Efficacy and safety of early versus late initiation of warfarin during heparin therapy in acute thromboembolism

Unfractionated heparin versus low molecular weight heparins for avoiding heparin-induced thrombocytopenia in postoperative patients

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction presenting as a prothrombotic disorder related to antibody-mediated platelet activation. It is a paradoxical immune reaction resulting in thrombin generation in vivo, which leads to a hypercoagulable state and the potential to initiate venous or arterial thrombosis. A number of factors are thought to influence the incidence of HIT including the type and preparation of heparin (unfractionated heparin (UFH) or low molecular weight heparin (LMWH)) and the heparin-exposed patient population, with the postoperative patient population at higher risk.Although LMWH has largely replaced UFH as a front-line therapy, there is evidence supporting a lack of superiority of LMWH compared with UFH regarding prevention of deep vein thrombosis and pulmonary embolism following surgery, and similar frequencies of bleeding have been described with LMWH and UFH. The decision as to which of these two preparations of heparin to use may thus be influenced by harmful effects such as HIT. We therefore sought to determine the relative impact of UFH and LMWH on HIT in postoperative patients receiving thromboembolism prophylaxis. This is an update of a review first published in 2012.

OBJECTIVES

The objective of this review was to compare the incidence of heparin-induced thrombocytopenia (HIT) and HIT complicated by venous thromboembolism in postoperative patients exposed to unfractionated heparin (UFH) versus low molecular weight heparin (LMWH).

SEARCH METHODS

For this update, the Cochrane Vascular Information Specialist searched the Specialised Register (May 2016), CENTRAL (2016, Issue 4) and trials registries. The authors searched Lilacs (June 2016) and additional trials were sought from reference lists of relevant publications.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in which participants were postoperative patients allocated to receive prophylaxis with UFH or LMWH, in a blinded or unblinded fashion. Studies were excluded if they did not use the accepted definition of HIT. This was defined as a relative reduction in the platelet count of 50% or greater from the postoperative peak (even if the platelet count at its lowest remained greater than 150 x 10⁹/L) occurring within five to 14 days after the surgery, with or without a thrombotic event occurring in this timeframe. Additionally, we required circulating antibodies associated with the syndrome to have been investigated through laboratory assays.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias. Disagreements were resolved by consensus with participation of a third author.

MAIN RESULTS

In this update, we included three trials involving 1398 postoperative participants. Participants were submitted to general surgical procedures, minor and major, and the minimum mean age was 49 years. Pooled analysis showed a significant reduction in the risk of HIT with LMWH compared with UFH (risk ratio (RR) 0.23, 95% confidence interval (CI) 0.07 to 0.73); low-quality evidence. The number needed to treat for an additional beneficial outcome (NNTB) was 59. The risk of HIT was consistently reduced comparing participants undergoing major surgical procedures exposed to LMWH or UFH (RR 0.22, 95% CI 0.06 to 0.75); low-quality evidence. The occurrence of HIT complicated by venous thromboembolism was significantly lower in participants receiving LMWH compared with UFH (RR 0.22, 95% CI 0.06 to 0.84); low-quality evidence. The NNTB was 75. Arterial thrombosis occurred in only one participant who received UFH. There were no amputations or deaths documented. Although limited evidence is available, it appears that HIT induced by both types of heparins is common in people undergoing major surgical procedures (incidence greater than 1% and less than 10%).

AUTHORS' CONCLUSIONS

This updated review demonstrated low-quality evidence of a lower incidence of HIT, and HIT complicated by venous thromboembolism, in postoperative patients undergoing thromboprophylaxis with LMWH compared with UFH. Similarily, the risk of HIT in people undergoing major surgical procedures was lower when treated with LMWH compared to UFH (low-quality evidence). The quality of the evidence was downgraded due to concerns about the risk of bias in the included studies and imprecision of the study results. These findings may support current clinical use of LMWH over UFH as front-line heparin therapy. However, our conclusions are limited and there was an unexpected paucity of RCTs including HIT as an outcome. To address the scarcity of clinically-relevant information on HIT, HIT must be included as a core harmful outcome in future RCTs of heparin.

