An objective study of alternative methods of heparin administration

Subcutaneous unfractionated heparin for the initial treatment of venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE) is a prevalent and serious condition. Its medical treatment requires anticoagulation, usually with either unfractionated or low molecular weight heparin (LMWH). Administration of unfractionated heparin (UFH) is usually intravenous (IV) but can be subcutaneous as well. This is an update of a review first published in 2009.

OBJECTIVES

To assess the effects of subcutaneous UFH versus intravenous UFH, subcutaneous LMWH or any other anticoagulant drug for the initial treatment of venous thromboembolism.

SEARCH METHODS

For this update, the Cochrane Vascular Information Specialist searched the Specialised Register (last searched 30 November 2016) and CENTRAL (2016, Issue 10). The Cochrane Vascular Information Specialist also searched trials registries for details of ongoing or unpublished studies.

SELECTION CRITERIA

Randomised controlled trials comparing subcutaneous UFH to control, such as subcutaneous LMWH, continuous intravenous UFH or other anticoagulant drugs in participants with acute venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Two review authors (JS and LR) independently extracted data and assessed the risk of bias in the trials. We used meta-analyses when we considered heterogeneity low. The primary outcomes were symptomatic recurrent venous thromboembolism (deep vein thrombosis and/or pulmonary embolism), VTE-related mortality, adverse effects of treatment including major bleeding, and all-cause mortality. We calculated all outcomes using an odds ratio (OR) with a 95% confidence interval (CI).

MAIN RESULTS

We included one additional study in this update, bringing the total number of studies in the review to 16 randomised controlled trials, with a total of 3593 participants (1745 participants in the intervention group and 1848 participants in the control group). Eight trials used intravenous UFH as the control treatment, seven trials used LMWH, and one trial had three arms with both drugs as the controls. We did not identify trials comparing subcutaneous UFH with other anticoagulant drugs. We downgraded the quality of the evidence to low due to lack of blinding in studies, which led to a risk of performance bias, and also for imprecision, as reflected by the wide confidence intervals.When comparing subcutaneous versus IV UFH, there was no difference in the incidence of symptomatic recurrent VTE at three months (odds ratio (OR) 1.66, 95% confidence interval (CI) 0.89 to 3.10; 8 studies; N = 965; low-quality evidence), symptomatic recurrent deep vein thrombosis (DVT) at three months (OR 3.29, 95% CI 0.64 to 17.06; 1 study; N = 115; low-quality evidence), pulmonary embolism (PE) at three months (OR 1.44, 95% CI 0.73 to 2.84; 9 studies; N = 1161; low-quality evidence), VTE-related mortality at three months (OR 0.98, 95% CI 0.20 to 4.88; 9 studies; N = 1168; low-quality evidence), major bleeding (OR 0.91, 95% CI 0.42 to 1.97; 4 studies; N = 583; low-quality evidence) or all-cause mortality (OR 1.74, 95% CI 0.67 to 4.51; 8 studies; N = 972; low-quality evidence). There were no episodes of asymptomatic VTE occurring within three months of the commencement of treatment.When comparing subcutaneous UFH versus LMWH, there was no difference in the incidence of recurrent VTE at three months (OR 1.01, 95% CI 0.63 to 1.63; 5 studies; N = 2156; low-quality evidence), recurrent DVT at three months (OR 1.38, 95% CI 0.73 to 2.63; 3 studies; N = 1566; low-quality evidence), PE (OR 0.84, 95% CI 0.36 to 1.96; 5 studies, N = 1819; low-quality evidence), VTE-related mortality (OR 0.53, 95% CI 0.17 to 1.67; 8 studies; N = 2469; low-quality evidence), major bleeding (OR 0.72, 95% CI 0.43 to 1.20; 5 studies; N = 2300; low-quality evidence) or all-cause mortality (OR 0.73, 95% CI 0.50 to 1.07; 7 studies; N = 2272; low-quality evidence). There were no episodes of asymptomatic VTE occurring within three months of the commencement of treatment.

AUTHORS' CONCLUSIONS

There is no evidence of a difference between subcutaneous versus intravenous UFH for preventing VTE recurrence, VTE-related or all-cause mortality, and major bleeding. According to GRADE criteria, the quality of the evidence was low. There is also no evidence of a difference between subcutaneous UFH and LMWH for preventing VTE recurrence, VTE-related or all-cause mortality or major bleeding.

