DEEP VEIN THROMBOSIS let.pptx

7/28/2019 DEEP VEIN THROMBOSIS let.pptx

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EPIDEMIOLOGY2 MILLION VENOUS THROMBOTIC EVENTS OR VTE500,000 ARE DEEP VEIN THROMBOSIS

200,000 PULMONARY EMBOLISM


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OVER 150 YEARS, VIRCHOW POSTULATEDTHAT THROMBUS FORMATION ANDPROPAGATION RESULTED FROM

ABNORMALITIESBLOOD FLOWVESSEL WALLBLOOD COMPONENTS


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1. BLOOD FLOW- VENOUS STASISABNORMALITIES OF HAEMOORHEOLOGY ANDTURBULENCE AT VESSEL BIFURCATIONS AND

STENOTIC REGIONS


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2. Vessel walls- impaired function of vesselwallAbnormalities in the endothelium, such as

atherosclerosis, and associated vascularinflammation


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3.Blood components- changes in bloodconstituentsAbnormalities in coagulation and fibrinolytic

pathways


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Initiated by action of tissue factor (TF) inFactor VII after injury to vessels exposes thesubendothelium and promotes platelet

adhesion and aggregation to forma primaryplatelet plug


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The process is completed by actions of multiple components and factors in the bloodthat generate thrombin, potent rate-

regulating enzyme, which interacts withfibrinogen and Factor XIII to form aninsoluble clot


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Malignancies, sustain venous damage(surgical procedure) there is up regulation of thrombin. TF, fibrin and thrombin have

angiogenic properties that can interfere withtissue properties by degrading matrixmetalloproteinases, promoting cell migrationand enhancing metastasis.


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Tumors up regulate the production of TF andplasminogen activator inhibitor-1 (PAI-1)again promoting generation of procoagulant

activity


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In addition to postsurgical reactions, there isincrease in fibrinogen, Factor V, Factor VIII,and Von Willebrand factor which promote

platelet adhesion and function


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Increases platelet number, normalfibrinolytic response is blunted by theincrease PAI-1 and thrombin, activable

fibrinolysis inhibitor (TAFI)


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Fibrinolytic system is non-functionalfollowing surgeryPreventings degradation of fibrin


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Venous stasis is the cornerstone of postoperative thrombosisResults to platelet activation, promotingadhesions of platelets to endothelial cellslining the vessel, stressed to procoagulantmodeThese encourage the development of athrombus


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The most common type of VTE is DVTDVT is the formation of a blood clot in adeep vein, usually in a calf or thigh muscle


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Venous return from the lower extremity isdecreased by half during surgical proceduresbecause of the impact of muscle relaxationfrom anesthetic agentsLower extremity blood flow has been shownto decrease to about 75% of the normaldrainage flow immediately after surgery


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This is an important reflection of virchows triad on the role of adequate vessel flow.This reduction in flow persists for about 14

days after surgery because of the loss of muscl pumping function in the legs


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The major site of thrombus formation is thesoleal venous sinuses of the calf


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Another contributing factor to venous stasisduring prolonged surgery is the use of tightpacking of the intestines in the upperabdomen with obstruction of the underlyingvena cava


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Thrombus/ clot embolizes to the lungsMild PE, could be asymptomatic, or severeenough to cause an immediate cardiac attack


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AGE >40 YEARS OLDOBESITY >20% ABOVE IDEAL WEIGHTPROLONGED SURGERY

IMMOBILITY (PRE-, PERI-, POST OPERAITVE)PELVIC MALIGNANCYPRIOR VTE

TRAUMA


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THOMBOPHILIADIABETESHEART FAILURE

PRIOR RADIATIONCHRONIC OBSTRUCTIVE PULMONARY DISEASEVARICOSE VEINSSEPSIS

ACUTE INFLAMMATORY DISEASE WITHIMMOBILIZATIOI\N


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Molecular Hypercoagulable stateDeficiency anti thrombinProtein C

Protein SHeparin cofactor IIFactor V LeidenProthrombin variant 20210A


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Antiphopholipid antibodiesLupus anticoagulantAnticardiolipin

HyperhomocystinuriaDysfibrinogenemiaDec plasminogenDec Plasminogen activatorsHeparin-induced thrombocytopenia


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PregnancyEstrogen therapy (OCP)Inflammatory bowel disease

Nephrotic syndromeHyperviscosity


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Classically = calf pain, tenderness, swelling,redness and Homans sign Overall sens/spec = 3-91% Unreliable for diagnostic decisions Up to 50% have none of these

Wells developed and tested a clinicalprediction model for DVT


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Swelling in one or both legsPain or tendernessWarmth in the skin of the affected leg

Red or discolored skinVisible surface veinsLeg fatigue


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Dyspnea, pleuritic pain and cough mostcommon symptoms

