Other Venous Conditions/Tests Ch.29-30,32,35 Flashcards
Capabilities of Impedance Plethysmography (IPG)
Can detect thrombi in the iliac, femoral, or popliteal veins
Limitations of IPG
False positive results- caused by extrinsic compression (tight clothing, tumors, ascites, pregnancy, obesity, improper positioning, pain, or anxiety)
False negative results- chronic venous occlusion with large collaterals
Does not detect isolated calf thrombus
Physical Principles of IPG
IPG measures volume changes in a limb by measuring the hindrance to the passage of an alternating electrical current
Capabilities of Strain Gauge Plethysmography (SPG)
SPG is used to detect venous obstruction in the large veins above the knee
Limitations of SPG
Extreme sensitivity limits its usefulness
extrinsic compression
Physical Principles of SPG
Utilizes a mercury-in-Silastic strain gauge that indirectly senses changes in blood volume by measuring the circumference of the limb
Capabilities of Air Plethysmography
Can determine the presence or absence of venous insufficiency
Can quantify venous reflux
Limitations of air plethysmosgraphy
Cannot be preformed if patient is not able to maintain positions or perform exercise
Presence of a cast, traction, or heavy nonremovable bandages
Cannot be used to diagnose incompetent perforators
Physical Principles of air plethysmography
Pneumatic cuff wrapped around the limb detects volume changes
Additional testing: Venous Reflux testing with patient in the standing position
With patient standing he/she rests one leg on a stool while the other holds their weight
May evaluate the size of the GSV in this position (measure at prox, mid, distal thigh and prox, mid, distal calf)
May evaluate with an automatic cuff inflator placed on the leg to mimic augmentations and evaluate for reflux.
Patient standing- test popliteal for reflux and test CFV (Valsalva maneuver) for reflux
Abnormal Reflux Time
With patient standing: deep veins > or = to 1 sec GSV, SSV > or = to 0.5 sec perforator veins > 0.35 sec Longer durations observed in supine patients
GSV diameter consistent with reflux
SFJ > 9.0 mm
Mid thigh > 7.0 mm
Mid calf > 5.0 mm
D-Dimer
Blood test that measures the product in the blood that is present during a thrombotic process going on in the body (anywhere in the body)
Positive D-Dimer result
Not really helpful, just shows that there is lysis of a thrombus going on somewhere in the body (lots of false positives for DVT)
Negative D-Dimer result
Very helpful , implies the absence of a thrombotic process.
Contrast Venography
Goldstandard, however the most reliable method of diagnosing DVT is duplex ultrasound.
Injection of a dye with x-rays.
Ascending venography
Dye injected into a vein on the dorsum of the foot.
Used to detect obstruction. Evaluates acute deep venous thrombosis, congenital venous disease and or anomalies, and chronic venous changes.
Descending venography
Dye injected into the Common femoral vein.
Used to detect reflux.
Venography deviations from normal
a filling defect indicating the displacement of contrast material by thrombus
Lung Perfusion Scan
Detects pulmonary embolism in the lungs
Radioactive contrast medium is injected, usually into an arm vein.
Scans are interpreted as representing high, moderate or low probability of pulmonary emblism.
Gold standard- in the diagnosis of a PE
Pulmonary angiography
CTA is more sensitive and more readily available
Lung Perfusion Scan limitations
emphysema, asthma, pneumonia, cancer of the bronchus, congestive heart failure, liver cirrhosis, radiotherapy, multiple blood transfusions, and postoperative phenomena.
Therapeutic Intervention for DVT- Medical therapy
Controlling risk factors-
decrease venous stasis- by limiting long periods of inactivity or bed rest.
Promote venous drainage- wearing support hose or compression stockings, elevation of legs, using intermittent pneumatic calf compression during and after surgery, and reducing weight
trauma/endothelial damage
hypercoagulability states- follow prescribed treatment plan.
Medical Therapy for DVT- Anticoagulant Therapy for Prophylaxis
Low dose unfractionated heparin (5000 units subcutaneously every 12 hours before and after surgery, decreases the postoperative risk of DVT).
Low-molecular weight heparin (Lovenox) administered subcutaneously, provides anticoagulation when Coumadin must be discontinued for an invasive procedure.
Anticoagulant therapy for acute DVT and/or PE
Loaded dosage of 10,000 units of Heparin followed by continuous intravenous infusion for 5-10 days may be recommended for the treatment of acute DVT.
Patients receiving intravenous Heparin
Will be placed on strict bed rest to decrease the risk of an embolic process secondary to muscular contraction.
How does Heparin prevent propagation of the clot?
Heparin interferes with the formation of a blood clot by slowing down the conversion of prothrombin to thrombin, increasing the effect of antithrombin III, and decreasing platelet adhesiveness.
Lytic therapy is used when…
A patient has an acute iliofemoral thrombosis and or is at risk of limb loss.
Partial Thromboplastin Time (PTT)
Time needed for a fibrin clot to form is 1.5 -2 times normal.
Low molecular weight Heparin used for outpatient anticoagulation
Lovenox- Administered subcutaneously and after 30 mins of administration the patient is safe to ambulate.
Oral anticoagulation
Coumadin- Regulated to ensure that the patient’s prothrombin time (PT) is 1.5-2 times normal.
Discontinuing Heparin
Heparin is discontinued after 5-10 days if there is sufficient overlap with Coumadin (min 4 days), if PT and PTT remain at therapeutic levels, and if there are no signs of active thrombosis.
Surgical and endovascular therapy- Acute DVT or PE - Vena caval interruption
For patients with acute DVT, who cannot be anticoagulated to prevent a PE
Procedure for Vena Caval interruption
Using fluoroscopy and using an interruption device such as a Greenfield or bird’s nest filter placed in the IVC via the jugular vein or FV.
External Caval clip
May be placed around the IVC during abdominal surgery to decrease the risk of PE.
What are IVC filters used temporarily used for?
IVC filters can be used permanently but also termporarily for certain surgical procedures such as gastric bypass.
What is iliofemoral venous thrombectomy used for?
Removal of a clot, performed in a patient with impending limb loss (because of phlegmasia cerulea dolens) Done if thrombolytic therapy does not dissolve the clot.
Thrombosis at or near the SFJ vs. isolated superficial system thrombosis
Thrombosis of the GSV at or near the SFJ may require more aggressive treatment then an isolated superficial system thrombosis.(Ligation of the GSV to prevent propagation into the deep system).
Thrombosis at or near the saphenopopliteal junction vs. isolated superficial system thrombosis
More aggressive treatment required for thrombosis at or near the saphenopopliteal junction compared with isolated superficial system thrombosis.(Ligation of the SSV to prevent propagation into the deep system).
