Rapid Sequence Induction
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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.