Antithrombotic therapy for venous thromboembolic disease

The historical origins of modern international normalized ratio targets

Prothrombin time (PT) and its derivative international normalized ratio (INR) are frequently ordered to assess the coagulation system. Plasma transfusion to treat incidentally abnormal PT/INR is a common practice with low biological plausibility and without credible evidence, yet INR targets appear in major clinical guidelines and account for the majority of plasma use at many institutions. In this article, we review the historical origins of INR targets. We recount historical milestones in the development of the PT, discovery of vitamin K antagonists (VKAs), motivation for INR standardization, and justification for INR targets in patients receiving VKA therapy. Next, we summarize evidence for INR testing to assess bleeding risk in patients not on VKA therapy and plasma transfusion for treating mildly abnormal INR to prevent bleeding in these patients. We conclude with a discussion of the parallels in misunderstanding of historic PT and present-day INR testing with lessons from the past that might help rationalize plasma transfusion in the future.

The Risk Factors for New-Onset Calf Muscle Venous Thrombosis after Hip Fracture Surgery

BACKGROUND

Calf muscle venous thrombosis (CMVT) is among the most important medical complications after hip surgery. CMVT has been known for many years, but many opinions about the incidence and risk factors of CMVT are still controversial. The objective of this retrospective study was to investigate the incidence and associated risk factors of postoperative CMVT in patients with hip fractures.

METHODS

Patients with hip fractures from January 2020 to April 2022 (n = 320) at Shenzhen Second People's Hospital were recruited in this study. The personal characteristics and clinical data of CMVT and no-CMVT patients were compared and analyzed. Binary logistic regression analyses were performed to identify potential risk factors of CMVT in patients with hip fractures. Finally we performed a receiver operating characteristic (ROC) curve analysis to compare the diagnostic values of different variables.

RESULTS

The overall incidence of new-onset CMVT in patients with hip fractures was 18.75% (60 of 320). Among the 60 CMVT patients, 70% (42 of 60) were diagnosed with femoral neck fractures, 28.3% (17 of 60) with intertrochanteric fractures, and 1.7% (1 of 60) with subtrochanteric fractures. No pulmonary embolism (PE) occurred. High preoperative D-dimer (OR = 1.002, 95%CI 0.97-1.03), sex (OR = 1.22, 95%CI 0.51-2.96), the caprini score (OR = 2.32, 95%CI 1.05-5.16) and the waterlow score (OR = 1.077, 95%CI 0.35-3.36) significantly increased the risk of developing postoperative new-onset CMVT.

CONCLUSIONS

CMVT has become a common clinical disease, and its harm should not be underestimated. Our study found that D-dimer, sex, the caprini score and the waterlow score were independent risk factors for postoperative CMVT. According to our clinical work, we should pay attention to identifying the risk factors of CMVT formation and targeted intervention measures to prevent new-onset CMVT.

The effects of anticoagulant therapy re-initiation after gastrointestinal bleeding: A systematic review and meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Long-term anticoagulant/antithrombotic therapy is widely used for the management of thromboembolic conditions. Gastrointestinal bleeding is a common collateral manifestation of anticoagulant/antithrombotic therapy that complicates its administration. The continuation or discontinuation of anticoagulant/antithrombotic therapy after an episode of gastrointestinal bleeding has been a matter of debate. Despite recent positive reports from retrospective cohort studies suggesting a reduction in morbidity- and mortality-related outcomes with continued administration of anticoagulant/antithrombotic agents (even after gastrointestinal bleeding), no consensus or comparisons about the efficacies of continued or discontinued antithrombotic administration exist. Therefore, we developed this current state-of-evidence analysis evaluating the comparative effects of continuation and discontinuation of anticoagulant/antithrombotic drugs after gastrointestinal bleeding on the overall incidences of gastrointestinal bleeding, thromboembolic events and mortality events.

