Junior Doctor Notes 🩺

Pulmonary Embolism

9 min read

Massive PE Resuscitation

  • Oxygen via:
    • Nonrebreather @ 15L/min + nasal cannula @ 15L/min
    • High flow nasal prongs
  • Thrombolysis
    • Standard dose: 100 mg alteplase (10-20 mg bolus, then remainder over 2 hours).
    • Cardiac arrest: 50 mg bolus.
  • Vasopressors
    • First choice: Adrenaline or noradrenaline infusion
    • Adjuncts: Vasopressin (for pressure support), dobutamine (for RV inotropy)
    • Consider: adrenaline if severe refractory RV failure
  • Inhaled pulmonary vasodilators
    • Nitroglycerine
    • Milrinone
    • Nitric oxide
  • Fluid-conservative therapy

Presentation

  • See: Dyspnoea
  • A small PE causes sudden dyspnoea, pleuritic pain and possibly haemoptysis, with few physical signs. Look for a low-grade pyrexia (>38°C), tachypnoea (>20/min), tachycardia and a pleural rub
  • A major PE causes dyspnoea, chest pain and light-headedness or collapse, followed by recovery. Look for cyanosis, tachycardia, hypotension, a parasternal heave, raised JVP and a loud delayed pulmonary second sound
  • Clinical signs of a DVT may be present

Red Flags

  • On Examination
    • Diaphoresis
    • Signs of hypoperfusion: mottling, cool extremities, confusion, agitation
  • Vital signs
    • Bradycardia ⇒ may indicate impending brady-asystolic arrest
    • Shock index (HR/SBP) > 1
    • Hypotension
    • Hypertension (some patients with PE have excess adrenaline production), often indicated by elevated lactate
    • Tachypnoea > 30
  • Labs
    • Elevated troponin
    • Elevated lactate

Investigations

Bedside

  • Weight

Bloods

  • Consider performing an ABG
    • Do not routinely unless pulse oximetry is unreliable or demonstrates unexplained hypoxia on room air
    • Low , Low , High pH
    • Characteristic findings include acute respiratory alkalosis, or hypoxia and a raised A-a gradient
  • D-dimer
    • Age adjusted cutoff 0.01 x age if >50 y/o
  • Coags, FBC, EUC, LFT
  • beta-HCG in women of child bearing age
  • Troponin (if chest pain or otherwise indicated)

ECG

  • Significant PE may cause right axis deviation and right BBB but most common sign is sinus tachycardia (S1Q3T3 is neither specific nor sensitive for PE)
  • Other ECG findings: Qr in V1, STE in V1, Complete RBBB, S1Q3T3, R axis deviation, STE in III, STD in V4-6, AF, TWI in precordial/inferior leads

Imaging

  • Calculate the clinical pre-test probability of PE before requesting any diagnostic imaging
  • Can use D-dimer to exclude PE in low probability pre-test patients
  • Can use ELISA D-dimer to exclude PE in moderate probability pre-test patients
  • If >6 proceed directly to definitive diagnostic imaging

NOTE

Only send a D-dimer test in

  • Patients ≥50 years with a low pre-test probability or
  • In any patient <50 with a low pre-test probability but who fails to fulfil one or more PERC criteria
    • If all PERC criteria are fulfilled, the patients does not have a PE and does not need a D-dimer test sent

NOTE

Patients with high pre-test probability should be commenced on treatment if there are no contra-indications. Treatment can commence prior to definitive imaging. Consideration should be given to treating low and moderate risk patients with positive D-Dimer and no contra-indications.

