Muhammad Abdelghani

Prophylaxis of Thromboembolic Disease

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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.

Epidemiology

Risk of DVT without thromboembolic prophylaxis: 25% for major general and cardiovascular surgery40–80% for major hip and knee surgery

Pulmonary Embolism (PE)

Pulmonary emboli: are a major cause of mortality for surgical

patients.account for 10% of inpatient deaths in the

UK.

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.

Risk Factors for PE

Age >40 yearsObesityImmobilisationPrevious DVTGeneral anaestheticMajor abdominal/orthopaedic surgeryPregnancy/postpartumMalignancy, particularly ovarian and pancreatic cancerHypercoaguable states, e.g., deficiency of antithrombin 3, protein

C or protein SMedical illness, incl. myocardial ischaemia, respiratory

insufficiency.

Risk Groups

Surgical patients can be divided into low-, medium- and high-risk groups for venous thrombosis and pulmonary embolism.

Risk Groups

Typical low-risk patient:Age <40 yearsSurgery lasting <30 min, particularly avoiding

general anaestheticRapidly mobilised postoperativelyNo other risk factors

Risk Groups

Typical moderate-risk patient:Age >40 yearsModerate obesityNeed abdominal operation requiring general

anaestheticOne other risk factor

Risk Groups

Typical high-risk patient:Middle-aged or elderly, undergoing major

surgery (orthopaedic or cancer surgery)Need prolonged mobilisationMay have pelvic trauma or pelvic surgeryMay have suffered orthopaedic trauma

generally: e.g., fractured neck of femur;Multiple risk factors.

Risk Groups

All moderate- to high-risk patients should receive prophylaxis.

It is not easy to categorise every patient.When in doubt, institute

thromboprophylaxis.

Methods of ProphylaxisGeneral

Early ambulationUse 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.

Methods of ProphylaxisModerate- and High-Risk Patients

These patients require pharmacological intervention with antithrombotic drugs.Low-dose subcutaneous heparinLow-molecular-weight heparin (LMWH)Anticoagulants (e.g. warfarin)Antiplatelet agents

Methods of ProphylaxisModerate- 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.

Methods of ProphylaxisModerate- 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.

Methods of ProphylaxisModerate- 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.

Methods of ProphylaxisModerate- 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.

Methods of ProphylaxisModerate- 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.

Methods of ProphylaxisModerate- 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

Thromboprophylaxis according to Risk Group

Low-risk groups:Leg elevationEarly mobilization

Moderate-risk groups:Leg elevationEarly mobilization Graduated thromboembolic deterrent

(TED) compression stockings Subcutaneous LMWH once daily.

High-risk groups:Leg elevationEarly mobilizationTED stockingsSubcutaneous LMWH,Mechanical calf compression

Methods of ProphylaxisPostoperative 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.

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.