Aspiration Syndrome

Aspiration syndrome is inhalation of oropharyngeal or gastric contents into the lower airway. It produces one or more of:

• Chemical pneumonitis (Mendelson syndrome, from acid of pH less than 2.5 and volume more than about 25 mL in adults or 0.4 mL/kg).
• Bacterial aspiration pneumonia.
• Airway obstruction by food or other particles.
• Chronic microaspiration (bronchiolitis, bronchiectasis, interstitial fibrosis).

• Risk factors:
  • Reduced consciousness (alcohol, drugs, seizure, stroke, anaesthesia, head injury).
  • Dysphagia (stroke, dementia, Parkinson disease, motor neurone disease, head and neck cancer).
  • Vomiting, reflux, achalasia, nasogastric tubes and enteral feeding, tracheostomy, and poor dentition.
  • In infants, reflux and swallowing incoordination.
• Aspiration pneumonia accounts for about 5 to 15% of community acquired pneumonia and a larger share in care home residents; mortality is about 10 to 30%.
• Mechanism: acid causes immediate epithelial injury, then neutrophilic inflammation and oedema in the first 2 to 6 hours; bacterial infection (usually oral flora) follows in a minority of cases over 24 to 72 hours.

Witnessed vomiting or choking, then sudden breathlessness, cough, wheeze, fever, pink frothy sputum, tachypnoea, hypoxaemia within 2 to 5 hours (pneumonitis).

• Aspiration pneumonia: fever, productive cough, purulent or foul sputum, pleuritic pain developing over 2 to 5 days; lung abscess presents after 1 to 2 weeks with putrid sputum, weight loss and clubbing.
• Particulate aspiration: sudden choking, stridor, unilateral wheeze, or lobar collapse.
• Chronic microaspiration: recurrent cough with meals, recurrent chest infections, unexplained wheeze.
• Dependent segments are involved: posterior segments of the upper lobes and superior segments of the lower lobes in the supine patient, basal segments of the lower lobes when upright, and the right lung more often than the left.
• Differential diagnosis: community or hospital acquired bacterial pneumonia, pulmonary oedema, pulmonary embolism, acute respiratory distress syndrome, asthma, anaphylaxis, tuberculosis, lung cancer with obstruction.
• Complications: acute respiratory distress syndrome, respiratory failure, lung abscess, empyema, necrotising pneumonia, bronchiectasis, obliterative bronchiolitis, recurrent aspiration and death.

Clinical diagnosis: risk factor plus new infiltrate in a dependent segment.

• Chest X-ray, then CT chest for abscess, empyema, obstruction or failure to improve in 72 hours.
• Arterial blood gas, lactate, full blood count, CRP and procalcitonin, urea and creatinine, blood cultures, sputum or tracheal aspirate for culture (and bronchoalveolar lavage in ventilated patients).
• Bronchoscopy for particulate obstruction or when the cause of collapse is unclear.
• Swallow assessment: bedside screening by a trained nurse or speech and language therapist, then videofluoroscopy or fibreoptic endoscopic evaluation of swallowing; pH and impedance monitoring and upper endoscopy for suspected reflux.
• Exclude other diagnoses: ECG, troponin, natriuretic peptide, CT pulmonary angiography when embolism is plausible.

Immediate care: turn to the lateral position or sit up, suction the oropharynx, remove visible particles, give oxygen to SpO2 94 to 98% (88 to 92% if hypercapnic), and give intravenous fluids.

• Intubate for Glasgow Coma Scale 8 or less, failure to protect the airway, or refractory hypoxaemia; use lung protective ventilation (tidal volume 6 mL/kg predicted body weight, plateau pressure less than 30 cmH2O).
• Particulate aspiration: rigid or flexible bronchoscopy to remove material; bronchial lavage with saline is not useful for acid.
• Chemical pneumonitis alone:
  • Supportive care; corticosteroids are not helpful.
  • Do not give prophylactic antibiotics.
  • Give antibiotics if there is no improvement in 48 hours or fever persists, or if the aspiration happened in a patient with gastric colonisation such as on acid suppression or small bowel obstruction.
• Aspiration pneumonia, community onset:
  • Amoxicillin-clavulanate 1.2 g IV every 8 hours (625 mg orally three times daily when stable), or ampicillin-sulbactam 3 g IV every 6 hours.
  • Penicillin allergy: moxifloxacin 400 mg daily, or clindamycin 600 mg IV every 8 hours (300 to 450 mg orally four times daily) plus ceftriaxone 2 g daily if no severe allergy.
• Hospital onset or healthcare exposure:
  • 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 (levels guided) or linezolid 600 mg IV every 12 hours when methicillin-resistant Staphylococcus aureus is suspected.
• Duration:
  • 5 to 7 days for pneumonia if improving by day 3.
  • 3 to 6 weeks (until the cavity has largely resolved) for lung abscess, switching to oral amoxicillin-clavulanate 625 mg three times daily or clindamycin 300 to 450 mg four times daily.
  • Empyema needs a chest drain with intrapleural alteplase 10 mg and dornase alfa 5 mg twice daily for 3 days when loculated.
• Anaerobic cover (metronidazole 500 mg IV every 8 hours) is needed only for abscess, empyema or severe periodontal disease with a regimen that lacks it.
• Prevent recurrence:
  • Nurse upright at 30 to 45 degrees for feeds and for 1 hour afterwards; thickened fluids and texture modified diets guided by the swallow assessment; supervised feeding; speech therapy.
  • Nasogastric feeding (continuous, head up) for up to 4 weeks, and gastrostomy if swallowing is unsafe for longer; gastrostomy does not remove the risk of aspiration of saliva or reflux.
  • Tooth brushing twice daily and dental treatment; treat reflux with omeprazole 20 to 40 mg daily; metoclopramide 10 mg three times daily before meals for gastroparesis (maximum 5 days at a time).
  • Review sedatives, antipsychotics and opioids; treat the neurological cause.
• Special groups:
  • Children: thicken feeds, treat reflux with omeprazole 1 mg/kg daily, amoxicillin-clavulanate 25 to 30 mg/kg of the amoxicillin component three times daily.
  • Pregnancy and labour: fasting, sodium citrate 0.3 M 30 mL before caesarean section, omeprazole 40 mg the night before and morning of elective surgery, rapid sequence induction with cricoid pressure, avoid doxycycline and fluoroquinolones.
  • Elderly: swallow screening on admission after stroke, palliative discussion in advanced dementia since feeding tubes do not prevent aspiration.
  • Renal impairment: adjust piperacillin-tazobactam and vancomycin.
  • Anaesthesia: fasting 6 hours for solids, 2 hours for clear fluids, premedication for high risk.
• Red flags: respiratory failure, septic shock, lung abscess or empyema, no improvement at 72 hours, haemoptysis, recurrent episodes, upper airway obstruction.
• Follow-up: chest X-ray at 6 weeks to confirm resolution (CT if smoker or older than 50); swallow review and reflux treatment; nutrition assessment; repeat imaging for abscess every 2 to 4 weeks.