Overview
Definition:
Venous thromboembolism (VTE) is a spectrum of venous disorders comprising deep vein thrombosis (DVT) and pulmonary embolism (PE)
VTE prophylaxis refers to measures taken to prevent the occurrence of VTE in at-risk patients, particularly those undergoing surgical procedures.
Epidemiology:
VTE is a significant cause of morbidity and mortality in surgical patients, with reported incidence rates varying from 5% to 50% depending on the type of surgery and patient risk factors
General surgery, orthopedic surgery (hip and knee arthroplasty), and major abdominal or pelvic surgery are associated with higher risks.
Clinical Significance:
Preventing VTE is crucial as it can lead to debilitating sequelae such as post-thrombotic syndrome, chronic thromboembolic pulmonary hypertension, and even death due to massive PE
Effective prophylaxis strategies improve patient outcomes, reduce hospital stays, and lower healthcare costs.
Risk Stratification
Caprini Score:
The Caprini score is a widely used tool for assessing VTE risk in general surgical patients
It assigns points based on various risk factors such as patient age, history of VTE, malignancy, obesity, and type/duration of surgery
Higher scores indicate increased risk.
Other Scoring Systems:
Other risk stratification tools exist, including the Padua prediction score for medical patients, but the Caprini score is specifically validated for surgical populations.
Risk Factors:
Key risk factors include: older age, previous VTE, active malignancy, reduced mobility, major surgery (especially orthopedic, trauma, cancer), obesity, estrogen therapy, and inherited thrombophilia.
Prophylactic Strategies
Pharmacological Prophylaxis:
Low molecular weight heparins (LMWH) such as enoxaparin or dalteparin are commonly used
Unfractionated heparin (UFH) is an alternative, especially in patients with renal impairment or those requiring rapid reversal
Direct oral anticoagulants (DOACs) are increasingly used in specific orthopedic settings.
Mechanical Prophylaxis:
Intermittent pneumatic compression (IPC) devices and graduated compression stockings (GCS) are used, particularly when anticoagulation is contraindicated or as an adjunct
IPC provides external pressure to promote venous return and reduce stasis.
Early Mobilization:
Encouraging early ambulation and physical therapy is a fundamental component of VTE prophylaxis, helping to improve venous circulation and reduce venous stasis.
Pharmacological Prophylaxis Details
Lmwh Dosing:
Enoxaparin 40 mg subcutaneously once daily for general surgery, or 30 mg twice daily for hip/knee arthroplasty
Dalteparin 5000 IU subcutaneously once daily
Adjustments may be needed for renal impairment (CrCl < 30 mL/min).
Ufh Dosing:
5000 units subcutaneously every 8 hours
Monitor aPTT if indicated, though routine monitoring is often not required for prophylaxis doses.
Doacs:
Rivaroxaban or Apixaban are options in orthopedic surgery, initiating 6-12 hours post-operatively at standard prophylactic doses
Contraindicated in severe renal impairment.
Duration Of Therapy:
Typically continued for 7-14 days post-operatively, or until full mobility is achieved
Extended prophylaxis may be considered for high-risk patients undergoing major orthopedic or cancer surgery (up to 35 days).
Mechanical Prophylaxis Details
Intermittent Pneumatic Compression:
Devices applied to the legs, inflating and deflating to mimic walking and promote venous blood flow
Should be used continuously while the patient is in bed
Contraindicated in patients with severe peripheral arterial disease or acute DVT.
Graduated Compression Stockings:
Applied to the legs, providing graduated pressure that is highest at the ankle and decreases proximally
Should be fitted correctly and worn during waking hours
Evidence for effectiveness in general surgery is less robust than IPC or pharmacoprophylaxis.
Combinations And Timing
Combination Therapy:
In high-risk patients, mechanical and pharmacological prophylaxis can be used in combination
For instance, IPC may be used alongside LMWH.
Timing Of Initiation:
Pharmacological prophylaxis should ideally be initiated within 24 hours post-operatively
For major orthopedic surgery (hip/knee arthroplasty), it can be initiated 12-24 hours pre-operatively or post-operatively
Mechanical prophylaxis can be started as soon as the patient is admitted to the operating room or post-operatively.
Contraindications And Special Considerations
Absolute Contraindications:
Active bleeding, recent hemorrhagic stroke, hypersensitivity to anticoagulants or compression devices.
Relative Contraindications:
Peptic ulcer disease, severe liver disease, uncontrolled hypertension, spinal anesthesia, pregnancy
Careful risk-benefit assessment is needed.
Renal Impairment:
Dose adjustments for LMWH are critical based on creatinine clearance
UFH or DOACs may be preferred in certain scenarios
Renal function should be monitored closely.
Bleeding Risk Assessment:
Tools like the ACCP VTE risk score or other physician-based assessments can help identify patients with elevated bleeding risks, guiding the choice and intensity of prophylaxis.
Complications Of Prophylaxis
Bleeding:
The primary complication of pharmacological prophylaxis
Can range from minor bruising to life-threatening hemorrhage
Close monitoring for signs of bleeding is essential.
Hematoma:
Injection site hematomas are common with subcutaneous injections
Proper technique and pressure application can minimize this.
Skin Necrosis:
Rare complication associated with heparin use, particularly in patients with heparin-induced thrombocytopenia (HIT).
Discomfort And Compliance:
Mechanical devices can be uncomfortable, leading to poor patient compliance
GCS can be hot and difficult to wear
Patient education is vital.
Key Points
Exam Focus:
Understand the risk stratification tools (Caprini score), indications for different types of prophylaxis (pharmacological vs
mechanical), common drug choices (LMWH, UFH), dosages, and duration of therapy
Be aware of contraindications and management of bleeding complications.
Clinical Pearls:
Always tailor prophylaxis to the individual patient's risk factors and potential for bleeding
For patients with renal impairment, consider UFH or DOACs
Discuss VTE prophylaxis with the surgical team and anesthesia early in the perioperative period.
Common Mistakes:
Underestimating VTE risk in specific surgical procedures or patient populations
Inadequate duration of prophylaxis
Failure to adjust doses in renal impairment
Not considering mechanical prophylaxis in patients with contraindications to anticoagulation.