Can atelectasis cause fever?

Atelectasis and Fever: The Evidence-Based Connection

Atelectasis is often considered to be a cause of postoperative fever, but the clinical evidence supporting this association is lacking. 1

Understanding Atelectasis

Atelectasis refers to a state of collapsed and non-aerated regions of otherwise normal lung parenchyma. It commonly occurs in three ways:

• Airway obstruction
• Compression of lung parenchyma by extra/intrathoracic processes
• Increased surface tension in alveoli and bronchioli 2

Atelectasis is one of the most common abnormalities seen in chest radiology and can present as:

• Segmental, lobar, or whole lung collapse
• Subsegmental collapse
• Platelike, linear, or discoid patterns
• Round atelectasis
• Generalized or diffuse collapse 3

The Relationship Between Atelectasis and Fever

Evidence Against the Association

• A systematic review of eight studies including 998 cardiac, abdominal, and maxillofacial surgery patients found that only one study reported a significant association between postoperative atelectasis and fever, while the remaining studies showed no association 1
• The diagnostic odds ratio for early postoperative fever as a predictor of atelectasis was poor (pooled diagnostic OR, 1.40; 95% CI, 0.92-2.12) 1
• Current guidelines from the Society of Critical Care Medicine and Infectious Diseases Society of America (2023) list atelectasis as a noninfectious cause of fever in ICU patients but do not establish a causal relationship 4

Clinical Context

• Atelectasis is common during general anesthesia, occurring in approximately 90% of all subjects, regardless of whether they are breathing spontaneously or are muscle-paralyzed 5
• In the postoperative setting, fever in the initial 48 hours after surgery is usually non-infectious in origin 4
• Guidelines state that "atelectasis is often considered to be a cause of postoperative fever, although this should be a diagnosis of exclusion" 4

Diagnostic Approach to Fever When Atelectasis is Suspected

When evaluating fever in a patient with suspected atelectasis:

1. Recognize timing patterns:

   • Early postoperative fever (within 48 hours) is usually non-infectious 4
   • Fever beyond 96 hours postoperatively is more likely to represent infection 4

2. Perform appropriate imaging:

   • Chest radiographs in both anterior-posterior and lateral projections are necessary to document atelectasis 2
   • A chest radiograph is not mandatory for evaluation of early postoperative fever unless respiratory symptoms are present 4
   • CT scanning provides better sensitivity than plain radiography for detecting atelectasis 4

3. Consider other causes of fever:

   • Infectious causes should be ruled out, especially pneumonia, urinary tract infections, and wound infections 4
   • Other noninfectious causes of fever should be considered (see comprehensive list in guidelines) 4

Management Implications

If atelectasis is present:

• Treatment varies depending on duration and severity of the underlying condition 2
• Interventions may include:
  • Chest physiotherapy
  • Postural drainage
  • Bronchodilator therapy
  • Anti-inflammatory therapy
  • Bronchoscopy for persistent mucous plugs 2
• Prevention strategies during anesthesia:
  • Use of positive end-expiratory pressure (PEEP)
  • Lung recruitment maneuvers
  • Using appropriate oxygen concentrations during ventilation 5

Clinical Pitfalls and Caveats

1. Diagnostic challenges:

   • Atelectasis can be overlooked when pulmonary opacification is minimal or absent 3
   • It may be misinterpreted as pneumonia 3
   • The diagnosis of atelectatic pneumonia should be based on clinical signs and symptoms of pneumonia coupled with identification of pathogenic bacteria, not just radiographic findings 3

2. Association with infection:

   • Atelectasis is associated with infection in patients with neuromuscular respiratory failure 6
   • Infection often occurs soon after intubation in ventilated patients 6

3. Evaluation priorities:

   • When fever occurs in a patient with atelectasis, clinicians should still search for other causes, particularly infectious etiologies 4
   • The clinician must be alert to the possibility of aspiration during the perioperative period or pre-existing infections 4

In conclusion, while atelectasis is commonly cited as a cause of fever, particularly in the postoperative setting, the clinical evidence supporting this association is weak. Atelectasis should be considered a diagnosis of exclusion when evaluating fever, and clinicians should maintain a high index of suspicion for infectious causes.