DSI Newsletter: Post-Op Venous Thromboembolism Prevention

DSI Newsletters, Issue 60:
Post-Op Venous Thromboembolism Prevention

One of the most common postoperative complications is venous thromboembolism (VTE), a term encompassing deep vein thrombosis and pulmonary embolism. Deep venous thrombosis (DVT) is a common and highly preventable perioperative complication. The true prevalence of perioperative pulmonary embolism (PE) is unknown, and it varies according to the type of surgery, the use and type of prophylaxis, and the mode of diagnosis. Estimates indicate that without prophylaxis, fatal PE occurs in 0.1-0.8% of patients undergoing elective general surgery, 2-3% of those undergoing elective hip replacement, and up to 4-7% of those undergoing surgery for a fractured hip. Despite overwhelming evidence for the effectiveness of regimens for DVT prophylaxis, the concern over bleeding risks often dissuades physicians to comply with guidelines.
The Virchow triad (ie, stasis, hypercoagulability, intimal injury) is often used to explain the development of perioperative DVT. The first component of the triad is stasis, which is a result of the venous pooling that accompanies both the supine positioning and the effects of anesthesia. The second component, hypercoagulability, occurs as a consequence of decreased clearance of the procoagulant factors, with or without underlying coagulopathies. The third component, intimal injury, results from excessive vasodilation caused by vasoactive amines and anesthesia. The combined influence of these factors promotes the development of venous thrombi in low-flow areas (eg, subadjacent to the venous valves or adjacent to foci of intimal disruption). The propagation of thrombus leads to the development of overt DVT.
Implementing an optimal thromboprophylaxis regimen requires simultaneous assessment of the risks of VTE and the risks of bleeding. It is important for the internist to discuss the risks, benefits and alternative procedures with the surgeon to come to a compromise on bleeding vs. clotting risk in regards to which method to choose and how long to treat. The currently available methods for thromboprophylaxis include:

Early ambulation.

Elastic Graduated Compression Stockings (GCS) like Ted Hose.

Mechanical Prophylaxis with Intermittent Pneumatic Compression (IPC) or Spontaneous Compression devices (SCD).

No mechanical prophylaxis option has been shown to reduce the risk of death or PE.
Good for use in patients at high risk of bleeding.
Adjunct to anticoagulant-based prophylaxis.

Inferior vena cava filters.

And a variety of pharmacologic agents such as:

Unfractionated regular good old heparin.
Warfarin (Coumadin).
Aspirin.

Not good for VTE prophylaxis alone.

Low molecular weight heparin (Lovenox).
Pentasaccharides: Arixtra (Fondaparinux), a selective inhibitor of factor Xa, is the first of a new class of antithrombotic compounds, the synthetic pentasaccharides.
Direct Thrombin Inhibitors.

Exanta®
Dabigatran

The American College of Chest Physicians (ACCP) criteria for VTE risk stratification categorize risk on the basis of: age; type of surgery; and, other thromboembolic risk factors. A patient aged 40-60 who was getting non-major surgery would have moderate risk if they weren't obese or had prior clots. So, SCDs/IPCs alone would suffice without pharmacologic agents, but they suggest considering pharmacologic therapy concomitantly in the Sixth ACCP Conference whereas in September 2004 they came out and recommended you use pharmacologic measures for VTE prophylaxis in the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. The observed rate of fatal PE in general surgery cases without VTE prophylaxis is 0.2-0.9%. Approximately 10% of symptomatic PE episodes are fatal within 1 hour of symptom development. (See ref. # 2)
Traditional risk factors for VTE include:

Cancer
Previous VTE
Obesity
Varicose Veins
Estrogen use
Pregnancy
Increasing age: 40-60 moderate risk
Type of Anesthesia: Spinal better than general
Type of surgery: Major, Ortho, Neuro
Chronic Medical Conditions like: CHF, COPD, MI, IBD, P. Vera, Thrombophilia, CVA, Immobilizations
Ethnicity: Asians higher risk
General Perioperative care:

