Week 7: Chp 31: Deep Vein Thrombosis (DVT) Flashcards
What is a Deep Vein Thrombosis (DVT)?
a blood clot in a large vein, usually in the leg or pelvis
Pulmonary embolism
where a DVT detaches from the site of formation and becomes mobile in the bloodstream; if the circulating clot moves through the heart to the lungs, it can block an artery supplying blood to the lungs
-can cause death, particularly when one or more of the vessels that supply the lungs with blood is completely obstructed
Venous thromboembolism (VTE)
disease process that includes DVT and/ or pulmonary embolism (PE)
- a person can develop another VTE within 5 years of first one if they survive the first occurrence
- hospitalization is a risk factor (injury and surgery are causes of vascular injury and the prolonged bedrest)
What are the risk factors for Venous thromboembolism (VTE)
hospitalization; injury and surgery are causes of vascular injury and the prolonged bedrest associated with hospitalization can cause venous stasis leading to clot formation
-half of new VTE cases occur during a hospital stay or within 90 days of an inpatient admission or surgical procedure, and are not diagnosed until after discharge`
Risk Factors of Deep Vein Thrombosis
-increasing patient age
-active cancer with or without concurrent chemotherapy
-varicose veins
-prior venous thrombosis
-pregnancy
postpartum period
-oral contraceptive and hormone therapy
-surgery
-trauma
-hospital or nursing home confinement resulting in immobility
-procedures such as central vein catheterization or transvenous pacemaker insertion
Virchow’s Triad
describes the factors implicated in the formation of a venous thrombosis
-decreased flow rate of the blood or stasis of blood flow, damage to the blood vessel wall; endothelial injury, and an increased tendency of the blood to clot (hypercoagulability)
Where is DVT most commonly located
DVT, more common in the veins of the lower extremity, develop in the deep veins of the calf muscles, or, less frequently, in the proximal deep veins of the lower extremity or upper arm
-the deep veins that lie near the center of the leg are surrounded by powerful muscles that contract and force deoxygenated blood back to the lungs and heart; one-way valves prevent the backflow of blood between the contractions; blood is squeezed up the leg against gravity, and the valves prevent it from flowing back to the feet; when the circulation of the blood slows down because of illness, injury, or inactivity, blood can accumulate or “pool”, which provides an ideal setting for clot formation
Clinical Manifestations
may or may not have symptoms
- the clots can cause partial or complete blockage of circulation in the vein, which can lead to pain, swelling, tenderness, discoloration, or redness and warmth in the affected area
- clinical manifestations vary depending on the size, location, degree of vessel occlusion, and adequacy of collateral circulation
- the presence of Homans’ sign, calf pain elicited on dorsiflexion of the foot, may indicate presence of DVT
Medical Management: Diagnosis
include a combination of pre-test probability (PTP) testing, D-dimer testing, and compression ultrasonography (CUS)
- evaluation of a patient with a suspected DVT begins with an assessment of a set of clinical prediction rules, pre-risk probability to DVT
- the Wells score is a PTP scoring system that categorizes patients as high, moderate, or low probability; this is based on clinical features commonly associated with DVT and an identification of an alternative diagnosis
Most accurate, safe, and effective diagnosis tools for DVT
combination of pre-test probability (PTP) testing, D-dimer testing, and compression ultrasonography (CUS)
D-dimer Testing
the next step if a patient has low or moderate probability in the DVT PTP scoring system
- the test is a global marker of coagulation activation by measuring fibrin degradation products produced from fibrinolysis (clot breakdown)
- a negative D-dimer test can exclude DVT without an ultrasound
- an elevated D-dimer suggest DVT but requires further testing to confirm the diagnosis because of the low specificity of the test; low specificity is caused by increase of the D-dimer because of other conditions including infection, inflammation, cancer, surgery and trauma etc.
Compression Ultrasonography (CUS)
in the presence of a positive D-dimer and high probability PTP, the next step is CUS
-it allows rapid clear visualization of thrombi, including identification of unstable or floating thrombi, which may cause emboli
What is the first step in treatment of DVT?
prevention
Treatment: Prevention
- in low risk patients, early ambulation may be all that is necessary
- Venous thromboembolism (VTE) prophylaxis is indicated in at-risk hospitalized populations
- in patients with a low bleeding risk, pharmacological prevention is recommended; preferred medications are low molecular weight heparin (LMWH), unfractionated heparin, or, in patients with heparin-induced thrombocytopenia (HIT), fondaparinux can be used
- in patients with a higher risk of bleeding mechanical VTE prophylaxis is indicated; includes use of graduated compression stockings, venous foot pumps, and active external intermittent compression devices
Intermittent Compression Devices
apply external pressure to the limb which which promotes blood flow velocity, reduces venous stasis, and increases levels of systemic fibrinolysis
Medications
consists of anticoagulation with unfractured heparin or low molecular weight heparin (LMWH) followed by long-term oral anticoagulation with warfarin
- these conventional anticoagulant therapies are widely used but have limitations
- require regular monitoring to maintain safe levels
- newer oral anticoagulant agents, including direct thrombin inhibitors (e.g dabigatran etexilate) and direct factor Xa inhibitors (e.g rivaroxaban, apixaban, and edoxaban) have been developed to overcome some of the limitations of conventional anticoagulant therapy
- thrombolytics are only used under certain circumstances; patients who have failed conventional therapy with a clot that has been present for fewer than 14 days and have a low bleeding risk, size and location of the clot and preexisting conditions
Safety Alert: Essential Teaching Points for patients on Warfarin
- Immediately report blood in sputum, emesis, stool, or urine
- take the medication at the same time everyday
- never skip a dose of medication
- have laboratory values (international normalized ratio (INR)) checked on a regular basis
- ensure that laboratory levels are safe to continue current dosage or change dosage
- limit intake or maintain a consistent intake of green leafy vegetables that contain vitamin K (kale, spinach, collard greens, broccoli, okra, cabbage) that may counteract the action of warfarin - limit any physical activities that will increase bleeding risk such as contact sports
- use an electric razor when shaving
- use a soft toothbrush
Signs + Symptoms with DVT: Calf thrombosis
- calf tenderness
- distal swelling of affected extremity
Signs + symptoms with DVT: Femoral thrombosis
- tenderness and pain in distal thigh and popliteal regions
- swelling more prominent than with calf vein thrombosis alone
- swelling may extend to the knee
Signs + Symptoms with DVT: Iliofemoral thrombosis
- massive swelling in affected extremity
- tenderness and pain involving enire extremity