METHODS

We performed a systematic academic literature search according to the PRISMA guidelines across five databases: Web of Science, Embase, CENTRAL, Scopus and MEDLINE. Moreover, we conducted a random effect meta-analysis to compare the effects of continuation and discontinuation of anticoagulant/antithrombotic drugs after an event of gastrointestinal bleeding on the overall incidences of gastrointestinal bleeding, thromboembolic events and mortality events.

RESULTS

We found seven eligible studies (from 1397 candidates) with 2532 participants (mean age, 73.1 ± 4.1 years). Our meta-analysis revealed lower odds of thromboembolic events (OR, -0.21), mortality outcomes (OR, -0.39) and an increase in the incidence of gastrointestinal bleeding (OR, 2.4) in the group with continued anticoagulant/antithrombotic therapy than in the group discontinuing the therapy.

WHAT IS NEW AND CONCLUSION

We provide an updated evidence on the comparative effects between continuation and discontinuation of anticoagulant/antithrombotic drugs after gastrointestinal bleeding events based on the overall incidences of gastrointestinal bleeding, thromboembolic events and mortality events. This study reports confirm an overall lower incidence of thromboembolic events and mortality outcomes for the continuation group than for the discontinuation group.

Minidose Warfarin and Failure to Prevent Deep Vein Thrombosis After Joint Replacement Surgery Despite Inhibiting the Postoperative Rise in Plasminogen Activator Inhibitor Activity

In a prospective randomised study in patients undergoing elective total hip or knee replacement surgery, the antithrombotic efficacy of fixed-minidose warfarin (1 mg daily commenced 7 days before surgery) was compared with that of subcutaneous calcium heparin (Calciparine, 5,000 IU t.d.s. commenced 2 h before surgery). Both regimens were continued until venography of the operated limb was performed 9-14 days postsurgery. Venographically detected deep vein thromboses (DVTs) occurred in 15 of the 31 patients (48.4%) in the minidose warfarin group and in eight of the 37 patients (21.6%) receiving heparin. The absolute difference in the incidence of DVT was 26.8% in favour of heparin (95%l confidence interval [CI] -4.&--48.8%; p = 0.039). Proximal DVTs were detected in three patients receiving minidose warfarin and in none of those on heparin (p = 0.09). Minidose warfarin appeared to prevent the postoperative rise in the activity of plasminogen activator inhibitor (PAI) that occurred with heparin, although preoperative PAI activity was greater in the warfarin group. The prothrombin time (PT) and activated partial thromboplastin time (APTT) were within the normal range on the day of surgery in both treatment groups. Postsurgery, the minidose warfarin regimen produced a small, but significant prolongation of the PT compared with the group receiving heparin, In contrast to heparin, 1 mg warfarin daily failed to prevent postoperative acceleration of the APTT. There was no significant difference between the two regimens in bleeding complications. In conclusion, the fixed-minidose warfarin regimen cannot be recommended for prevention of DVT after hip or knee replacement surgery. Inhibition of the postoperative rise in PAI activity appears not to protect against DVT after major joint replacement surgery. Key Words: Warfarin—Heparin—Deep vein thrombosis prophylaxis—Coagulation—Fibrinolysis— Plasminogen activator inhibitor.

Update on the diagnosis and management of pulmonary embolism

Pulmonary embolism (PE) is a common and often fatal disease. In the US, an estimated 40-53 people per 100,000 are diagnosed with PE annually and approximately 60,000 die from the disease. Diagnosis is difficult because symptoms are non-specific; however, a quick and accurate diagnosis is critical because, with appropriate therapy, the risk of recurrent (and potentially fatal) PE can be greatly reduced. Recent publication of prediction rules and improved non-invasive diagnostic tools have simplified diagnostic algorithms for PE. The efficacy of the standard treatment for PE, initial administration of continuous i.v. unfractionated heparin overlapped with long-term oral anticoagulation, is well established. However, newer treatment options such as low-molecular-weight heparins and the pentasaccharides may offer similar efficacy with improved convenience.

