Angela Says:
SURGICAL MANAGEMENT:
DVT:
Surgical treatment tends to be used when medical management, i.e. fibrinolysis or anticoagulation is inadequate to dissolve the clot or when it is contraindicated due to recent surgery, trauma to the CNS etc.
Venous thrombectomy is used to extract the clot and maintain venous patency.
· Firstly the location and extent of the clot is worked out using ultrasound or venography
· The patient is placed on heparin (if not already done so)
· An incision is made to expose the femoral vein and a “Fogarty” catheter is inserted until it squeezes past the clot
· The balloon on the catheter is inflated and the catheter is pulled out slowly, dragging the clot with it
· There is a risk that the clot may become dislodged or break into smaller pieces during the procedure which could lead to PE
· Venous valves may sometimes prevent the passage of a catheter in a retrograde direction down the leg. In this case, the leg may be wrapped tightly with an Esmarch bandage in an attempt to force clot extrusion.
· Heparin is given for 6-12 months after surgery and leg compression devices may also be used.
· If thrombosis is associated with an underlying defect, it must be identified and corrected after the resolution of the DVT, or the thrombosis will recur.
Other procedures:
New percutaneous mechanical techniques have been developed, such as angioscopic thromboembolectomy (same procedure without making an incision in the vein, rather a scope is inserted), mechanical disruption thrombectomy (a laser or other device is used the shake up the clot without invasive surgery) and aspiration thromboembolectomy (aspirates the clot through a needle).
Some of the mechanical devices available today combine clot maceration with suction removal (eg, AngioJet, Hydrolyser, Oasis), while others (eg, the Amplatz device) use clot maceration alone. Maceration at the catheter tip can be achieved by use of physical cutting blades, by vortex, by high- or low-pressure saline jets, by suction alone, or by ultrasonic liquefaction.
After the thrombus has been removed, construction of a small arteriovenous fistula may assist in maintaining patency by increasing the flow velocity through a thrombogenic venous segment.
Source: emedicine: DVT
PULMONARY EMBOLISM (PE):
Treatment usually focuses on oxygen therapy and blood-thinners, drugs to raise blood pressure may also be given.
Again, a catheter technique can be used, the most common being suction thrombectomy. The catheter shoots a salt solution into the blocked vessel, which by increasing the blood osmolarity, pulls water out of the cells and into the vessel which helps break up the clot. Mechanical devices as mentioned above may also be used.
Rarely, physicians recommend open surgery for a pulmonary embolism as mortality can be as high as 25%. The procedure is called pulmonary embolectomy and can involve inserting a catheter via the femoral or internal jugular vein and using fluoroscopic guidance to navigate into the pulmonary artery. Emboli are then extracted from the pulmonary bed using a cup device and syringe suction. Alternatively open surgery may be required but this is extremely rare. Cardiopulmonary bypass (heart-lung machines) may be used to stabilise the patient before the surgery.
Indications for surgical intervention include:
-massive pulmonary embolism
-patient is very ill with no response to anticoagulation or thrombolysis, or thrombolysis is contraindicated because of:
--Recent surgery - within 5 days of operation (10 days of hip operation
--Active bleeding from the bowel or urinary tract etc.
A metal filter, inserted via a catheter, may be placed into the superior and/or inferior vena cava to prevent recurrence
Sources:
-VascularWeb: Pulmonary Embolism, available at: http://www.vascularweb.org/_CONTRIBUTION_PAGES/Patient_Information/NorthPoint/Pulmonary_Embolism.html
-GP notebook: Pulmonary embolectomy, available at:
http://www.gpnotebook.co.uk/cache/-1590362084.htm
-ABC7chicago.com: Pulmonary Embolism, available at:
http://ww2.abc7chicago.com/global/story.asp?s=1230257
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Complications
Potential complications include:
- Embolisms, esp. pulmonary embolisms, which occurs when a thrombus is dislodged and an embolus travels in the bloodstream and becomes lodged in the pulmonary vein and blocks blood flow. This can happen hours or days after the formation of the clot in the leg.