Anticoagulation Management Practices and Outcomes in Elderly Patients with Acute Venous Thromboembolism: A Clinical Research Study

Whether anticoagulation management practices are associated with improved outcomes in elderly patients with acute venous thromboembolism (VTE) is uncertain. Thus, we aimed to examine whether practices recommended by the American College of Chest Physicians guidelines are associated with outcomes in elderly patients with VTE. We studied 991 patients aged ≥65 years with acute VTE in a Swiss prospective multicenter cohort study and assessed the adherence to four management practices: parenteral anticoagulation ≥5 days, INR ≥2.0 for ≥24 hours before stopping parenteral anticoagulation, early start with vitamin K antagonists (VKA) ≤24 hours of VTE diagnosis, and the use of low-molecular-weight heparin (LMWH) or fondaparinux. The outcomes were all-cause mortality, VTE recurrence, and major bleeding at 6 months, and the length of hospital stay (LOS). We used Cox regression and lognormal survival models, adjusting for patient characteristics. Overall, 9% of patients died, 3% had VTE recurrence, and 7% major bleeding. Early start with VKA was associated with a lower risk of major bleeding (adjusted hazard ratio 0.37, 95% CI 0.20–0.71). Early start with VKA (adjusted time ratio [TR] 0.77, 95% CI 0.69–0.86) and use of LMWH/fondaparinux (adjusted TR 0.87, 95% CI 0.78–0.97) were associated with a shorter LOS. An INR ≥2.0 for ≥24 hours before stopping parenteral anticoagulants was associated with a longer LOS (adjusted TR 1.2, 95% CI 1.08–1.33). In elderly patients with VTE, the adherence to recommended anticoagulation management practices showed mixed results. In conclusion, only early start with VKA and use of parenteral LMWH/fondaparinux were associated with better outcomes.

The adherence to initial processes of care in elderly patients with acute venous thromboembolism

BACKGROUND

We aimed to assess whether elderly patients with acute venous thromboembolism (VTE) receive recommended initial processes of care and to identify predictors of process adherence.

METHODS

We prospectively studied in- and outpatients aged ≥65 years with acute symptomatic VTE in a multicenter cohort study from nine Swiss university- and non-university hospitals between September 2009 and March 2011. We systematically assessed whether initial processes of care, which are recommended by the 2008 American College of Chest Physicians guidelines, were performed in each patient. We used multivariable logistic models to identify patient factors independently associated with process adherence.

RESULTS

Our cohort comprised 950 patients (mean age 76 years). Of these, 86% (645/750) received parenteral anticoagulation for ≥5 days, 54% (405/750) had oral anticoagulation started on the first treatment day, and 37% (274/750) had an international normalized ratio (INR) ≥2 for ≥24 hours before parenteral anticoagulation was discontinued. Overall, 35% (53/153) of patients with cancer received low-molecular-weight heparin monotherapy and 72% (304/423) of patients with symptomatic deep vein thrombosis were prescribed compression stockings. In multivariate analyses, symptomatic pulmonary embolism, hospital-acquired VTE, and concomitant antiplatelet therapy were associated with a significantly lower anticoagulation-related process adherence.

CONCLUSIONS

Adherence to several recommended processes of care was suboptimal in elderly patients with VTE. Quality of care interventions should particularly focus on processes with low adherence, such as the prescription of continued low-molecular-weight heparin therapy in patients with cancer and the achievement of an INR ≥2 for ≥24 hours before parenteral anticoagulants are stopped.

Should vitamin K antagonist therapy be started simultaneously with parenteral anticoagulation: a meta-analysis?

