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Core Conditions - Respiratory > Pulmonary Embolism > Flashcards

Pulmonary Embolism Flashcards

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1
Q

What is the most common cause of a pulmonary embolism?

A

it is most commonly a complication of venous thromboembolism (VTE) from another source

e.g. clot in the legs (DVT) becomes dislodged and flows via the bloodstream, through the right side of the heart, and becomes lodged in the pulmonary circulation

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2
Q

Other than a clot, what other things can cause a pulmonary embolism?

A
  • fat
  • air
  • amniotic fluid

for fat and amniotic fluid, these often resolve themselves with supportive care

air is often an iatrogenic cause

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3
Q

What is the mortality like for a PE caused by venous thromboembolism?

A
  • <5% if there is no haemodynamic instability
  • 30% if shock is present
  • 70% with cardiac arrest (in hospital)
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4
Q

What lifestyle factors act as risk factors for VTE pulmonary embolism?

A
  • immobility
    • bed rest > 24 hours
    • immobiity > 48 hours
    • plaster of paris (POP) over limb
  • smoking
  • dehydration
  • obesity
  • trauma / surgery (especially pelvic & orthopaedic)
  • pregnancy (oestrogen)
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5
Q

What other medical conditions can increase the risk for VTE pulmonary embolism?

A
  • malignancy
  • infection
  • previous DVT / embolism
  • recent MI
  • congestive heart failure
  • varicose veins
  • antithrombin deficiency
  • protein C deficiency
  • inherited clotting deficiencies (thrombophilia , factor V Leiden)
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6
Q

What are other risk factors for VTE pulmonary embolism?

A
  • age
  • family history
  • oestrogen therapy
    • HRT or OCP
    • only the combined pill, not the progesterone only one
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7
Q
A
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8
Q

How do clinical features for PE vary?

What question is it important to always ask about?

A

symptoms can be wide ranging from none at all to sudden death

symptoms are usually correlated to severity

it is important to always ask about a family history of thrombosis

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9
Q

What are the clinical signs of pulmonary embolism?

A
  • pyrexia
  • cyanosis
  • tachypnoea
    • 90% of patients have RR > 16
  • tachycardia
  • hypotension
  • raised JVP
  • pleural rub
  • pleural effusion
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10
Q

What are the typical symptoms of pulmonary embolism?

A
  • pleuritic chest pain (pain worse on inspiration)
  • breathlessness
  • cough
  • haemoptysis (as a result of pulmonary infarct)
  • dizziness / pre-syncope
  • syncope (loss of consciousness / fainting)
  • non-pleuritic chest pain
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11
Q

What is usually the first symptom of PE that presents?

A

Shortness of breath typically occurs within seconds to minutes of onset

pain then develops later

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12
Q

What symptom of PE is it important to pay special attention to?

A

patients with unexplained syncope

around 25% of patients admitted to hospital with unexplained syncope have PE

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13
Q

What are the 2 tools to use to help define the risk of the probability of PE?

A
  • PERC score
    • pulmonary embolism rule-out criteria
  • Well’s score
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14
Q

When is the PERC score used to rule out PE?

A

This is used to rule out PE in low-risk patients

if the patient’s score is 0, then there is a <2% chance of PE

in the absence of convincing clinical signs, you can usually safely exclude PE as a differential

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15
Q

What are the factors that are measured in the PERC score?

A
  • age > 50
  • heart rate > 100
  • SaO2 on room air <95%
  • unilateral leg swelling
  • haemoptysis
  • recent surgery or trauma
  • previous PE or DVT
  • exogenous oestrogen
    • oral contraceptives, hormone replacement or other oestrogen hormones
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16
Q

How is the PERC score calculated?

What does it mean if someone scores more than 0?

A

Each factor gives a score of 1 if present

If the patient scores 0, and in the absence of convincing clinical signs, you can usually safely exclude PE

If the patient scores 1 or more, the PERC criteria CANNOT be used to safely rule out PE and the Well’s score is used

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17
Q

What is the purpose of calculating the Well’s score?

A

it will stratify patients as low or high risk

in high risk patients, you should proceed straight to imaging

in a low risk patient, you should consider a D-dimer test

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18
Q

How is the Well’s score calculated?