- Without treatment, patients develop long term symptoms in the calf. Post thrombotic syndrome occurs if a DVT damages the valves in the vein and the blood pools in the lower leg. This can then cause pain, swelling and ulcers in the leg. Post thrombotic syndrome is more likely to occur in thigh veins, overweight patients and people with more than one DVT in the same leg.
- Inflammation and leg ulcers
References:
Deep Vein Thrombosis - hcd2.bupa.co.uk/fact_sheets/mosby_factsheets/Deep_Vein_Thrombosis.html
DVT - http://www.patient.co.uk/showdoc/23068982/
DVT clinically
The signs and symptoms of DVT are caused by obstruction of the venous outflow and inlflammation of the vessel wall.
•Oedema, principally unilateral
•Leg pain and tenderness (usually confined to calf muscles or over the deep veins in the thigh)
•Pain occuring on dorsiflexion of the foot with the knee straight (Homans sign)
•Warmth and erythema over the area of the thrombosis
•Venous distension and prominence of the subcutaneous veins
•Low grade fever
•Reddish purple discolourations (from venous engorgement and obstruction)
-occasionally leg may be cyanotic as a result of a ileofemoral obstruction, the resulting pale and pulseless leg suggests acute arterial occlusion however the distended veins and swelling indicate venous obstruction.
DVTs can also be asymptomatic
Wells Clinical Score for DVT*
Clinical Parameter Score
Active cancer (treatment ongoing, or palliative) + 1
Paralysis or recent plaster immobilization of the lower extremities +1
Recently bedridden for >3 d or major surgery <4 wk +1
Localized tenderness along the distribution of the deep venous system +1
Entire leg swelling +1
Calf swelling >3 cm compared to the asymptomatic leg +1
Pitting edema (greater in the symptomatic leg) +1
Previous DVT documented +1
Collateral superficial veins (nonvaricose) +1
Alternative diagnosis (as likely or > that of DVT) -2
Total of Above Score
High probability >3
Contraceptives and the Blood
Now we don't know whether or not Anne is on the pill, but plenty of girls are so it's important to know!
Many forms of contraception exist, and hormonal contraception is one type. There are numerous forms of hormonal contraception, which contain different active agents and have different effects.
Oestrogen, an active agent in many forms of contraception, can have some adverse effects on clotting. Increased oestrogen leads to increased circulating levels of factors II, VII, IX, X, antithrombin III and plasminogen, and also increases platelet adhesiveness. This combines to promote coagulation.
As a result, any contraceptive containing oestrogen increases the risk of thromboembolic events, such as deep vein thrombosis. Those women who have past or family history of thromboembolic events, or with hypercoagulative disorders such as factor V Leiden, are advised against oestrogen-containing contraceptives.
Contraceptives containing oestrogen:
• Combined oral contraceptive pill (OCP, the Pill – many formulations)
• Vaginal ring (NuvaRing)
• Contraceptive patch (Ortho Evra)
Contraceptives that do not contain oestrogen:
• Progesterone only pill (POP, minipill)
• Implants (Implanon, Jadelle)
• Progesterone IntraUterine System (IUS)
• Progesterone injection (Depo Provera)
Emergency contraception (the ‘morning after’ pill) comes in many formulations, some containing only progesterone, and some that are combined oestrogen and progesterone. Therefore, the risk of thromboembolic events from these pills varies.
References:
O. Samra, Contraception, eMedicine 2006
Pathophysiology of DVT:
A thrombus forms in a vein and any inflammation in the vein wall is secondary to this. Thrombosis commonly occurs after periods of immobilization, but it can occur in normal individuals for no obvious reasons. Veins contain bicuspid valves which prevent backflow and venous pooling. DVT’s commonly occur at these valves causing irreversible damage. During leg movements such a walking, calf muscles decrease venous pressure by approx 70% in the lower extremities. With rest, pressures return to normal in about 30 secs. In diseased veins, movements decrease venous pressures by 20%. When movement is inhibited, the vein lumen increases slowly, returning to normal over a period of minutes.
