Aspiration Under Anaesthesia

Aspiration - inhalation of oropharyngeal or gastric contents into the lower airways

• May lead to aspiration pneumonitis or aspiration pneumonia
• The leading cause of airway-related anaesthetic deaths (NAP4)



Aspiration pneumonitis - acute, chemically-induced inflammation of the lung parenchyma caused by the acid in aspirated gastric contents

• Extent of damage depends on both volume and acidity of the inhaled material
• Severe damage is termed Mendelson's syndrome; a disease on the ARDS spectrum
• Does not necessarily lead to aspiration pneumonia therefore antibiotic prophylaxis is not routinely recommended



Aspiration pneumonia - a pneumonia caused by superimposed infection following aspiration

• Most commonly seen in patients who suffer long-term 'silent' aspiration e.g. those with neurological disorders
• May occur following acute aspiration if:
• Aspirate colonised with upper airway flora
• Patient has bowel obstruction & gastric contents are colonised by gut bacteria

• Incidence is variably quoted, with ranges from 1 in 600 anaesthetics (emergency cases) up to 1 in 10,000 anaesthetics
• A narrower incidence of 1 in 3,000 - 6,000 anaesthetics may be closer to the mark
• Incidence of fatal aspiration was 1 in 350,000


• Commonly quoted as requiring 25ml of aspirate of pH <2.5 to cause an aspiration pneumonitis
• This is derived from unpublished work in Rhesus monkeys and extrapolated to humans
• In general, aspiration of higher volumes or more acidic fluid is associated with increased morbidity and mortality


• Responsible for >50% of airway-related deaths in anaesthesia
• Implicated in 23% of all NAP4 cases as either a primary or secondary event
• Increased risk if higher ASA grade or emergency surgery (1 in 600)


• Overall mortality from aspiration <5%
• A systematic review (BJA, 2017) of aspiration during procedural sedation found mortality was:
• ~2.7% for patients undergoing endoscopic procedures
• ~2.9% for patients undergoing non-endoscopic procedures

• Other anatomical abnormalities such as pharyngeal pouches or oesophageal strictures may also increase risk

• Emergency surgery
• Gastrointestinal surgery
• Positioning head down or lithotomy
• Laparoscopy, cholecystectomy

• Light plane of anaesthesia
• Use of SAD, especially first generation
• PPV
• Duration of surgery >2hrs
• Difficult airway
• General anaesthesia (vs. sedation; aspiration risk with procedural sedation approximately 30 - 50% of that of GA)
• Use of propofol (vs. ketamine, with the latter preserving airway reflexes & associated with lower aspiration risk especially during sedation)

• Identification of at risk patients as above
• Risk-reducing pharmacotherapy:
• Antacids (ranitidine, sodium citrate, PPI)
• Prokinetics (metoclopramide)
• Consider placing NG tube and aspirating of gastric contents prior to surgery
• Adherence to perioperative fasting guidelines:

• NB Clear fluid means one can read the label writing through the liquid itself

• Use of RSI ± cricoid pressure (contentious, as ever)
• If SAD, use second-generation device
• Head-up positioning if possible

• Aspirate NG (if present) prior to extubation
• Thorough suctioning of pharynx prior to extubation
• Extubate fully awake after return of airway reflexes
• Consider extubating in a non-supine position e.g. sat upright, laid head-down, laterally

Unexpected aspiration represents an emergency and I would call for help, whilst making a rapid but thorough assessment of the patient

• Ask the surgeon to stop
• Suction the airway
• Administer 100% oxygen
• If possible place in the left lateral position with head down
• Maintain the airway and if necessary intubate the patient
• Suction down ETT prior to application of PPV
• Consider bronchoscopy/BAL

• CXR
• No radiographic evidence in 25% of patients with known aspiration
• Aim sats 94 - 98%
• Transfer to an appropriate care area post-operatively - this may be HDU/ICU if requires CPAP or IPPV
• Bronchodilators
• Chest physiotherapy
• There is no evidence administering steroids either reduces mortality or improves outcome


• Empirical antibiotic therapy is discouraged
• Inappropriate administration is linked to VAP with more virulent organisms e.g. Pseudomonas, Acinetobacter
• 20 - 30% will develop a pneumonia requiring antibiotics
• Bacterial infection is most commonly with Gram-negative bacilli
• Consider antibiotics if:
• Aspiration pneumonitis not resolving within 48hrs
• Bowel obstruction
• Patient takes regular PPI (increases chance of bacterial colonisation of the stomach due to reduced pH)
• Prescribe antibiotics as per local trust guidelines and advice from microbiology team

• Document in patient's notes
• Fulfil duty of candour
• Complete critical incident form