacokinetic studies.

Risk stratification, perioperative and periprocedural management of the patient receiving anticoagulant therapy

As a result of the aging US population and the subsequent increase in the prevalence of coronary disease and atrial fibrillation, therapeutic use of anticoagulants has increased. Perioperative and periprocedural management of anticoagulated patients has become routine for anesthesiologists, who frequently mediate communication between the prescribing physician and the surgeon and assess the risks of both thromboembolic complications and hemorrhage. Data from randomized clinical trials on perioperative management of antithrombotic therapy are lacking. Therefore, clinical judgment is typically needed regarding decisions to continue, discontinue, bridge, or resume anticoagulation and regarding the time points when these events should occur in the perioperative period. In this review, we will discuss the most commonly used anticoagulants used in outpatient settings and discuss their management in the perioperative period. Special considerations for regional anesthesia and interventional pain procedures will also be reviewed.

Image-guided intervention in the coagulopathic patient

Determining practice parameters for interventional procedures is challenging due to many factors including unreliable laboratory tests to measure bleeding risk, variable usage of standardized terminology for adverse events, poorly defined standards for administration of blood products, and the growing numbers of anticoagulant and antiplatelet medications. We aim to address these and other issues faced by radiologists performing invasive procedures through a review of available literature, and experiential guidance from three academic medical centers. We discuss the significant limitations with respect to using prothrombin-time and international normalized ratio to measure bleeding risk, especially in patients with synthetic defects due to liver function. Factors affecting platelet function including the impact of uremia; recent advances in laboratory testing, including platelet function testing; and thromboelastography are also discussed. A review of the existing literature of fresh-frozen plasma replacement therapy is included. The literature regarding comorbidities affecting coagulation including malignancy, liver failure, and uremia are also reviewed. Finally, the authors present a set of recommendations for laboratory thresholds, corrective transfusions, as well as withholding and restarting medications.

Hemostatic management of patients undergoing ear-nose-throat surgery

Perioperative hemostatic management is increasingly important in the field of otolaryngology. This review summarizes the key elements of perioperative risk stratification, thromboprophylaxis and therapies for bridging of antithrombotic treatment. It gives practical advice based on the current literature with focus on patients undergoing ENT surgery.

Rivaroxaban in the Prevention of Stroke and Systemic Embolism in Patients with Non-Valvular Atrial Fibrillation: Clinical Implications of the ROCKET AF Trial and Its Subanalyses

Atrial fibrillation (AF) is an increasingly common cause of stroke and systemic embolism. While warfarin has been the mainstay of stroke prevention in patients with AF, newer novel oral anticoagulant medications are now available. Rivaroxaban, a direct factor Xa inhibitor with a rapid onset and offset after oral administration, offers potential advantages over warfarin, predominantly due to its predictable pharmacokinetics across wide patient populations. It requires no coagulation monitoring, and only two different doses are needed (20 mg daily for patients with normal renal function and 15 mg daily in those with reduced renal function). A large randomized trial (ROCKET AF) has shown non-inferiority to warfarin for preventing stroke or systemic embolism in the per-protocol population and superiority to warfarin in the on-treatment safety population. Several subanalyses confirm that the treatment effect of rivaroxaban is consistent across different patient subgroups, including those with reduced renal function. The tolerability of rivaroxaban appears similar to that of warfarin, with comparable overall bleeding rates in clinical trials. In ROCKET AF, significantly lower rates of fatal and intracranial bleeding were seen with rivaroxaban, while lower rates of gastrointestinal bleeding were seen with warfarin. Important contraindications to rivaroxaban include valvular AF, the presence of a prosthetic valve (mechanical or bioprosthetic) or valve repair, the need for concurrent dual antiplatelet therapy, and creatinine clearance <30 ml/min. Once-daily dosing and the lack of coagulation monitoring may increase utilization and adherence compared with warfarin, potentially decreasing the large burden of care associated with stroke secondary to AF. Overall, rivaroxaban offers a useful alternative to warfarin for stroke prevention in patients with AF.

