Venous thromboembolism
 refers to a spectrum of disease that includes deep venous thrombosis and
pulmonary embolism.
 Pulmonary embolism, which remains the most preventable cause of hospital death,
usually arises from deep venous thrombosis occurring in the deep veins of the
lower extremities at or proximal to the popliteal veins
 Sequelae of venous thromboembolism include
1. pulmonary or systemic embolism
2. post thrombotic syndrome
3. recurrent venous thromboembolism
Incidence
General Surgery
 incidence of fatal pulmonary embolism in patients who do not receive any form of
prophylaxis is 0.1 to 0.8 % in patients undergoing elective general surgery
 incidence of PE 1-2% in obese bariatric patients
 Hamad. Obes Surg Nov 2005. Enoxaparin for thromboprophylaxis in morbidly
obese patients undergoing bariatric surgery
o 668 patients undergoing primary bariatric surgery (retrospective)
o 0.9% pulmonary embolisms (PE) and 0.1% occurrence of deep vein
thrombosis (DVT); all but 1 occurred after the cessation of
thromboprophylaxis.
 Prtstowsky JB. Prospective analysis of the incidence of deep venous thrombosis in
bariatric surgery patients. Surgery. 2005 Oct
o Prophylaxis of heparin and sequential compression devices appears
satisfactory in preventing DVT with only a 1% incidence in patients
with no prior history of VTE
o In those with a previous history of VTE, 33% showed evidence of
thrombus postoperatively.
o A temporary caval filter should be placed preoperatively in RYGB
patients with a history of VTE.
Orthopedic Surgery
 2- 3% in patients undergoing elective hip replacement,
 4-7% in patients undergoing surgery for a fractured hip
Abdominoplasty
 1.2% incidence of DVT, 0.8% PE
 Increased risk when combined with other procedures (Hester) but adding SAL to
abdominoplasty does not increase the risk of DVT or PE
SAL
 Large volume SAL (>5L) – DVT (0.6%) and PE (0.005 %)
 1 study (Newall, Aesthetic Plast Surg Feb 2006) showed no DVT/PE and no
bleeding with use of LMWH (enoxeparin)
Facelift
 0.39% of deep venous thrombosis and a 0.16% risk of pulmonary embolism in face
lift patients.
 83.7 percent of the face lift patients who developed venous thromboembolism had
received general anesthesia, whereas only 16.3 percent of the venous
thromboembolism cases occurred with local anesthesia and sedation
 Anticoagulation for treatment of VTE lead to hematomas
Breast Reduction
 1.3% DVT
Breast Reconstruction
 1-20% DVT (higher if obese)
 1% PE
Head and Neck Resection
 0.3% DVT and 0.2% PE
Burns
J Trauma 2003
 148 thermally injured patients studied prospectively with duplex
 VTE rate 6%
 prevalence of VTE in burn patients is similar to that of moderate- to high-risk
general surgical patients for whom VTE prophylaxis is recommended.
 VTE prophylaxis of burn patients, especially those requiring central venous lines
and more than 4 units of packed red blood cells, should be considered.
J Trauma 2001
 Record review of 1,300 patients
 overall DVT/PE incidence of 2.9%
 higer risk with larger TBSA burns, increasing age and obesity
Risk Factors
Virchows triad
1. changes in blood flow (stasis)
2. changes in blood constituents (hypercoagulable)
3. changes in vessel endothelium (local vessel trauma)
1. Acute provoking factors
a. Hospitalization
b. Surgery
c. Trauma or fracture of lower limbs
d. Long haul flight
e. IV line
f. Recently commenced oestrogens
g. GA>1 hour (linear increase in risk with time >1 hour)
2. Chronic predisposing factors
a. Inherited thrombophilia
i. Factor V Leiden (most common – 3-5% of population)
ii. Prothrombin gene mutation
iii. Protein C,S, antithrombin III deficiency
iv. High plasma homocysteine
v. Anticardiolipin antibodies
vi. Antiphospholipid antibodies
vii. High levels of Lipoprotein a, factor VIII, IX, XI
b. Acquired
i. Age
ii. Obesity
iii. Cancer
iv. Paraplegia
v. Oestrogen therapy
1. increasing prothrombotic factors and inducing activatedprotein-C resistance
2. with OCP, pooled OR of 2.48
3. HRT risk is controversial , originally not thought be cause risk
but lately come into question
vi. Pregnancy
vii. History of pelvic irradiation
viii. Varicose veins
1. summation of current evidence suggests a significant
association
ix. Smoking
x. Previous venous thromboembolism
1. Meta-analysis of three studies produced a pooled OR of 5.18
2. This supports a strong association between a past history of
thromboembolism and the occurrence of postoperative DVT.
Recommendation for prophylaxis
American College of Chest Physicians
1. Low-risk group:
a. patients having minor surgery (<30minutes)
b. under the age of 40 years
c. have absolutely no clinical risk factors.
2. Moderate-risk group
a. undergoing minor surgery with additional risk factors
b. between the ages of 40 and 60 years with no additional risk factors
c. less than 40 years old having major surgery with no additional risk
factors.
3. High-risk group
a. having no-nmajor surgery who are older than 60 years
b. have additional risk factors
c. those having major surgery who are older than 40 years or have an
additional risk factor.
