Author:
Alan M.Kumar
Christine A.Babcock
Description
- The majority of pulmonary embolisms (PEs) arise from thrombi in the deep veins of the lower extremities and pelvis
- Thrombi also originate in renal and upper-extremity veins
- After traveling to lungs, the size of the thrombus determines signs and symptoms
Etiology
- Most patients with PE have identifiable risk factor:
- Recent surgery
- Pregnancy
- Previous deep vein thrombosis (DVT)/PE
- Stroke or recent paraplegia
- Malignancy
- Age >50 yr
- Obesity
- Smoking
- Oral contraceptives
- Major trauma
- Hematologic risk factors:
- Factor V Leiden
- Protein C or S deficiency
- Antithrombin III deficiency
- Antiphospholipid antibody syndrome
- Lupus anticoagulant
Pediatric Considerations |
- Thromboembolic disease is quite rare
- Risk factors in children:
- Presence of central venous catheter
- Immobility
- Heart disease
- Trauma
- Malignancy
- Surgery
- Infection
|
Signs and Symptoms
- Variability in signs and symptoms make diagnosis difficult
- Most common:
- Dyspnea
- Pleuritic chest pain
- Tachypnea
- General:
- Fevers (rarely >102°F)
- Diaphoresis
- Pulmonary:
- Cough
- Hemoptysis (rarely massive)
- Rales
- Cardiovascular:
- Extremities:
- Cyanosis
- Evidence of thrombophlebitis
- Lower-extremity edema
- Abdominal pain
- Symptoms similar in elderly but typically more subtle if age <40 yr
Essential Workup
- Routine labs are nonspecific
- CXR:
- Used to rule out other causes
- Most common findings with PE:
- Normal
- Nonspecific parenchymal abnormality
- Atelectasis
- Other findings with PE:
- Pleural effusions
- Pleural-based opacities (Hampton hump)
- Elevated hemidiaphragm
- Local oligemia (Westermark sign)
- ECG:
- To rule out cardiac etiology
- Usually normal in PE
- Other findings include:
- Nonspecific ST-T-wave changes (most common abnormality)
- Sinus tachycardia
- Left axis deviation
- Right bundle branch block pattern
- S1Q3T3 pattern is uncommon and not specific enough to rule in/out diagnosis
- Modified Wells criteria:
- Popular decision rule that can assist with risk stratification in combination with d-dimer
- Each criterion is given numeric value and if total value <4, along with negative d-dimer, risk of PE is <2%:
- Clinical signs/symptoms of DVT: 3 pts
- PE is no. 1 diagnosis: 3 pts
- Heart rate >100 bpm: 1.5 pts
- Surgery or immobilization for 3 d within last 4 wk: 1.5 pts
- Previous PE or DVT: 1.5 pts
- Hemoptysis: 1 pt
- Malignancy with treatment within last 6 mo: 1 pt
- Pulmonary embolism rule-out criteria (PERC):
- Useful in low-prevalence setting (ED) in combination with low clinical suspicion:
- Age <50 yr
- Heart rate <100 bpm
- O2 saturation ≥95%
- No hemoptysis
- No estrogen use
- No prior DVT or PE
- No unilateral leg swelling
- No surgery or trauma requiring hospitalization within the past 4 wk
- <1% risk for PE/DVT in 45 d if PERC score 0
Diagnostic Tests & Interpretation
Lab
- Arterial blood gas:
- Can show hypoxemia, hypocapnia, respiratory alkalosis, or increased alveolar-arterial (A-a) gradient
- PE still possible with normal A-a gradient
- Does not aid in diagnosis of PE
- CBC:
- Anemia may be contributing factor to dyspnea
- d-dimer enzyme-linked immunosorbent assay:
- d-dimers are detectable at levels >500 ng/mL in nearly all patients with PE
- High sensitivity (close to 100%) with low specificity for PE
- Almost always elevated in patients with malignancy or surgery within the last 3 mo
- Multiple studies confirm that negative enzyme-linked immunosorbent assay d-dimer in combination with low clinical suspicion effectively rules out PE
- Patients >50 yr with low pretest probability may be evaluated with age adjusted d-dimer (age adjusted d-dimer cutoff = (age × 10) mcg/L
Imaging
- Spiral chest CT with IV contrast:
- Has ability to also detect alternative pulmonary abnormalities
- Accurate for identifying PE in proximal pulmonary tree:
- In patients with high pretest probability, positive predictive value of 96%
- In patients with low pretest probability, negative predictive value of 96%
- Ventilation-perfusion scan (V/Q):