Management of Anticoagulant and Antiplatelet Medications in Adults Undergoing Percutaneous Interventions

OBJECTIVE

Many radiologists are unfamiliar with the new antithrombogenic medications and how to modify patient management before nonvascular percutaneous procedures performed in a radiology department. In this article, we review the indications for use, mechanism of action, pharmacokinetics, dosing, and recommendations for periprocedural management of patients using these medications.

CONCLUSION

To improve patient safety, radiologists involved in percutaneous procedures should have knowledge of the antithrombotics that will be encountered routinely in clinical practice.

Estimation of dabigatran plasma concentrations in the perioperative setting. An ex vivo study using dedicated coagulation assays

The perioperative management of dabigatran is challenging, and recommendations based on activated partial thromboplastin time (aPTT) and thrombin time (TT) are unsatisfactory. Dedicated coagulation tests have limitations at plasma concentrations < 50 ng/ml. Therefore, a more sensitive test, which is available 24/7, is required. It was the aim of this study to investigate the performance of the Hemoclot Thrombin Inhibitors® LOW (HTI LOW) kit, a diluted thrombin time, and the STA® - ECA II(ECA-II) kit, a chromogenic variant of the ecarin clotting time, that were developed to measure low dabigatran concentrations, compared to reference dabigatran analysis by liquid chromatography tandem mass-spectrometry (LC-MS/MS). This study included 33 plasma samples from patients treated with dabigatran etexilate who had plasma concentrations < 200 ng/ml. HTI LOW and ECA-II were performed along with HTI, aPTT (STA®-C. K.Prest® and SynthasIL®) and TT (STA® - Thrombin). All procedures were performed according to recommendations by the manufacturers. Linear (or curvilinear) correlations and Bland-Altman analyses were calculated. For free dabigatran concentrations < 50 ng/ml, the R² of linear correlations were 0.69, 0.84 and 0.61, with HTI, HTI LOW and ECA-II, respectively. The R² for TT, STA®-C. K.Prest® and SynthasIL® were 0.67, 0.42 and 0.15. For HTI, HTI LOW and ECA-II, Bland-Altman analyses revealed mean differences of -6 ng/ml (95 %CI: -25-14 ng/ml), 1 ng/ml (95 %CI: -18-19 ng/ml) and -1 ng/ml (95 %CI: -25-23 ng/ml), demonstrating that tests dedicated to measuring low concentrations are more accurate than HTI. In conclusion, the use of HTI LOW or ECA-II to assess low plasma dabigatran concentrations is supported by our findings.

Antiphospholipid syndrome in renal transplantation

Antiphospholipid syndrome (APS) may occur in isolation or in association with systemic lupus erythematosus (SLE), with the potential to cause renal failure via several distinct pathologies. Renal transplantation in the presence of APS carries a risk of early graft loss from arterial or venous thrombosis, or thrombotic microangiopathy (TMA). Whilst perioperative anticoagulation reduces the risk of large vessel thrombosis, it may result in significant haemorrhage, and its efficacy in preventing post-transplant TMA is uncertain. Here, we report a patient with end-stage kidney disease (ESKD) due to lupus nephritis and APS, in whom allograft TMA developed soon after transplantation despite partial anticoagulation. TMA resolved with plasma exchange-based therapy albeit with some irreversible graft damage and renal impairment. We discuss the differential diagnosis of post-transplant TMA, and current treatment options.

Traumatic intracranial hemorrhage correlates with preinjury brain atrophy, but not with antithrombotic agent use: a retrospective study

BACKGROUND

The impact of antithrombotic agents (warfarin, clopidogrel, ASA) on traumatic brain injury outcomes is highly controversial. Although cerebral atrophy is speculated as a risk for acute intracranial hemorrhage, there is no objective literature evidence.

MATERIALS AND METHODS

This is a retrospective, consecutive investigation of patients with signs of external head trauma and age ≥60 years. Outcomes were correlated with antithrombotic-agent status, coagulation test results, admission neurologic function, and CT-based cerebral atrophy dimensions.