For patients with an acute episode of venous thromboembolism (VTE), the optimal starting time of long-term therapy with vitamin K antagonists (VKA) and how much overlap should occur with heparin are unclear and the current guidelines and practice are not based on high-quality data. The objective of this study was to perform a meta-analysis on the evidence comparing early versus late initiation of VKA on the effectiveness and safety of anticoagulation. We searched for randomized controlled trials in Medline, EMBASE, Cochrane CENTRAL, IPA and ClinicalTrials.gov. Studies were included if they compared early initiation of VKA (within approximately 24 h) and late initiation (>4 days) of the onset of heparin therapy. Data were pooled using the Review Manager 5 software and the quality of evidence was appraised with Grading of Recommendations, Assessment, Development and Evaluation profiler. Five studies were included in the review, with a total of 840 patients. Meta-analysis of recurrence of VTE, death and major bleeding revealed no significant differences between the two treatment regimens. Minor bleeding [RR 0.65, 95% confidence interval (CI) 0.43-0.98] and hospital stay (mean difference 3.92 days, 95% CI -4.57 to -3.28) were reduced in the early VKA group (P < 0.05). The quality of evidence for each outcome except hospital stay was low. Results from this meta-analysis favour the early start of VKA (within 24 h of the initiation of heparin) based on minor bleeding and resource utilization. However, these results should be interpreted with caution, as the quality and quantity of evidence is limited.

Unfractionated heparin versus low molecular weight heparin for avoiding heparin-induced thrombocytopenia in postoperative patients

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction presenting as a prothrombotic disorder related to antibody-mediated platelet activation. It is a poorly understood paradoxical immune reaction resulting in thrombin generation in vivo, which leads to a hypercoagulable state and the potential to initiate venous or arterial thrombosis. A number of factors are thought to influence the incidence of HIT including the type and preparation of heparin (unfractionated heparin (UFH) or low molecular weight heparin (LMWH)) and the heparin-exposed patient population, with the postoperative patient population presenting a higher risk.Although LMWH has largely replaced UFH as a front-line therapy, there is evidence supporting a lack of superiority of LMWH compared with UFH regarding prevention of deep vein thrombosis and pulmonary embolism following surgery, and similar frequencies of bleeding have been described with LMWH and UFH. The decision as to which of these two preparations of heparin to use may thus be influenced by adverse reactions such as HIT. We therefore sought to determine the relative impact of UFH and LMWH specifically on HIT in postoperative patients receiving thromboembolism prophylaxis.

OBJECTIVES

The objective of this review was to compare the incidence of HIT and HIT complicated by thrombosis in patients exposed to UFH versus LMWH in randomised controlled trials (RCTs) of postoperative heparin therapy.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (March 2012) and CENTRAL (2012, Issue 2). In addition, the authors searched LILACS (March 2012) and additional trials were sought from reference lists of relevant publications.

SELECTION CRITERIA

We were interested in comparing the incidence of HIT occurring during exposure to UFH or LMWH after any surgical intervention. Therefore, we studied RCTs in which participants were postoperative patients allocated to receive UFH or LMWH, in a blinded or unblinded fashion. Eligible studies were required to have as an outcome clinically diagnosed HIT, defined as a relative reduction in the platelet count of 50% or greater from the postoperative peak (even if the platelet count at its lowest remained > 150 x 10(9)/L) occurring within five to 14 days after the surgery, with or without a thrombotic event occurring in this timeframe. Additionally, circulating antibodies associated with the syndrome were required to have been investigated through laboratory assays.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias. Disagreements were resolved by consensus with participation of a third author.