  • PERC needs to be 0 to rule out PE
  • If PERC positive → YEARS score + D-dimer
  • Arrange a CTPA or V/Q scan in:
    • All patients with a high or intermediate pre-test probability
    • Those with a positive D-dimer

CTPA

  • CTPA has >95% sensitivity for segmental or larger PEs and ~75% for subsegmental
  • CTPA is the preferred first line imaging except for patients <40 years with a normal XR chest where V/Q scan is available within hours
  • Contrast-induced risks in patients with renal insufficiency can be mitigated with:
    • IV pre-hydration and adequate hydration afterwards
    • Witholding metformin, NSAIDs, ACE-i
  • More useful if the CXR is abnormal (V/Q scan is difficult to interpret in these cases and indertiminate result more likely)
  • Arrange sequential V/Q scan ±lower limb Doppler u/s or CT venogram if doubt remains

V/Q Scan

  • V/Q scan preferred over CTPA if:
    • Patient is allergic to contrast dye
    • Patient has renal failure
    • When the CXR is normal
    • Younger females
  • A normal V/Q scan rules out clinically important PE in patients with low-to-moderate pre-test probability
  • Interpretation of results
    • Normal Scan = No PE. Consider alternate diagnosis
    • Low Probability Scan + Low PTP = No PE. Consider alternate diagnosis
    • Low Probability Scan + Intermediate or High PTP = Inconclusive result – Further testing (CTPA) required
    • Intermediate Probability Scan = Inconclusive result – Further testing (CTPA) required
    • High Probability Scan = PE. Commence treatment.

Chest-Xray

  • Frequently normal; mainly to exclude other diagnoses such as pneumonia or pneumothorax
  • Plate or linear atelactasis
  • Unilateral pleural based wedge shaped pulmonary infiltrate
  • Unilateral pleural effusion
  • Raised hemidiaphragm
  • Dilated pulmonary artery in massive PE
  • Areas of oligaemia in massive PE

Pregnancy

  • D-dimer cannot be used for risk stratification in pregnant patients
  • Bilateral lower limb ultrasound remains the first test of choice
  • In suspected PE in pregnancy, if compression ultrasonography of the legs is normal and a XR chest has not further aided the diagnostic process, the decision then needed is whether to investigate further with CTPA or V/Q or treat empirically

Risks

  • The average human receives about 3mSv of “background” radiation per year. In general, the comparative radiation dose to a patient with CTPA is 12 mSv whilst it is 2.3mSv with V/Q scan.
  • The natural background dose for a foetus during pregnancy is 1.1-2.5mGy. The foetal dose of radiation from CTPA is 0.37mGy, whilst it is 0.4mGy from a V/Q scan in early pregnancy and 0.75mGy at 6 months. The risk of childhood cancer in exposed offspring is slightly higher with V/Q scan than with CTPA (1 in 280,000 for V/Q and %3C1 in 1,000,000 for CTPA)

  • CUS = Lower limb ultrasound

Management

General measures

  • Give high-dose oxygen, aiming for oxygen saturation >95%
  • Lie patient flat to increase venous return
  • Give IV normal saline to support BP if necessary (can trial 250mL normal saline bolus)
    • **Avoid excessive fluid ∵ worsens RV dilation → septal shift → worsens LV function **
    • Patients who are really unwell from massive PE have elevated filling pressures, the potential risk of fluid generally outweighs the potential benefit in these patients
  • Vasopressors: Norad first line, dobutamine
  • Relieve pain with titrated morphine 2.5 mg IV boluses
  • Can use PESI score or simplified PESI score to determine risk of 30 day mortality (see here)
  • Measure weight and creatinine clearance before selecting anticoaglant
  • See contraindications to thrombolysis and anticoagulation here

Anticoagulation

  • Commence anticoagulation when:
    • The diagnosis is confirmed or
    • When there is an intermediate or high pre-test probability of PE but a delay to testing (in the absence of contraindications)
  • 2 anticoagulation options exist:
    • Heparin: UFH or LMWH
    • NOAC
  • Duration
    • Provoked: minimum 3 months
    • Unprovoked: >3 months
    • Cancer associated: >6 months
      • Can use DOAC or clexane
        • LMWH for GI/GI cancers and high bleeding risk
      • DOAC can be used for lung, breast, prostate, haem (unless thrombocytopenia), ovarian, brain

