Venous thromboembolism

Question 1

What is a venothromboembolism?

Answer 1

A thromboembolic event within the venous system
DVT= deep vein thrombosis
PE= pulmonary embolism (in lungs)

Question 2

What is the difference in a vte to a clot in MI or cva?

Answer 2

Unlike in CVA or MI, the vessel is normal- there is no atherosclerotic plaques

Question 3

Risk factor for vte?

Answer 3

Age
obesity
varicose veins
long haul flight
immobility (e.g bed rest)
pregnancy
previous vte- increased risk up to 5x
male

predisposing conditions:
Trauma or surgery esp if to hips, pelvis, lower limbs
Malignancy- chemo or radiotherapy
cardiac failure, recent mi
infection

Question 4

What are the symptoms of a DVT?

Answer 4

60% are in calf veins
can be asymptomatic
unilateral leg swelling
tenderness, warmth, redness
superficial veins
calf pain
oedema in ankles

Question 5

How are vte risk patients stratified?

Answer 5

Using the Wells clinical score
Gives probability of vte as opposed to an alternative diagnosis
High probability = >3
Moderate = 1 or 2
Low <0

Gives 1 point for each of the following:
- Active cancer
- paralysis or recent immobilisation
- bedridden for 3+ days
- major surgery in past 4 weeks
- entire leg swelling
- localised tenderness
- oedema
- calf swelling of >3cm of asymptomatic leg
- oedema
- previous DVT

Question 6

How can you test for a DVT?

Answer 6

via the d-dimer test
Di-dimer is a fibrin degradation product that is released after fibrin breakdown
- diagnostic imaging- mainly duplex ultrasonography

Question 7

What are the differential diagnoses for DVT?

Answer 7

Only 1/3 of presentations are actually vte, so can be:
cellulitis
ruptured bakers cyst- fluid filled swelling at back of knee
oedema
physical trauma

Question 8

What are the treatment options for a DVT?

Answer 8

1st choice = Immediate management with an injectable anti-coagulant:
- Unfractioned heparin
- low molecular weight heparin e.g. enoxaparin

• oral anticoagulants e.g. warfarin or DOACs e.g. rivaroxaban, edoxaban
• compression stockings

Question 9

What are the differences when using an unfractioned and low molecular weight heparin in DVT?

Answer 9

UFH:
- Works on intrinsic pathway - inhibits factor Xa and do reduces thrombin production
- IV/SC administration
- Side effects- haemorrhage, hyperkalameia, osteoporosis, alopecia
- Need to measure the activated partial thromboplastin time (APTT)- Relates to changes in intrinsic pathway and report APTT ratio ( patents APTT / APTT reference value)
- Normal APTT = 30-40 seconds- measures time taken for blood to clot

LMWH:
- less effect on thrombin
- Doesn’t require APTT monitoring as it has a more predictable effect
- Longer half-life- OD dosing as opposed to an infusion
- decreased risk of thrombocytopenia and osteoporosis

Question 10

What is the APPT measurement?

Answer 10

Activated partial thromboplastin time
- measure the time taken for blood to clot and calculate a ratio: patients APTT/reference APTT value

• Normal = 30-40 seconds, target with a heparin = 80-100 seconds
• Target APTT ratio = 1.5-2.5 - if below = increase rate of infusion of heparin , if too high = decrease rate of infusion

Question 11

What is the pathophysiology of a pulmonary embolism?

Answer 11

A blood clot or thrombus forms in the venous system
It then breaks free and embolises to the lungs (often from the calf veins)
- This obstructs the pulmonary artery system

Question 12

Symptoms of a PE?

Answer 12

Acute onset chest pain
malaise
dyspnoea
haemoptysis- coughing up blood
cough
tachypnea
abdo pain
anxiety

Question 13

How is a pulmonary embolism diagnosed?

Answer 13

• chest x-ray- look for pleural effusion (excess fluid in pleural cavity), elevated diaphragm, westermark singn( collapse of pulmonary blood vessels)
• VIQ scan- gold standard: Given radioactive isotopes of labelled human albumin and inhaled xenon-133 gas - in PE images would show decreased perfusion due to blood clot but ventilation Is not affected
• lab tests- arterial oxygen saturation using pulse oximeter on finger, increase in WBC , ESR and d-dimer
• ECG

Question 14

What are the treatment therapies for PE?

Answer 14

• Supportive therapy- oxygen, pain relief
• immediate anti-coagulation (same as dvt e..g heparins)
• Fibrinolytic agents e.g. urokinase, alteplase (most common), recteplase- these activate plasminogen to breakdown fibrin

Question 15

What risk factors are assessed in hospital when doing a VTE risk assessment (NICE)?

Answer 15

• Active cancer/treatment
• Critical care admision
• 60+
• Dehydration
• High BMI
• comorbidities e.g. heart disease, metabolic/endocrine/ respiratory illness
• Personal/family history of vte
• Use fo HRT
• Use of oestrogen contraceptives
• varicose veins

Question 16

What are options of mechanical and pharmacological vte prophylaxis?

Answer 16

Mechanical:
Thigh-length graduated compression stocking

Pharmacological:
Usually Low molecular-weight heparins e.g. enoxaparin 40mg SC
Need to consider pre-existing anticoagulation/anti-platelet therapy- may not need LMWH