RESULTS

Of 198 consecutive patients, 36% were antithrombotic-negative and 64% antithrombotic-positive. ASA patients had higher arachidonic acid inhibition (p = 0.04) and warfarin patients had higher INR (p<0.001), compared to antithrombotic-negative patients. Antithrombotic-positive intracranial hemorrhage rate (38.9%) was similar to the antithrombotic-negative rate (31.9%; p = 0.3285). Coagulopathy was not present on the ten standard coagulation, thromboelastography, and platelet mapping tests with intracranial hemorrhage and results were similar to those without hemorrhage (p≥0.1354). Hemorrhagic-neurologic complication (intracranial hemorrhage progression, need for craniotomy, neurologic deterioration, or death) rates were similar for antithrombotic-negative (6.9%) and antithrombotic-positive (8.7%; p = 0.6574) patients. The hemorrhagic-neurologic complication rate was increased when admission major neurologic dysfunction was present (63.2% versus 2.2%; RR = 28.3; p<0.001). Age correlated inversely with brain parenchymal width (p<0.001) and positively with lateral ventricular width (p = 0.047) and cortical atrophy (p<0.001). Intracranial hemorrhage correlated with cortical atrophy (p<0.001) and ventricular width (p<0.001).

CONCLUSIONS

Intracranial hemorrhage is not associated with antithrombotic agent use. Intracranial hemorrhage patients have no demonstrable coagulopathy. The association of preinjury brain atrophy with acute intracranial hemorrhage is a novel finding. Contrary to antithrombotic agent status, admission neurologic abnormality is a predictor of adverse post-admission outcomes. Study findings indicate that effective hemostasis is maintained with antithrombotic therapy.

Pharmacology and safety of new oral anticoagulants: the challenge of bleeding persists

New oral anticoagulants (NOACs) are increasingly replacing vitamin K antagonists and older parenteral agents in clinical practice. NOACs offer several advantages compared with standard agents, including rapid onset of action, fixed dosing, and no requirement for routine coagulation monitoring. However, like all anticoagulants, NOACs carry a risk of bleeding. Here, we discuss the pharmacology and safety of NOACs, with particular emphasis on the risks of bleeding associated with NOACs versus standard anticoagulants, and we provide an overview of current bleeding management strategies.

New oral anticoagulants in practice: pharmacological and practical considerations

Although highly effective, warfarin use is complicated by its unpredictable narrow therapeutic window, genetic heterogeneity in pharmacokinetic response, numerous food and drug interactions, and the need for regular international normalized ratio (INR) monitoring. Currently, several novel oral anticoagulant (NOAC) drugs (dabigatran, rivaroxaban, apixaban) are available on the market as alternatives to warfarin. These agents all feature more predictable pharmacodynamic and pharmacokinetic properties than warfarin. Additionally, the NOACs do not require routine monitoring of coagulation parameters, and have a relatively lower potential for interactions with drug, herb, and dietary constituents, which enhances the convenience of management for both patients and health professionals alike. However, there are other considerations regarding the use of NOACs that must be taken into account during management of therapy. In contrast to warfarin, most NOACs need dosage adjustments in renal impairment and are contraindicated in severe liver impairment, and there are no specific antidotes for treating NOAC-related over-anticoagulation. The more frequent dosing needed for NOACs may reduce adherence, especially in elderly patients with polypharmacy. Furthermore, NOACs, especially dabigatran, are not as well tolerated as warfarin in patients with gastrointestinal diseases. Overall, the availability of the NOACs has expanded the treatment armamentarium, but they are not without risk. Given the limited experience with the NOACs, their limited range of indications, and their cost, the characteristics of each anticoagulant must be carefully considered to carefully select the agent that will provide the optimal risk/benefit profile in the individual patient.

Patients with disorders of thrombosis and hemostasis

Surgery, by definition, is a challenge to the hemostatic system. In addition, a surgical procedure may provoke inappropriate venous or arterial thrombosis, such as is suggested historically by Virchow's Triad. For these reasons, proper functioning of the hematologic system is integral in a successful and safe perioperative period. Patients with a disorder of either coagulation or hemostasis, therefore, present an exciting challenge to the preoperative physician. Diagnosis of a hematologic disorder may be more or less occult. A proper bleeding and clotting history can serve to elucidate such a disorder and is therefore paramount to the preoperative workup. For those patients with a previously diagnosed disorder of the hematologic system, appropriate laboratory investigation and a concise therapeutic plan for the day of surgery can help to minimize risks in the perioperative period.

