Can pulmonary embolisms cause fever?

Pulmonary Embolism and Fever

Yes, pulmonary embolisms can cause fever, with approximately 14-25% of patients with acute PE experiencing fever without any other identifiable cause. 1, 2

Relationship Between PE and Fever

Prevalence and Characteristics

• Fever occurs in approximately 14% of patients with angiographically proven PE who have no other source of fever 1
• A more recent study found fever in 25.7% of patients within one week of PE diagnosis 2
• Fever patterns in PE:
  • Low-grade fever is more common but high-grade fever (>39°C) can occur 1, 3
  • Fever may occur early in the course of PE 3
  • Fever may persist for up to a week 3

Clinical Significance of Fever in PE

• Patients with PE and fever tend to have:
  • Higher clot burden (more likely to have massive or submassive PE) 2
  • Higher incidence of concurrent deep vein thrombosis (33.3% vs 17.4%) 2
  • Greater likelihood of requiring intensive care admission (69.5% vs 35.7%) 2
  • Longer hospital stays (19.8 days vs 12.2 days) 2
  • Higher requirement for mechanical ventilation (30.5% vs 6.6%) 2
  • Potentially higher in-hospital mortality (22.0% vs 10.4%) 2

Pathophysiological Mechanisms

While the exact mechanism of fever in PE is not fully described in the guidelines, several potential mechanisms may contribute:

• Inflammatory response to the thrombus
• Areas of pulmonary infarction and alveolar hemorrhage (although research shows fever occurs with similar frequency regardless of whether pulmonary infarction is present) 1
• Secondary inflammatory response that can develop 24-48 hours after acute PE 4

Clinical Implications

Diagnostic Considerations

• Fever should not deter clinicians from considering PE in the appropriate clinical setting 3, 5
• PE should be included in the differential diagnosis for patients with unexplained fever, especially those with risk factors such as bed confinement 5
• Fever persisting beyond 6 days, especially with temperatures over 38.5°C, should prompt investigation for causes other than PE 3

Case Examples

• There are documented cases of saddle pulmonary embolism presenting with high-grade fevers that resolved after anticoagulation therapy 6
• Fever may be the predominant symptom in some cases, potentially leading to diagnostic confusion with infectious processes

Pitfalls and Caveats

• Assuming fever automatically indicates infection may lead to missed or delayed PE diagnosis
• Broad-spectrum antibiotics alone will not resolve fever due to PE 6
• Fever in PE may resolve with appropriate anticoagulation therapy 6
• Always consider PE in patients with risk factors who present with unexplained fever, especially when:
  • Fever persists despite appropriate antibiotic therapy
  • No clear source of infection is identified
  • Patient has risk factors for venous thromboembolism

Understanding that PE can cause fever is important for avoiding diagnostic delays and ensuring appropriate treatment is initiated promptly, which can significantly impact patient outcomes given the higher morbidity associated with PE presenting with fever.