Tachypnea, rales and tachycardia mostcommon signs


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PE Assign Pretest Probability


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The following were assigned a point valueof 1 if present


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Paralysis or plaster immobilization Bedrest > 3 d or surgery in past 4 wks Localized tenderness

Entire leg swollen Calf > 3cm larger than unaffected leg Pitting edema greater than unaffected leg Collateral superficial veins

Alternative diagnosis more likely than DVT = - 2 points Probability High ( 3), Moderate (1-2) or Low (0 or less) DVT risk: High 75%, Moderate 17%, Low 3%


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Single most important step in the diagnosisof pulmonary embolismMay be done based on clinical judgment oraided by a clinical scoring system

Modified Wells Criteria is the most widelyused and studiedReliably stratifies patients by likelihood of PEto allow selection of safe (


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33 year old, female4 major surgeries due to intestinalobstruction

Prolonged surgeryImmobilization post-operativePost blood transfusion


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Signs and symptomsOn and off low grade fever of unknown originUpper extremity pain and edema on the left, 7 th post operative daySudden onset of cough, chest pain, dyspneatachycardia


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EKG- arrythmiaCXR -


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Drug feverThrombophlebitis


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I125 labeled Fibrinogen scanning

It involves the intravenous injections of isotope-

labeled fibrinogen, which is expected to beincorporated into the evolving thrombus and can beimaged by a scintillation scanner. Because of the useof isotopes, it is technically cumbersome and rarelyused, despite many large studies


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Impedance Plethysmographybased on the principal of electricalresistance in specific areas of the body.

When there is resistance to blood flow that isdue to a thrombus, there is markedreduction in the electrical resistance overthat vessel.


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Doppler UltrasoundDoppler ultrasound, often with computer colorenhancementmeasurement of flow velocity in larger blood vessels.

In this technique, a reflected sound signal isconverted to both an audible form and visual imageon a computer screen. In the presence of athrombosis, there is a decrease in the reflectedsignal that can be heard or, more likely, can bevisualized.


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Real-Time UltrasoundCompression UltrasoundDuplex Doppler Ultrasound

real-time and Doppler methods in a procedureknown as B modevisualize the vessel and identify any thrombus init


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Light Reflection RheographyRadioisotope ImagingIndirect Computed Tomography Venography


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Magnetic Resonance Imaging/MagneticResonance Imaging Venography

differences in signal intensities to distinguishflowing blood from stagnant blood


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Nonimaging Methodsautomated quantitative D-dimer assay

Blood test to measure fibrin degradationfragments generated by fibrinolysisIndicates thrombotic processUsed as an adjunct to non-invasive testing


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Sensitive d-dimer testing can rule out DVTin low-moderate risk patients


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With symptoms of DVTPositive D Dimer
http://www.ualberta.ca/~cw9/images/ddimer.jpg


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3 GoalsTo prevent PEHalt further thrombus formationDissolve existing thrombus

Cornerstone of DVTDose adjusted IV unfractionated heparin

which preventsbformation of new thrombi


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Bolus dose of heparin: 5000-10000 U EVInitial maintenance dose of heparin: 32000 UEV per 24h by continuous

infusion or 17000 U subcutaneously to berepeated after adjustment at 12h


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Adjust dose of heparin at 6h according tonormogram.Maintain aPTT 2 times the control

Repeat aPTT 6 times every hour until intherapeutic range and thendaily (see nomogram)Start warfarin 10mg at 24h and 10mg next

day.


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Overlap heparin and warfarin for at least 4daysPerform PT daily and adjust warfarin dose tomaintain INR at 2.0-3.0Continue heparin for a minimum of 5 days,then stop if INR has been intherapeutic range for at least 2 consecutive

days.


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Continue warfarin for 3 months and monitorPT daily until in therapeuticrange, then 3 times during first week, twiceweekly for 2 weeks , or until

dose response is stable, and then every 2weeksObtain pretreatment hemoglobin level,platelet count, PT, and aPTT.

Repeat platelet count daily until heparinstopped.


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Low Risk> Hospitalized medical patients without

risk factors

> Surgical patients under age 40, surgerylasting < 30 minutes, no additional riskfactors

Ambulatory leg exercises


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Moderate risk >Hospitalized medical patientswith one or more risk factors>>Low dose heparin

>Surgical patients over age 40 having abdominalor thoracic surgery lasting > 30 minutes>>Low-dose heparin

> Neurosurgery or others patients with highbledding risk-Intermittent pneumaticcompression odf legs


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High risk Hip fracture >> Warfarin(low dose regimen)Hip replacement

>Warfarin(low dose regimen) or LMWH Kneereplacement >>Warfarin(low dose regimen) andintermittent pneumatic compression of the legsGynecology Malignancy Intermittent pneumaticcompression of legs


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Bleeding


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DEEP VEIN THROMBOSIS let.pptx

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