Aspiration Pneumonia

Bacterial lung infection that follows inhalation of oropharyngeal or gastric contents. It differs from aspiration pneumonitis, which is a chemical injury from acidic gastric fluid that develops within 2 to 5 hours and is not infectious at first.

• It accounts for about 5 to 15% of community acquired pneumonia and a higher share in nursing home residents and hospital patients. Mortality is about 20 to 30% in hospitalised patients.
• Risk factors: dysphagia after stroke, dementia, Parkinson disease, motor neurone disease, reduced consciousness (alcohol, sedatives, seizures, anaesthesia, head injury), gastro oesophageal reflux, vomiting, nasogastric feeding, poor dentition and periodontal disease, oesophageal disease, and bulbar weakness.
• Organisms: the usual respiratory pathogens now predominate (Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Gram negative enteric bacilli, including in hospital Pseudomonas). Anaerobes (Prevotella, Fusobacterium, Peptostreptococcus) matter mainly with poor dentition, lung abscess, necrotising pneumonia or empyema.
• Dependent segments are affected: posterior segments of the right upper lobe and the superior and basal segments of the right lower lobe (upright aspiration affects the basal segments; supine aspiration affects the posterior upper and superior lower segments).

• Witnessed aspiration or cough on swallowing, then fever, cough, purulent or foul sputum, dyspnoea, pleuritic pain, and confusion in older patients. Many have silent aspiration with no cough. Onset may be indolent, over days to weeks, in abscess formation.
• Signs: crackles and bronchial breathing in dependent zones, poor oral hygiene, drooling, wet voice, reduced gag, tachypnoea, hypoxaemia.
• Differential diagnosis: aspiration pneumonitis (rapid, hypoxic, often improves in 24 to 48 hours without antibiotics), community acquired pneumonia from other causes, lung abscess, tuberculosis, lung cancer with obstruction, pulmonary infarction, foreign body, and organising pneumonia.
• Complications: lung abscess, empyema, necrotising pneumonia, bronchopleural fistula, ARDS, sepsis, recurrent aspiration, and malnutrition.

• Chest X-ray or CT: consolidation in dependent segments, cavitation, air fluid levels, effusion.
• Blood cultures; sputum or tracheal aspirate culture (anaerobic culture adds little); bronchoscopy for foreign body or obstruction; pleural fluid for empyema.
• Full blood count, CRP, procalcitonin, urea and electrolytes, glucose, lactate, arterial blood gas, HIV test.
• Swallow assessment: bedside screening, then videofluoroscopy or fibreoptic endoscopic evaluation of swallowing to define the aspiration mechanism and guide diet. Assess dentition, reflux, and neurological disease, and review sedating drugs.

• Aspiration pneumonitis (chemical): oxygen, suction, positioning and supportive care. Do not give prophylactic antibiotics or corticosteroids. Start antibiotics only if there is no improvement in 48 hours, the aspirate was infected, or the patient has bowel obstruction or gastric colonisation (acid suppression, enteral feeding).
• Aspiration pneumonia, community onset:
  • Ampicillin sulbactam 3 g IV every 6 hours, or co-amoxiclav 1.2 g IV every 8 hours then 625 mg orally three times daily.
  • Ceftriaxone 2 g IV daily is adequate for most patients without abscess or empyema. Routine added anaerobic cover (metronidazole) is not needed; add metronidazole 500 mg IV or orally every 8 hours only for lung abscess, empyema or necrotising disease.
  • Penicillin allergy: moxifloxacin 400 mg daily, or clindamycin 600 mg IV every 8 hours then 300 to 450 mg orally every 6 to 8 hours.
• Hospital onset or severe, or with risk of resistant organisms:
  • Piperacillin tazobactam 4.5 g IV every 6 hours, or meropenem 1 g IV every 8 hours.
  • Add vancomycin 15 to 20 mg/kg IV every 8 to 12 hours (trough 15 to 20 mg/L) when methicillin resistant Staphylococcus aureus is likely.
• Duration: 5 to 7 days when stable by day 3; 3 to 6 weeks (until the cavity or infiltrate has largely resolved) for lung abscess, usually switched to oral co-amoxiclav 625 mg three times daily or clindamycin 300 to 450 mg four times daily after clinical response; empyema needs drainage and 2 to 6 weeks.
• Supportive care: oxygen to SpO2 94 to 98%, non-invasive or invasive ventilation as needed, IV fluids, enoxaparin 40 mg SC daily, chest physiotherapy, nutrition.
• Procedures: chest drain for empyema (intrapleural alteplase 10 mg plus dornase alfa 5 mg twice daily for 3 days if loculated); bronchoscopy to remove foreign body or particulate matter; percutaneous drainage or surgery for abscess not responding to 4 to 6 weeks of therapy, haemoptysis or large size.
• Prevention of recurrence:
  • Swallowing therapy and texture modification (thickened fluids, soft diet) by a speech and language therapist; upright feeding position at 90 degrees and for 30 minutes after meals; assisted feeding.
  • Oral hygiene: toothbrushing twice daily and dental treatment.
  • Stop or reduce sedatives, anticholinergics and antipsychotics where possible; treat reflux (omeprazole 20 mg daily only when indicated, since acid suppression raises pneumonia risk).
  • Nasogastric or gastrostomy feeding does not remove aspiration risk; keep the head up and give small, slow feeds.
  • ACE inhibitors may improve cough reflex; evidence is limited.
• Special groups:
  • Stroke and dementia: early swallow screening, goals of care and advance care planning.
  • Pregnancy: ampicillin sulbactam or co-amoxiclav; avoid fluoroquinolones; prevent aspiration at anaesthesia (fasting, antacid prophylaxis).
  • Children: neurological impairment and gastro oesophageal reflux; amoxicillin clavulanate 25 to 45 mg/kg/day of amoxicillin in 2 divided doses; feeding assessment.
  • Renal impairment: adjust doses.
• Red flags: foul sputum with cavitation, persistent fever after 72 hours, haemoptysis, empyema, hypoxaemia, shock.
• Follow up: chest X-ray at 6 weeks (CT if there is a persistent opacity to exclude cancer); speech therapy review; nutrition and dental review.