# Rapid Sequence Induction

> Rapid sequence induction for Anaesthesia Technology: preoxygenation, cricoid pressure doses, drug choices, succinylcholine limits and failed intubation drill.

- Canonical URL: https://prepelephant.com/topics/allied/anaesthesia-technology/rapid-sequence-induction-at
- Exam / course: Allied Health · Subject: Anaesthesia Technology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Rapid Sequence Induction", PrepElephant, https://prepelephant.com/topics/allied/anaesthesia-technology/rapid-sequence-induction-at

## Direct answer

Rapid sequence induction (RSI) is the technique for patients at risk of aspirating gastric contents: three minutes of preoxygenation (or eight vital-capacity breaths) with head-up 20-30 degree positioning, a prefetched induction agent (propofol 1.5-2.5 mg/kg or thiopentone 3-5 mg/kg), cricoid pressure at 10 newtons while awake increased to 30-40 newtons on loss of consciousness, then succinylcholine 1-1.5 mg/kg or rocuronium 1.0-1.2 mg/kg, with no mask ventilation, laryngoscopy at about 45-60 seconds, and cricoid pressure released only after tracheal placement is confirmed by capnography and the cuff inflated. Obstetrics, full-stomach emergencies, ileus, obstruction and trauma are the standard indications; the whole ritual compresses the unprotected-airway window to under a minute, and a failed intubation here follows the difficult-airway algorithm with waking the patient as the default escape.

## What you must remember

- **Why the stomach is dangerous:** pregnancy, obesity, pain, opioids, bowel obstruction and trauma all raise gastric volume and lower lower-oesophageal-sphincter tone; every emergency is a full stomach regardless of fasting hours.
- **Preoxygenation targets:** 3 minutes of tidal breathing of 100% oxygen or 8 vital-capacity breaths, aiming at denitrogenation and an end-tidal oxygen above 80-85%; head-up 20-30 degrees extends the safe apnoea time.
- **Cricoid arithmetic:** 10 newtons (1 kg) applied while the patient is still awake and compliant, increased to 30-40 newtons (3-4 kg) after loss of consciousness; released only after cuff inflation and capnographic confirmation — and released or eased if the view is poor, since excessive cricoid pressure distorts the larynx.
- **Drug doses:** propofol 1.5-2.5 mg/kg (reduced in shock and pregnancy), thiopentone 3-5 mg/kg, ketamine 1-2 mg/kg for the haemodynamically unstable; succinylcholine 1-1.5 mg/kg for paralysis at 45-60 seconds or rocuronium 1.0-1.2 mg/kg when succinylcholine is contraindicated.
- **Succinylcholine contraindications:** malignant hyperthermia susceptibility, existing hyperkalaemia, burns beyond the first 24-48 hours until about a year, denervation and prolonged immobility, and neuromuscular disease — each can precipitate lethal potassium release.
- **Assistant's timing errors:** cricoid too early (patient gags and vomits awake), too late (unprotected interval), or too forceful (impaired laryngoscopic view) — the technician's hands are graded, not just present.
- **Failed intubation plan:** declared after the limited attempts of the difficult-airway algorithm, with waking the patient as the default; a second-generation supraglottic airway is the oxygenation rescue.
- **Modified RSI:** gentle mask ventilation between induction and intubation is now accepted in some patients (paediatrics, compromised oxygenation), a hedge between classic teaching and physiology.

## A category-one caesarean under general anaesthesia

A parturient for an emergency caesarean has a failed regional attempt and placental abruption: general anaesthesia by RSI is the pathway, and the technician's preparation is the backbone. Suction under the pillow; two working laryngoscopes; a 7.0 mm tube with stylet plus a 6.5 spare; drugs drawn and labelled — thiopentone 4 mg/kg or propofol 2 mg/kg (reduced if shocked), succinylcholine 1.5 mg/kg calculated aloud; sodium citrate 30 mL of 0.3 molar if time allows. Left uterine displacement, head-up tilt, three minutes of 100% oxygen through a tight mask.

The sequence itself takes ninety seconds and everyone's role is fixed. Cricoid at 10 newtons awake; thiopentone; loss of consciousness confirmed; cricoid to 30-40 newtons; succinylcholine; fasciculations watched and gone; intubation at 45-60 seconds without a single mask breath. The cuff inflates, capnography shows six sustained traces, and only then does the cricoid hand release — the most commonly mistimed step in real theatres. If laryngoscopy fails, the i-gel size 4 is the oxygenation rescue and waking the patient is weighed against fetal distress — the anaesthesiologist's decision, prepared for by the technician who stocked the difficult-airway trolley that morning.

## Where students slip

The exam traps are consistent. Cricoid pressure numbers are misquoted in kilograms rather than newtons or vice versa — examiners accept 30-40 newtons, roughly 3-4 kg force. The timing of release is placed after "tube seen in trachea" rather than after capnographic confirmation with the cuff inflated. The rocuronium dose is quoted as the routine 0.6 mg/kg instead of the RSI-specific 1.0-1.2 mg/kg for intubating conditions within about 60 seconds, paired with sugammadex 16 mg/kg as the escape reversal. Finally, the burns question: succinylcholine is avoided from about day 2 up to a year after burns or denervation, because upregulated receptors flood the circulation with potassium — an MCQ that appears nearly every year.

## Frequently asked questions

### Which patients require rapid sequence induction?

Anyone with a full stomach or aspiration risk: obstetric patients, emergencies, trauma, bowel obstruction and ileus, active vomiting, and conditions delaying gastric emptying such as diabetes with gastroparesis or opioid use.

### How is cricoid pressure applied and when is it released?

Ten newtons while awake, increased to 30-40 newtons on loss of consciousness using the thumb and one or two fingers on the cricoid cartilage; released only after tracheal placement is confirmed by sustained capnography with the cuff inflated.

### What dose of rocuronium is used for RSI?

One to 1.2 mg/kg intravenously, producing intubating conditions in about 60 seconds; if reversal becomes necessary, sugammadex 16 mg/kg terminates the block within minutes.

### Why is succinylcholine avoided in burns and denervation?

Regenerating or upregulated extrajunctional receptors release large amounts of potassium on depolarisation, causing hyperkalaemic arrest; the danger period extends from roughly 24-48 hours after injury up to about a year.

### What is the rescue if intubation fails during RSI?

Declare failed intubation, maintain or ease cricoid pressure, oxygenate with a second-generation supraglottic airway, and wake the patient unless the surgery is immediately life-saving — the difficult-airway algorithm applied with waking as default.