Incidence of pulmonary embolism in patients with isolated calf deep vein thrombosis

BACKGROUND

The severity of pulmonary embolism (PE) after isolated calf deep vein thrombosis (C-DVT) is controversial, which leads to inconsistent clinical decision making when treating C-DVT. This systematic review assessed PE frequency and severity in patients with C-DVT.

METHODS

Database searches were completed using MEDLINE and Scopus along with cross-referencing. Two independent reviewers used using rigorous inclusion and exclusion criteria to screen the papers. Data concerning PE and C-DVT characteristics as well as methods of detection were abstracted. Studies reporting combined outcomes for patients with proximal and C-DVT, those with concurrent PE at diagnosis, and retrospective studies not allowing the determination of C-DVT and PE as separate events were excluded.

RESULTS

Of 586 papers that were screened, 21 met inclusion criteria, which included eight randomized clinical trials and 13 prospective cohort studies. There was data heterogeneity among patients, methods of diagnosis, and follow-up. PE diagnosis was often based on ventilation/perfusion scanning, where more recent studies used computed tomography angiography. The PE is usually overestimated because it includes concurrent events. The incidence of PE from isolated C-DVT in our review was 0% to 6.2%. No fatal PEs were reported. No data were found on PE severity and patient outcomes regarding this complication.

CONCLUSIONS

Reported adverse outcomes of PE from C-DVT are infrequent, and clinical severity is unclear. Further studies are necessary to determine the actual risk associated with PE after C-DVT to establish proper treatment.

Deep Venous Thrombosis and Pulmonary Embolism in Trauma Patients

Trauma patients are at exceedingly high risk for the development of deep venous thrombosis and pulmo nary embolism. The incidence, pathophysiology, diag nosis, prophylaxis, and therapy of deep venous throm bosis and pulmonary embolism in the trauma patient are reviewed. The type of injury, systemic pertubations, and enforced immobility are important factors in pathogenesis. Patients with lower extremity injuries and spine fractures with paraplegia appear to be at highest risk. Orthopedic devices used to treat these injuries of ten preclude the conventional noninvasive diagnostic modalities. Further, hemorrhagic risk often impacts the judgment regarding the use of prophylactic measures as well as the therapy once deep venous thrombosis is diagnosed. Better data regarding the incidence of ve nous thromboembolism and the applicability of existing diagnostic, prophylactic, and treatment approaches in this population are needed.

Accidents are responsible for over 140,000 deaths and approximately 70 million nonfatal injuries an nually in the United States [1]. Most of the fatalities occur within hours of injury as a result of exsangui nation or a lethal head injury, but approximately 20% survive for days or weeks [2], usually in the intensive care unit. The primary causes of late death are sepsis and multiple-organ failure [2]. Increasing evidence, however, suggests that pulmonary embo lism (PE) is now becoming a leading cause of late death, especially in some high-risk groups [3-5]. The increase in the incidence of PE is due in part to improvements in trauma care, which have lowered the early mortality rate [6-8], leaving more patients at risk for late death. In addition, autopsy examina tions, used more frequently to audit trauma care systems [6,9], have documented an increase in clini cally unsuspected deep venous thrombosis (DVT) and PE.

This review was prompted because of the appar ent increase in DVT and PE in the trauma popula tion, and because the trauma patient presents very difficult and unique problems compared with the nontrauma patient with regard to the diagnosis, prophylaxis, and treatment of these disorders. In this review, we address the incidence, pathophys iology, diagnosis, treatment, and prophylaxis of DVT and PE in the trauma patient. We do not con sider the entities of fat embolism or pulmonary microemboli as a cause of late pulmonary failure.

Subcutaneous unfractionated heparin for the initial treatment of venous thromboembolism

BACKGROUND

Venous thromboembolism is a prevalent condition with potentially dire consequences. Its medical treatment requires anticoagulation, which is usually achieved with either unfractionated or low molecular weight heparin (LMWH). Unfractionated heparin (UFH) is usually administered intravenously, but can be applied subcutaneously as well.

