Pulmonary embolism

Background

• Suspect in pt w/ dyspnea, tachypnea, or pleuritic pain
• Only 40% of ambulatory ED pts w/ PE have concomitant DVT

Types

1. Massive
   1. Sustained hypotension (sys BP <90 for at least 15min or requiring inotropic support)
   2. Pulselessness
   3. Persistent profound bradycardia (HR <40 with signs of shock)
2. Submassive
   1. Sys BP >90 but with either RV dysfunction or myocardial necrosis
      1. RV dysfunction
         1. RV dilation or dysfunction on TTE
         2. RV dilation on CT
         3. Elevation of BNP (>90)
         4. ECG: new complete or incomplete RBBB, anteroseptal ST elevation/depression or TWI
      2. Myocardial necrosis: Troponin I >0.4

Diagnosis

Wells Criteria

1. Symptoms of DVT - 3pts
2. No alternative diagnosis better explains the illness - 3pts
3. HR > 100 - 1.5 pts
4. Immobilization within prior 4wks - 1.5pts
5. Prior history of DVT or PE - 1.5pts
6. Active malignancy - 1pt
7. Hemoptysis - 1pt

Wells Score

1. 0-1 point: Low probability (3.4%)
2. 2-6 points: Moderate probability (27.8%)
3. 7-12 points: High probability (78.4%)

Workup by Probability

Low Probability

• If low prob and PERC Rule neg then d/c
• If low prob and PERC Rule pos then d-dimer

Moderate Probability

• Obtain d-dimer

High Probability

• Consider anticoagulation before imaging!
• CTPA if GFR >60
• V/Q if GFR <60

• Also consider V/Q in young females in order to minimise radiation exposure to breast tissue
• Also consider V/Q vs CTPA in pregnant females depending on multiple considerations including the above + radiation burden to foetus

Treatment

Anticoagulation

• Indicated for all patients with confirmed PE or high clinical suspicion (don't wait for imaging)
• Treatment options:
  • LMWH SC
    • 1st line for most hemodynamically stable pts
    • contraindicated in renal failure
  • UFH
    • Consider in pts w/:
      • Persistent hypotension
      • Increased risk of bleeding
      • Recent sx/trauma
      • Renal failure (GFR <30)
      • Morbid obesity or anasarca (poor sc absorption)
      • Thrombolysis is being considered
    • 80 units/kg bolus; then 18 units/kg/hr
      • Check PTT after 6hr; adjust infusion to maintain PTT at 1.5-2.5x control

Thrombolysis

Indications

1. Pt w/ massive PE and acceptable risk of bleeding complications
2. Pt w/ submassive PE w/ e/o adverse prognosis + low risk of bleeding complications
   1. Hemodynamic instability
   2. Worsening resp insufficiency
   3. Severe RV dysfunction
   4. Major myocardial necrosis

Instructions

1. Review contraindications
2. Discontinue heparin during infusion
3. tPA 100mg over 2hr OR 0.6 mg/kg over 2min
4. After infusion complete measure PTT
   1. Once value is <2x upper limit restart anticoagulation

Absolute contraindications

1. Any prior intracranial hemorrhage,
2. Known structural intracranial cerebrovascular disease (e.g. AVM)
3. Known malignant intracranial neoplasm
4. Ischemic stroke within 3mo
5. Suspected aortic dissection
6. Active bleeding or bleeding diathesis
7. Recent surgery encroaching on the spinal canal or brain
8. Recent closed-head or facial trauma w/ radiographic evidence of bony fx or brain injury

Relative contraindications

1. Age >75 years
2. Current use of anticoagulation
3. Pregnancy
4. Noncompressible vascular punctures
5. Traumatic or prolonged CPR (>10min)
6. Recent internal bleeding (within 2 to 4 weeks)
7. History of chronic, severe, and poorly controlled hypertension
8. Severe uncontrolled HTN on presentation (sys BP >180 or dia BP >110)
9. Dementia
10. Remote (>3 months) ischemic stroke
11. Major surgery within 3 weeks

IVC Filter

• Indications
  • anticoagulation contraindicated in pt with PE
  • failure to attain adequate anticoagulation during treatment

PE in Pregnancy

• Heparin and Enoxaparin are safe (coumadin is not)
• Consider utz as initial test
• CT (with shield) vs. V/Q is roughly equilivalent radiation exposure
• D-Dimer MAY BE (no RCTs) used with following limits:
  • 1st trimester: <750 (+50% increase from normal lab threshold)
  • 2nd trimester: <1000 (+100% from normal)
  • 3rd trimester: <1250 (+150% from normal)

Algorithm

1. Clinical features suggestive of PE
   1. Bilateral LE Ultrasound
      1. Positive-->LMWH
      2. Negative-->CTA

External Links

• MDCalc - Well's Criteria for Pulmonary Embolism
• MDCalc - PERC Rule for Pulmonary Embolism

References

• Circulation. 2011 Apr 26;123(16):1788-830
• Tintinalli
• D-Dimer Concentrations in Normal Pregnancy: New Diagnostic Thresholds Are Needed. Kline et all. Clinical Chemistry May 2005 vol. 51 no. 5 825-829 http://www.clinchem.org/content/51/5/825.long