What is each factor worth?

A

Factors that score 3 points:

  • clinically suspected DVT
  • PE is the most likely diagnosis

Factors that score 1.5 points:

  • tachycardia > 100 bpm
  • immobilisation > 3 days or surgery in past 4 weeks
  • history of DVT or PE

Factors that score 1 point:

  • haemoptysis
  • malignancy
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19
Q

How is the Well’s score interpreted?

A
  • Score > 6.0 means high probability of PE
  • Score 2.0 - 6.0 means moderate probability of PE
  • Score < 2.0 means low probability of PE
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20
Q

What is D-dimer?

Why is it useful when there is a suspected PE?

A

D-dimer is a fibrin degradation product

Levels of D-dimer are raised by the presence of a blood clot in the circulation

D-dimer can be useful to RULE OUT a PE or DVT as a differential

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21
Q

Why can D-Dimer alone not be diagnostic of a PE?

Study These Flashcards
A

There are many factors that can cause a positive D-Dimer

having a raised D-dimer does not necessarily mean there is a clot

a positive D-dimer usually indicates the need for further investigation

22
Q

When should D-dimer be used in practice?

Study These Flashcards
A

it should only be used as a “rule-out” test in low probability cases (based on Well’s score)

A negative D-dimer + a low Well’s score means that PE or DVT is extremely unlikely

23
Q

What is important to remember about another reason why D-dimer might be raised before requesting this test?

Study These Flashcards
A

almost any factor that causes inflammation will also result in raised D-dimer

Even if the patient has a low Well’s score, D-dimer may not be the best option if they have had a recent cellulitis / infection

24
Q

When is D-dimer not necessary?

