Can pulmonary embolism (PE) under anesthesia be transient and self-resolving?

Transient Self-Resolving Pulmonary Embolism Under Anesthesia

Yes, pulmonary embolism (PE) can be transient and self-resolving during anesthesia, particularly when associated with major transient risk factors such as surgery with general anesthesia. This phenomenon is recognized but requires careful monitoring and management.

Clinical Presentation of Intraoperative PE

Intraoperative PE presents with distinctive features due to the patient being under anesthesia:

• Key diagnostic clue: Sudden decrease in end-tidal CO₂ (PETCO₂) with simultaneous increase in arterial CO₂ (PaCO₂) 1
• Unexplained hypoxemia (SaO₂ <90%) despite supplemental oxygen
• Hemodynamic changes:
  • Sudden hypotension
  • Tachycardia
  • Increased central venous pressure
• Increased pulmonary vascular resistance
• Right ventricular dysfunction visible on transesophageal echocardiography (TEE)

Pathophysiology of Transient PE

Transient, self-resolving PEs can occur due to several mechanisms:

1. Small clot burden that undergoes endogenous fibrinolysis
2. Positional or mechanical factors during surgery that temporarily obstruct pulmonary blood flow
3. Surgical manipulation causing release of small emboli that rapidly dissolve
4. Air emboli that can resolve more quickly than thrombotic emboli

Risk Stratification

The ESC guidelines categorize PE risk factors based on recurrence risk 2:

Risk Level	Associated Factors
Low (<3% per year)	Major transient factors (surgery with general anesthesia >30 min, hospitalization ≥3 days)
Intermediate (3-8% per year)	Minor transient factors (pregnancy, reduced mobility)
High (>8% per year)	No identifiable risk factor, active cancer, previous VTE

Management Approach for Suspected Intraoperative PE

1. Immediate assessment:

   • Monitor PETCO₂ and PaCO₂ for the separation phenomenon
   • Provide supplemental oxygen for SaO₂ <90%
   • Consider TEE for diagnosis if available

2. Hemodynamic support:

   • Cautious fluid management (≤500 mL) if central venous pressure is low 2
   • Avoid aggressive volume expansion which may worsen RV function
   • Consider vasopressors if hypotension persists

3. Ventilation strategy:

   • Prefer non-invasive ventilation or high-flow nasal cannula when possible
   • If mechanical ventilation is necessary:
     • Use tidal volumes of ~6 mL/kg lean body weight
     • Keep plateau pressure <30 cm H₂O
     • Apply PEEP cautiously to avoid worsening RV failure 2

4. Decision on anticoagulation:

   • For confirmed PE: Start anticoagulation unless contraindicated
   • For suspected transient PE that appears to resolve: Multidisciplinary consultation to weigh risks/benefits

Monitoring for Resolution

For suspected transient PE:

• Continuous monitoring of PETCO₂
• Serial arterial blood gases
• Hemodynamic parameters
• Consider repeat imaging post-operatively

Important Caveats

1. Do not assume all intraoperative PEs will self-resolve - even transient PEs can be harbingers of more serious events

2. Beware of false reassurance - apparent resolution may be temporary, and the patient remains at risk for recurrent PE

3. Consider post-operative prophylaxis - patients with intraoperative PE are at higher risk for recurrent events

4. Document the event thoroughly - this affects future risk stratification and anticoagulation decisions

Follow-up Considerations

• Risk assessment for recurrent VTE using validated tools
• Consider extended thromboprophylaxis for high-risk patients
• Evaluate for underlying thrombophilia if no clear precipitating factor
• Regular follow-up at 3-6 months to assess for chronic complications 3

While transient self-resolving PEs can occur during anesthesia, they should always prompt thorough evaluation and consideration of appropriate prophylactic measures to prevent more serious thromboembolic events.