The evolution and impact of the American College of Chest Physicians consensus statement on antithrombotic therapy

The evolution of the American College of Chest Physicians consensus on antithrombotic therapy is reviewed, specifically with regard to the prevention and treatment of venous thromboembolism and the rules of evidence applied. A perspective on the impact of the recommendations is offered.

Integrated analysis of thrombotic/vascular event occurrence in epoetin alfa-treated patients undergoing major, elective orthopedic surgery

Data from four prospective, multicenter, randomized studies involving 869 major, elective orthopedic surgery patients were examined by means of a retrospective integrated analysis to evaluate whether perioperative Epoetin alfa use was associated with the occurrence of thrombotic/vascular events. The incidence of thrombotic/vascular events was similar between 619 patients treated with Epoetin alfa and 250 patients receiving placebo (7.4% versus 8.0%, respectively). Regression analyses identified age, cardiac history, hypertension, and cardiac medications, but not Epoetin alfa, as risk factors for thrombotic/vascular events. The analysis did not implicate an increase in the rate of rise in hematocrit or maximum hematocrit obtained prior to surgery as contributors to thrombotic events. Thus, Epoetin alfa, which enhances preoperative erythropoiesis and increases hematocrit, did not affect the probability of thrombotic/vascular events.

Anticoagulation therapy in patients with venous thromboembolic disease

OBJECTIVE

To determine, in a representative sample of patients drawn from a variety of hospitals, the degree of adherence to consensus recommendations for anticoagulation among patients with deep vein thrombosis or pulmonary embolism.

DESIGN

Cross-sectional review of a population-based random sample.

SETTING

Twenty-one randomly selected Pennsylvania hospitals.

PATIENTS

Of 357 randomly selected Medicare beneficiaries discharged from study hospitals with a diagnosis of deep venous thrombosis or pulmonary embolism during 1992, 43 charts were not reviewed for administrative reasons, 31 were miscoded or not treated with intravenous administration of heparin, and 13 were excluded for other reasons, leaving 270 in the final sample.

MEASUREMENTS AND MAIN RESULTS

Overall, 179 patients (66%, 95% confidence interval [CI] 59%, 72%) received therapeutic anticoagulation (two consecutive partial thromboplastin times more than 1.5 times control) within 24 hours of starting heparin. Platelet counts were checked at least once during the first week of heparin therapy in 66% (95% CI 58%, 74%). At least 5 days of heparin therapy was given to 84% (95% CI 79%, 87%). Among 266 (99%) of the patients receiving warfarin, 193 (72%; 95% CI 63%, 80%) received heparin until the prothrombin time ratio or International Normalized Ratio was therapeutic. Patients who were started on warfarin therapy within 2 days of heparin had decreased length of stay (geometric mean 8.2 vs 9.7 days, p = .003). Compliance varied among hospitals.

CONCLUSIONS

In a wide variety of hospitals, we found fair, but variable, compliance with consensus recommendations for anticoagulation of patients with venous thromboembolic disease. Simple interventions to improve compliance with these recommendations might improve quality of care and reduce costs.

Preoperative assessment of older adults

Caring for older patients who need surgery presents challenging medical situations. The clinical paradigm involves identifying coexisting disease, defining the urgency of the intervention, and predicting postoperative complications based on the type of surgery planned. The prime function of the medical consultant is searching for correctable medical conditions. The consultant must carefully identify coexisting and comorbid conditions. Emergency surgery should be avoided, if possible, by elective planning. The risk of surgery varies with the procedure. Non-body cavity surgery, with the exception of hip fracture repair, is usually tolerated well. Age is a risk factor for surgery, but coexisting disease is more important than age alone. The net effect of improvements in surgical outcome advances the age at which surgical risk becomes prohibitive.