MAIN RESULTS

In total two studies involving 923 participants met all the inclusion criteria and were included in the review. Pooled analysis showed a statistically significant reduction in the risk of HIT with LMWH compared with UFH (risk ratio (RR) 0.24, 95% confidence interval (CI) 0.07 to 0.82; P = 0.02). This result suggests that patients treated with LMWH would have a relative risk reduction (RRR) of 76% in the probability of developing HIT compared with patients treated with UFH.Venous thromboembolism (VTE) complicating HIT occurred in 12 of 17 patients who developed HIT. Pooled analysis showed a statistically significant reduction in HIT complicated by VTE with LMWH compared with UFH (RR 0.20, 95% CI 0.04 to 0.90; P = 0.04). This result indicates that patients using LMWH would have a RRR of 80% for developing HIT complicated by VTE compared with patients using UFH. Arterial thrombosis occurred in only one patient who received UFH and there were no amputations or deaths documented.

AUTHORS' CONCLUSIONS

There was a lower incidence of HIT and HIT complicated by VTE in postoperative patients undergoing thromboprophylaxis with LMWH compared with UFH. This is consistent with the current clinical use of LMWH over UFH as front-line heparin therapy. However, conclusions are limited by a scarcity of high quality evidence. We did not expect the paucity of RCTs including HIT as an outcome as heparin is one of the most commonly used drugs worldwide and HIT is a life-threatening adverse drug reaction. To address the scarcity of clinically-relevant information on the topic of HIT as a whole, HIT should be included as an outcome in future RCTs of heparin, and HIT as an adverse drug reaction should be considered in clinical recommendations regarding monitoring of the platelet count for HIT.

Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

High-quality anticoagulation management is required to keep these narrow therapeutic index medications as effective and safe as possible. This article focuses on the common important management questions for which, at a minimum, low-quality published evidence is available to guide best practices.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

Most practical clinical questions regarding the management of anticoagulation, both oral and parenteral, have not been adequately addressed by randomized trials. We found sufficient evidence for summaries of recommendations for 23 questions, of which only two are strong rather than weak recommendations. Strong recommendations include targeting an international normalized ratio of 2.0 to 3.0 for patients on vitamin K antagonist therapy (Grade 1B) and not routinely using pharmacogenetic testing for guiding doses of vitamin K antagonist (Grade 1B). Weak recommendations deal with such issues as loading doses, initiation overlap, monitoring frequency, vitamin K supplementation, patient self-management, weight and renal function adjustment of doses, dosing decision support, drug interactions to avoid, and prevention and management of bleeding complications. We also address anticoagulation management services and intensive patient education.

CONCLUSIONS

We offer guidance for many common anticoagulation-related management problems. Most anticoagulation management questions have not been adequately studied.

Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

This article addresses the treatment of VTE disease.

METHODS

We generated strong (Grade 1) and weak (Grade 2) recommendations based on high-quality (Grade A), moderate-quality (Grade B), and low-quality (Grade C) evidence.

RESULTS

For acute DVT or pulmonary embolism (PE), we recommend initial parenteral anticoagulant therapy (Grade 1B) or anticoagulation with rivaroxaban. We suggest low-molecular-weight heparin (LMWH) or fondaparinux over IV unfractionated heparin (Grade 2C) or subcutaneous unfractionated heparin (Grade 2B). We suggest thrombolytic therapy for PE with hypotension (Grade 2C). For proximal DVT or PE, we recommend treatment of 3 months over shorter periods (Grade 1B). For a first proximal DVT or PE that is provoked by surgery or by a nonsurgical transient risk factor, we recommend 3 months of therapy (Grade 1B; Grade 2B if provoked by a nonsurgical risk factor and low or moderate bleeding risk); that is unprovoked, we suggest extended therapy if bleeding risk is low or moderate (Grade 2B) and recommend 3 months of therapy if bleeding risk is high (Grade 1B); and that is associated with active cancer, we recommend extended therapy (Grade 1B; Grade 2B if high bleeding risk) and suggest LMWH over vitamin K antagonists (Grade 2B). We suggest vitamin K antagonists or LMWH over dabigatran or rivaroxaban (Grade 2B). We suggest compression stockings to prevent the postthrombotic syndrome (Grade 2B). For extensive superficial vein thrombosis, we suggest prophylactic-dose fondaparinux or LMWH over no anticoagulation (Grade 2B), and suggest fondaparinux over LMWH (Grade 2C).