OBJECTIVES

To explore the effectiveness of subcutaneous UFH for the initial treatment of venous thromboembolism compared with other treatment modalities.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched 14 July 2009) and the Cochrane Central Register of Controlled Trials (CENTRAL) (last searched The Cochrane Library 2009, Issue 3). We searched MEDLINE and EMBASE (last searched February 2009).

SELECTION CRITERIA

Randomised controlled trials, in which treatment with subcutaneous UFH was compared to control, such as subcutaneous LMWH continuous intravenous UFH in patients with acute venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality.

MAIN RESULTS

Fifteen randomised controlled trials were included with a total of 3054 participants (1475 patients in the intervention group and 1579 patients in the control group). The results for all the major outcomes were statistically non-significant. The odds ratio (OR) for recurrent deep vein thrombosis (DVT) or pulmonary embolism (PE) during three months follow up were 1.68 (95% confidence interval (CI) 0.92 to 3.04) and 1.18. (95% CI 0.54 to 2.56), favouring the control arm. The odds ratio for developing PE during heparin treatment also favoured the control group (OR 1.10, 95% CI 0.46 to 2.62). The ORs for major bleeding during heparin treatment and throughout three months follow up were non significant (1.07, 95% CI 0.64 to 1.79, and 0.66, 95% CI 0.33 to 1.32, respectively). Disease or treatment related deaths as well as total mortality during heparin treatment and at three months follow up did not differ between study groups.

AUTHORS' CONCLUSIONS

Subcutaneous unfractionated heparin for the treatment of venous thromboembolism cannot be considered non-inferior to other treatment modalities in terms of recurrent DVT and PE at three months, but seems as safe and effective with regards to rates of major bleeding and death.

Hemorrhagic Complications of Anticoagulant Treatment

This chapter about hemorrhagic complications of anticoagulant treatment is part of the seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Bleeding is the major complication of anticoagulant therapy. The criteria for defining the severity of bleeding varies considerably between studies, accounting in part for the variation in the rates of bleeding reported. The major determinants of vitamin K antagonist-induced bleeding are the intensity of the anticoagulant effect, underlying patient characteristics, and the length of therapy. There is good evidence that vitamin K antagonist therapy, targeted international normalized ratio (INR) of 2.5 (range, 2.0 to 3.0), is associated with a lower risk of bleeding than therapy targeted at an INR > 3.0. The risk of bleeding associated with IV unfractionated heparin (UFH) in patients with acute venous thromboembolism (VTE) is < 3% in recent trials. This bleeding risk may increase with increasing heparin dosages and age (> 70 years). Low molecular weight heparin (LMWH) is associated with less major bleeding compared with UFH in acute VTE. UFH and LMWH are not associated with an increase in major bleeding in ischemic coronary syndromes, but are associated with an increase in major bleeding in ischemic stroke. Information on bleeding associated with the newer generation of antithrombotic agents has begun to emerge. In terms of treatment decision making for anticoagulant therapy, bleeding risk cannot be considered alone, ie, the potential decrease in thromboembolism must be balanced against the potential increased bleeding risk.

Disseminated intravascular coagulation: a review of etiology, pathophysiology, diagnosis, and management: guidelines for care

The pathophysiologic mechanisms, clinical, and laboratory manifestations of DIC are complex in part due to interrelationships within the hemostasis system. Only by clearly understanding these extraordinarily complex pathophysiologic interrelationships can the clinician and laboratory scientist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. Many therapeutic decisions to be made are controversial and lack validation. Nevertheless, newer antithrombotic agents, and agents that can block, blunt, or modify cytokine activity and the activity of vasoactive substances appear to be of value. The complexity and variable degree of clinical expression suggests that therapy should be individualized depending on the nature of DIC, age, etiology of DIC, site and severity of hemorrhage or thrombosis and hemodynamics and other appropriate clinical parameters. At present, treatment of the triggering event, low-dose heparin or antithrombin concentrate and wise choice of components when indicated appear to be the most effective modes of therapy.

