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Download DVT Prophylaxis and Pulmonary Embolism in Surgical Patients DVT Prophylaxis and Pulmonary Embolism in Surgical Patients Bradley J. Phillips, MD Burn-Trauma-ICU

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  • DVT Prophylaxis and Pulmonary Embolism in Surgical Patients DVT Prophylaxis and Pulmonary Embolism in Surgical Patients Bradley J. Phillips, MD Burn-Trauma-ICU Adults & Pediatrics
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  • Pulmonary Embolism Pathogenesis Vichows triad Clot dislodgement Release of vasoactive substances increased pulmonary vascular resistance bronchoconstriction Epidemiology Incidence = 1/1000 per year Mortality (1 year) = 15 %
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  • Risk Factors - Acquired Medical Prior PE Age > 40 Obesity Malignancy CHF CVA Nephrotic Syndrome Estrogen Pregnancy Surgical General anesthesia > 30 minutes Hip arthroplasty Knee arthroplasty Major trauma Spinal Cord Injury Open prostatectomy Neurosurgical procedures
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  • Risk Factors - Hereditary Protein C deficiency Protein S deficiency Antithrombin III deficiency Factor V leiden mutation
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  • Risk Assessment Profile Significant risk in trauma patients Risk assessment profile of thromboembolism (RAPT) by Greenfield 5 or more (out of 14) increases risk 3 times Underlying condition Obese, malignancy, hx of thromboembolism Iatrogenic factors CVL, operations > 2 hrs, major venous repair Injury-related factor Spinal factures, coma, pelvic fx, plegia Age > 40 (highest risk > 75)
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  • Diagnosis Clinical features ABG Chest X-ray EKG D-Dimer Lung Scan LE doppler Spiral CT PA catheter TTE Gold Standard: Pulmonary Angiogram
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  • Clinical Presentation Symptoms Dyspnea 80% Apprehension 60% Pleurisy 60% Cough 50% Hemotysis 27% Syncope 22% Chest pain CHF (right) Hypotension Signs Tachypnea 88% Tachycardia 63% Increased P2 60% Rales 51% Pleural rub 17% Fever Wheezes JVD Cyanosis Shock
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  • Prospective Investigation of PE Diagnosis: PIOPED Prospective trial (817 patients) Clinical probability - history, PE, CXR, ABG, and EKG prior to V/Q and pulmonary angiogram Results: High likelihood (>80%) 32 % negative Low likelihood (< 20%) 9 % positive Indeterminant 30 % positive Clinical Angiogram
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  • Bottom Line: Subtle Manifestations Clinical features are vague, variable, and nonspecific Unexplained dyspnea Worsening hypoxia or hypocapnia in spontaneously ventilating patient Worsening hypoxia or hypercapnia in a sedated patient on controlled ventilation Worsening dyspnea, hypoxemia, and a reduction in arterial PCO2 in a patient with COPD and known CO2 retention
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  • ABGs Typical: hypoxia, hypocarbia, high A-a Nonspecific and limited value when used alone PIOPED normal ABG in 38% (without cardiopulmonary disease) normal ABG in 14% (with cardiopulmonary disease) If present, hypoxia roughly correlates with extent of embolism as judged by V/Q
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  • CXR Essential for possible Exclusion Poor sensitivity and specificity PIOPED 85% of PE had abnormal CXR atelectasis (most common) infiltrates Other findings: Hamptons hump, Westermarks sign, enlarged hilum, pleural effusion, cardiomegaly
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  • EKG Abnormalities are common in PE Diverse and nonspecific Changes T-wave inversion (most common) Classic (uncommon, massive PE) S1, Q3, T3 Pseudo-infarct pattern right heart strain
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  • EKG - Predicting PE Am J Cardio, 1994 49 patients seven defined features of ischemia/R strain if 3/7 positive, 76 % probably PE Chest, 1997 80 patients T-wave inversion in one or more precordial 68% of patients with PE Reversibility with thrombolysis =good outcome
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  • V/Q Scan Most algorithms use V/Q as first step PIOPED Most value if very low, low, or high probability when concordant clinical picture However, 4x incidence PE with V/Q very low/low prolonged immobilization lower limb trauma recent surgery central venous instrumentation
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  • Probability of PE Clinical Suspicion V/Q ScanProbability (%) High High96 Moderate High80 Low High50 Low Low 5
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  • V/Q scan PIOPED (understated) majority of patients with suspected PE did not fall into high probability or normal scan majority of patients with PE did not fall into high probability Most patients without PE did not have normal scan Significant percentage of patients with intermediate (33%) and low probability (16%) did have PE by angiogram