CONCLUSION

Strong recommendations apply to most patients, whereas weak recommendations are sensitive to differences among patients, including their preferences.

Effect of early or delayed administration of warfarin with heparin on thrombosis in pulmonary thromboembolism

OBJECTIVE

The aim of this study was to investigate the effect of early or delayed warfarin administration with unfractionated heparin (UFH) on coagulation parameters in pulmonary thromboembolism (PTE).

PATIENTS AND METHODS

This study was performed between November 2006 and July 2007. Thirty-three patients with PTE were sequentially slotted to early (n = 16) and delayed (n = 17) warfarin treatment groups. In the early group, both UFH infusion and warfarin were started simultaneously and in the delayed group, warfarin was added (1-3 days later) based on when partial thromboplastin time reached the therapeutic level with UFH. The proteins C and S, D-dimer, hematocrit levels, and platelet counts for all patients were studied prior to treatment and 6, 24, and 48 h after warfarin treatment. In order to determine the overall effect of early and delayed warfarin treatment on clot formation, a thromboelastogram was performed simultaneously.

RESULTS

In both groups, a similar chronological decrease in protein C levels reaching maximum at 24 h with warfarin treatment was observed. However, intragroup or intergroup decreases in protein S levels were not different. On thromboelastogram, INTEM and EXTEM clotting times were significantly prolonged chronologically, but this prolongation was not different between groups.

CONCLUSION

The suppressor effect of warfarin on proteins C and S in the early period of double anticoagulant treatment did not appear to aggravate the risk of thrombosis in patients with PTE in whom warfarin was started simultaneously with UFH.

African American race was associated with an increased risk of complications following venous thromboembolism

OBJECTIVE

Limited data exist on the quality of care for patients with venous thromboembolism (VTE), and it is unknown whether the processes and outcomes of care for this illness differ between African Americans and whites.

STUDY DESIGN AND SETTING

We retrospectively studied 168 patients hospitalized for VTE in two Veterans Affairs hospitals during fiscal years 2000-2002. Patient characteristics, information about processes of care, and medical outcomes at 90 days after the index VTE event were abstracted from medical records. We used logistic regression to explore associations between race, processes of care, and the overall 90-day complication rate (i.e., death, bleeding, or recurrent VTE), adjusting for patient baseline characteristics.

RESULTS

Multivariable analysis demonstrated that administration of warfarin within 1 day of starting heparin (odds ratio [OR] 0.20, 95% confidence interval [CI]: 0.05-0.42) and overlap of heparin and warfarin treatment >or=4 days (OR 0.09, 95% CI: 0.02-0.50) were associated with a lower complication rate, and African American race was associated with a higher complication rate (OR 5.2, 95% CI: 1.3-21.6). Race was not significantly associated with the performance of processes of care in multivariable analysis.

CONCLUSION

Although African Americans had an increased risk of complications following VTE, race was not independently associated with the use of processes of care for VTE.

Acute thrombotic disorders

The acquired hypercoagulable states are responsible for a broad range of thrombotic and thromboembolic disorders. Symptoms and signs of acute ischemia or organ dysfunction will lead many of these patients to seek care in EDs. Proper diagnosis and therapy must be based on an understanding of epidemiology and pathophysiology. Immediate anticoagulation with heparin may not always be the treatment of choice; careful analysis of clinical and laboratory parameters is necessary to arrive at the safest and most effective course of action. Newer anticoagulants, including low-molecular-weight heparins and nonheparin compounds, are changing the therapeutic approach to many of these disorders.

Management of oral anticoagulants in the treatment of venous thromboembolism

Venous thromboembolism still represents a major public health problem. After initial heparin therapy, oral anticoagulants are the treatment most often used. Bleeding is the major risk of such a therapy. This review of the literature emphasises the practical aspects of the clinical management of oral anticoagulant therapy, such as initiation, monitoring, interaction, withdrawal, optimal duration, bleeding complications and non-haemorrhagic adverse reactions.

