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

A Prospective Study of Adequacy of Anticoagulation with Fixed Dose Weight Adjusted Unfractionated Heparin in Patients with Deep Vein Thrombosis

Weight adjusted fixed dose subcutaneous unfractionated heparin (UFH) is one of the options for the treatment of deep vein thrombosis (DVT), but the degree of its anticoagulant effect has not been tested in India. This was a prospective observational study, conducted at a tertiary care hospital in South India between September 2012 and March 2014. DVT was diagnosed using compression ultrasonography. UFH was given as an initial loading dose of 333 U/kg followed by a maintenance dose of 250 U/kg twice daily subcutaneously. aPTT was done on day 2 and day 4 after 6 h of the morning dose of heparin. Patients were categorized based on aPTT ratios. Fifty five patients treated for proximal lower limb DVT had received UFH. Their median age was 41 years. DVT was secondary to malignancy, immobilisation or pro-coagulant state. No obvious etiology was found in 47 % of the patients. The mean aPTT on day 2 was 41.8 s and 51.7 s on day 4. The aPTT ratio was subtherapeutic in 63.6 % and therapeutic in 32.7 % of the patients on day 2. Five patients had adverse events in the hospital. Three patients died and two other patients had confirmed pulmonary embolism. Death was due to pulmonary embolism in one patient and metastatic malignancies in the other two. No bleeding manifestation had occurred. Caution is required in implementing this UFH regimen as this preliminary investigation has found predominantly subtherapeutic aPTT ratios during the initial phase of anticoagulation.

Perioperative management of patients on chronic antithrombotic therapy

Perioperative management of antithrombotic therapy is a situation that occurs frequently and requires consideration of the patient, the procedure, and an expanding array of anticoagulant and antiplatelet agents. Preoperative assessment must address each patient's risk for thromboembolic events balanced against the risk for perioperative bleeding. Procedures can be separated into those with a low bleeding risk, which generally do not require complete reversal of the antithrombotic therapy, and those associated with an intermediate or high bleeding risk. For patients who are receiving warfarin who need interruption of the anticoagulant, consideration must be given to whether simply withholding the anticoagulant is the optimal approach or whether a perioperative “bridge” with an alternative agent, typically a low-molecular-weight heparin, should be used. The new oral anticoagulants dabigatran and rivaroxaban have shorter effective half-lives, but they introduce other concerns for perioperative management, including prolonged drug effect in patients with renal insufficiency, limited experience with clinical laboratory testing to confirm lack of residual anticoagulant effect, and lack of a reversal agent. Antiplatelet agents must also be considered in the perioperative setting, with particular consideration given to the potential risk for thrombotic complications in patients with coronary artery stents who have antiplatelet therapy withheld.

Perioperative management of patients on chronic antithrombotic therapy

Perioperative management of antithrombotic therapy is a situation that occurs frequently and requires consideration of the patient, the procedure, and an expanding array of anticoagulant and antiplatelet agents. Preoperative assessment must address each patient's risk for thromboembolic events balanced against the risk for perioperative bleeding. Procedures can be separated into those with a low bleeding risk, which generally do not require complete reversal of the antithrombotic therapy, and those associated with an intermediate or high bleeding risk. For patients who are receiving warfarin who need interruption of the anticoagulant, consideration must be given to whether simply withholding the anticoagulant is the optimal approach or whether a perioperative "bridge" with an alternative agent, typically a low-molecular-weight heparin, should be used. The new oral anticoagulants dabigatran and rivaroxaban have shorter effective half-lives, but they introduce other concerns for perioperative management, including prolonged drug effect in patients with renal insufficiency, limited experience with clinical laboratory testing to confirm lack of residual anticoagulant effect, and lack of a reversal agent. Antiplatelet agents must also be considered in the perioperative setting, with particular consideration given to the potential risk for thrombotic complications in patients with coronary artery stents who have antiplatelet therapy withheld.

Subcutaneous unfractionated heparin compared with low-molecular-weight heparin for the initial treatment of venous thromboembolism

PURPOSE OF REVIEW

Low-molecular-weight heparin is the preferred choice for the initial treatment of acute, uncomplicated venous thromboembolism. In this context, unfractionated heparin is as safe and effective as low-molecular-weight heparin but requires strict laboratory monitoring. Twice-daily subcutaneous unfractionated heparin is more effective than, and as safe as, intravenous unfractionated heparin and may simplify patient treatment in or out of the hospital, being possibly cost saving, especially if it is used in weight-based, fixed, unadjusted doses. The present review focuses on the relative values of low-molecular-weight heparin and subcutaneous unfractionated heparin for the initial treatment of venous thromboembolism.

RECENT FINDINGS

The major advantages of low-molecular-weight heparin over unfractionated heparin seem to be ease of administration and cost savings associated with home therapy or early hospital discharge; however, many patients with venous thromboembolism are still admitted to the hospital for treatment, and unfractionated heparin is extensively used to this purpose, especially in the United States. Subcutaneous unfractionated heparin, adjusted according to activated partial thromboplastin time algorithms, is as safe and effective as low-molecular-weight heparin for the treatment of venous thromboembolism, allows for quick mobilization and early discharge of suitable patients, and represents a cost-effective strategy. Fixed-dose unfractionated heparin, like low-molecular-weight heparin, may be used for the home treatment of deep vein thrombosis.

SUMMARY

Subcutaneous unfractionated heparin, targeted on activated partial thromboplastin time results or in fixed doses, may be used in or out of the hospital for the treatment of venous thromboembolism, being possibly cost effective; however, these findings need confirmation through appropriate, large-sample, randomized clinical trials.

New Therapeutic Approaches in Pulmonary Embolism

Pulmonary embolism as a part of venous thromboembolic disease has a broad spectrum of clinical presentations from minimal disease to life-threatening right heart failure. Therapy has to be guided by the risk associated with the individual clinical state of the patient. As long as hemodynamics are entirely stable, anticoagulation is given in order to prevent early or late recurrence, thereby allowing for endogeneous thrombolysis and recovery. In hemodynamically instable patients, i.e. patients under cardiopulmonary resuscitation or in shock, there is the need for a rapid reduction of thrombus mass in order to restore right ventricular function. Systemic thrombolysis is the most feasible modality to reduce the thrombus burden of the pulmonary circulation in the short term. For hemodynamically stable patients with right ventricular dysfunction as assessed by echocardiography, there is still some controversy as to whether thrombolysis improves the long-term outcome. At the least, thrombolysis may positively modify the short-term course of acute disease in patients with an extremely low risk of bleeding. When the acute phase has been overcome, secondary prophylaxis with vitamin K antagonists has to be given. The duration of secondary prophylaxis requires an individual assessment of both the risk of recurrence and the risk of bleeding. In the near future, new anticoagulant drugs such as direct thrombin and factor Xa inhibitors will offer new treatment modalities for the acute phase as well as for secondary prophylaxis.