Pulmonary embolism Flashcards
PE depends on what?
- Extent of vasculature exclusion
- Rate at which obstruction accumulates
- Pre-existing cardiopulmonary status of the patient
Discuss the Pathophysiology of the PE
Read pg 10 of slides
- Decreased in the cross-sectional area of the pulmonary vasculature bed > which will increase vasculature resistance and RV afterload
- More than 50% of the pulmonary vasculature bed needs to be obstructed to increase pulmonary resistance
- Mediators released from platelets may induce vaso-bronchoconstriction
- Increase alveolar dead space > ventilation-perfusion mismatch and hypoxemia
- This will stimulate irritant receptors > hypoventilation
Discuss the 4 clinical forms of PE
- Acute Minor PE > short sudden onset > less then 50% vasculature obstruction (VO) > PST: Dyspnoea ,pleuritic chest pains ,haemoptysis > PAP & RAP normal
- Acute massive PE > Short sudden onset > >50% VO and thrombus volume is >30 ml > Right side heart strain ,haemodynamic instability and syncope > PAP Increased & RAP 12
- Subacute massive PE > Several weeks > > 50%VO > Dyspnoea with right heartstrain > PAP increases and RAP 8
- Chronic thromboembolic pulmonary hypertension > Months to years > >50% VO > Slowly progressing dyspnoea with exercise intolerance and right heart strain > PAP increased & RAP 6
History that might suggest PE
- Dyspnoea at rest or exertion usually onset
- Pleuritic chest pain
- calf pain or swelling
- coagh
- wheeze
- haemopytysis
- syncope
The examination that might suggest PE
- Tachypnoea
- Signs of DVT
- Tachycardia
- pulmonary crackles
- loud pulmonary component of second heart sound
- Elevated jugular venous pressure
Investigating PE: Arterial blood gas
- Doesn’t exclude minor PE but it is good evidence against major PE
- Decreased pO2 and Increased pCO2
- Widen alveolar-arterial O2 gradient
Investigating PE: Chest X-ray
- Usually abnormal (80%) but it is a nonspecific diagnosis therefore it may provide an alternative diagnosis
- Normal cardiac shadow with plump pulmonary artery segments
- Palla sign: Abrupt cut off of pulmonary artery
- Westermark sign: Oligeamia of the affected segment
- Hampton s hump: peripheral semicircular / wedge shape in contact with the pleural surface
- small pleural effusion, atelectasis, and raised hemidiaphragm
Investigating PE: ECG
ECG changes are common in PE but are nonspecific
- Sinus tachycardia
- S1Q3T3 pattern is uncommon
Investigating PE: Well’s Criteria for a clinical assessment for PE
- Symptoms of DVT (leg swelling with pain ,warmth ,palpation ) : 3
- Other diagnosis less likely than PE : 3
- HR > 100 bpm : 1,5
- Immobalization for more than 3 days or surgery in the past 4 weeks : 1,5
- Previous DVT / PE : 1,5
- Hemoptysis : 1
- malignancy 1
Simplified clinical assessment(mordified Wells criteria)
>4: PE likely
< 4: PE unlikely
Traditional clinicall probability assessment (Wells criteria)
- High :>6
- moderate : 2-6
- Low: <2
What to do when the patient is likely PE and haemodynamically stable after resus
- Start full anticoagulation and do definitive diagnostic imaging (CTPA) which will give us 2 types of results either PEor no PE
- When no PE stop full anticoagulation and investigate other causes for circulatory collapse
What to do when the patient is likely PE and hemodynamically unstable despite resus
- Bedside transthoracic or oesophagus echo which will give us 2 types of results
either Clot visualization in RV or proximal pulmonary arteries after considering empiric thrombolysis - Clot visualised no other cause for instability and RV dysfunction
What to expect when performing echocardiography in a likely PE situation
- Transthroracic: May see clot in RA
- Transoesophageal: Allows visualization of proximal pulmonary arteries
- Can assess for the presence of RV dysfunction
Using D dimer to determine PE
1.Determine if PE likely / PE unlikely
- IF PE unlikely :
* D-dimer assay
* if <500 ng/mL then exclude PE and offer no treatment
* if >500 ng/mL then CT pulmonary angiogram (CTPA) - If PE likely
* CTPA which will give us one of 3 different results
* Negative > PE excluded
* Possivtive > PE confirmed > Treatment
* Inconclusive > Additional testing eg V/Q which will ether confirm PE / not
Are elevated D-dimer levels enough to confirm PE
- NO, however, it should raise suspicions for VTED and prompt further testing even if well s modified criteria is PE unlikely
- Normal D dimer levels with likely PE is not enough to exclude PE but can exclude PE in patients with PE unlikely
Investigating PE : V/Q scan
Mismatch of inhaled and injected compounds on the lung scan suggest PE
When to use Pulmonary angiography
when other investigations are inconclusive
Treatment of PE: General resuscitation
- Analgesia: caution with opiates
- Oxygenation: facemask / mechanical ventilation
- Careful fluid resuscitation
- Inotropes
- Empiric anticoagulation depending on clinical suspicion for PE, risk of bleeding, and expected timing of diagnostic tests
Treatment of with established diagnosis in severely impaired circulation
- If thrombolysis contraindication > embolectomy
- If not thrombolysis contraindicated > thrombolysis with / without clot fragmentation if susscessful > heparin / LMWH
if not sussessful > embolectomy
Treatment of with established diagnosis in stable circulation
Either :
heparin / LMWH > oral anticoagulants / recurrent emolism
or
if anticoagulant C/I > vena caval interuption
Discuss the goals and agents of parental anticoagulation
Goals
- inhibition of thrombus propagation
- prevention of early recurrences
- allows for endogenous fibrinolysis
Agents
- UFH IV or Protein S/C to maintain PTT 2,5 normal
- LMWH
- Fondaparinux
efficacy depends on achieving the therapeutic level of anticoagulation within 24 hrs
List the oral anticoagulant agents
- Vitamin k antagonist (warfarin ) ; initiate after parental anticoagulation started for 5 days
- Factor Xa inhibitors: Do not require monitoring but do not use in haemodynamically unstable patients
Long term management of PE
Goals: prevent delayed recurrences and sequelae eg Posy thrombotic syndrome and Pulmonary Hypertension
agents
- Warfarin : INR maintained at 2-3
- LMWH
- Rivaroxaban (factor Xa inhibitor )
What is thrombolysis and when to use it
aCTIVE DISSOLUTION OF THROMBUS WITH PARENTERAL ANTITHROMBOTIC ENZYMES EG STREPTOKINASEE OR ALTEPLASE
*Reserved for patients with hypotension will not survive long enough for spontaneous fibrinolysis and severe hypoxaemia and RV dysfunction
When to do embolectomy
When other measures have failed and in acute PE to prevent death