Heparin + Warfarin

  • Give LMWH such as enoxaparin 1mg/kg SC BD
    • LMWH does not require aPTT monitoring
  • In patients with haemodynamic compromise, give UFH (80 U/kg IV bolus) followed by maintenance infusion of 18 U/kg/h titrated to aPTT (1.5-2.5x control value)
  • If patient already on warfarin and has a PE consult cardiothoracics for consideration of transvenous vena caval filter
  • Commence first dose of warfarin 5mg PO on the first day of heparin therapy and titrate ssubsequent daily doses to achieve an INR of 2.5-3.5

NOAC/DOAC

  • NOAC such as rivaroxaban 15mg PO 12 hourly or apixabanm 10mg PO 12-hourly
  • Check renal function
  • Cannot use in child-pugh class B or worse without specialist input

Dabigatran

Dabigatran requires at least 5 days of parenteral anticoagulant to be given first. Dose is 150mg PO 12-hourly. Dose modification is required based of renal function

Massive PE

  • Consider when the probability of PE is high (or confirmed) and:
    • The patient is hypotensive despite fluid resuscitation and/or
    • Has evidence of acute RV failure and/or
    • Is peri-arrest
  • High risk (previously massive) PE:
    • Acute PE (confirmed on VQ, CTPA or bedside echocardiogram) accompanied by any of:
      • Sustained hypotension (systolic BP <90 mmHg for at least 15 min or requiring ionotropic support not due to a cause other than PE)
      • Pulselessness
      • Persistent profound bradycardia (heart rate <40 bpm with symptoms or signs of shock)
  • Intermediate high risk (previously sub-massive) PE:
    • Acute PE without systemic hypotension (systolic BP >90 mmHg) but with either right ventricular dysfunction and/or myocardial necrosis:
      • RV dysfunction defined as at least one of:
        • RV dilation (apical 4-chamber RV diameter divided by LV diameter ≥0.9) or RV systolic dysfunction on echocardiography
        • RV dilation (4 chamber RV diameter divided by LV diameter ≥0.9) on CT
        • Elevation of BNP (>90 pg/mL) or pro BNP (>500 pg/mL)
        • ECG changes indicating RV dysfunction (new RBBB, anteroseptal ST elevation or depression or T wave inversion)
      • Myocardial necrosis defined by:
        • Elevation of troponin T >50ng/L
  • Call immediate senior help and MET Activation Criteria
  • Stat fibrinolytic doses can be given in cases of cardiac arrest considered related to a massive PE
  • Catheter directed thrombolysis indicated for patients with acute PE associated with hypotension who have:
    • High bleeding risk
    • Failed systemic thrombolysis
    • Shock that is likely to cause death before systemic thrombolysis can take effect (e.g. within hours)

Other Management in Massive PE

Avoid Intubation

  • Avoid intubation unless the patient has lost mental status or has developed respiratory exhaustion as it often precipitates cardiac arrest because:
    • Sedatives drop blood pressure
    • Positive pressure reduces preload
    • Over-distention of the lungs may compress pulmonary capillaries, increasing the pulmonary vascular resistance
  • Avoid intubation by:
    • High flow nasal cannulas combined with pulmonary vasodilators
    • Give thrombolysis first (if indicated) then intubate later
  • Optimising for intubation:
    • Increase SBP to 130-140 with adrenaline/noradrenaline infusion
    • Use sedatives that are haemodynamically stable (e.g. ketamine)
    • Following intubation, don’t over-distend the lungs (i.e. avoid over-vigorous bag ventilation)

Careful Administration of Fluids

  • Evaluate with ultrasound
  • If clear evidence of hypovolaemia (e.g. small IVC with variation with respiration), give fluid in small amounts
    • Small IVC rarely occurs in massive PE; if seen should consider alternative diagnoses to massive PE
  • If IVC dilated do not give fluid
  • If already received fluid consider diuresis

Inotropes and Vasopressors

  • Noradrenaline
  • Establishing an adequate mean arterial pressure (e.g. >65 mm) will help ensure adequate perfusion of the right coronary artery and thereby support right ventricular function
  • See Inotropes

Inhaled Pulmonary Vasodilators

Sources

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