Degree of mobilization
Fluid status
Transfusion practices

Although the risk of developing postoperative DVT is highest within the first week or two after undergoing general surgery, VTE complications, including fatal PE, may occur later. For major surgery in high risk patients, consideration for VTE prophylaxis for 2-3 weeks post-op should be made.
For minor surgery in patients < 40 without traditional risk factors, early and persistent mobilization is recommended.
For moderate risk patients the latest Sept. 2004 ACCP is to recommend pharmacologic prophylaxis.
Kaboli published in Med. Clin N Am 87 (2003) 77-110 (Kaboli, P.J., Henderson, M.C., White, R.H. DVT Prophylaxis and Anticoagulation in the Surgical Patient. In Clinics of North America, March 2003) a review of VTE prevention in the surgical patient. He refers to the Sixth ACCP Consensus on Antithrombotic Therapy guidelines. (The seventh came out September 2004). Thromboprophylaxis is divided up into nonpharmacologic and pharmacologic measures. The nonpharmacologic ones include: early ambulation; elastic stockings; intermittent pneumatic compression devices; and, IVC filter. On page 84 he has table 3 entitled, “Venous thromboembolism prophylaxis options in surgical patients.” Under moderate risk he includes the following as acceptable for solo prophylaxis for VTE prevention, including:

Mechanical Prophylaxis with Intermittent Pneumatic Compression (IPC) or Spontaneous Compression devices (SCD).
Elastic Stockings.

On page 12 of The Sixth ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines there is table # 4 that describes what is recommended prophylaxis for a patient at moderate risk. For the Sixth ACCP this included as one can clearly see the solo use of ES (Elastic Stockings) or IPC (Intermittent Pneumatic Compression).
In conclusion, in order to implement a thromboprophylaxis regimen successfully, consulting internists must balance the bleeding risk of using prophylactic agents against the risk of thromboembolism associated with the operative procedure. Direct discussions between the surgeon and the internist are imperative. Each has his own bias as surgeons are naturally more concerned about bleeding as they treat hematomas on a daily basis whereas internists treat the sequella of blood clots and treat VTE daily. Hospitals should strive to initiate local guidelines thru routine clinical pathways for postoperative VTE prevention that are jointly written by surgeons and internists. This way we can all work together to limit postoperative VTE which can shorten hospital stay, limit re-hospitalization and save money.

References

Sincerely:
Joseph Saponaro, MD, DABIM, FACP, CPI, CCI, CCTI, CCRC, CCRP
PI (Principal Investigator), DSI (Drug Study Institute)
Board Certified Internist, JPMC (Jupiter Preventive Medicine Center)
DABIM (Diplomat American Board of Internal Medicine)
FACP (Fellow American College of Physicians)
CPI (Certified Physician Investigator) by the AAPP/APPI
(American Academy of Pharmaceutical Physicians/ Academy of Pharmaceutical Physicians and Investigators)
CCTI (Certified Clinical Trial Investigator) by the ACRP (Association of Clinical Research Professionals)
CCI (Certified Clinical Investigator) by the DIA (Drug Information Association)
CCRC (Certified Clinical Research Coordinator) by the ACRP (Association of Clinical Research Professionals)
CCRP (Certified Clinical Research Professional) by SoCRA (Society of Clinical Research Associates)
IRB Member, Jupiter Medical Center
Ethics Committee Member, Jupiter Medical Center
Member, ARENA (Applied Research Ethics National Association)
Member, PRIM&R (Public Responsibility in Medicine and Research)
Member: The American College of Preventive Medicine
Member, SIMPD (Society for Innovative Medical Practice Design)
Member, ACPM (American College Preventive Medicine)
Founder, CertifiedResearchers.com
Expert Medical Witness, ExpertMD

The right upper quadrant illustrates a photo of a blood clot in the popliteal vein (DVT or Deep Vein Thrombosis) by the knee.
Bottom shows an enlargement of an area in a vein just below the valve where platelets are just beginning to clump together causing the blood to clot and form a DVT.

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