Respiratory: PE Flashcards
Describe the primary factors that contribute to a thrombus formation [3]
Virchows triad:
Endothelial damage:
- Alters blood flow dynamics: creates turbulence and increasing flow friction within a vessel
Hypercoagulable state:
Blood stasis
State risk factors for PE
Increasing age
DVT diagnosis / previous VTE event
Surgery within last 2 months
Bed rest > 5 days
Fx of VTE
Active malignancy
Recent trauma
Pregnancy / post-natal period
Smoking
Obesity
Factor V Leiden mutation
Antithrombin deficiency
Prothrombin deficiency
Protein C & S deficiencies
Antiphospholiipid syndrome
Which inherited disorders increase the risk of PE? [5]
Factor V Leiden mutation:
- Normally used for blood clotting: helps enzyme reaction to form fibrin in blood clot
- Once the coagulation process is turned on in people with factor V Leiden, it turns off more slowly than in people with normal factor V
Antithrombin deficiency
- Normally anti-thrombin acts as the inhibitory component to thrombin formation
Prothrombin deficiency
Protein C & S deficiencies
Antiphospholiipid syndrome
Which type of hormone therapy increases the risk of PE? [1]
Hormone therapy with oestrogen (e.g., combined oral contraceptive pill or hormone replacement therapy)
Describe the presentation of PE
dyspnoea
- most common symptom
- can be acute or severe
- tachopynea is common in acute PE
chest pain:
- acute onset
- localised to one side of the chest (unlikely to be central!)
signs of concurrent deep vein thrombosis (DVT):
- Typically pain and swelling in one leg, although both legs may be affected
hypoxaemia:
- Oxygen saturations < 94% (or < 88% in patients at risk of hypercapnic respiratory failure).
failure to meet Pulmonary Embolism Rule-out Criteria (the PERC rule)
Cough
Haemopytsis
What is important to note about symptoms of dysopnea in PE? [1]
Symptoms of PE usually come on acutely rather than gradually.
Explain what is meant by the PERC rule
The pulmonary embolism rule-out criteria (PERC) are recommended by the NICE guidelines (2020) when the clinician estimates less than a 15% probability of a pulmonary embolism to decide whether further investigations for a PE are needed. If all the criteria are met, further investigations for a PE are not required.
Which factors make up the PERC rule? [8]
Age < 50 years
Heart rate < 100 bpm
SaO 2 on room air ≥95%
No unilateral leg swelling
No haemoptysis
No recent surgery or trauma (≤4 weeks ago requiring treatment with general anaesthesia)
No prior PE or DVT
No hormone use (oral contraceptives, hormone replacement, or oestrogenic hormones used in male or female patients).
What is next step if a patient fails the PERC test? [1]
Request D-dimer testing for any patient in whom the PERC rule fails to rule out a PE (i.e., one or more criteria not fulfilled)
What Well’s score indicates likelihood of PE? [1]
How do you use the Wells score to create a management plan for PE? [2]
> 4: PE likely
< 4: PE unlikely
Plan:
Likely: perform a CT pulmonary angiogram (CTPA) or alternative imaging
Unlikely: perform a d-dimer, and if positive, perform a CTPA
Describe the investigations you would conduct for a ptx suspected with PE
computed tomographic pulmonary angiography (CTPA)
- preferred investigation for definitive confirmation of PE
echocardiography:
- presence of any signs of right ventricular (RV) dysfunction is sufficiently suggestive of PE to confirm the diagnosis and justify urgent reperfusion treatment
- used if CTPA not immediately available / contraindicated
D-dimer:
- Elevated
- Used if Wells Score < 4.
ECG:
- An ECG is not diagnostic of PE but can be useful to support the diagnosis of PE or rule out other causes.
- S1Q3T3 pattern
urea and electrolytes:
- guides CTPA use
Why might a CTPA be contraindicated for PE investigation? [2]
The contrast dye used in CTPA for the evaluation of PE may cause nephropathy.
Radiation from CT is considered to be a risk factor for certain cancers.
Explain a specific sign seen on echocardiogram that would indicate a PE [1]
60/60 sign :a combination of
- pulmonary acceleration time (PAT) less than 60 milliseconds
and
- tricuspid regurgitation (TR) jet gradient of less than 60 mmHg
What is the McConnell sign? [1]
What does it indicate? [1]
reduced contractility of the RV free wall compared with the RV apex
indicates PE
Typically this looks as if the apex of the RV is a trampoline bouncing up and down while the rest of the RV remains still
Ty
Why do you need to conduct coagulation studies when suspicious of PE / VTE? [2]
Order international normalised ratio (INR), prothrombin time (PT), and activated partial thromboplastin time (aPTT). These are needed to establish baseline values before starting anticoagulation.
Also aids decisions about the safety and choice of initial anticoagulation.
What ABG results would indicate PE? [1]
Explain your answer [1]
TOM TIP: Patients with a pulmonary embolism often have respiratory alkalosis on an ABG.
Hypoxia causes a raised respiratory rate.
Breathing fast means they “blow off” extra CO2.
A low CO2 means the blood becomes alkalotic.
What are the two causes of respiratory alkolosis in an ABG? [2]
How do you differentiate between them? [2]
PE
and
Hyperventilation syndrome.
Patients with PE will have a low pO2
Patients with hyperventilation syndrome will have a high pO2.
Describe an alternative imaging method for investigating PE than CTPA
V/Q scan:
- radioactive isotopes and a gamma camera to compare ventilation with the perfusion of the lungs
- First, the isotopes are inhaled to fill the lungs, and a picture is taken to demonstrate ventilation
- Next, a contrast containing isotopes is injected, and a picture is taken to illustrate perfusion
- The two images are compared
- With a pulmonary embolism: there will be a deficit in perfusion as the thrombus blocks blood flow to the lung tissue
A V/Q scan is of limited use in patients with which co-morbidities? [3]
A V/Q scan is of limited use in patients with:
* significant underlying lung disease
* left ventricular failure
* congestive cardiac failure
When is a V/Q scan indicated for suspected PE? [3]
Patients with:
* renal impairment
* contrast allergy
* risk from radiation
Label A [1]
Saddle embolus
State 4 reasons that may cause V/Q mismatch [4]
old pulmonary embolisms
AV malformations
vasculitis
previous radiotherapy
Describe the treatment algorithm for patients who have initial PE suspected and are haemodynamically unstable AND OR are hypoxaemic [2]
Oxygen
- Give high-concentration oxygen if oxygen saturations are < 90%, targeting an initial oxygen saturation of 94% to 98%
Consider fluid resuscitation
- Give intravenous fluids if SBP is < 90 mmHg and the JVP is not elevated
- fluid challenge of ≤500 mL over 15-30 minutes
What is the leading cause of death for patients with massive PE? [1]
The leading cause of death in patients with high-risk (massive) PE is acute right ventricular (RV) failure with resulting hypotension.[65]