4. Highest-risk group:
a. patients older than 40 years having major surgery and a known history
of venous thromboembolism, cancer, or a hypercoagulable state
b. hip or knee arthroplasty; hip fracture surgery; major trauma; or spinal
cord injury
Strategies for Prevention
Methods
1. Aspirin
a. meta-analysis has shown that aspirin decreasesd the incidence of venous
thromboembolism in both orthopedic and general surgery patients but this
reduction is significantly less than that achieved by other agents
2. Elastic Compression Stockings
a. Graded elastic compression stockings have been shown to reduce the
incidence of deep venous thrombosis.
b. mechanism of action is to increase venous return by applying constant
pressure to the lower extremity.
c. when used in combination with low-dose unfractionated heparin, elastic
compression stockings have been shown to provide better prophylaxis
than either agent used alone.
d. also evidence that intermittent pneumatic compression stockings may have a
beneficial effect when combined with elastic compression stockings
e. not recommended as monotherapy
3. Intermittent Pneumatic Compression Stockings
a. recommended for solo prophylaxis in both the moderate- and high-risk groups
b. prevent venous thromboembolism by two distinct mechanisms
i. reduce stasis by increasing venous return through the deep veins of the
legs. A
ii. via a poorly understood mechanism, reduces the level of plasminogen
activator-1, which in turn increases fibrinolytic activity
c. advantage of not causing increase in bleeding
d. use should be initiated before the induction of anesthesia
e. may be used with TEDS
f. avoided in patients with peripheral vascular disease or in those who have
been immobilized for more than 72 hours.
g. should continue into the postoperative period until the patient is fully
ambulatory
4. Heparin vs LMWH
a. both equally effective in preventing deep venous thrombosis in general and
orthopedic surgery patient
b. have different risk profiles
i. at proper dosing (<3400 anti-Xa units), LMWH is equally effective as
heparin with less bleeding complications
ii. doses higher than 3400 anti-Xa units daily are more likely to cause
bleeding than the standard 5000 units of heparin administered every 8 or
12 hours.
iii. Advantages of LMWH
1. once daily injection
2. has greater bioavailability when administered by subcutaneous
injection, its effect is more closely correlated with body weight.
3. associated with a significantly lower incidence of heparin-induced
thrombocytopenia than heparin: 0 versus 2.7 percent
iv. slightly higher risk of bleeding with preoperative dosage versus
postoperative dosage
c. Warfarin
i. is only indicated for patients in the highest-risk group.
ii. low-molecular-weight heparin is significantly more effective than warfarin
in preventing venous thromboembolism.
iii. There is a slightly increased risk of bleeding and wound hematoma with
the use of low-molecular-weight heparin
iv. little rationale for the use of warfarin in venous thromboembolism
prophylaxis in plastic surgery patients
Protocol
In All Patients
Cease smoking
 evidence not convincing (ANZ J Surg 2004)
Cease herbal medications
 Some may be prothrombotic – herbal phytopestrogens
Positioning
 comfortable positioning on the operating table
 slight knee flexion with pillow under the knees to enhance popliteal return
 Maximum blood flow through the popliteal vein occurs with the knee slightly
flexed at 5 degrees
 Avoid external pressure on legs
Low Risk
 Early mobilization
Moderate risk
 Early mobilization
 Intermittent pneumatic compression device
 Optional with low dose heparin
 TED stockings
High Risk
 Consider preoperative review by hematologist
 Early mobilization/TEDS
 Intermittent pneumatic compression device
 Consider preop dose of heparin 1-2 hours prior – most DVT occur intraoperative
 Postop low dose heparin
 Consider anticoagulation
Highest Risk
 preoperative review by hematologist
 consider preoperative vena caval filter placement in patients with prior
pulmonary embolus, prior deep venous thrombosis, evidence of venous stasis, or
known hypercoagulable state.
 Preoperative heparin
 Intraoperative heparin
 Postoperative low dose heparin
 Consider postoperative anticoagulation for 3 months
Clinical
DVT
 Most occur intraoperatively
 50% resolve spontaneously within 72 hours
 When symptomatic, 88% are above knee
 50% of symptomatic proximal DVT have clinically silent PE at time of
diagnosis and 10% have symptomatic PE
 Without treatment 50% of patients will experience recurrent symptomatic VTE
within 3 months
Clinical
 Leg oedema, tenderness
 Calf pain on dorsiflexion (Homans sign)
 Palpable calf cords
PE
 10% who experience an acute event die within 30 minutes, well before any
beneficial therapy can be initiated. Those that survive, if treated early have a
mortality of 2-8%
 5% of survivors will have significant right sided heart disease after 1 year

Clinical
 Dyspnoea, pleuritic pain, cough, hemoptysis, wheezing
Post –thrombotic syndrome
 Characterized by chronic leg pain, swelling, venous stasis and leg ulcers
 Occurs in 20% of patients with symptomatic DVT after 2 years
Investigations
1. ABG
 AA gradient
 Possible to have a large PE and normal AA gradient
2. D Dimer
 degradation product of cross-linked fibrin. High level with VTE
 Best used to rule our DVT
3. CXR
 Best used to rule out other chest pathologies (pneumonia, CCF)
4. Duplex US
 95% sensitivity and 96% specificity in patients with leg symptoms
 62% sensitivity and 75% specificity in patients with no leg symptoms
(majority of below knee DVTs)
 As 50% of patients with PE have no leg symptoms, US is not useful to predict
PE.
 Recommended to repeat US in 1 week to look for above knee propagation
5. VQ scan
 Only VQ scan of high probability are clinical useful
 Intermediate probability should undergo CT angiography
6. CT/MRI
 MRI has greater sensitivity and specificity
7. Pulmonary Angiography
 Gold standard
 May cause DVT in 2-4% of patients
Treatment
1. Anticoagulation
a. 3 month course for DVT
b. 6 months for PE
c. Patients who cant tolerate heparin or warfarin, consider newer hirudin based
anticoagulants
2. Thrombolytic therapy
a. Reserved for massive embolus with hemodynamic instability
3. Caval filters
a. Indicated where anticoagulation is contraindicated in the short term (active
bleeding elsewhere, severe thrombocytopenia)
4. Surgery
a. Pulmonary embolectomy
b. Endovascular venous stenting