Conformance of clinical practice to established recommendations for the diagnosis and treatment of venous thromboembolic disease: Robin revisited

Over a decade ago, Dr. Robin expressed concern regarding overdiagnosis and overtreatment of pulmonary embolism. Since that time, significant advances have been forthcoming in the diagnosis and treatment of venous thromboembolic disease. Using Continuous Quality Improvement concepts, this study revisits Robin's concerns and assesses the conformance of clinical practice at one institution with established requirements for the diagnosis and treatment of venous thromboembolic disease to identify remaining opportunities to improve care. The study design is a retrospective chart review. Medical records of all patients (N = 63) discharged from a university-affiliated teaching hospital from 7/1/89 to 6/30/90 with a diagnosis of primary venous thromboembolic disease were studied. Requirements for the diagnosis and treatment were established through review of the medical literature. Conformance to these requirements was assessed and described. Descriptive statistics were used. Only 7 of 63 charts (11%) met all requirements for the diagnosis and treatment of venous thromboembolic disease. Fifty-six charts (89%) failed to meet at least one criterion. There was no evidence of overdiagnosis of venous thromboembolic disease in patients with a discharge diagnosis of pulmonary embolism (N = 17). Eight of 62 patients (13%) demonstrated potential overdiagnosis of venous thromboembolic disease involving the lower extremities. Nine of 60 (15%) heparin therapies demonstrated significant nonconformance to recommendations. Fifty-four of 59 (91%) warfarin therapies failed to conform to recommendations. Eighty-three percent of these warfarin errors were considered to be technical. However, 17% were determined to be clinically significant. Of 5 patients treated with a transvenous filter device, 1 failed to meet therapeutic requirements. No patients received thrombolytic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Cause of death in an emergency department

A retrospective review was done of 601 consecutive emergency department deaths. Nontrauma causes accounted for 77% of the deaths and this group had an average age of 64 years and a male to female ratio of 1.9:1. Trauma caused 23% of the fatalities and this group had a younger average age of 29 years and a male to female ratio of 4.6:1. The most common causes of nontrauma death were sudden death of uncertain cause (34%), coronary artery disease (34%), cancer (5%), other heart disease (4%), chronic obstructive lung disease (3%), drug overdose (3%), and sudden infant death syndrome (2%). The most common causes of trauma death were motor vehicle accidents (61%) and gunshot wounds (16%). The overall autopsy rate was 40%. Death certificates were often in error.

Dose- and shear rate-dependent effects of heparin on thrombogenesis induced by rabbit aorta subendothelium exposed to flowing human blood

The effect of heparin on thrombogenesis induced by the subendothelium of rabbit aorta was investigated in 24 healthy volunteers after intravenous injection of different doses (0, 1000, 2500, and 5000 IU). By using an ex vivo perfusion chamber system, the interaction between flowing blood and exposed subendothelium was measured at low (50 s-1), intermediate (650 s-1), and high (2600 s-1) wall shear rates. The low shear rate simulated blood flow in venous, the intermediate shear rate in arterial, and the high shear rate in small or stenosed arterial vessels. Deposition of fibrin, platelets, and platelet thrombi on vascular subendothelium (SE) was quantified by morphometrical and immunological techniques. Fibrin deposition prevailed at low shear rates and was only minimal at high shear rates (30 +/- 1% vs. 1 +/- 0.4% coverage of SE with fibrin, means +/- SEM, p less than 0.001). In contrast, the interaction of platelets with SE was more intense at high compared to low shear rates, as indicated by higher platelet adhesion (54 +/- 5% vs. 4 +/- 1% coverage of SE with platelets, p less than 0.001) and platelet thrombus volumes (4.8 +/- 1.3 vs. 0.5 +/- 0.1 microns 3/microns 2, p less than 0.001). Fibrin deposition on SE was inhibited by heparin in a dose-dependent manner and was abolished after high doses. In addition, high doses of heparin reduced the height and volume of platelet thrombi at low and intermediate wall shear rates, but no effect was found at the high shear rate. Our data show that heparin inhibits the formation of both fibrin and platelet thrombi on vascular subendothelium. The lack of effect of heparin on platelet thrombus formation at high shear rates indicates that thrombin modulates the growth rate and/or stability of platelet thrombi at low and intermediate shear rates, whereas additional factors may control platelet thrombus growth and stability at high shear conditions.