The effects of heparin and oral anticoagulants on thrombus propagation and prevention of the postphlebitic syndrome: a critical review of the literature

Based on a comprehensive literature search, this report aims to examine the effects of heparin and oral anticoagulants on thrombus propagation and prevention of the postphlebitic syndrome. The effects on recurrence of thromboembolic disease have not been addressed. It is concluded that published reports of serial venograms and ultrasound examinations of patients treated with conventional anticoagulant therapy for deep venous thrombosis show either no change or thrombus extension in the first few months in approximately 50% of cases. Approximately two thirds of patients will have damage to the venous valves, leading to incompetence or other hemodynamic changes. More than one third of patients so treated may have oedema, leg pain, or other severe symptoms on long-term follow-up. The consistency with which these outcomes have been observed, particularly in many large, recent, prospective trials, adds to the credibility of these figures. The results of prospective controlled trials have failed uniformly to show any significant local benefits of anticoagulant therapy for deep vein thrombosis compared with other treatments or placebo. There does not seem to be any convincing evidence that heparin exerts a favorable influence on pulmonary embolism in situ or on portal vein thrombosis. Use of anticoagulant therapy to limit thrombus propagation therefore cannot be said to be "evidence based." These generally poor outcomes with regard to postphlebitic complications should lead to an active exploration of alternative methods of management. Substantial uncertainties surrounding many fundamental aspects of the treatment of this disease remain, and further placebo-controlled trials are needed.

Management of venous thromboembolic disease in the lower limb

Thromboembolic disease continues to cause significant morbidity and mortality in our community, despite extensive research into the aetiological factors and significant resources invested in the development of pharmacological agents for treating this condition. Development of more sensitive and specific modalities for identifying venous thromboses has improved their early detection, particularly in the commonest site, the lower limb. A rational evidence-based management pathway has not been formulated as debate continues over the most appropriate method of treatment. This review outlines the pathophysiology of the disease, provides a clinical pathway for the management of lower limb thromboembolic disease using reliable available evidence and briefly discusses the efficacy of drug therapy.

Hemorrhagic complications of anticoagulant treatment

Bleeding is the major complication of anticoagulant therapy. The criteria for defining the severity of bleeding varied considerably between studies, accounting in part for the variation in the rates of bleeding reported. Since the last review, there have been several meta-analyses published on the rates of major bleeding in trials of anticoagulants for atrial fibrillation and ischemic heart disease. The major determinants of oral anticoagulant-induced bleeding are the intensity of the anticoagulant effect, underlying patient characteristics, and the length of therapy. There is good evidence that low-intensity oral anticoagulant therapy (targeted INR of 2.5; range, 2.0 to 3.0) is associated with a lower risk of bleeding than therapy targeted at a higher intensity. Lower-intensity regimens (INR < 2.0) are associated with an even smaller increase in major bleeding. In terms of treatment decision making for anticoagulant therapy, bleeding risk cannot be considered alone, ie, the potential decrease in thromboembolism must be balanced against the potential increased bleeding risk. The risk of bleeding associated with IV heparin in patients with acute venous thromboembolism is < 3% in recent trials. There is some evidence to suggest that this bleeding risk increases with the heparin dosage and age (> 70 years). LMW heparin is not associated with increased major bleeding compared with standard heparin in acute venous thromboembolism. Standard heparin and LMW heparin are not associated with an increase in major bleeding in ischemic coronary syndromes, but are associated with an increase in major bleeding in ischemic stroke.

Syndromes of disseminated intravascular coagulation in obstetrics, pregnancy, and gynecology. Objective criteria for diagnosis and management

This article presents current understanding of the causes, pathophysiology, clinical, and laboratory diagnosis, and management of fulminant and low-grade DIC, as they apply to obstetric, pregnant, and gynecologic patients. General medical complications leading to DIC, which may often be seen in these patients, are also discussed. Considerable attention has been given to interrelationships within the hemostasis system. Only by clearly understanding these pathophysiologic interrelationships can the obstetrician/gynecologist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. Objective clinical and laboratory criteria for diagnosis of DIC have been outlined to eliminate unnecessary confusion and the need to make empiric decisions regarding the diagnosis. Particularly in the obstetric patient, if a condition is observed that is associated with DIC, or if any suspicion of DIC arises from either clinical or laboratory findings, it is imperative to monitor the patient carefully with clinical and laboratory tools to assess any progression to a catastrophic event. In most instances of DIC in obstetric patients, the disease can be ameliorated easily at early stages. Many therapeutic decisions are straightforward, particularly in obstetric and gynecologic patients. For more serious and complicated cases of DIC in these patients, however, efficacy and choices of therapy will remain unclear until more information is published regarding response rates and survival patterns. Also, therapy must be highly individualized according to the nature of DIC, patient's age, origin of DIC, site and severity of hemorrhage or thrombosis, and hemodynamic and other clinical parameters. Finally, many syndromes that are often categorized as organ-specific disorders and are sometimes identified as independent disease entities, such as AFE syndrome, HELLP syndrome, adult shock lung syndrome, eclampsia, and many others, either share common pathophysiology with DIC or are simply a form of DIC. These entities represent the varied modes of clinical expression of DIC and illustrate the diverse clinical and anatomic manifestations of this syndrome.

