[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anaesthesia and ICU](https://durgical.com/en/anaesthesia/) › [Preoperative assessment](https://durgical.com/en/anaesthesia/areas/preop/) › Premedication and aspiration prophylaxis # Premedication and aspiration prophylaxis - Concept Some patients receive medicines before anaesthesia to ease anxiety or to make stomach contents less acidic and smaller, lowering harm if they are inhaled. Updated Nov 13, 2026 ## Key points - Routine aspiration prophylaxis in healthy elective patients is not recommended; it is targeted at those at high risk. - H2 antagonists and proton pump inhibitors raise gastric pH but need time before induction to act. - Use a clear, non-particulate antacid (sodium citrate) just before induction; particulate antacids worsen lung injury if aspirated. - Metoclopramide speeds gastric emptying and is contraindicated in mechanical bowel obstruction. - Benzodiazepine premedication can cause delirium in older adults and respiratory depression in sleep apnoea; avoid by default in both. ## What it is Premedication means drugs given before induction for a specific goal: reducing anxiety, providing analgesia, drying secretions, preventing nausea or lowering the risk and harm of pulmonary aspiration. It is no longer routine; good information and a calm environment reduce anxiety for most adults. Benzodiazepines are the usual anxiolytics but can cause respiratory depression, paradoxical agitation and postoperative delirium, especially in older adults and patients with sleep apnoea, and they add to opioids and other sedatives. Anticholinergics such as glycopyrronium or atropine reduce secretions before awake fibreoptic intubation or in some children. Aspiration of gastric contents causes chemical pneumonitis and can progress to pneumonia; the harm is greater with acidic, large-volume or particulate material. For patients at high risk (emergency surgery, pregnancy, bowel obstruction, gastro-oesophageal reflux, gastroparesis, obesity, reduced consciousness), prophylaxis aims to raise gastric pH and reduce volume: H2 receptor antagonists or proton pump inhibitors given in time to work, a clear non-particulate antacid just before induction in obstetrics, and a prokinetic such as metoclopramide when no obstruction exists. These drugs do not replace fasting or a rapid-sequence induction. ## Key points - Goals of premedication: anxiolysis, analgesia, reduced secretions, reduced nausea and reduced harm from aspiration. - High aspiration risk: full stomach or emergency, pregnancy, bowel obstruction, reflux, diabetic gastroparesis, obesity, GLP-1 agonist use. - Aspiration pneumonitis is chemical lung injury from acidic gastric contents; aspiration pneumonia is infection that may follow. - Prophylaxis works by raising gastric pH and lowering volume; it does not empty the stomach of solid food. - Non-drug anxiety measures: clear information, a parent present at induction for some children, and a short wait. ## How it works - Benzodiazepines enhance GABA-A receptor activity, giving anxiolysis, sedation and amnesia. - H2 antagonists block histamine on parietal cells; proton pump inhibitors block the acid pump itself. - Sodium citrate neutralises acid already in the stomach within minutes, but its effect is short. - Metoclopramide is a dopamine antagonist that increases gastric emptying and lower oesophageal sphincter tone. - Anticholinergics block muscarinic receptors in salivary and bronchial glands, drying the airway. ## In practice - In caesarean section, many units give an H2 antagonist and sodium citrate before surgery, with a rapid-sequence induction if general anaesthesia is needed. - An anxious child may receive a sedative premedication; plan for a longer stay in recovery. - Benzodiazepine overdose causes sedation and respiratory depression; support breathing first, and reverse with caution in long-term users because of seizures. - If aspiration occurs, suction, position, oxygenate and secure the airway; most pneumonitis needs supportive care rather than antibiotics at first. - Ondansetron prevents nausea and vomiting after surgery but does not lower the risk of aspiration during induction. ## Next step - At the visit, record the aspiration risk factors and the anxiety level, and plan premedication only when it has a clear goal. - Time any H2 antagonist or proton pump inhibitor so it works by induction, and give sodium citrate