CHAPTER 2 VENOUS THROMBOEMBOLISM
Objectives Venous Thromboembolism (VTE) Prevalence Patho-physiology Risk Factors Diagnosis Pulmonary Embolism (PE) Management of DVT/PE Prevention
VTE Patho-physiology Virchow s Triad Venous stasis. Endothelial injury. Hyper-coagulability. Brotman DJ, Deitcher SR, Lip GY, Matzdorff AC. Virchow's triad revisited. South Med J. 2004;97:213-214.
VTE Patho-physiology Dislodgement of blood clot Lower Extremities (65%-90%) Pelvic venous system Renal venous system Upper Extremity Right Heart http://www.realage.com/health_guides/dvt/img/dvt_art_v1.jpg
VTE Patho-physiology http://www.nursinglink.com/nfs/nursinglink/attachment_images/0 009/1991/DVT-main_Full.jpg http://clistersbackchannel.files.wordpress.com/2009/03/dvt1.jpg
VTE Risk Factors Pre-existing Conditions Thrombophilic Disorders Stroke Heart Disease Respiratory Disease Malignancy Varicose Veins Procedures Central Venous catheter/port/pacemaker.
VTE Risk Factors History of venous thrombo-embolism Increasing age (> 60 yrs) Surgery within prior 3 months or requiring >30mins of anesthesia. Immobility Recent travel (within prior 2weeks, >4 hrs).
VTE Risk Factors Specific to women: Obesity BMI 29 Pregnancy Hypertension Heavy smoking (> 25cigs/day) Hormone replacement therapy OCP s 10-30/100,000 users vs. 4-8/100,000 non-users.
Exam Findings
Anatomy of the Deep Venous System http://www.wsiat.on.ca/images/mlo/medial_veins.jpg
Exam Findings Calf tenderness Homan s Sign Differential Swelling www.netterimages.com
Well s Criteria (DVT) Well s Criteria (DVT) Active cancer (tx within <6 mos or palliative care) (1) Calf swelling (3 cm difference 10 cm below tib tub) (1) Collateral superficial veins (1) Paralysis, paresis, or recent immobilization LE (1) Pitting edema confined to involved leg (1) Bedridden within 3 days or surgery w/anesth <3mths (1) Swollen leg (1) Alternate diagnosis more likely (-2) Probability: Low (0 pts) Intermediate (1-2) High (3) Lancet 2002;350:1796.
D-Dimer 96-100% Sensitivity for active VTE if measured by ELISA or immunoturbidimetric method. Most studies use cutoff <500 ng/ml. Not highly sensitive if measured by semiquantitative latex agglutination. A low Well s Score Criteria plus a normal D-Dimer implies a LOW clinical risk of VTE. 0.5% of patients develop DVT in 3 months. Can defer further testing. What is the risk of DVT in a patient with a moderate or high risk Well s score and a normal D-Dimer? Moderate: 3.5% High risk: 21% Fancher TL, White RH, Kravitz RL. Combined use of rapid D-dimer testing and estimation of clinical probability in the diagnosis of DVT: systematic review. BMJ. 2004;329:821 Ann Fam Med 2007;5:57-62.
Venography Gold standard Invasive Expensive Primarily a research tool http://www.jaapa.com/media/images/48/dximaging1207fig2_47609.jpg
Ultrasonography Duplex scan of LE Compressibility of the vein Doppler flow within the vein Asymptomatic patient with proximal LE DVT Sensitivity: 47-62% Symptomatic patient with proximal LE DVT Sensitivity: 89-96% Specificity: 94-99% Symptomatic patient with distal LE DVT Sensitivity: 73-93%
Treatment of DVT Not Pregnant Low Molecular Weight Heparin (LMWH) 1 mg/kg q 12 hrs or 1.5 mg/kg q 24 hrs Coumadin x 3 months (Goal INR 2-3) LMWH should be overlapped until both of the following conditions are met: INR >2 x days At least five days of LMWH given Pressure stockings
Treatment of DVT Pregnant LMWH Monitor anti-factor Xa levels q 4 weeks (4 hrs after dose) Goal: 0.6 1.0 IU/ml (bid dosing) or 1-2 IU/ml for q day dosing Heparin bridge Stop LMWH 2 weeks before delivery. No epidural within 24 hrs of LWMW. Start Unfractionated Heparin with goal PTT 1.5-2.3 X normal Hold for delivery with restart 6 hours after vaginal delivery or 12 hours after C-section. Coumadin in the post-partum period Three to Six months Need to cover at least six weeks post-partum Ok for breast-feeding.
Treatment of DVT Obesity: Enoxaparin Drop dose by 25% for patients >144 kg Dalteparin Drop dose by 25% for patients > 190 kg
Treatment of DVT Chronic Kidney Disease No consensus guidelines exist for choice of anticoagulation in patients with GFR < 30 ml/min Bleeding risk and recurrent VTE risk are higher in such patients. If using LMWH, consider monitoring anti-factor Xa levels.