Optimal dosing of subcutaneous unfractionated heparin for the treatment of deep vein thrombosis

Twice-daily, inpatient, subcutaneous unfractionated heparin is at least as effective and safe as continuous intravenous unfractionated heparin for the treatment of acute deep vein thrombosis. Subcutaneous unfractionated heparin therefore may be suitable for outpatient treatment of deep vein thrombosis. The purpose of this study was to develop a dosing nomogram for a dose each 12 hours (2 doses per day) 12-hourly subcutaneous unfractionated heparin that is suitable for outpatient treatment of acute deep vein thrombosis. A cohort study was performed in patients with acute deep vein thrombosis in two phases. In both phases, the first subcutaneous loading dose of unfractionated heparin was 317 U/kg, and the second dose was 231 U/kg. The activated partial thromboplastin time was measured daily, 6 hours after the morning injection, and subsequent doses of unfractionated heparin were adjusted according to a nomogram, which was modified for phase II. Warfarin was started with unfractionated heparin. In phase I (14 outpatients), activated partial thromboplastin time results were frequently subtherapeutic (9:14) the day after starting unfractionated heparin (day 1), and were frequently supratherapeutic (27:40) after the first 2 days of unfractionated heparin therapy. In phase II (21 patients), to explain the frequently subtherapeutic activated partial thromboplastin time results that were obtained on day 1, the activated partial thromboplastin time results were measured after the initial loading dose. Mean activated partial thromboplastin time results of 86 and 61 seconds were obtained 6 and 12 hours after this dose, suggesting that 317 U/kg is a suitable subcutaneous loading dose. In contrast to phase I, in phase II, unfractionated heparin dose was not increased on day 1 in response to a low activated partial thromboplastin time result. This reduced the frequency of supratherapeutic activated partial thromboplastin time results during the early days of therapy without increasing the frequency of subtherapeutic results. Warfarin therapy had a substantal effect on the activated partial thromboplastin time that appeared to account for a high frequency of supratherapeutic results during the later days of unfractionated heparin therapy; the activated partial thromboplastin time increased by 20 seconds (95% CI, 14-27 seconds) with each increase in the International Normalized Ratio of 1.0. We had limited success at developing a dosing nomogram for subcutaneous unfractionated heparin that reliably achieved activated partial thromboplastin time results within the therapeutic range. However, as oral anticoagulants directly increased activated partial thromboplastin time results, we suggest that adjusting unfractionated heparin dose to achieve prespecified activated partial thromboplastin time results may not be appropriate in patients who are receiving concomitant warfarin therapy.

Anticoagulation

Outpatient management of women requiring treatment and prophylaxis against thromboembolic conditions during pregnancy and the postpartum period requires a coordinated effort between the patient, her obstetrician and, in certain cases, a hematologic consultant. The anticoagulation regimen should be tailored to the clinical situation, with patient compliance and cost taken into consideration.

