Examqo › Examqo library › Anesthesiology › Airway and induction · IMLE
Rapid sequence induction (RSI) and aspiration
With a full stomach the time between loss of consciousness and cuff inflation is made as short as possible: preoxygenation, an induction agent and a fast-acting relaxant together, and a cuffed tube — to prevent aspiration.
Why it matters in the exam
The exam presents an acute abdomen, bowel obstruction, late pregnancy or trauma, and asks what is special about the anaesthetic: which relaxant, at what dose, when succinylcholine is forbidden, and what the role of cricoid pressure is. Other questions deal with aspiration that has happened: what the treatment is, and whether antibiotics or steroids are given.
The aspiration risk rises whenever the stomach has not emptied or the lower oesophageal sphincter is weak: a recent meal, obstruction, pregnancy from the second trimester, active reflux, diabetic gastroparesis, marked obesity, pain and opioid use. Drug prophylaxis (an H2 blocker or a PPI, a non-particulate antacid such as sodium citrate, metoclopramide) reduces gastric volume and acidity, but it does not replace the RSI itself.
Remember that RSI is a sequence of decisions and not a single drug: the induction agent is chosen by the haemodynamic state (ketamine or etomidate in a shocked patient, a reduced dose of propofol in a stable one), the relaxant by its contraindications, and what to do if intubation fails is planned in advance. In a patient with bowel obstruction the stomach is emptied through a nasogastric tube before induction, and in a pregnant woman uterine displacement and an antacid are added. In exam questions a common distractor is "ventilate well by mask before intubation" — with a full stomach that is not the right answer.
Key points
- RSI = preoxygenation, induction and a fast relaxant together, a cuffed tube.
- Succinylcholine 1–1.5 mg/kg or rocuronium 1.2 mg/kg.
- Cricoid pressure 30 N, controversial, released when it gets in the way.
- Prophylaxis: H2 blocker/PPI, sodium citrate, metoclopramide.
- Aspiration: suction and PEEP; no steroids and no routine antibiotics.
Summary table
| Component | What is done | Exam details |
|---|---|---|
| Preoxygenation | 3 minutes of 100% oxygen through a tight mask | Lengthens the safe time before desaturation |
| Relaxant | Succinylcholine 1–1.5 mg/kg or rocuronium 1.2 mg/kg | High-dose rocuronium when succinylcholine is forbidden; sugammadex available for reversal |
| Cricoid pressure | 10 N awake and 30 N after loss of consciousness | Controversial; release it if it hinders laryngoscopy or if there is active vomiting |
| Mask ventilation | The classic approach avoids it; gentle ventilation below 20 cmH2O is now allowed | Mainly in a patient who oxygenates poorly |
| Aspiration has happened | Suction, head down, PEEP, bronchoscopy only for particles | No routine antibiotics or steroids |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Anesthesiology, Emergency medicine, General surgery, Medical licensing exam (IMLE).
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- Miller's Anesthesia, 9th edition (2020) — Airway Management in the Adult
- ASA Practice Guidelines for Preoperative Fasting, 2017 — Pharmacologic prevention of pulmonary aspiration
- Morgan & Mikhail's Clinical Anesthesiology, 7th edition (2022) — Airway Management
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.