#84 Prevention Of DVT and PE Flashcards
What is the prevalence of DVT in patients undergoing major gynecologic surgery?
15-40% (without thromboprophylaxis)
In people who die from pulmonary embolism, what is the typical window from time of event to death?
Within 30 minutes
VTE risk factors?
Surgery Trauma (major or lower extremity) Immobility Malignancy Cancer therapy (hormonal, chemo, radiation) Previous VTE Increasing age Pregnancy and postpartum period Estrogen SERMs Acute medical illness Cardiac or respiratory failure Inflammatory bowel disease Myeloproliferative disorders Paroxysmal nocturnal hemoglobinuria Nephrotic syndrome Obesity Smoking Varicose veins Central venous catheterization Inherited or acquired thrombophilia
What is the incidence of a first VTE?
1-2 per 1000 individuals per year
What is case-fatality risk for PE?
11-12%
In patient with highest risk for VTE, should you use mechanical or chemical prophylaxis, or both?
Both has been shown to be better in gen surg and Neuro surg literature
What is a low risk surgery for VTE?
Surgery lasting less than 30 minutes in patients <40yos with no additional risk factors
What is the preferred VTE prevention strategy for a low risk surgery?
No specific prophylaxis, early and “aggressive” mobilization
What is a moderate risk surgery for VTE?
Surgery lasting less than 30 mins in patients with risk factors; surgery lasting less than 30 mins age 40-60yo with no additional risk factors; major surgery in patients <40 with no additional risk factors
VTE prophylaxis recommendation for moderate risk surgery?
SQH 5000u q12, LMWH (2500u dalteparin or 40mg enoxaparin daily), graduated compression stockings, or pneumatic compression device
What is high risk surgery for VTE?
Surgery lasting less than 30 mins in patients >60yo or with additional risk factors; major surgery in patients >40yo or with additional risk factors
Preferred VTE prophylaxis for high risk surgery? inpneumatic
SQH 5000u q8, LMWH (5000 dalteparin or 40mg lovenox daily), or intermittent pneumatic compression device
What classifies a surgery as highest risk for VTE?
Major surgery in patients >60yo plus prior VTE, cancer, or molecular hypercoagulable state
Preferred VTE prophylaxis for highest risk surgery?
SQH 5000u q8, LMWH (5000u dalteparin or 40mg Lovenox daily), or intermittent pneumatic compression device/graduated compression stockings + SQH or LMWH. Consider continuing prophylaxis 2-4weeks after discharge
What is the most common inherited thrombophelia?
Factor V Leiden (5% of Caucasian population with this mutation)
What is the increased risk of VTE in patients with heterozygous vs homozygous factor 5 Leiden deficiency?
3-8x more likely heterozygous
50-80x more likely with homozygous
How do you diagnose Factor V Leiden deficiency?
Abnormal activated protein c resistance assay or DNA analysis
What are the most common mutations found in a person with a VTE?
Factor V Leiden and prothrombin G20210A
How do you test for antiphospholipid syndrome?
Functional assay (dilute russel viper venom time), anticardiolipin antibodies, beta 2 glycoprotein-1 antibodies
What common hypercoagulable states cannot be tested during acute thrombosis?
Antithrombim 3, protein C, or protein S deficiencies (also unreliable to test for these when on anticoagulation)
What causes acquired hyperhomocysteinemia?
Associate with diet deficiencies in folate, B6, and B12
What type of thrombosis is antiphospholipid syndrome associated with?
Both arterial and venous
What timeframe and where do thrombi develop post surgery?
Within 24 hours in capacitance veins of the calf
How effective are graduated compression stockings in preventing DVT?
Decrease formation of DVT by 50%
For how long should you use pneumatic compression stockings post operatively?
Used continuously until ambulation and continued until discharge
What is the recommendation for thromboprophylaxis In benign major gyn cases?
Unfractionated heparin 2 hours pre op and then q12
What is the recommendation for thromboprophylaxis in patient Ms undergoing major gyn surgery with malignancy
Unfractionated heparin 2 hours pre up and then q8 after
How often do patients with SLE test positive for antiphospholipid antibodies?
50%
Which APLS test best correlates with thromboembolic complications/pregnancy morbidity?
Lupus anticoagulant, which tests for beta2-glycoprotein-1 antibodies
When do most post operative thrombi form?
