[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anaesthesia and ICU](https://durgical.com/en/anaesthesia/) › [Intraoperative crises](https://durgical.com/en/anaesthesia/areas/crises/) › Pulmonary aspiration

# Pulmonary aspiration

- Crisis

Stomach contents can flow back up and into the lungs while a patient is anaesthetised; acid and food then injure the airways and lungs.

Updated Nov 13, 2026

## Key points

- Highest risk: full stomach, emergency surgery, bowel obstruction, pregnancy, delayed gastric emptying, obesity and light anaesthesia.
- First moves: head-down tilt and turn to the side if not intubated, suction the pharynx, then secure the airway with a cuffed tube.
- Suction the trachea through the tube before positive-pressure ventilation where possible, so material is not pushed deeper.
- Steroids and routine prophylactic antibiotics are not recommended; antibiotics are for pneumonia that develops or for heavily contaminated (bowel) contents.
- A patient who has no new cough, wheeze, oxygen need or radiograph change after about two hours is unlikely to develop pneumonitis.

On this page

- The basics Key points
- What it is
- How to recognise it
- Why it happens
- What to do at once
- Costly mistakes
- Next step
- Memory aid
- Elsewhere in DurgiPedia

- Study Test yourself

- Connections Connections

## What it is

Pulmonary aspiration is the passage of gastric contents (acid, bile, food particles) past the vocal cords into the lungs. Anaesthesia removes the protective reflexes of coughing and swallowing and relaxes the lower oesophageal sphincter, so regurgitated material can run into the airway, most often at induction, during airway manipulation and at emergence. The lung injury has three overlapping forms: chemical pneumonitis from acid (classically called Mendelson syndrome), mechanical obstruction of airways by solid particles, and, later, bacterial aspiration pneumonia. Risk is highest with a full stomach (emergency surgery, recent food, bowel obstruction, pregnancy, delayed gastric emptying from diabetes, opioids or newer weight-loss drugs), with gastro-oesophageal reflux, obesity, a difficult airway, light anaesthesia and head-down positions. Prevention rests on fasting, aspiration prophylaxis and rapid-sequence induction; when it happens, the response is to stop more material entering the lungs, clear what is there, secure the airway and support oxygenation. Many patients who aspirate stay well; those who develop symptoms within a few hours can progress to severe hypoxaemia and acute respiratory distress syndrome.

## How to recognise it

- Gastric fluid or food seen in the mouth, pharynx, around a supraglottic airway or inside the tracheal tube.
- Falling oxygen saturation that does not respond as expected to more oxygen.
- Wheeze, bronchospasm, coughing or laryngospasm, and a rise in airway pressure under ventilation.
- Crackles on auscultation and, later, infiltrates on the chest radiograph in the dependent lung segments.
- Tachypnoea, tachycardia and fever in the hours after the event if the patient was awake or extubated.

## Why it happens

- Anaesthetic drugs abolish the cough and swallow reflexes that normally protect the larynx.
- Lower oesophageal sphincter tone falls, while a full stomach, raised intra-abdominal pressure or a head-down position raises the pressure pushing contents up.
- Acid burns the airway lining and alveoli, causing leaky capillaries, oedema and loss of surfactant: a chemical pneumonitis.
- Solid particles block small airways and cause collapse beyond them; bacteria carried in later cause pneumonia.
- The right lower lobe is often affected because the right main bronchus is wider and more vertical; supine patients soil the posterior segments.

## What to do at once

- Call for help and tell the surgeon — aspiration is a team problem and surgery may need to pause.
- If not intubated, tilt head-down and turn the patient to the side — gravity drains material out of the mouth instead of into the trachea.
- Suction the mouth and pharynx with a wide-bore sucker — clearing the upper airway limits further soiling.
- Release cricoid pressure if there is active vomiting — pressure against a forceful vomit risks oesophageal injury.
- Give the highest oxygen concentration available — hypoxaemia follows quickly from airway soiling and bronchospasm.
- Secure the airway with a cuffed tracheal tube, usually by rapid sequence — the cuff seals the trachea against further aspiration.
- Suction down the tube before ventilating where possible — this removes fluid before positive pressure drives it to the periphery.
- Treat bronchospasm with inhaled bronchodilators and add positive end-expiratory pressure as needed — this reopens airways and collapsed alveoli.
- Consider bronchoscopy if solid material was aspirated or lobar collapse appears — particles must be removed physically.
- Pass an orogastric tube to empty the stomach — this lowers the risk of a second episode.

## Costly mistakes

- Lavaging the lungs with saline: it spreads the acid and worsens oxygenation.
- Giving corticosteroids or prophylactic antibiotics by reflex; neither prevents the pneumonitis.
- Ventilating hard by mask before suctioning, which blows the aspirate deeper into the lungs.
- Extubating or sending the patient home too early after a witnessed aspiration, before the observation period has shown they are well.
- Forgetting the cause: an unrecognised full stomach, bowel obstruction or delayed gastric emptying will recur at the next anaesthetic.

