Venous Thromboembolic Disease Flashcards
What is DVT?
Deep vein thrombosis
Formation of thrombi within the lumen of the vessels that make up the deep venous system (sites of stasis)
What is distal DVT?
Vein thrombosis distal to the popliteal pulse
What is proximal DVT?
Vein thrombosis of popliteal or femoral vein
What is PE?
Pulmonary embolism
Thromboemboli detach and travel through the right side of the heart to block vessels in the lungs
What are the three aspects to Virchow’s triad?
- Endothelial injury
- Circulatory stasis
- Hypercoaguable state
What may be causes for endothelial injury?
- Venous disorders
- Venous valvular damage
- Trauma or surgery
- Indwelling catheters
What may be the cause of circulatory stasis?
- LV dysfunction
- Immobility or paralysis
- Venous insufficiency or varicose veins
- Venous obstruction from tumour, obesity or pregancy
What may be the cause of hypercoaguable blood?
- Malignancy
- Pregancy
- Oestrogen therapy
- IBD
- Sepsis
- Thrombophilia
What are the consequences of venous thromboembolism?
- Death (PE)
- Risk of recurrence
- Post thrombotic syndrome
- Chronic thromboembolic pulmonary hypertension
- Reduced quality of life
What are the symptoms of post thrombotic syndrome?
- Pain
- Oedema
- Hyperpigmentation
- Eczema
- Varicose collateral veins
- Venous ulceration
What is chronic thromboembolic pulmonary hypertension?
A serious complication of PE
Dyspnoea and hypoxaemia progressively develop
Right heart failure can occur
The disease is caused by original embolic material being converted to fibrous tissue, which can eventually incorporate itself inot the intima and media of pulmonary arteries and cause occlusion
What are the best investigations for venous thromboembolic disease?
D-dimer - breakdown product of fibrin (so absence rules out a clot)
Ultrasound - Doppler ultrasound can view blood flow
What is a Well’s score?
A scoring system to determine probability of VTE
Which imaging techniques can be used for venousthromboembolic disease?
CT angiography - gold standard
CXR - can show infarct and usually associated pleural effusions
V/Q scan - useful in pregancy due to low radiation dose
Which types of drugs can treat DVT and PE?
- Anticoagulation
- Thrombolysis
- Analgesia
As well as drugs, what else can be used to treat DVT and PE?
- Compression stockings
- IVC filters - can capture emboli
- Screening for underlying cause - cancer, thrombophilia (tendency of blood to clot)
What are the two main drug classes used to treat VTE?
- Vitamin K antagonists (warfarin)
- Non-vitamin K antagonist oral anticoagulants (dabigatran, apixiban)
What are the pros and cons of vitamin K antagonists?
Pros
- Can be used in patients with renal impairment
- Anticoagulation can be reversed with vitamin K
Cons
- Slow onset
- Narrow therapeutic window
- Variability in individual to same doses
- Needs INR (international normalised ratio) a test to determine how long blood takes to clot
What are the pros and cons of Non-vitamin K antagonists?
Pros
- Predictable pharmological profiles
- Absence of major food/drug interactions
- Does not require INR
Cons
- No antidote
- No long-term data
- Not readily available for special circumstances such as a major bleed
NOACs (Non-vitamin K antagonists) which can be used for VTE include what?
- Dabigatran
- Apixiban
- Edoxaban
- Rivaroxiban
Which drugs can be used as an option for the prevention of venous thromboembolism in adults after surgery?
Rivaroxiban, apixiban and dabigatran
Which drug is most suitable for treating a diagnosis of acute DVT in adults or for preventing recurrent DVT/PE?
Rivaroxiban
In special cases involving IV drug users, how should VTE be treated?
Rivaroxiban or dalteparin (LWMH)
When would thrombolysis ever be considered for DVT?
Ileofemoral DVT with less than 14 days duration and:
- Life expectancy > 1 year
- Low bleeding risk
- Good functional status
When would thrombolysis be considered for PE?
There is haemodynamic instability (abnormal or unstable blood pressure)
(do not offer when there is haemodynamic stability and PE)
After thrombosis, how long should compression stockings be worn?
2 years
What is the only treatment of post phlebitis syndrome (venous stress disorder occuring as a long term complication of DVT)?
Compression stockings
Which patients may be offered an IVC filter?
Proximal DVT/PE patients who cannot have anticoagulation treatment
or
Patients with recurrent proximal DVT/PE despite coagulation treatment and increased target INR
Why are IVC filters not an ideal replacement for anticoagulants?
They can thrombose themsleves
What is an abdominal aortic aneurysm (AAA)?
The dilation of a vessel by more than 50% of its normal diameter
What are the two types of aneurysm?
- True - all three vessel layers are intact
- False - there is a breach in the vessel wall and surrounding structures must act as the vessle wall to compress the aneurysm and prevetn expansion
What are the three aneurysm morphologies?
- Saccular
- Fusiform
- Mycotic - arises secondary to infection and involves all 3 layers
What are the causes of true aortic aneurysms?