Within 24 hours
Where do post operative thrombi form most often?
Capacitance veins of the calf
How much do compression stockings decrease rate of DVT post op?
50%
Which option is most effective at preventing DVTs as individual therapy between low-dose heparin, LMWH, or pneumatic compression devices?
Are all equal in decreasing DVT incidence
When/how long should you use pneumatic compression devices?
Continuously until ambulation, continue until hospital discharge
How effective is unfractionated heparin at preventing fatal PE?
2/3 reduction compared to placebo
What is recommended dosing/timing of unfractionated heparin perioperatively with patient high risk for DVT/VTE?
5000 units, 2 hours pre op and then q8h post op.
What affect does 5000u unfractionated heparin 2 hours pre op have on bleeding?
No increase in intraop bleeding. Increased post operative bleeding, in particular with wound hematoma formation
How common is heparin-induced thrombocytopenia?
6% of patients received extended heparin administration (usually at least 4 days)
What are the benefits of LMWH compared to unfractionated heparin?
Greater bioavailability, once daily dosing, more predictable pharmacokinetics. Equally effective when compared to low-dose unfractionated heparin. Heparin-induced thrombocytopenia is rare associated with LMWH.
What are major risk factors for development of clincal VTE?
Age > 60yo, previous VTE, prolonged surgery or bed rest.
Of cancer patients who get a VTE after surgery, what percentage will get a VTE >21 days after surgery?
40%
Is it better to combine compression stockings and low-dose unfractionated heparin vs low-dose unfractionated heparin along?
Yes. Combo 4x more effective
What is the difference between general and regional anesthesia in DVT risk?
Regional with 50% decrease in DVT risk compared to general anesthesia.
What are the recommendations regarding stopping platelet inhibitors prior to spinal/epidural anesthesia?
Discontinue platelet inhibitors 5-14 days prior
What are the recommendations regarding stopping low dose unfractionated heparin prior to spinal/epidural anesthesia?
Discontinue 8-12 hours prior
What are the recommendations regarding stopping twice daily dosing LMWH prior to spinal/epidural anesthesia?
Discontinue 8-12 hours prior
What are the recommendations regarding stopping once daily dosing LMWH prior to spinal/epidural anesthesia?
Discontinue 18 hours prior
How long should you wait after removal of epidural or spinal catheter to start anticoagulation?
2 hours
What genetic conditions, even if a patient has not had a previous VTE, should patient receive perioperative VTE prophylaxis?
Deficiencies of protein C, protein S, or AT-III, and for heterozygous carriers of the factor V Leiden or prothrombin gene mutation G20210A
Does pre operative administration of LMWH or unfractionated heparin increase risk of life threatening bleeding?
No
Should patients discontinue use of hormonal contraceptives or postmenopausal hormone therapy before surgery?
No trials exist that show a reduction in postsurgical venous thromboembolism with preoperative discontinuation of hormone therapy; thus, this practice should not be routinely recommended.
How long after discontinuation of OCPs does the prothrombic effect last?
Prothrombotic clotting factor changes appear to persist for 4–6 weeks after discontinuing
What are the considerations of thromboprophylaxis for patients taking OCps undergoing surgery?
No need for prophylaxis for minor cases. Consider risk/benefit of discontinuing OCPs 4wks prior to surgery (vs risk of pregnancy) vs continued OCP and heparin ppx.
What should caucasians with hx of VTE be tested for?
Factor V Leiden
Who should be tested for antiphospholipid antibodies?
Patients with a history of thrombosis, recurrent fetal loss, early or severe preeclampsia, severe unexplained intrauterine growth restriction, or unexplained thrombocytopenia
How do you measure activity of LMWH?
Antifactor Xa level
What Herbs and Supplements May Interfere With Anticoagulant Therapy?
Chinese wolfberry, Coenzyme Q10, Cranberry juice, Curbicin, Danshen, Devil’s claw, Dong quai, Fenugreek, Garlic, Ginger, Gingko, Ginseng, Glucosamine-chondroitin, Grapefruit juice, Green tea, Melatonin, Omega-3 fish oil, Papaya extract, Quilinggao, St. John’s wort
Does normalization of factor Xa levels decrease risk of spinal hematoma?
No