shortly before induction when indicated. - Call a senior for a full stomach that cannot wait, suspected bowel obstruction or a sedated patient who becomes hard to rouse. - After a sedative premedication, keep the patient monitored and never leave them alone without oxygen saturation monitoring. - If aspiration is suspected, report it, take a chest radiograph if symptoms appear, and watch for hypoxaemia over the next hours. ## Test yourself Think of the answer, then tap the question to see it. ## Why is a particulate antacid avoided for aspiration prophylaxis? If aspirated, solid particles cause more severe lung injury than clear liquid; a non-particulate antacid such as sodium citrate is used instead. ## In which situation is metoclopramide contraindicated before anaesthesia? Mechanical bowel obstruction, because increasing gut motility against an obstruction can cause perforation and does not help the stomach empty. ## Which patients have a high risk of pulmonary aspiration at induction? Those with a full stomach or emergency surgery, pregnancy, bowel obstruction, reflux, gastroparesis, obesity, GLP-1 agonist use or reduced consciousness. ## Why are benzodiazepines avoided as routine premedication in older adults? They increase the risk of postoperative delirium, over-sedation and falls, and add to the respiratory depression of opioids and anaesthetics. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anaesthesia/premedication-and-aspiration-prophylaxis/) ## Elsewhere in DurgiPedia - [Gastric acid secretion](https://durgical.com/en/physiology/gastric-acid-secretion/) - [Gastric motility and emptying](https://durgical.com/en/physiology/gastric-motility-and-emptying/) - [Dysphagia and aspiration precautions](https://durgical.com/en/nursing/dysphagia-and-aspiration-precautions/) ## Connections ## Related 7 - [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/) - [Pulmonary aspiration](https://durgical.com/en/anaesthesia/pulmonary-aspiration/) - [Levels of sedation and procedural sedation safety](https://durgical.com/en/anaesthesia/levels-of-sedation-and-procedural-sedation-safety/) - [Postoperative nausea and vomiting](https://durgical.com/en/anaesthesia/postoperative-nausea-and-vomiting/) - [Obstetric anaesthesia and caesarean section](https://durgical.com/en/anaesthesia/obstetric-anaesthesia-and-caesarean-section/) - [Postoperative delirium](https://durgical.com/en/anaesthesia/postoperative-delirium/) ## Related conditions 7 - [Aspiration pneumonia and pneumonitis](https://durgical.com/en/conditions/aspiration-pneumonia-and-pneumonitis/) - [Gastro-oesophageal reflux disease (GERD)](https://durgical.com/en/conditions/gastro-oesophageal-reflux-disease/) - [Gastroparesis (delayed gastric emptying)](https://durgical.com/en/conditions/gastroparesis/) - [Small bowel obstruction](https://durgical.com/en/conditions/small-bowel-obstruction/) - [Obesity](https://durgical.com/en/conditions/obesity/) - [Obstructive sleep apnoea](https://durgical.com/en/conditions/obstructive-sleep-apnoea/) - [Generalized anxiety disorder](https://durgical.com/en/conditions/generalized-anxiety-disorder/) ## In Pharmacology 12 - [Benzodiazepines](https://durgical.com/en/pharmacology/classes/benzodiazepines/) - [Midazolam](https://durgical.com/en/pharmacology/midazolam/) - [Clonidine](https://durgical.com/en/pharmacology/clonidine/) - [H2 receptor antagonists (H2 blockers)](https://durgical.com/en/pharmacology/classes/h2-receptor-antagonists/) - [Famotidine](https://durgical.com/en/pharmacology/famotidine/) - [Proton pump inhibitors (PPIs)](https://durgical.com/en/pharmacology/classes/proton-pump-inhibitors/) - [Omeprazole](https://durgical.com/en/pharmacology/omeprazole/) - [Antacids](https://durgical.com/en/pharmacology/classes/antacids/) - [Metoclopramide](https://durgical.com/en/pharmacology/metoclopramide/) - [Glycopyrronium](https://durgical.com/en/pharmacology/glycopyrronium/) - [Atropine](https://durgical.com/en/pharmacology/atropine/) - [Ondansetron](https://durgical.com/en/pharmacology/ondansetron/) [← 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); [Anxiolytics and Sedative-Hypnotics Toxicity](https://www.ncbi.nlm.nih.gov/books/NBK562309/) (StatPearls (NCBI Bookshelf), 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anaesthesia/premedication-and-aspiration-prophylaxis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anaesthesia/premedication-and-aspiration-prophylaxis/