What is plastic flu?

What is Plastic Bronchitis?

Plastic bronchitis is a rare but life-threatening complication of influenza characterized by the formation of bronchial casts that can cause severe respiratory distress and lung atelectasis. 1

Clinical Presentation

Plastic bronchitis typically presents with:

• Acute respiratory distress
• Lung atelectasis (collapse of lung tissue)
• Symptoms of underlying influenza infection including:
  • Fever (>38.5°C)
  • Cough (often productive)
  • Respiratory distress
  • Hypoxemia (oxygen saturation <90%)

Pathophysiology

Plastic bronchitis involves the formation of cohesive, branching casts within the bronchial tree that can partially or completely obstruct airways. While the exact mechanism in influenza-associated cases is not fully elucidated, it appears to involve:

• Inflammatory response to influenza virus infection
• Exudative material accumulation in the airways
• Formation of fibrinous casts that take the shape of the bronchial tree

Diagnosis

Diagnosis should be made through:

• Bronchial endoscopy (bronchoscopy) - the gold standard diagnostic approach 1
• Histopathological examination of the removed bronchial casts
• Chest imaging (X-ray or CT scan) showing areas of atelectasis or airway obstruction
• Laboratory confirmation of influenza infection

Management

Management of plastic bronchitis requires prompt intervention:

• Immediate removal of bronchial casts through bronchoscopy 1
• Antiviral therapy with oseltamivir (drug of choice) if within the treatment window 2, 3
• Antibiotic coverage for potential secondary bacterial infections:
  • For children under 12 years: co-amoxiclav is the drug of choice 2
  • For penicillin-allergic patients: clarithromycin or cefuroxime 2
  • For children over 12 years: doxycycline is an alternative 2
• Supportive care including:
  • Oxygen therapy to maintain saturation >92% 2
  • Hydration to help thin secretions
  • Respiratory support as needed

Monitoring and Hospital Discharge Criteria

Patients can be safely discharged when they 2:

• Are clearly improving
• Are physiologically stable
• Can tolerate oral feeds
• Have a respiratory rate <40/min (<50/min in infants)
• Have an awake oxygen saturation of >92% in air

Prognosis and Complications

Plastic bronchitis associated with influenza is a serious condition with potential for:

• Respiratory failure requiring mechanical ventilation
• Prolonged hospitalization
• Mortality if not diagnosed and treated promptly

Prevention

Prevention strategies include:

• Annual influenza vaccination
• Early antiviral therapy for high-risk patients with influenza
• Prompt medical attention for influenza patients developing respiratory distress

Clinical Pearls

• Consider plastic bronchitis in any child with influenza who develops acute respiratory distress or atelectasis 1
• Early bronchoscopy is both diagnostic and therapeutic
• Delayed diagnosis and treatment significantly increase morbidity and mortality
• This is distinct from the colloquial term "plastic flu" which is not a recognized medical condition