## Next step

- Observe for at least about two hours with saturation, respiratory rate and a chest examination; a patient who stays well can follow the usual pathway.
- Obtain a chest radiograph and an arterial blood gas if there are symptoms, an oxygen need or a fall in saturation.
- Call a senior and arrange high-dependency or intensive care for persistent hypoxaemia; ventilate with a lung-protective strategy if acute respiratory distress develops.
- Start antibiotics only for signs of pneumonia that appear later, or at once if the aspirate came from an obstructed bowel.
- Decide with the surgeon whether to continue the operation, then tell the patient, document the event and plan aspiration precautions for future anaesthetics.

## Memory aid

Tip, Turn, Suck, Tube: tip the head down, turn to the side, suction the pharynx, then protect the trachea with a cuffed tube.

## Test yourself

Think of the answer, then tap the question to see it.

## Which patients are at highest risk of pulmonary aspiration under anaesthesia?

Those with a full stomach (emergency surgery, recent food, bowel obstruction), pregnancy, delayed gastric emptying, reflux, obesity, a difficult airway or light anaesthesia.

## Why should the trachea be suctioned before positive-pressure ventilation after aspiration, where possible?

Ventilating first pushes the aspirated fluid and particles further into the small airways and alveoli, spreading the injury.

## Are corticosteroids or prophylactic antibiotics recommended after aspiration of gastric contents?

No. Neither prevents chemical pneumonitis; antibiotics are kept for pneumonia that develops or for aspirate from an obstructed, contaminated bowel.

## Which lung segment is most often affected by aspiration, and why?

The right lower lobe, because the right main bronchus is wider and more vertical; in supine patients the posterior segments are soiled most.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anaesthesia/pulmonary-aspiration/)

## Elsewhere in DurgiPedia

- [The causes of hypoxemia](https://durgical.com/en/physiology/the-causes-of-hypoxemia/)
- [Ventilation–perfusion matching and West zones](https://durgical.com/en/physiology/ventilation-perfusion-matching-and-west-zones/)
- [Airway suctioning: oral, nasal and artificial airways](https://durgical.com/en/nursing/airway-suctioning-oral-nasal-and-artificial-airways/)
- [Dysphagia and aspiration precautions](https://durgical.com/en/nursing/dysphagia-and-aspiration-precautions/)

## Connections

## Related 6

- [Premedication and aspiration prophylaxis](https://durgical.com/en/anaesthesia/premedication-and-aspiration-prophylaxis/)
- [Preoperative fasting: what and why](https://durgical.com/en/anaesthesia/preoperative-fasting-what-and-why/)
- [Rapid-sequence induction and intubation](https://durgical.com/en/anaesthesia/rapid-sequence-induction-and-intubation/)
- [Bronchospasm and laryngospasm](https://durgical.com/en/anaesthesia/bronchospasm-and-laryngospasm/)
- [Intraoperative hypoxaemia: a stepwise approach](https://durgical.com/en/anaesthesia/intraoperative-hypoxaemia-a-stepwise-approach/)
- [Ventilating ARDS: low volumes, prone position and more](https://durgical.com/en/anaesthesia/ventilating-ards-low-volumes-prone-position-and-more/)

## Related conditions 3

- [Aspiration pneumonia and pneumonitis](https://durgical.com/en/conditions/aspiration-pneumonia-and-pneumonitis/)
- [Acute respiratory distress syndrome (ARDS)](https://durgical.com/en/conditions/acute-respiratory-distress-syndrome/)
- [Hospital-acquired and ventilator-associated pneumonia](https://durgical.com/en/conditions/hospital-acquired-and-ventilator-associated-pneumonia/)

## In Pharmacology 4

- [Beta-2 adrenergic agonists](https://durgical.com/en/pharmacology/classes/beta-2-adrenergic-agonists/)
- [Salbutamol](https://durgical.com/en/pharmacology/salbutamol/)
- [H2 receptor antagonists (H2 blockers)](https://durgical.com/en/pharmacology/classes/h2-receptor-antagonists/)
- [Proton pump inhibitors (PPIs)](https://durgical.com/en/pharmacology/classes/proton-pump-inhibitors/)

[← All of anaesthesia](https://durgical.com/en/anaesthesia/)

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: [Aspiration Pneumonia](https://www.ncbi.nlm.nih.gov/books/NBK470459/) (StatPearls (NCBI Bookshelf), 2024).

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Source: https://durgical.com/en/anaesthesia/pulmonary-aspiration/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anaesthesia/pulmonary-aspiration/