2. Epidemiology
Preoperative management of the surgical patient
includes planning to avoid fatal complication of
pulmonary thromboembolism.
Clinically significant but non-fatal thromboembolism
occurs in about 1:100 postoperative patients.
Fatal pulmonary embolism occurs in 1:1000.
3. Epidemiology
Risk of DVT without thromboembolic
prophylaxis:
25% for major general and cardiovascular surgery
40–80% for major hip and knee surgery
4. Pulmonary Embolism (PE)
Pulmonary emboli:
are a major cause of mortality for surgical
patients.
account for 10% of inpatient deaths in the
UK.
5. Pulmonary Embolism (PE)
Origin of the pulmonary embolus:
Usually thrombosis in the veins of calf muscles.
Thrombosis may spread to iliofemoral and pelvic veins.
The development of venous thrombosis in these
veins is usually silent and may only manifest itself as
an episode of PE.
Hence the emphasis on prophylaxis to prevent this
serious complication.
6. Risk Factors for PE
Age >40 years
Obesity
Immobilisation
Previous DVT
General anaesthetic
Major abdominal/orthopaedic surgery
Pregnancy/postpartum
Malignancy, particularly ovarian and pancreatic cancer
Hypercoaguable states, e.g., deficiency of antithrombin 3, protein
C or protein S
Medical illness, incl. myocardial ischaemia, respiratory
insufficiency.
7. Risk Groups
Surgical patients can be divided into low-,
medium- and high-risk groups for venous
thrombosis and pulmonary embolism.
8. Risk Groups
Typical low-risk patient:
Age <40 years
Surgery lasting <30 min, particularly avoiding
general anaesthetic
Rapidly mobilised postoperatively
No other risk factors
9. Risk Groups
Typical moderate-risk patient:
Age >40 years
Moderate obesity
Need abdominal operation requiring general
anaesthetic
One other risk factor
10. Risk Groups
Typical high-risk patient:
Middle-aged or elderly, undergoing major
surgery (orthopaedic or cancer surgery)
Need prolonged mobilisation
May have pelvic trauma or pelvic surgery
May have suffered orthopaedic trauma
generally: e.g., fractured neck of femur;
Multiple risk factors.
11. Risk Groups
All moderate- to high-risk patients
should receive prophylaxis.
It is not easy to categorise every
patient.
When in doubt, institute
thromboprophylaxis.
12. Methods of Prophylaxis
General
Early ambulation
Use of venous support compression stockings,
particularly where local venous insufficiency
problems exist in the limbs
Intermittent pneumatic calf stimulation during
operations under general anaesthetic.
These methods are sufficient prophylaxis for fit low-risk
patients.
13. Methods of Prophylaxis
Moderate- and High-Risk Patients
These patients require pharmacological
intervention with antithrombotic drugs.
Low-dose subcutaneous heparin
Low-molecular-weight heparin (LMWH)
Anticoagulants (e.g. warfarin)
Antiplatelet agents
14. Methods of Prophylaxis
Moderate- and High-Risk Patients
Low-dose subcutaneous heparin:
Effective in reducing thrombosis in the peripheral veins.
Dose: 5000 units bd subcutaneously.
Heparin at this dose does not alter standard coagulation screening studies.
Main complications:
Bruising and local wound haematoma if injection is given close to operative
site.
Allergic thrombocytopaenia.
This may be associated with thrombosis.
Heparin must be ceased.
15. Methods of Prophylaxis
Moderate- and High-Risk Patients
Low-molecular-weight heparin
(LMWH):
Given as a single daily dose.
Advantages: As effective as heparin in
preventing thrombosis, with fewer platelet
side-effects.
Disadvantages: LMWH is expensive and is
not routinely used for this reason.
16. Methods of Prophylaxis
Moderate- and High-Risk Patients
Low-molecular-weight heparin
(LMWH):
Insertion and removal of epidural catheters (used for
perioperative analgesia) have been associated with the
development of epidural haematomas in anticoagulated
patients, with potentially serious neurologic consequences.
Current recommendations:
Delay insertion or removal of an epidural catheter for 12h after a
dose of LMWH.
Delay subsequent doses of LMWH for 2h following catheter
insertion or removal.
17. Methods of Prophylaxis
Moderate- and High-Risk Patients
Anticoagulants:
Warfarin, either in low or full
anticoagulation dose, is effective in
reducing thromboembolism.
However, bleeding complications are
common and accordingly warfarin is not
in regular use for this purpose.
18. Methods of Prophylaxis
Moderate- and High-Risk Patients
Antiplatelet agents:
Aspirin:
An effective antiplatelet agent.
Disadvantages: Ineffective as the sole agent to
prevent DVT.
Dextrans:
Reduce the incidence of postoperative venous
thrombosis.
Disadvantages: Expensive, must be given IV and are
more difficult to administer than SC heparin.
Not used routinely.
19. Methods of Prophylaxis
Moderate- and High-Risk Patients
In some areas of surgery, particularly where
the surgeon wishes to avoid intraoperative
anticoagulation, mechanical compression is
a useful option for the medium- and high-
risk groups
21. Methods of Prophylaxis
Postoperative Care
Check the limbs daily for early signs of venous
thrombosis (e.g. calf tenderness and leg swelling).
If there is any suggestion of the development of
clinical venous thrombosis, a Doppler ultrasound
and/or venogram is required to diagnose the
peripheral venous thrombosis prior to the
commencement of full anticoagulation.
22. References
Kingsnorth AN, Bowley DM (eds.):
Fundamentals of Surgical Practice, 3rd
Ed. Cambridge
University Press 2011.
Kingsnorth AN, Majid AA (Eds): Fundamentals
of Surgical Practice; 2nd
ed. Cambridge University
Press, 2006.
Kirk RM, Ribbans WJ: Clinical Surgery in
General: RCS Course Manual; 4th
ed. Churchill
Livingstone, 2004.