Study These Flashcards
A

In cases with a high probability of PE, as based on the Well’s score

D-dimer should be skipped and imaging performed straight away

25
How does D-dimer change with age? How do new reference ranges reflect this?
D-dimer **rises with age** normal range of D-dimer is **_\< 0.50_** for anyone **aged \< 50** for anyone **aged \>50**, normal range is **_\<0.50 plus 0.1 for every decade of life_** over the age of 50 e.g. age 60 - normal \< 0.60 age 70 - normal \< 0.70
26
What are other factors known to cause an increased D-dimer?
* liver disease * high rheumatoid factor * malignancy * trauma * pregnancy * recent surgery
27
Why is a chest X-ray performed as part of an investigation into PE?
CXR will often be **_normal_** in PE the main reason to perform a CXR is to **_exclude other causes_**
28
What signs may be present on a CXR for pulmonary embolism?
* may show **_pulmonary oedema_** signs such as **raised hemidiaphragm** * may show **_atelectasis_** - little areas of **collapsed lung** * this occurs because there is **loss of blood** to some areas of the lungs, resulting in **collapse** fo these areas
29
What results from CXR will raise the suspicion of pulmonary embolism?
* if CXR is normal but the patient is breathless * if CXR has bilateral changes but the patient only has unilateral pain these both raise the suspicion of PE
30
What ECG changes can occur in PE?
ECG changes are common but often non-specific the most common findings are **_T wave inversion_** and **_sinus tachycardia_** (ECG shows T wave inversion)
31
What "classic sign" is present on ECG in \<20% of cases of PE? Why does it happen?
larger emboli can cause **_right heart strain_**, which results in the "classical" **_S1Q3T3 pattern_** of ECG changes * S waves present in lead I * Q waves present in lead III * T wave inversion in lead III
32
What is a CTPA? What are the benefits and downfalls of using this?
**_CT-pulmonary angiogram_** it is a **CT with contrast** that assesses the **pulmonary blood vessels** it's main use is in the diagnosis of PE as it is much more sensitive and specific than a VQ scan
33
In what groups might a VQ scan be considered over a CTPA and why?
VQ is considered in **_young females_** and **_pregnant females_** this is because CTPA uses a **high dose of radiation**
34
What is shown in this CTPA image?
this CTPA shows a saddle PE the red arrows are indicative of thrombus and show lack of contrast in the pulmonary vessels
35
When is a VQ scan used?
They are used to assess for PE in patients who are at risk from **higher radiation doses** e.g. pregnant women and young women they use **_much less radiation_** than a CTPA
36
What is the downfall of using a VQ scan? How are they interpreted?
they are much **less accurate** at diagnosing a PE and need to be interpreted carefully by a radiologist a **_negative VQ scan_** has a very **_high negative predictive value_**, but positive scans are less useful the result of a VQ scan is given as a **_risk probability_** - high, intermediate or low risk
37
What is shown in images A and B of VQ scans?
***_Image A:_*** * inhaled radioactive element (usually **_Xenon gas_**) showing **_normal perfusion_** throughout the bronchial tree ***_Image B:_*** * this image follows injection of **_technetium_** * **patchy update** in different regions of the lungs indicates multiple areas of **_reduced blood flow_**, likely due to **PE**
38
What patients are not suitable for VQ scans?
VQ is only suitable for patients who have been **previously well** and **not those with chronic disease** any CXR abnormalities are likely to cause abnormalities on VQ
39
What might an ABG show for someone with PE?
* **O2** may often be **_low_** * **CO2** may often be **_normal or low_** * the patient may be **hyperventilating**, hence the **low CO2**
40
What condition is seen on ABG in someone with a massive PE? Can it be used for diagnosis?
**_metabolic acidosis_** is commonly seen in patients with a **massive PE** and **cardiovascular collapse** A PE **_CANNOT be excluded_** with an arterial blood gas
41
Why might troponin be raised in PE? What is higher troponin associated with?
troponin is raised in **20-40%** of patients with PE as a result of the **_extra stress and stretch_** placed on the **_right ventricle_** this is due to **_increased pulmonary arterial pressure_** higher troponin is associated with **worse prognosis**
42
When might an Echocardiogram be used to look at PE? What can this scan predict?
it is used to look for **_right ventricle strain_** and **_dilatation_** in patients with **suspected massive PE** the degree of **RV dysfunction** can be used as a **predictor of death**
43
What is the initial treatment for PE?
* anticoagulate with **low molecular weight heparin** (LMWH) - e.g. **_dalteparin_ 200u / kg / 24hrs** the maximum dose is 18,000u * at the same time start **_oral warfarin 10mg_**
44
When should heparin and warfarin be stopped in the treatment of PE?
* heparin is stopped when **_INR \> 2_** * warfarin is continued for a **_minimum of 3 months_**, aiming for an **INR of 2 - 3**
45
What treatment can be given to patients who continue to develop thrombi despite anticoagulation?
a **_vena cava filter_** can be placed in patients who continue to develop thrombi despite anticoagulation BUT implanting a filter without adequate anticoagulation will increase the risk of thrombus
46
When can thrombolysis be used as a treatment for PE? What dose is given?
thrombolysis can be used if the PE is deemed **_"massive"_** as long as there are **no contraindications** **_50mg of alteplase_** is used
47
How long should warfarin be continued at the very minimum? How about for those with idiopathic disease and risk factors?
* Warfarin should be continued for **_6 weeks_** at the **very minimum** * it should be continued for **_3 months_** in those with an **identifiable & reversible risk factor** * it should be continued for **_6 months_** in those with **idiopathic disease**
48
What is a paradoxical embolism?
an embolism that goes through a **_defect in the heart_** and goes on to cause a **_stroke_** the clot passes **from a vein to an artery**, through some sort of **"fistula"** (usually a cardiac defect such as **patent foramen ovale**)
49
How could a paradoxical embolism result from a DVT?
* DVT embolises and travels to the **heart** * it enters the **right atrium** via the vena cava * this would usually end up travelling to the lungs and causing a PE * it travels **_from the right side of the heart to the left side_** via a **defect** in the heart * the embolism **_misses out the pulmonary circulation_** and is free to travel in the **_arterial circulation_** * it travels until it reaches an artery that is **so small** it cannot travel down it, and causes an **_ischaemic blockage_**
50
What are the potential differential diagnoses for pulmonary embolism?
* acute coronary syndrome * pleuritic chest pain - pneumonia * pericarditis * musculoskeletal back pain * embolus of other cause (fat, amniotic fluid, air) * dissecting aortic aneurysm * anxiety * exacerbation of COPD * syncope of another cause

Core Conditions - Respiratory (10 decks)

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