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VENOUS THROMBOEMBOLISM - MANAGEMENT
Deep vein thrombosis is a frequent manifestation of venous thromboembolism in which there is a blood clot blocking a deep vein.
Clinical findings are important to the diagnosis of deep vein thrombosis but are poor predictors of the presence or severity of thrombosis.
Pulmonary embolism is the blockage of the blood vessels in the lungs usually due to blood clots from the veins, especially veins in the legs and pelvis.
Dyspnea, pleuritic chest pain, syncope and tachypnea occur in most cases of pulmonary embolism.
Massive pulmonary embolism has the prime symptom of dyspnea and systemic arterial hypotension that requires pressor support is the predominant sign.

Monitoring

During Anticoagulation

  • International normalized ratio (INR) should be checked at least weekly during the 1st several weeks of Warfarin therapy
  • If stable, monitor every 2 weeks then every 4 weeks
  • Target INR is 2.5 for most patients and 3.0 for patients with recurrent VTE

Without Anticoagulation Therapy

  • Recommended for patients with isolated distal leg DVT and no severe symptoms or risk factors of extension, and those with subsegmental PE without proximal leg DVT
  • Serial ultrasound imaging of both legs for 2 weeks is suggested for patients with isolated distal leg DVT without severe symptoms or risk factors of extension

Follow Up

  • Patients with acute PE have a high frequency (20-50%) of symptomatic extension of thrombus and/or recurrent VTE and therefore require long-term anticoagulant treatment
  • Treatment with oral anticoagulant is the preferred method of long-term management of most patients with PE
  • Adjusted doses of unfractionated Heparin (UFH) or low-molecular-weight Heparin (LMWH) may be indicated for selected patients in whom oral anticoagulants are contraindicated or impractical
    • LMWH regimens are preferred in cancer patients since they have been found to be more effective and at least as safe for the 1st 3-6 months of therapy

Low-Molecular-Weight Heparin (LMWH)

  • Patients with PE and cancer, LMWH is preferred and should be used for the 1st 3-6 months of long-term anticoagulant therapy
    • After which, these patients should receive oral anticoagulant therapy indefinitely or until cancer has resolved
  • Treatment option for patients with recurrent VTE unresponsive to vitamin K antagonists (VKA) therapy
    • Dose may be increased if there is treatment failure to present dose

Oral Anticoagulant

  • Duration of anticoagulation is dependent on the type of event and the coexistence of prolonged risk factors:
    • Continue x ≥3 months: 1st event with reversible or time-limited risk factors
    • Continue x ≥6 months: 1st episode, idiopathic VTE 
    • Continue x ≥12 months: Recurrent, idiopathic VTE or continuing risk factor
    • Continue x 6-12 weeks: Symptomatic isolated calf vein thrombosis
    • Consider for indefinite anticoagulation: 2nd episode of unprovoked PE, or patients with PE and cancer without high bleeding risk
  • For patients with leg DVT or PE, non-vitamin K oral anticoagulants (NOACs) are preferred over VKA agents for the 1st 3 months of long-term anticoagulant therapy
    • VKA agents are preferred over LMWH for patients with VTE
    • For VTE patients with cancer, LMWH is preferred over VKA agents and NOACs

Aspirin

  • May be considered for the prevention of recurrent VTE in patients with unprovoked proximal DVT or PE who discontinued anticoagulant therapy

Risk Factors for Major Bleeding During Anticoagulation

  • Age >75 years old
  • Previous gastrointestinal (GI) bleeding
  • Previous noncardioembolic stroke
  • Chronic hepatic and renal disease
  • Concomitant antiplatelet therapy
  • Poor anticoagulant control
  • Suboptimal monitoring of therapy
  • Comorbid illness

International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) Bleeding Risk

  • Used to assess a confined patient’s risk for bleeding prior to initiation of therapy
  • Score of ≥7 signifies increased bleeding risk
 Score  Medical History
 4.5 Active gastric or duodenal ulcer 
 4 Bleeding event <3 months before consultation; thrombocytopenia (platelet count <50 x 103/L)
 3.5 ≥85 years of age
 2.5 Liver failure (INR >1.5); severe renal failure (GFR <30 mL/min/1.73 m2); ICU/CCU admission
 2 Central venous catheter; rheumatic/autoimmune disease; current malignancy
 1 40-84 years of age; male; moderate renal failure (GFR 30-59 mL/min/1.73 m2)

Prompt Management of Clinical Instability

O2 Supplementation

  • May be necessary in patients with hypoxemia
  • Hypoxemia can usually be reversed with nasal O2 so that mechanical ventilation is rarely necessary

Mechanical Ventilation

  • May be needed temporarily in patients who appear toxic and hypoxic
  • Care should be taken to limit its hemodynamic adverse effects
    • Positive intrathoracic pressures induced by mechanical ventilation may reduce venous return and worsen RV failure
  • Low tidal volumes of approximately 6 ml/kg body weight are recommended

Hemodynamic Support

Fluid Loading

  • Fluids may be administered initially and cautiously, but other vasoactive therapy should promptly follow
  • The usefulness of fluid challenge is controversial and should not exceed 500 mL
    • May be harmful when systemic hypotension is present

Adrenergic Agonists

  • Should be considered for patients with low cardiac index and normal blood pressure or with impending hypotension

Dobutamine

  • Considered 1st-line agent to treat right-sided heart failure and cardiogenic shock
  • Action: Affects vasodilatation of both systemic and pulmonary vascular beds, increases myocardial contractility while decreasing right-sided filling pressures

Dopamine

  • Has also been used for hemodynamic support in PE patients
  • Use may be limited by the development of tachycardia

Epinephrine

  • May be effective when shock complicates acute PE
  • Action: Vasoconstrictor effect similar to Norepinephrine, inotropic effect more due to potent β1 stimulation rather than β2 effect, accounting for improved pulmonary vascular resistance

Norepinephrine

  • May be appropriate in acute massive PE when there is profound hypertension
  • Action: Stimulates both α-adrenergic (inducing vasoconstriction) and β1-adrenergic receptors (augmenting cardiac contractility) resulting in improved systemic blood pressure, cardiac output, pulmonary vascular resistance and right ventricular pressure
  • Combination with other vasoactive agents (eg Dobutamine) needs further evaluation

Nitric Oxide Inhalation

  • May be indicated in patients with pulmonary hypertension and a patent foramen ovale
  • Effects: May improve the hemodynamic status and gas exchange in patients with PE
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