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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. Pulmonary Embolism. Pathogenesis Vichow’s triad Clot dislodgement Release of vasoactive substances increased pulmonary vascular resistance bronchoconstriction

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DVT Prophylaxis and Pulmonary Embolism in Surgical Patients

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  1. DVT Prophylaxis and Pulmonary Embolism in Surgical Patients Bradley J. Phillips, MD Burn-Trauma-ICU Adults & Pediatrics

  2. Pulmonary Embolism • Pathogenesis • Vichow’s triad • Clot dislodgement • Release of vasoactive substances • increased pulmonary vascular resistance • bronchoconstriction • Epidemiology • Incidence = 1/1000 per year • Mortality (1 year) = 15 %

  3. 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 Risk Factors - Acquired

  4. Risk Factors - Hereditary • Protein C deficiency • Protein S deficiency • Antithrombin III deficiency • Factor V leiden mutation

  5. 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)

  6. Clinical features ABG Chest X-ray EKG D-Dimer Lung Scan LE doppler Spiral CT PA catheter TTE Diagnosis Gold Standard: Pulmonary Angiogram

  7. 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 Clinical Presentation

  8. 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 ClinicalAngiogram

  9. 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

  10. ABG’s • 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

  11. CXR • Essential for possible Exclusion • Poor sensitivity and specificity • PIOPED • 85% of PE had abnormal CXR • atelectasis (most common) • infiltrates • Other findings: Hampton’s hump, Westermark’s sign, enlarged hilum, pleural effusion, cardiomegaly

  12. 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

  13. 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

  14. 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

  15. Probability of PE Clinical Suspicion V/Q Scan Probability (%) High High 96 Moderate High 80 Low High 50 Low Low 5

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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”

  25. Unproven Test • Echocardiogram • Spiral CT scan • D-Dimer (plus ?) • MRI (for DVT)

  26. 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

  27. 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

  28. Spiral CT role is undefined, but emerging as standard of care 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)

  29. 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)

  30. 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 %

  31. D-Dimer • Perrier, 1996 • normal d-dimer and nondiagnostic V/Q excludes PE (>90%) • Egermayer,1998 • parameters • D-dimer positive or negative • PaO2 < or > 80 mmHG • RR < or > 20

  32. 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 • Inconsistent confirmation test • ? Patients with pre-diagnosis PaO2 < 80

  33. D-Dimer • Critical deterrents • problems in development of rapid reproducible standardized assay • clinical conditions in ICU can result in accelerated fibrinolysis and elevated d-dimer • recent surgery • infection • malignancy • Bottom-line: D-dimer useful if negative and V/Q scan low probability

  34. Management • Anticoagulation • Thrombolytic therapy • IVC Filter • Embolectomy

  35. Anticoagulation • Heparin/Coumadin - mainstay therapy • Alternatives • Low molecular weight heparin • no difference in disease recurrence, death, or major bleeding • more convenient, but more expensive • presently not approved • Thrombocytopenia and HIT • Heparinoids • Hirudin • Ancrod

  36. Length of Therapy • Controversial • Schulman, 1996 • 6 weeks vs 6 months • former group twice recurrence, no difference hemorrhage • British Thoracic Society, 1992 • 4 weeks vs 3 months • former significant higher recurrence and failure of resolution • subgroup post-operative DVT/PE no difference

  37. Thrombolysis • Significantly accelerated resolution of pulmonary emboli • No significant difference in mortality but trend in massive PE • Complications • significantly higher hemorrhage rates • ? Higher stroke rates • ? role in post-operative patients • use of lower doses • 7-14 days post surgery reported studies

  38. IVC Filter • Indications • ABSOLUTE • Contraindication to anticoagulation • Failure on anticoagulation • RELATIVE • relative contraindication to anticoagulation • free floating iliocaval thrombus • compromised pulmonary vasculature • intention to administer thrombolytic therapy

  39. IVC Filter • Efficacy • No large scale prospective trial • 4% recurrent PE • 3% caval thrombosis • Complications (<10%) • death (0.12%) • filter migration • filter erosion • IVC obstruction • insertion technique

  40. Embolectomy • Trendelenburg pioneered surgery for acute PE in dogs (1920’s) • No bypass • Sternotomy • Partial occlusion clamps applied to pulmonary truck and cavas occluded • Incised truck and clot removed • Predictor of death is preoperative or perioperative death

  41. Embolectomy • Indications • angiographic evidence of pulm vascular obstruction ( Miller index > 27) • 60% deficit in perfusion scan • refractory hypotension • pulmonary hypertension mean > 35 mmHg

  42. Embolectomy • Kieny, 1991 • reviewed 134 (122 under bypass, 12 modified T-berg) • 30 day survival 84 % • Deaths • 15% bypass • 41 % modified T-berg • Meyer, 1991 • 60% survival in 96 patients under bypass • Percutaneous extraction (Greenfield) • 76 % success rate, 30 survival 70%

  43. Newer Prevention Strategies? • Low-weight molecular heparin • General Surgery • No significant difference for overall group • Orthopedics • Total hip and knee arthroplasty • Spinal cord injury • Oncologic Surgery • More effective than unfractionated heparin • *Outpatient Prophylaxis (1 month) Bergqvist et al, NEJM, 346(13):975-80, 2002 • Trauma • Geerts et al, NEJM, 335:701, 1996 • Knudson et al, J Trauma, 41:446, 1996 • Greenfield et al, J Trauma, 42:100, 1997

  44. Problems with Studies

  45. LMWH and Cancer Surgery Mismetti et al, British Journal of Surgery. 88(7):913-30, 2001

  46. LMWH and Trauma Geerts et al, NEJM, 1996

  47. Trauma and LMWH Knudson et al, J Trauma, 1996

  48. Trauma and LMWH Greenfield et al, J Trauma, 1997

  49. Outcomes LMWH in Trauma • Lower incidence of DVT • Bleeding complications low overall • Only small studies • Haven’t fully address safety from bleeding • Bottom-line • Better prophylaxis in high-risk patients • Bleeding risk still unknown vs unfractionated heparin • Mutlicenter trial needed to assess bleeding risk

  50. Summary • Prevention of DVT/PE • Identify patients at risk (most if not all surgery patients) • Methods vary • Consider high risk patients for LMWH • IVC filter in patients you can not anticoagulant • ? Surveillance doppler in high-risk asymptomatic patients • Probably of benefit in pelvic fractures • PE Diagnosis • High level of suspicion even if with only symptom is dyspnea • Spiral CT scan with IV contrast excellent to rule-out proximal PE and other lung parenchyma disease, but limited • Consider pulmonary angiogram if suspicion high and other test equivocal

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