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Deep Venous Thrombosis – General Discussion

- See:
     - Coagulation Cascade
     - Pulmonary Embolus
     - DVT in Hip Frx and Surgery:
     - DVT Following THR:
     - DVT Following TKR:
     - DVT / PE arising from Trauma and Fractures

- Discussion:
    - thromboembolism is amoung the most serious complications in orthopedics
    - classic "Vichow's" triad:
           - damage to venous endothelium;
           - venous stasis
           - hypercoagulable states and conditions
    - prevalence:
           - varies depending on the sensitivity of the study and the degree of prophylaxis
           - theoretically every surgery patient probably develops microscopic thrombi which embolize to the lungs, but these may not be clinically relevant;
           - in the literature, the prevalence varies between 30-50% of patients will develop DVT following major orthpaedic procedures
           - in one study of 100 TKR patients, there was a 7% occurance of proximal DVT, and a 20% occurance of distal DVT (Grady-Benson, et al (1994));
           - in a total hip arthroplasty study by Colwell, et al (1999), the overall rate of throboembolic disease was 3.6% for patients receiving
                   lovenox versus 3.7 % for patients receiving adjusted dose coumadin;
           - about 8% of patient will develop some signs of PE (depending on extent of prophylaxis);
           - note that in patients that receive some form of DVT prophylaxis, the majority of DVT which do occur, will form in the calf vessels, and only 5% will form in the proximal veins;
                  - note that ultrasound is very poor at picking up popliteal clots;
    - thrombi develop at the time of surgery in most cases, and the risk of PE is directly related to the the size of the clot and clot extension into the proximal vessels;
           - about 20% of calf thrombi can be expected to propagate into the proximal vessels;
           - mortality for pulmonary embolism may approach 10 %.
    - the precise features and prognosis of DVT is dependent on the cause.
    - Postoperative surveillance for deep venous thrombosis with duplex ultrasonography after total knee arthroplasty.
    - Comparison of Enoxaparin and Warfarin for the Prevention of Venous Thromboembolic Disease After Total Hip Arthroplasty. Evaluation During Hospitalization and Three Months After Discharge
    - is prophylaxis necessary following major procedures:
           - risk of postphlebitic syndrome:
                   - post thrombotic syndrome occurs due to vein dilitation and damage to vein valves;
                   - even patients with asymptomatic DVT may develop symptomatic venous congestion (58% of patients vs 38% of patients w/o DVT);
                   - patients who develop postphlebitic syndrome may complain of venous congestion years after surgery;
                   - clinical signs of post thrombotic syndrome include leg swelling, pain, and venous stasis ulcers;
           - risk of PE:
                   - the answer seems obvious, but there is surprisingly little data to document that prophylaxis against DVT actually prevents fatal PE;
                   - this is especially true, now that more recent studies have documented that the mortality from postoperative DVT is rare
                   - Prevention of venous thromboembolism
- Without prophylaxis:
 45-57% of THA will have DVT (23-36% proximal)
                 40-84% of TKA will have DVT (9-20% proximal)
                    - Without prophylaxis:
Up to 30% of THA will have PE
Up to 7% of TKA will have PE
Mortality of PE in total joint population 3-6%
           - references:
                   - Thrombophylaxis in elective orthopaedic surgery - what is the purpose? 
                   - Long term clinical observations and venous functional abnormalities after asymptomatic venous thrombosis following total hip and knee arthroplasty
                   - Does total hip arthroplasty predispose to chronic venous insufficiency? 
                   - Postphlebitic syndrome after hip arthroplasty: 43 patients followed at least 5 years.  
                   - Does DVT matter in hip surgery? Venous functional sequelae at five years.  
- risks based on specific procedures:
            - DVT in hip frx and surgery:
            - DVT following THR:
            - DVT following TKR:
            - DVT / PE arising from trauma and fractures:
            - elective spine surgery:
                  - risk of DVT may be less than is seen w/ other orthopaedic procedures;
                  - consider use of intermittent compression stockings w/o use of anticoagulant agents;
     - prognosis:
            - in the study by Sorensen HT, et al, the authors studied the prognosis of survival of patients who
                  received a diagnosis of cancer at the same time as or after an episode of venous thromboembolism;
                  - their survival was compared w/ that of patients with cancer who did not have DVT (control patients), who were matched in 
                          terms of type of cancer, age, sex, and year of diagnosis;
                  - of 668 patients who had cancer at the time of an episode of DVT, 44.0 % of those with data on the spread of disease (563 
                          patients) had distant metastasis, as compared with 35.1 % of 5371 control patients;
                  - in the group with cancer at the time of DVT, the one-year survival rate was 12 %, as compared with 36 % in the control 
                          group (P<0.001), and the mortality ratio for the entire follow-up period was 2.20 (95 % CI, 2.05 to 2.40);
                  - patients in whom cancer was diagnosed within one year after an episode of venous thromboembolism had a slightly increased risk of
                          distant metastasis at the time of the diagnosis (prevalence ratio, 1.23 and a relatively low rate of survival at one year  (38 %
                          vs. 47 % in the control group; P<0.001);
                  - cancer diagnosed at the same time as or within one year after an episode of venous thromboembolism is associated with an 
                          advanced stage of cancer and a poor prognosis;
                  - ref: Prognosis of Cancers Associated with Venous Thromboembolism.


Comparison of Enoxaparin and Warfarin for the Prevention of Venous Thromboembolic Disease After Total Hip Arthroplasty. Evaluation During Hospitalization and Three Months After Discharge