Venous hypertension in diseased veins is thought to cause chronic venous insufficiency by (Incorporates Virchow’s Triad):
-Increased venous pressure transcends the venules to the capillaries, impeding flow – leg veins distend damaging epithelium.
-Low flow states within the capillaries cause leukocyte trapping.
-Trapped leukocytes release proteolytic enzymes and oxygen free radicals which damage capillary basement membranes – enhanced coagulation.
-Plasma proteins such as fibrinogen leak into the surrounding tissues forming a fibrin cuff – thrombus formation and may lead to embolism.
-Interstitial fibrin and resultant oedema decrease oxygen delivery to the tissues resulting in local hypoxia, inflammation and tissue loss as a result.
-May resolve completely following clot retraction fibrinolysis.
Virchow’s Triad – Factors contributing to Thrombus Formation.
-Trauma and damaged epithelium
-Venous stasis – slow blood flow
-Hypercoagulability
Bibliography:
•eMedicine
•Kumar & Clark: Clinical Medicine
Incidence:
1.from BMJ:kills 60,000 people in the UK every year with autopsy data indicating about 10% of deaths in hospital were due to pulmonary embolism.
2.from the New Australian 'Stop the Clot' guidelines released by the National Institute of Clinical Studieslast week said about 30,000 people were hospitalised with Venous Thromboembolism yearly in Australia and out of this amount, 2000 died as a result.
Reference:
Australian Doctor. Australia's leading Independent Medical Publication. 25th may 2007
Definition:
DVT ( deep venous thrombosis ) is a pathological coagulation or clotting of blood in the deep veins of the body, usually in the legs.
robb said...
Prognosis
Deep Venous Thrombosis can have a varying prognosis depending on the severity/extent of the thrombosis, the position of the thrombosis and the treatment given to the patient.
- Without treatment the thrombosis is likely to produce micro-emboli that lodge in the pulmonary trunk/vessels to form a pulmonary embolism. Failure to treat a PE has a high probability of death.
- With only anticoagulant treatment the progression of the thrombosis may be halted, and any further thrombi may be prevented, but the thrombus already present is not affected and may fail to recanalize, or recanalize incompletely producing an obstruction to venous blood flow. Even if the thrombus is spontaneously recanalized it usually leaves behind some venous damage, destroying venous valves, producing a valveless channel that can lead to venous reflux and venous hypertension. 65% of patients treated with anticoagulant therapy alone will go on and develop chronic venous insufficiency (CVI), also known as postphlebitic syndrome. The symptoms of this syndrome include the development of varicose vessels, chronic dermatitis, chronic ulcerations, chronic pain and swelling and increased incidence of recurrent DVT.
- Treatment with fibrinolytic and anticoagulant therapies cocurrently is associated with 50% decreased risk of CVI.
- The best prognosis is associated with surgical intervention.
References:
eMedicine, www.emedicine.com
Kumar & Clarke, Clinical Medicine, 5th Edition
RISK FACTORS/CAUSES of DVT:
Inherited =
- Positive family history, ie. Inherited thrombophilia (Factor 5 Leidin)
Acquired =
- Prolonged immobility, e.g. hospitalization, plane/car travel
- Surgery/Trauma, e.g. major orthopaedic and abdominal
- Pregnancy and postpartum period
- Oral Contraceptives and HRT
- Cancer
-AMI, CHF
- Previous Thrombosis
- Antiphospholipid antibodies
- Nephrotic Syndrome
References: Lecture 71 (Thrombosis), eMedicine.
Risk of DVT in long haul air travel
The increased risk of developing DVT in long-haul air travel is very small. It is estimated that there will be 1 in 6,000 DVT cases in air travel lasting more that 4 hours.