Prevention of venous thrombosis and pulmonary embolism

Deep vein thrombosis (DVT) leads to hospitalization for up to 600,000 persons each year in the United States. Venous thrombosis in itself may be benign, but the condition can lead to dangerous complications and has a high recurrence rate. Strategies to prevent DVT involve prevention of stasis and reversal of changes in blood coagulability that allow thrombi to form. Pharmacologic agents have been effective in reducing the incidence of DVT and pulmonary embolism. Low-dose subcutaneous heparin is considered a nearly ideal DVT preventative for surgically treated patients. The risk of hemorrhage is the main limitation to routine use of subcutaneous anticoagulants for DVT, but careful patient selection can minimize that risk. After anticoagulant therapy with heparin, generally for 7 to 10 days, oral warfarin is the drug of choice for maintenance anticoagulation to prevent DVT recurrence. Therapy for pulmonary embolism is the same as for DVT--immediate anticoagulation with heparin followed by maintenance with warfarin.

Heparin therapy for venous thrombosis and pulmonary embolism

Intravenous heparin is the initial treatment of choice for most patients with acute pulmonary embolism or proximal deep vein thrombosis. The primary objective of initial heparin therapy in such patients is to prevent recurrent venous thromboembolism. The efficacy of intravenous heparin for this purpose has been established by randomized clinical trials in patients with pulmonary embolism, and more recently, in patients with proximal vein thrombosis. Heparin is given as an initial intravenous bolus of 5000 units, followed by a maintenance dose of 30,000-40,000 units per 24 h by continuous intravenous infusion. A recent randomized trial in patients with proximal vein thrombosis indicates that failure to achieve an adequate anticoagulant response (APTT greater than 1.5 times control) is associated with a high risk (25%) of recurrent venous thromboembolism. Intravenous heparin administered in doses that prolong the activated partial thromboplastin time (APTT) to 1.5 or more times the control value is highly effective, and associated with a low frequency (2%) of recurrent venous thromboembolism. Heparin is continued for 7-10 days, overlapped with warfarin sodium during the last 4-5 days. Multiple randomized clinical trials indicate that this approach is highly effective. An alternative approach is to commence heparin and oral anticoagulants together at the time of diagnosis, and to discontinue heparin on the fourth or fifth day. A recent randomized trial in patients with submassive venous thrombosis or pulmonary embolism suggests that 4-5 days of initial heparin therapy is effective and safe, but this approach must be evaluated by further randomized trials before it is recommended for patients with extensive proximal vein thrombosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Prescribing and monitoring heparin

Aspects of heparin prescribing to include indications, dosing, administration and monitoring were investigated in 27 patients. Prescribing practices for heparin were investigated by interview of 28 physicians. Many inconsistencies in heparin prescribing were identified and monitoring was found to be haphazard.

The heparin flush syndrome: a cause of iatrogenic hemorrhage

The anticoagulant drug heparin is used extensively in modern hospital practice. The major therapeutic use of this drug remains treatment and prevention of systemic thrombosis. However, an increasing amount of heparin is being used in nontherapeutic protocols to implement newer, more invasive technology when the body's protective clotting mechanism would otherwise interfere. Buried in protocols, heparin has become ubiquitous in standard hospital practice. One such protocol is the use of heparinized solutions to "flush" arterial and venous catheters in order to maintain patency and thus, vascular access. Often these flush solutions are considered to be as innocuous as "simple saline." We report a patient who experienced post-operative bleeding resulting from overuse of "heparin flushes," and necessitating a second surgery. The excessive hemorrhage following this inadvertent anticoagulation has been named the "heparin flush syndrome," to call attention to the serious and sometimes fatal side-effects of heparinized solutions.