Laboratory assessment of rivaroxaban: a review

Research into new anticoagulants for preventing and treating thromboembolic disorders has focused on targeting single enzymes in the coagulation cascade, particularly Factor Xa and thrombin, inhibition of which greatly decreases thrombin generation. Based on the results of phase III clinical trials, rivaroxaban, a direct Factor Xa inhibitor, has been approved in many countries for the management of several thromboembolic disorders. Owing to its predictable pharmacokinetic and pharmacodynamic characteristics, fixed-dose regimens are used without the need for routine coagulation monitoring. In situations where assessment of rivaroxaban exposure may be helpful, anti-Factor Xa chromogenic assays (in tandem with standard calibration curves generated with the use of rivaroxaban calibrators and controls) could be used. It is important to note that test results will be affected by the timing of blood sampling after rivaroxaban intake. In addition, the anti-Factor Xa method measures the drug concentration and not the intensity of the drug’s anticoagulant activity, and a higher than expected rivaroxaban plasma level does not necessarily indicate an increased risk of bleeding complications. Therefore, clinicians need to consider test results in relation to the pharmacokinetics of rivaroxaban and other patient risk factors associated with bleeding.

Advanced drug delivery systems for antithrombotic agents

Despite continued achievements in antithrombotic pharmacotherapy, difficulties remain in managing patients at high risk for both thrombosis and hemorrhage. Utility of antithrombotic agents (ATAs) in these settings is restricted by inadequate pharmacokinetics and narrow therapeutic indices. Use of advanced drug delivery systems (ADDSs) may help to circumvent these problems. Various nanocarriers, affinity ligands, and polymer coatings provide ADDSs that have the potential to help optimize ATA pharmacokinetics, target drug delivery to sites of thrombosis, and sense pathologic changes in the vascular microenvironment, such as altered hemodynamic forces, expression of inflammatory markers, and structural differences between mature hemostatic and growing pathological clots. Delivery of ATAs using biomimetic synthetic carriers, host blood cells, and recombinant fusion proteins that are activated preferentially at sites of thrombus development has shown promising outcomes in preclinical models. Further development and translation of ADDSs that spare hemostatic fibrin clots hold promise for extending the utility of ATAs in the management of acute thrombotic disorders through rapid, transient, and targeted thromboprophylaxis. If the potential benefit of this technology is to be realized, a systematic and concerted effort is required to develop clinical trials and translate the use of ADDSs to the clinical arena.

Tutorial in oral antithrombotic therapy: biology and dental implications

Objectives: Recent developments of new direct oral anticoagulants that target specific clotting factors necessitate understanding of coagulation biology. The objective of this tutorial is to offer dental professionals a review of coagulation mechanisms and the pharmacodynamics of the conventional and new oral anticoagulants. Also, we summarized the dental implications of the conventional and new anticoagulants. Method: We searched Medline using search terms “antithrombotic”, “antihemostasis” or “anticoagulation” and combined them with the search results of “dental”, “oral surgery” or “periodontal”. We restricted the results to “human” and “English”. Results: The early coagulation cascade, the new cell-based coagulation model, the pharmacokinetics and pharmacodynamics of conventional antithrombotics, and new oral anticoagulants were reviewed. The new direct factor Xa inhibitors and the direct thrombin inhibitor (s), called direct oral anticoagulants (DOAs) have rapid onset of action, fast elimination on cessation, and fewer drug-drug or drug-food interactions than warfarin. However, the lack of antidotes raises concerns that some dental procedures may trigger serious hemorrhagic events. Additionally, careful perioperative withdrawal and resumption protocols for the DOAs are reviewed, because DOAs’ blood levels are dependent on renal function. Also, various reversal strategies in the event of excessive bleedings are summarized. Perioperative management of dental patients taking new DOAs and conventional oral anticoagulants are also discussed. However, the perioperative strategies for DOAs are yet to be validated in randomized trials.

Key words:Coagulation cascade, cell-based coagulation model, factor Xa inhibitors, direct thrombin inhibitors, prothrombin complex concentrates.