Measures taken to prevent Deep Vein Thrombosis on long-haul flights
-exercise foot and calf muscles every 30 minutes by flexing and extending legs, feet and toes when seated
-press balls of feet hard down onto the floor to increase blood flow to the legs
-walk up and down the aisle every hour or so
-drink plenty of water and avoid drinking alcohol to prevent dehydration
-don’t take sleeping tablets (prevents mobility)
-people at high risk may be advised to take anticoagulant medication (heparin injection before flying, however limited evidence)
-consider wearing compression stockings (helps to prevent blood ‘pooling’ in the calf)
Studies undertaken to prove efficacy of wearing compression stockings during long haul flights:
One particular study, published in 2001 by The Lancet, looked at the incidence of Deep Vein Thrombosis in long haul flights lasting more than eight hours in otherwise healthy people and not at high risk of developing DVT in normal circumstances.
Aims of Study:
-to prove a causal relationship between lower limb DVT and long-haul flights
-determine efficacy of compression stockings in its prevention
Although DVT is colloquially known as “Economy Class Syndrome”, the report showed that DVT also occurred in people who travelled in Business Class.
231 volunteers were split into two groups.
Group One: Group Two:
Group size 116 115
travelling as normal
wore compression socks
O/E with ultrasound 10% had DVT of legs No DVT of legs
Results: Wearing elastic compression stockings is associated with a reduced incidence of DVT during long-haul air travel.
References:
Patient UK, ‘Preventing DVT when you travel’, http://www.patient.co.uk/showdoc/23069201/
‘Airline Travel: A randomised trial to assess the incidence of asymptomatic DVT and prevention by graduated compression stockings’, Lancet 2001, http://www.jscurr.com/StudyFull.htm
by katie!
Investigations of Deep Venous Thrombosis
Duplex Doppler Ultrasonography
- most commonly used test to diagnose deep vein clots
- uses sound waves to evaluate the speed and direction of blood flow in veins
Contrast Venography
- a catheter is threaded into a vein and a dye is injected to allow the veins to be seen with x-ray.
- X-ray shows if blood flow in vein is slowed or obstructed
- generally reserved for situations in which ultrasound is not feasible
D-dimer Assay
- D-dimers are fragments generated in blood due to degradation of fibrin by plasmin
- Often found to be elevated in the blood of people with venous thromboembolism or PE
- Positive test shows presence of D-dimers, indicative of intravascular coagulation
Magnetic Resonance Imaging(MRI)
- uses a strong magnetic field to produce detailed pictures of the inside of the body
- as accurate as contrast venography
- expensive and limited to situations in which contrast venography cannot be performed, such as in patients with poor kidney function, during pregnancy, or because of allergy to the dye required in contrast venography
Investigations of Pulmonary Embolus
Ventilation-Perfusion Scanning (V/Q scan)
- commonly used to diagnose patients with a suspected PE, especially patients in whom a careful physical examination and routine diagnostic tests cannot explain the pulmonary symptoms.
- A radioactive substance is inhaled and injected into the bloodstream. A machine is used to examine how these radioactive substances are distributed within the lungs
- scanner can detect areas of blocked blood flow caused by the blood clot.
Spiral CT scan
- uses a combination of x-rays and computers to take detailed pictures of the inside of the body
- x-rays are taken after the injection of an intravenous dye, which highlights the vessels in the lung (CT angiography) or the leg veins (CT venography)
- not suitable for patients with poor kidney function or who are unable to have CT for other reasons (eg, pacemaker)
Pulmonary Angiography
- an invasive, but definitive diagnostic technique in PE
- performed by inserting a catheter through a vein in the thigh, which is guided into a branch of the pulmonary artery. Dye is injected through the catheter, which highlights the blood vessels around the lung on x-ray (fluoroscopy)
References:
- Haemostasis and Thrombosis – Dr. Paul Coughlin, Tutorial Notes, Week 14
- National Heart, Lung and Blood Institute http://www.nhlbi.nih.gov/health/dci/Diseases/Dvt/DVT_Diagnosis.html
- Uptodate Patient Info
http://patients.uptodate.com/topic.asp?file=blod_dis/7159
People should read this.
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