- Results reported in probabilities and correlated to clinical suspicion
- Probability of PE with V/Q results:
- Normal or near-normal V/Q scan: 4% probability for PE
- Low-probability V/Q scan with low clinical suspicion: 4% probability for PE
- Low-probability V/Q scan with high clinical suspicion: 16-40% probability for PE
- Intermediate V/Q scan: 16-66% probability for PE
- High-probability V/Q scan with low clinical suspicion: 56% probability for PE
- High-probability V/Q scan with high clinical suspicion: 96% probability for PE
- Lower-extremity duplex US:
- Used in patients who would otherwise require pulmonary angiogram
- Presence of DVT requires same anticoagulation as PE
- Negative lower-extremity duplex does not rule out PE
- Echocardiogram:
- Used to assess for right heart strain or patent foramen ovale when thrombolysis is a possibility
Diagnostic Procedures/Surgery
Pulmonary angiogram:
- Gold stand ard for diagnosis
- Used when diagnosis not confirmed or excluded
- Higher complication rate than other modalities
Differential Diagnosis
- Anxiety disorder
- Aortic dissection
- Asthma
- Cardiac dysrhythmias
- Costochondritis
- Myocardial infarction
- Pericarditis
- Pneumonia
- Pneumothorax
- Rib fracture
Prehospital
- Initial supplemental oxygen
- Establish IV access
- Cardiac monitor
Initial Stabilization/Therapy
- Airway, breathing, and circulation
- Provide supplemental oxygen to maintain adequate oxygen saturation
- Intubate if unable to provide adequate oxygenation
- Administer IV fluids carefully for hypotensive patients:
- IV vasopressor therapy is indicated if hypotension does not resolve with IV fluids
ED Treatment/Procedures
- Anticoagulation:
- Prevents additional thrombus from forming
- Stabilizes existent clot to prevent migration
- Risk of minor/major bleeding with therapy
- Unfractionated heparin:
- Dose titration fraught with difficulty leading to inadequate therapy
- Goal to maintain partial thromboplastin time test between 1.5 and 2.5 times the control value (60-80 s)
- Low-molecular-weight heparin:
- At least as effective as unfractionated heparin in multiple prospective rand omized trials
- Therapeutic goal automatic with weight-based dosing
- Easier administration and monitoring than heparin with some cost benefit
- Warfarin:
- Oral therapy for long-term anticoagulation
- Goal is international normalized ratio (INR) of 2-3
- Direct oral anticoagulants (DOAC):
- Oral factor 10a inhibitor
- Rivaroxaban, apixaban
- Recently approved for treatment of PE
- Does not require lab monitoring
- Not recommended in renal/hepatic insufficiency or pregnancy
- No specific antidote but has short half-life in case of bleeding
- Considered first-line therapy for uncomplicated VTE
- Thrombolysis:
- Initiate in hemodynamically unstable patients with confirmed PE
- Consider in stable patients with PE and severe hypoxemia, massive PE, or right ventricular dysfunction
- In intermediate risk patients death and hemodynamic decompensation are reduced but there is an increase in the risk of major hemorrhage and stroke
- Inferior vena cava filter:
- Indicated in patients who have contraindications to anticoagulation or have been therapeutic on anticoagulation but failed prevention of PE
- Surgical or catheter embolectomy:
- Consider in those with thrombolysis contraindications or failure, or deemed unstable for medical management
- Case-by-case basis
Medication
- Alteplase: 100 mg (peds: N/A) IV over 2 hr
- Enoxaparin: 1 mg/kg (peds: 0.75 mg/kg) SC q12h
- Reteplase: 10 units (peds: N/A) IV bolus q30min × 2
- Streptokinase: 250,000 units (peds: 3,500-4,000 U/kg) IV bolus over 30 min, then 100,000 units (peds: 1,000-1,500 U/kg) IV maintenance over 24 hr
- Unfractionated heparin:
- Bolus: 80 U/kg (peds: 75 U/kg) IV over 10 min
- Maintenance: 18 U/kg (peds: 20 U/kg) IV drip
- Do not use TBW to calculate dose in obese patients
- Warfarin: 5 mg (peds: 0.05-0.34 mg/kg/d) PO per day, adjust for INR goal 2-3
- Rivaroxaban: 15 mg b.i.d × 3 wk then 20 mg per day
- Apixaban: 10 mg b.i.d × 7 d then 5 mg b.i.d
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