DVT Prophylaxis and Pulmonary Embolism in Surgical Patients

1
DVT Prophylaxis and Pulmonary Embolism in
Surgical Patients

• Bradley J. Phillips, MD
• Burn-Trauma-ICU
• Adults Pediatrics

2
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

3
Risk Factors - Acquired

• Medical
• Prior PE
• Age gt 40
• Obesity
• Malignancy
• CHF
• CVA
• Nephrotic Syndrome
• Estrogen
• Pregnancy

• Surgical
• General anesthesia gt 30 minutes
• Hip arthroplasty
• Knee arthroplasty
• Major trauma
• Spinal Cord Injury
• Open prostatectomy
• Neurosurgical procedures

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 gt 2 hrs, major venous repair
• Injury-related factor
• Spinal factures, coma, pelvic fx, plegia
• Age
• gt 40 (highest risk gt 75)

6
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

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 (gt80) 32 negative
• Low likelihood (lt 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

10
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

11
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

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
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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

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

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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

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 lt 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 gt 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)

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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)

30
D-Dimer

• Elevated in gt90 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
  (gt90)
• Egermayer,1998
• parameters
• D-dimer positive or negative
• PaO2 lt or gt 80 mmHG
• RR lt or gt 20

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D-Dimer (Egermeyer, 1998)

• Confirmation with V/Q scan/ Angiogram
• Predictive value
• D-dimer negative 0.99
• PaO2gt 80 0.97
• RR lt 20 0.95
• D-dimer plus PaO2 1.0
• Problems
• Inconsistent confirmation test
• ? Patients with pre-diagnosis PaO2 lt 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 (lt10)
• death (0.12)
• filter migration
• filter erosion
• IVC obstruction
• insertion technique

40
Embolectomy

• Trendelenburg pioneered surgery for acute PE in
  dogs (1920s)
• 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 gt 27)
• 60 deficit in perfusion scan
• refractory hypotension
• pulmonary hypertension mean gt 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, 335701, 1996
• Knudson et al, J Trauma, 41446, 1996
• Greenfield et al, J Trauma, 42100, 1997

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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
• Havent 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

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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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Questions?