DVT complete diagnostic approach resident survival guide

Complete Diagnostic Approach

A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.

Characterize the symptoms in the involved extremity: ❑ Swelling ❑ Pain ❑ Erythema ❑ Warmth

Identify possible precipitating factors: ❑ Recent surgery ❑ Hospitalization ❑ Trauma ❑ Pregnancy ❑ Postpartum ❑ Heart failure ❑ Immobility ❑ Recent bed rest ❑ Recent cast of lower extremities ❑ Obesity ❑ Active malignancy ❑ Treatment for malignancy within the last 6 months ❑ Stroke ❑ Paralysis ❑ Paresis ❑ Oral contraceptive or hormone replacement therapy Obtain a detailed history: ❑ Previous episode of VTE ❑ Age ❑ Location ❑ Past medical history: ❑ Atherosclerosis ❑ Collagen vascular disease ❑ Heart failure ❑ Myeloproliferative disease ❑ Nephrotic syndrome ❑ History of thrombophilia ❑ Factor V Leiden mutation ❑ Prothrombin gene mutation G20210A ❑ Protein C or S deficiency ❑ Antithrombin (AT) deficiency ❑ Antiphospholipid antibody syndrome ❑ Abortion at second or third trimester of pregnancy (suggestive of an inherited thrombophilia or APS) ❑ Drugs that may induce APS ❑ Hydralazine ❑ Phenothiazine ❑ Procainamide

❑ Examine the patient: Extremities ❑ Unilateral calf or thigh tenderness ❑ Unilateral calf or thigh pitting edema ❑ Unilateral calf or thigh swelling ❑ Difference in calf diameters > 3 cm (the calf circumference is measured 10 cm below the tibial tuberosity) ❑ Difference in thigh diameters (the thigh circumference is measured 10-15 cm above the patella) ❑ Unilateral calf or thigh warmth ❑ Unilateral calf or thigh erythema ❑ Palpable cord (a thickened palpable vein suggestive of thrombosed vein) ❑ Dilatation of unilateral collateral superficial veins ❑ Localized tenderness upon palpation of the deep veins ❑ Posterior calf ❑ Popliteal fossa ❑ Inner anterior thigh ❑ Homan's sign: tenderness upon dorsiflexion of the foot (not reliable) ❑ Generalized edema (suggestive of nephrotic syndrome) Abdominal exam ❑ Ascites (suggestive of Budd Chiari syndrome, that is hepatic vein thrombosis) ❑ Hepatomegaly (suggestive of Budd Chiari syndrome, that is hepatic vein thrombosis)

Assess the pretest probability of DVT (Wells score shown below)

Consider alternative diagnoses: ❑ Muscle strain or muscle tear ❑ Immobilization that led to leg swelling ❑ Lymphedema ❑ Lymphangitis ❑ Chronic venous insufficiency ❑ Venous obstruction ❑ Baker's cyst ❑ Cellulitis ❑ Superficial thrombophlebitis ❑ Hypoproteinemia ❑ Nephrotic syndrome ❑ Cirrhosis

Order tests: ❑ CBC-D ❑ PT and aPTT ❑ Creatinine ❑ Liver function test

Is the suspected DVT a first or a recurrent episode?

First suspected episode

Suspected recurrent episode

Assess the pretest probability of DVT (Wells score shown below)

(Click here for the diagnostic approach)

Low pretest probability (Click here for the diagnostic approach)

Moderate pretest probability (Click here for the diagnostic approach)

High pretest probability (Click here for the diagnostic approach)

Initial Anticoagulation Choices (DVT)

❑ SC low molecular weight heparin (1st line)

❑ Enoxaparin 1.0 mg/kg every 12 hours OR 1.5 mg/kg once daily

❑ Tinzaparin 175 U/kg once daily

❑ SC fondaparinux (1st line)

❑ 5 mg once daily (if body weight <50 kg)

❑ 7.5 mg once daily (if body weight <50-100 kg)

❑ 10 mg once daily (if body weight >100 kg)

❑ IV unfractionated heparin

❑ 80 U/kg as bolus, followed by 18 U/kg/h, OR

❑ 70 U/kg as bolus, followed by 15 U/kg/h for stroke or cardiac patients

❑ Adjust the dosages according to the aPTT

❑ SC unfractionated heparin

❑ 333 U/kg as bolus, followed by 250 U/kg

Anticoagulation for VTE

Warfarin

• Begin with 10 mg warfarin for 2 days followed by dosing based on the INR
• Start at the 1st or 2nd day of the initial parenteral therapy
• Target INR is 2-3
• Monitor INR:
  • If stable, repeat INR every 12 weeks
  • If stable but one value 0.5 below or above the target range, continue the same dose and repeat INR within 1-2 weeks
• Avoid NSAIDs, COX2 selective NSAIDs and some antibiotics

Heparin

IV-UFH

• 80 U/kg as bolus, followed by 18 U/kg/h
• 70 U/kg as bolus, followed by 15 U/kg/h for stroke or cardiac patients

SC-UFH

• 333 U/kg as bolus, followed by 250 U/kg

LMWH: decrease dose in renal insufficiency (Creatinine clearance < 30 mL/min)

Fondaparinux

• 7.5 mg daily
• 10 mg daily if weight>100 Kg