Safety of warfarin anticoagulation in patients with heparin-induced thrombocytopenia

OBJECTIVES

Venous limb gangrene has been reported to occur after high warfarin doses in heparin-induced thrombocytopenia (HIT), and this observation has been used to exclude warfarin management in this condition. The outcome of patients receiving modest doses of warfarin was studied.

DESIGN

Retrospective study of 114 consecutive HIT patients who received diagnoses by platelet aggregometry; 51 of the 114 patients received warfarin.

SETTING

Tertiary-care medical center.

RESULTS

Thirty-five patients received warfarin for non-HIT indications, and 16 received warfarin for heparin-associated thrombosis. Warfarin was given to 23 patients (47%) 2.4 +/- 0.4 days prior to the onset of HIT, in 19 while receiving IV heparin for an overlap of 2.7 +/- 0.4 days. Twenty-eight patients (53%) received warfarin 2.8 +/- 1.0 days after the diagnosis of HIT. Patients received 11 +/- 1 doses of warfarin over 16 +/- 2 days, with a mean daily dose of 3.5 +/- 0.5 and a maximum dose of 9 +/- 0.5 mg. Prothrombin time at discharge was 17.3 +/- 0.4 s with a maximum of 22.8 +/- 0.8. The final international normalized ratio was 2.9 +/- 0. 3, and the maximum was 7.5 +/- 1.4. The minimum therapeutic range was reached in 59% of determinations. When compared to the 63 patients who did not receive warfarin, warfarin patients received more IV heparin (86% vs 41%; p < 0.001), open heart surgery (78% vs 43%; p < 0.001), and had a lower mortality (8% vs 43%; p < 0.001), but had no differences in thrombosis.

CONCLUSIONS

Modest doses of warfarin were not associated with a worse outcome in patients with HIT.

Inadequacy of current prevention strategies for heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia is one of the most difficult problems facing clinicians today. Despite recent understanding of the pathophysiology of this disorder, there are many unresolved issues about diagnosis, prevention, and treatment. In this article, difficulties physicians encounter when faced with a suspected heparin-induced thrombocytopenia patient will be reviewed as well as our experience in 113 patients with heparin-induced thrombocytopenia which highlights the failure of current preventive strategies for heparin-induced thrombocytopenia. The experience of using warfarin in 51 patients with heparin-induced thrombocytopenia will also be reviewed.

Oral anticoagulants for the treatment of venous thromboembolism

Oral anticoagulation has been the mainstay of therapy for the long-term treatment of venous thromboembolism since the 1940s. The rationale for the use of oral anticoagulation is based on the results of both empirical clinical evidence and animal models of thrombosis in the 1950s and 1960s. Higher-quality studies emerged in the 1970s and 1980s demonstrating the benefit of initial heparinization for venous thromboembolism followed by long-term oral anticoagulation. Good clinical outcomes with oral anticoagulation are highly dependent on the quality of dose management. Excellent management is best achieved in a programme of focused and co-ordinated care, often referred to as an anticoagulation clinic. Such programmes achieve better outcomes at reduced costs because of fewer adverse events. New models of anticoagulation management are emerging with the development of point-of-care testing that enables patients to do their own prothrombin time monitoring and anticoagulation dose adjustment. These models have the potential to improve care further, to increase patient satisfaction and to reduce costs.