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  • V/Q scans - Newer Studies Chest, 1996 223 critically ill patients diagnostic utility as accurate as in non-critical patients PISA-PED (1996) presence of wedge-shaped defects regardless of size, number, or ventilation abnormalities Grades - normal, near normal, abnormal c/w PE, abnormal not c/w PE Sens. 92%, Spec. 87% Selection bias - normal or near-normal no angiogram, abnormal 38% no angiogram
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  • V/Q - Can it be done with the V? CXR + Q = no less positive or negative predictive value is high or low probability Others studies supportive if scan is read as high or low probability Indeterminant Q scan, requires V scan In cardiopulmonary disease, both V/Q scans required
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  • V/Q - COPD PE mimics underlying disease V/Q more limited Chest, 1992 108 patients with COPD 60% fell into intermediate 91% fell into intermediate or low However, high probability or normal 100% positive and negative predictive value
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  • V/Q Final Word A normal scan essentially r/o PE A high probability scan with high clinical suspicious confirms PE Scan with low or intermediate probability should be considered nondiagnostic Perfusion scan alone ok if high probability or normal
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  • Doppler Valuable role Same therapeutic implications as PE Criteria for diagnosis non-compressible (most accurate) presence of echogenic material venous distension loss of phasicity and augmentation of flow Sensitive (95%) in symptomatic thrombosis but not asymptomatic (30-60%) Consider serial exams in indeterminant V/Q
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  • Doppler and Pelvic Fx Proximal DVT 25-35% of pelvic fx Surveillance in asymptomatic patients For Van Den Berg et al, Intern Angiology, 1999 Incidence 8.7% trauma patients Aside finding: LMWH + stocking better than unfractionated heparin + stockings (DVT 6% vs. 11.5%, p < 0.05) Against Schwarz et al, J of Vasc Surg, 2001 2% incidence of DVT in high-risk trauma patient Limited use of surveillance doppler in patient on Lovenox
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  • PA catheter If present at time of PE helpful in diagnosis Therapeutic if hemodynamically unstable Findings normal wedge pressure marked elevation in right ventricular and pulmonary artery pressures
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  • Pulmonary Angiogram Virtually 100% sensitive and specific Expensive and invasive Complications 5/1111 (0.5%) deaths in PIOPED study 9/1111 (0.8%) nonfatal complications majority of patients were critically ill with sever compromised cardiopulmonary function before procedure few would argue against the risk of coronary angiogram in suspected coronary ischemia, but question often the risk of pulmonary angiogram for the diagnosis of PE
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  • Unproven Test Echocardiogram Spiral CT scan D-Dimer (plus ?) MRI (for DVT)
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  • Echocardiogram TEE more sensitive than TTE Demonstrate intracardiac clot or signs of right ventricular failure Emboli observed = 42-50% mortality rate Indirect evidence right ventricular dilation dilated pulmonary artery abnl right ventricular wall motion dilated vena cava
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  • TEE Sensitivity/Specificity > 90% Detects pulmonary truck, right and left main pulmonary arteries Incapable of detecting distal pulmonary emboli Valuable in evaluating for other causes i.e. tamponade, R CHF, dissection Positive test is accurate, negative test non-diagnostic Primary usefulness unstable patients in ICU setting
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  • Spiral CT role is undefined, but emerging as standard of care in some institutions in some institutions Several prospective studies Sensitive 94%, Specific 96% (Van Rossum, 1996) Greater sensitivity than V/Q (Mayo, 1997) Useful in indeterminant V/Q (alternate pathology) Confident diagnosis higher with CT than V/Q although no difference in detection (Cross, 1998)
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  • Spiral CT vs V/Q scan Advantages probably greater sensitivity proximal emboli alternate pulmonary pathology after hours availability Disadvantages operator dependent lower accuracy for distal emboli need for IV contrast ( ? Why not angiogram)
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  • D-Dimer Elevated in >90% of patients with PE Rises with intravascular coagulation Meta-analysis (29 studies) D-dimer alone vs other diagnostic test Latex agglutination 48-96 % sensitivity Elisa 88-100% sensitivity Specificity ranges 10-100 %
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  • D-Dimer Perrier, 1996 normal d-dimer and nondiagnostic V/Q excludes PE (>90%) Egermayer,1998 parameters D-dimer positive or negative PaO2 80 mmHG RR 20
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  • D-Dimer (Egermeyer, 1998) Confirmation with V/Q scan/ Angiogram Predictive value D-dimer negative = 0.99 PaO2> 80 = 0.97 RR < 20 = 0.95 D-dimer plus PaO2 = 1.0 Problems Inconsiste