Disseminated intravascular coagulation. Objective criteria for diagnosis and management

Current concepts of the cause, pathophysiology, clinical and laboratory diagnosis, and management of fulminant and low-grade DIC have been presented. Considerable attention has been devoted to interrelationships within the hemostasis system. Only by clearly understanding these pathophysiological interrelationships can the clinician and laboratory scientist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. In this discussion, objective clinical and laboratory criteria for a diagnosis of DIC have been delineated, thus eradicating unnecessary confusion and empirical decisions regarding the diagnosis. Many therapeutic decisions to be made are controversial and will remain so until more is published about specific therapeutic modalities and survival patterns. Also, therapy must be highly individualized depending on the nature of DIC, age, cause of DIC, site and severity of hemorrhage or thrombosis, and hemodynamic and other clinical parameters. Also presented are clear criteria for severity of DIC and objective criteria for defining a response to therapy. Also, because it is often difficult for the individual physician to decide when to stop often extensive therapy, objective criteria whereby therapy may be stopped, as continuation is likely fruitless, have been presented as a guideline. Lastly, it should be appreciated that many syndromes that are often organ specific share common pathophysiology with DIC but are typically identified as an independent disease entity, such as hemolytic uremic syndrome, adult shock lung syndrome, eclampsia, and many other isolated organ-specific disorders.

The natural history and epidemiology of venous thrombosis

Epidemiologic studies over the past 30 years have provided much of the basis for the understanding of venous thromboembolic disease. There has been an evolution from simple descriptive studies using clinical diagnosis to various forms of comparative studies using objective diagnoses. Identification of high-risk cases in the hospitalized population has led to the development of both general and specific antithrombotic prophylactic regimens. This has occurred against a background of an increased understanding of the pathophysiology of venous thrombosis. Inhospital case interventions have allowed direct questions concerning pathophysiology to be addressed. Examples would include the use of certain types and dosages of anticoagulants and the use of mechanical devices to avoid stasis. Despite these advances, there are still areas that require further attention. One aspect of importance is to evaluate the thrombotic risk of new procedures. The possibility that a new procedure may be either less or more thrombotic than its predecessor should be addressed. In the case of the former, additional antithrombotic measures are needed. An example of this is the relatively disappointing results of regular low-dose heparin treatment in some orthopedic procedures. In the case of the latter, less severe measures may be indicated. Current antithrombotic methods are not without risks and may not be necessary with some of the new endoscopic surgical procedures. Another area of importance relates to the monitoring of compliance. The information on antithrombotic methods has been available for two decades, yet surveys of the application of these methods consistently show that antithrombotic protocols are used less in North America relative to their use in equivalent institutions in Europe. A third area that still needs further epidemiologic study is the incidence and effects of venous thrombosis in the general community. Despite the two recent descriptive studies cited above, relatively little, as compared with the in-patient perspective, is known about community risk factors and their prevention. With respect to the natural history of hospital-based cases it seems unlikely that much is to be gained from surveying the efficacy of heparin or heparin-like treatment for mortality end points. However, a large and still unsatisfactorily examined area is the true frequency and impact of the postphlebitic syndrome. This aspect is germane to both hospital- and community-acquired DVT and, with an aging population, clearly deserves a lot more attention.

Anticoagulant-related bleeding: clinical epidemiology, prediction, and prevention

OBJECTIVE

To review (1) the clinical epidemiology of bleeding during anticoagulant therapy with heparin or warfarin, (2) data useful in estimating the risk for bleeding in individual patients, and (3) the efficacy of methods for its prevention.

METHODS

Relevant literature was identified by a computerized search of the Medline database and by review of the bibliographies of original and review articles. Studies were classified according to their design. Estimates of the risk for bleeding during anticoagulant therapy, compared with the risk without therapy, were obtained from randomized trials. Estimates of the frequency of bleeding during the course of anticoagulant therapy and information about risk factors for bleeding were obtained primarily from longitudinal studies of inception cohorts of patients followed from the start of therapy.

MAIN RESULTS

The average daily frequencies of fatal, major, and major or minor bleeding during heparin therapy were 0.05%, 0.8%, and 2.0%, respectively; these frequencies are approximately twice those expected without heparin therapy. The average annual frequencies of fatal, major, and major or minor bleeding during warfarin therapy were 0.6%, 3.0%, and 9.6%, respectively; these frequencies are approximately five times those expected without warfarin therapy. The risk for anticoagulant-related bleeding is highest at the start of therapy: during warfarin therapy, the risk for major bleeding during the first month of therapy is approximately 10 times the risk after the first year of therapy. An individual patient's risk for major anticoagulant-related bleeding can be estimated on the basis of specific risk factors such as the intensity of the anticoagulant effect achieved and the presence of serious comorbid diseases, especially cerebrovascular, kidney, heart, and liver disease; older age and concurrent medicines may also be independent risk factors. Major bleeding most often affects the gastrointestinal tract, soft tissues, and urinary tract. Diagnostic evaluation of gastrointestinal bleeding and gross hematuria leads to identification of previously unknown lesions in approximately one-third of cases, even when the prothrombin time is elevated. Intracranial bleeding is rare, but it is frequently fatal. The frequency of bleeding during warfarin therapy is reduced by less intense therapy achieving a prothrombin time with an International Normalized Ratio of 2.0 to 3.0, which is efficacious for most indications.