[Current data on the treatment of venous thromboembolic disease]

Venous thromboembolism disease is frequently seen in medical practice. Its morbidity, mortality and long-term sequels, as well as its haemorrhagic iatrogenic complications, represent a major problem of public health. For therapeutic management, we can usually use in medical practice non-fractionated heparin or low molecular weight heparin, sometimes substituted by antivitamin K therapy. Vena cava filter, surgical thrombectomy or thrombolytic therapy are rarely used. Elastic contention should by systematically prescribed. Therapeutic guidelines have been published on the recommendation furnished by randomised controlled trials. Low molecular weight heparin and early substitution by antivitamin K permitted an ambulatory treatment for deep vein thrombosis. The optimal duration of anticoagulant therapy is still controversial. Adequate biological survey causes decreasing incidence of haemorrhagic complications.

Treatment of venous thrombo-embolism

Clinically suspected deep vein thrombosis (DVT) or pulmonary thromboembolism (PE) should be initially treated with heparin, and an objective diagnosis obtained. In pregnancy, heparin is usually continued until delivery, following which warfarin is substituted. In the absence of pregnancy, warfarin is substituted and usually continued for 3 months after a first thrombo-embolic event. Low molecular weight heparins are increasingly preferred to unfractionated heparin in non-pregnant patients with acute DVT, because of efficacy when given by daily subcutaneous injection without routine monitoring of coagulation assays, greater efficacy, and lower risks of major bleeding and of mortality. Unfractionated heparin requires monitoring by the APTT (target ratio 1.5-2.5), and warfarin requires monitoring by the International Normalized Ratio (INR) of the prothrombin time (target ratio 2.0-3.0). Graduated elastic compression stockings reduce post-thrombotic leg symptoms after DVT. Secondary prevention is important in future high risk situations.

Anticoagulants for venous thrombosis

The anticoagulant agents heparin and warfarin were introduced before the era of randomised clinical trials. As a result, the indications, dosages and monitoring techniques of these drugs have undergone re-evaluation in multiple clinical trials in the past years. Low molecular weight heparin has been developed, which has led to new approaches in anticoagulant management. Current levels of laboratory, pharmacology and clinical knowledge in the treatment of venous thromboembolism are discussed.

Management of suspected acute venous thromboembolism in a general and maternity hospital

A retrospective study of the management of patients with suspected acute deep venous thrombosis (DVT) and pulmonary thromboembolism (PTE) in a general and maternity hospital was conducted over a two month period in 1992. Ninety six patients with suspected DVT/PTE were identified, of whom only two were pregnant. Forty four patients had suspected DVT and confirmatory investigations were performed in 84%. The most common risk factor for DVT was intra-venous drug (IVD) use. Unfractionated heparin was prescribed to all patients except one with acute DVT at an average daily dose of 25,000 iu. In patients receiving heparin, 68% had measurements of the activated partial thromboplastin time (APTT) ratio and on 38% of occasions the result was subtherapeutic. Complications of heparin therapy were infrequent. Fifty two patients had suspected PTE and 50 underwent ventilation/perfusion (V/Q) scanning. No patient underwent pulmonary angiography. The management of patients with normal, low and high probability V/Q scans was in keeping with the guidelines, but only 8% [corrected] of patients with an intermediate V/Q scan result had further investigations and 33% received heparin. This study revealed suboptimal anticoagulation of patients with acute DVT and scope for improvement in the management of patients with an intermediate V/Q scan result.

A critical pathway to treat proximal lower-extremity deep vein thrombosis

To address variation in treatment of deep vein thrombosis (DVT) while maximizing the efficiency and quality of care, our institution developed a critical pathway guideline. This paper presents this critical pathway and the clinical rationale underlying its recommendations. The DVT pathway synthesizes recommendations for all aspects of patient care, including laboratory evaluation at admission, dosing and management of heparin therapy, timing of warfarin initiation, elements of patient education, discharge planning, and anticipated duration of heparinization and hospitalization. Differences among interpretations of the medical literature, patient populations, physician skills, test availability, and other variables make it unlikely that all elements of this pathway would best meet the needs of another institution. Nevertheless, the critical pathway format and the specific contents of this pathway may serve as a useful benchmark for others involved in creating clinical guidelines for this patient population.