Aneurysms are caused by medial degeneration (effects within the tunica media)
- Regulation elastin/collagen in aortic walls
- Aneurysmal dilatation
- Increas ein aortic wall stress
- Progressive dilatation
What are the risk factors for an AAA?
- Smoking
- Being male
- Age
- Hypertension
How may AAA present?
- Asymptomatic
- Pain (may mimic renal colic)
- Trashing - thrombus build up which eventually breaks off affecting the distal circulation
- Rupture
What does AAA rupture involve for the patient?
- Sudden epigastric pain - may radiate to back and mimic renal colic
- Collapse
What may be found on examination of AAA rupture?
- The patient may appear well
- Hypo or hypertensive
- Pain
- Transmitted pulses
- Peripheral pulses may be absent
When would it be necessary to intervene for an AAA?
- Symptoms present
- Greater than 5.5cm (AP)
- Rate of expansion is high (>0.5cm/6months or >1cm/year)
What is used to image an AAA?
Duplex ultrasound
Allows AP diameter to be determined (arterial wall to arterial wall - not lumen) and if other arteries are involved
CT scans
IV conrast is used can show shape, size and iliac involvement and is the only way to determine rupture
What is a haematoma?
A solid swelling of clotted blood in the tissue often as a result of aneurysm rupture
Describe a laparotomy as a management option for AAA
- Claming of aorta above iliac arteries
- Dacron (a polyester) is the type of graft used
- The tube graft anastomoses with the vessels
What is endovascular aneurysm repair?
Stents are used which separate the aorta from the aneurysm
The “tube” passes through the centre of the aneurysm
Acute limb threat involves which triad of pathologies?
- Acute limb ischaemia
- Acute on chronic limb ischaemia
- Diabtetic foot sepsis
What is acute limb ischaemia?
Sudden blood loss to a limb
Can be caused by:
- Embolism
- Atheroembolism
- Arterial dissection
- Trauma
- Extrinsic compression
What are the 6Ps in relation to acute limb ischaemia?
- Pain - excruciating
- Pale
- Pulseless
- Perishingly cold
- Paraesthesia - abnormal sensations
- Paralysis
In regards to pulses, what is it important to check for when suspecting acute limb threat?
Bilateral pulse presence
What is the timescale for acute limb ischaemia?
- 0-4hrs - white foot, pain, sensorimotor defect (salvageable)
- 4-12hrs - mottled, blanches on pressure (partially reversible and potentially salvageable)
- >12hrs - Fixed mottling, non-blanching, paralysis, compartments red and tender (not salvageable)
Which investigations should be undertaken for acute limb ischaemia?
- ABCDE if necessary
- Full blood count (haemoglobin)
- Renal function (potassium count)
- Creatinine kinase (muscle damage)
- Coagulation screen
- Troponin levels
Why will an ECG and CXR be done for acute limb ischaemia?
Determines MI or dysrhythmia
CXR can discover malignancies which may be causing embolism
When may a patient with suspected acute limb ischaemia go straight to theatre without imaging?
- There is no known prior history of claudication
- A known cause for embolism
- Full complement of contrelateral pulses
What are the three options if a limb is salvageable?
- Embolectomies - surgical removal of emboli
- Fasciotomies - fascia is cut to relieve pressure
- Thrombolysis
What are the three types of foor problem associated with diabetes?
- Diabetic neuropathy
- Peripheral vascualr disease (PVD)
- Infection
All can lead to tissue loss and potential amputation
In any foot problem associated with diabetes what are three sources of sepsis?
- Simple puncture wound
- Infection from nail plate or inter-digital space
- Infection from neuro-ischaemic ulcer (occurs in areas of high pressure or repeated trauma)
Why is infection a problem in the foot, especially in patients with diabetes?
Muscles in the foot are confined to rigid compartments.
They are bound by plater and interosseous fascia and metatarsal bones
This means pulse build-up cannot escape increasing pressure and impairing blood flow via capillaries furthering ischaemia and tissue damage
What are clinical findings for diabetic foot sepsis?
- Pyrexia
- Tachcardic
- Tachypnoeic
- Confused
- Kussmauls breathing - deep signing caused by entering shock - there is hypoperfusion of distal organs and hence lactic acid build-up, this breathing aims to ventilate the body and increase pH
What are the local effects of diabteic foor sepsis?
- Swollen affected digit
- Swollen forefoot - boggy feeling underneath
- Tenderness
- Ulceration with extruding pus
- Erythema - may track up limb
- Patches of necrosis
- Crepitus in soft tissues - due to gas forming organisms
Why should antibiotic be administered for diabetic foot sepsis?
Gram +ve/-ve and anaerobes may be present
- Gram +ve - S. aureus, Streptococcus spp
- Gram -ve - Bacilli (E.coli, Klebsiella sp, Enterobacter, proteus sp, pseudomonas sp
- Anaerobes - Bacteroids
What is important to remember for diabetic foot sepsis surgery?
- All infected tissue is removed
- The wound is left open to drain