CONCLUSION

Anticoagulant-related bleeding is common and often serious. The risk for bleeding can be estimated in an individual patient, giving the primary physician a quantitative basis for weighing the risks and benefits of therapy and for optimizing patient management. The frequency of anticoagulant-related bleeding is reduced by less intense warfarin therapy. Future studies should evaluate new approaches to management that may further reduce complications while maintaining efficacy.

Effect of aerosol heparin on the development of hypoxic pulmonary hypertension in the guinea pig

Chronic hypoxia produces pulmonary artery hypertension through vasoconstriction and structural remodeling of the pulmonary vascular bed. The present study was designed to test the effect of heparin administered via aerosol on the development of hypoxic pulmonary hypertension. Anesthetized, intubated, and mechanically ventilated guinea pigs received an aerosol of either 2 ml normal saline (hypoxic control, HC) or 4,500 units of heparin diluted in 2 ml normal saline via an ultrasonic nebulizer (hypoxic heparin, HH). After 24 h of recovery, the animals were placed in a hypoxic chamber (10% O2) for 10 days. Animals kept in room air served as normoxic controls (NC). Hypoxia increased mean pulmonary artery pressure from 11 +/- 1 (SEM) mm Hg in NC to 24 +/- 1 mm Hg in HC (p < 0.05). Pulmonary artery pressure was significantly lower in HH-treated animals (20 +/- 1 mm Hg, p < 0.05 versus HC) as was the total pulmonary vascular resistance (0.15 +/- 0.01 in HH versus 0.20 +/- 0.01 mm Hg/ml/min in HC, p < 0.05). There was no difference in cardiac output (146 +/- 12 in HH versus 126 +/- 7 ml/min in HC), hematocrit (57 +/- 2 in HH versus 56 +/- 2% in HC), partial thromboplastin time (30 +/- 2 in HH versus 32 +/- 3 s in HC), prothrombin time (46 +/- 1 in HH versus 48 +/- 4 s in HC) or room air arterial blood gas values after 10 days of hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Subcutaneous versus intravenous administration of heparin in the treatment of deep vein thrombosis; which do patients prefer? A randomized cross-over study

Patient preference for intravenous or subcutaneous heparin in the treatment of deep venous thrombosis was assessed in a randomized cross-over study. Twenty patients with venographically proven deep venous thrombosis were randomized to receive subcutaneous or intravenous heparin for 3 days followed by 3 days of the other treatment. Discomfort at the injection site, assessed by visual analogue scale, was significantly less for the subcutaneous than the intravenous administration route (P < 0.001), mobility was thought to be better when receiving subcutaneous heparin (P < 0.005) and patients' overall preference was for subcutaneous treatment (P < 0.001).

Antithrombotic therapy in deep vein thrombosis and pulmonary embolism

After 50 years of clinical use anticoagulants are still the mainstay of treatment for venous thromboembolism. Several studies have demonstrated that failure to attain or to maintain an adequate anticoagulant effect with heparin after venous thromboembolism is associated with an increased risk of recurrence. The safety and effectiveness of heparin administered by continuous intravenous infusion has been compared with administration by intermittent intravenous injection; three studies reported less bleeding with the former. The relative efficacy and safety of continuous intravenous and intermittent subcutaneous heparin appear to be comparable. The readily available and relatively inexpensive activated partial thromboplastin time test is used most commonly to monitor heparin therapy. Recent audits indicate that current practices in the administration of heparin are often suboptimal because of an inadequate starting dose, a delay in obtaining or responding to activated partial thromboplastin time test results, or inappropriate adjustments of heparin doses. Attempts have recently been made to improve practices in the administration of heparin by developing a standardization protocol. Recommendations for patient management are discussed.