"Rapid sequence induction exists to shorten the dangerous interval between loss of consciousness and a protected airway in the patient at risk of aspiration. Preoxygenate fully, give a predetermined dose of induction agent immediately followed by a rapid-onset muscle relaxant, and intubate — classically without intervening manual ventilation."
Synthesised from Miller's Anesthesia; Morgan & Mikhail's Clinical Anesthesiology; Barash — Clinical Anesthesia.When is RSI indicated?
- Full stomach / inadequate fasting, emergency surgery, acute trauma/pain, recent opioids.
- Bowel obstruction, ileus, acute abdomen; symptomatic GORD, hiatus hernia.
- Pregnancy (≥ ~16–18 weeks or symptomatic reflux) — reduced tone + raised intra-abdominal pressure.
- Raised intra-abdominal pressure (obesity, ascites); GLP-1 agonists (delayed gastric emptying); diabetic gastroparesis; critical illness.
The RSI sequence
Prepare — the 7 Ps
Plan, People, Position (ramp/head-up), Preparation of drugs & kit (checked laryngoscope, sized tubes, working suction, bougie, backup SGA & FONA kit), monitoring + capnography, IV access.
Preoxygenate
3 min tidal breathing (or 8 vital-capacity breaths) of 100% O₂ to EtO₂ >0.85–0.9. Add nasal apnoeic O₂ / HFNO, especially in obesity, pregnancy and critical illness. Head-up improves FRC.
Pretreatment / optimise (optional)
Fluids/vasopressor for the shocked patient; opioid (e.g. fentanyl) to blunt the pressor response where appropriate. In the ED, "resuscitate before you intubate".
Paralyse & induce
A predetermined induction agent immediately followed by a rapid-onset relaxant (suxamethonium 1–1.5 mg/kg or rocuronium 1.2 mg/kg). Classically no manual ventilation (gentle ventilation is acceptable in the modern/"controlled" RSI if desaturating).
Cricoid pressure (Sellick's)
Applied as consciousness is lost — see below. Release it if it worsens the view or ventilation, or if the patient actively vomits.
Placement & proof
Intubate, inflate the cuff, confirm with sustained capnography ("no trace, wrong place") + bilateral chest rise. Secure the tube, then release cricoid on the intubator's instruction.
Post-intubation care
Ventilator settings, sedation, orogastric tube to decompress the stomach, ongoing monitoring.
Drugs for RSI
| Drug | Role | Dose (IV) | Notes |
|---|---|---|---|
| Propofol | Induction | 1.5–2.5 mg/kg | Smooth; hypotension — reduce in the elderly/shocked |
| Ketamine | Induction (unstable) | 1–2 mg/kg | Maintains BP; bronchodilator; shock/asthma/trauma |
| Etomidate | Induction (cardiac-stable) | 0.3 mg/kg | Haemodynamically stable; transient adrenal suppression |
| Thiopentone | Induction (classic RSI) | 3–5 mg/kg | The traditional RSI agent; avoid extravasation/intra-arterial |
| Suxamethonium | RSI relaxant | 1–1.5 mg/kg | Fastest on/off (~45 s / ~6–10 min); avoid in hyperkalaemia, burns >24–48 h, denervation, MH |
| Rocuronium | RSI relaxant (alt.) | 1.2 mg/kg | Comparable intubating conditions; fully reversible with sugammadex |
| Sugammadex | Reversal (roc/vec) | 16 mg/kg (immediate rescue) | Reverses profound rocuronium block — the "can't intubate" pharmacological wake-up |
| Fentanyl | Obtund pressor response | 1–3 µg/kg | Blunts the laryngoscopy response; caution — apnoea/hypotension |
Real practice individualises the classic dogma: gentle mask ventilation (low pressures) is allowed to prevent hypoxia in the child, the obese and the critically ill; opioids are added to blunt the pressor response; and rocuronium + sugammadex increasingly replaces suxamethonium. The principles — full preoxygenation, minimal gastric insufflation, a checked plan and early capnographic confirmation — stay constant.
Sellick's manoeuvre (cricoid pressure)
Described by Brian Sellick in 1961: backward pressure on the cricoid cartilage compresses the upper oesophagus against the C6 vertebral body to reduce passive regurgitation of gastric contents during induction.
Cricoid pressure remains traditional in RSI but is debated: MRI shows the oesophagus is often lateral to the cricoid, correctly-applied force is rarely achieved, and it can worsen the view, impede mask/SGA ventilation and reduce lower-oesophageal-sphincter tone. The large IRIS trial (2019) did not prove non-inferiority of omitting it, so most guidelines still apply it but release early if it hinders airway management. It is an adjunct — never let it compromise oxygenation.