Rapid Sequence Intubation

Rapid Sequence Intubation (RSI), also called rapid sequence induction and intubation, is the near-simultaneous administration of a potent induction agent and a fast-acting neuromuscular blocker to secure the airway as quickly as possible while minimising the interval during which the patient is unprotected from aspiration. It is the default technique in any patient presumed to have a full stomach or high aspiration risk.

Definition and core concept

RSI is designed for the patient who cannot be assumed to be fasted. The fundamental problem it solves is the period between loss of consciousness (loss of airway protective reflexes) and inflation of the endotracheal tube cuff — the "at-risk window" during which regurgitated gastric contents can be aspirated into the lungs.

The classical solution has three pillars:

1. Avoid bag-mask ventilation between induction and intubation (so as not to insufflate the stomach and provoke regurgitation).
2. Use a rapidly-acting muscle relaxant so that intubating conditions are achieved within ~45–60 seconds.
3. Apply cricoid pressure (Sellick manoeuvre) to mechanically occlude the oesophagus.

High-yield: The single defining feature that separates RSI from a routine induction is the omission of routine positive-pressure bag-mask ventilation after induction. Everything else (cricoid pressure, choice of relaxant) is secondary and debatable.

Indications

RSI is indicated whenever the stomach is presumed full or gastric emptying is delayed:

Category	Examples
Inadequate fasting	Emergency surgery, trauma, recent meal
Delayed gastric emptying	Pregnancy (esp. labour), diabetes (gastroparesis), opioids, raised ICP
Mechanical obstruction	Intestinal obstruction, pyloric stenosis, acute abdomen
Incompetent lower oesophageal sphincter	Hiatus hernia, GORD, achalasia, previous gastric surgery
Reduced conscious level	Head injury, intoxication, sepsis

High-yield: Pregnancy beyond ~the second trimester is treated as a full stomach for any anaesthetic because of progesterone-mediated reduction in LES tone plus mechanical displacement of the stomach. RSI is the standard for caesarean section under general anaesthesia.

The stepwise approach — the "7 Ps"

A classic emergency-medicine framework. Memorise the sequence:

Preparation → Pre-oxygenation → Pre-treatment → Paralysis with induction → Positioning/Protection (cricoid) → Placement of tube → Post-intubation management

1. Preparation — check drugs, suction (Yankauer ready and working), two laryngoscopes, range of tube sizes, stylet/bougie, capnography, functioning IV, monitors, and a clear failed-intubation plan. Mnemonic for kit: SOAP-ME (Suction, Oxygen, Airway equipment, Pharmacology, Monitors, End-tidal CO₂).
2. Pre-oxygenation — see dedicated section below.
3. Pre-treatment — optional drugs (lidocaine, opioid, atropine in children) given 2–3 minutes before to blunt reflexes.
4. Paralysis with induction — induction agent immediately followed by the relaxant, given as a rapid bolus.
5. Protection / Positioning — cricoid pressure applied as consciousness is lost; head positioned (sniffing position).
6. Placement — laryngoscopy and intubation once fasciculations cease / 45–60 s elapsed; confirm with capnography.
7. Post-intubation — secure tube, release cricoid only after cuff inflation and confirmation, set ventilator, sedation.

Pre-oxygenation (denitrogenation)

Pre-oxygenation replaces nitrogen in the functional residual capacity (FRC) with oxygen, creating a reservoir that prolongs the safe apnoea time during the no-ventilation window.

• Target: end-tidal O₂ (EtO₂) ≥ 90% or expired O₂ fraction ~0.9, which corresponds to adequate denitrogenation.
• Techniques: 3 minutes of tidal-volume breathing of 100% O₂ via a tightly sealed mask, OR 8 vital-capacity (deep) breaths in 60 seconds for the urgent/uncooperative case.
• A good seal is more important than time; even small leaks entrain room air and prevent EtO₂ from rising.
• Apnoeic oxygenation: nasal cannula at 15 L/min left running during the apnoeic period (NO DESAT — "Nasal Oxygen During Efforts Securing A Tube") extends safe apnoea, especially valuable in the critically ill and obstetric patient.

High-yield: Adequate pre-oxygenation extends the safe apnoea time in a healthy adult to ~8 minutes, but in pregnancy, obesity, children and the critically ill, desaturation is much faster (high O₂ consumption + reduced FRC) — hence pre-oxygenation is most critical precisely in those patients.

Drug choice — induction agents

Agent	Dose (IV)	Best for	Caution
Thiopentone	3–5 mg/kg	Classic RSI agent	Hypotension; never in porphyria
Propofol	1.5–2.5 mg/kg	Haemodynamically stable	Marked hypotension, apnoea
Ketamine	1–2 mg/kg	Shock, asthma, trauma (haemodynamically unstable)	Raised ICP (relative), emergence reactions
Etomidate	0.3 mg/kg	Cardiovascular instability, head injury	Adrenal suppression, myoclonus

High-yield: Ketamine and etomidate are the haemodynamically stable induction agents preferred in the shocked/trauma patient. Etomidate gives the least cardiovascular depression but causes adrenal suppression (avoid repeated dosing in sepsis). Ketamine is the agent of choice in the hypotensive asthmatic/trauma patient.

Drug choice — neuromuscular blocker

This is the most heavily tested comparison in RSI.

Feature	Succinylcholine (Suxamethonium)	Rocuronium
Class	Depolarising	Non-depolarising (aminosteroid)
RSI dose	1–1.5 mg/kg	1.0–1.2 mg/kg (high dose)
Onset	~45 s (fastest available)	~60 s at high dose
Duration	~5–10 min (ultra-short)	30–60 min (long)
Reversal	None specific; spontaneous (plasma cholinesterase)	Sugammadex (rapid, complete)
Key adverse effects	Hyperkalaemia, malignant hyperthermia, bradycardia, fasciculations/myalgia, raised IOP/ICP/intragastric pressure	Anaphylaxis (rare), prolonged block

Succinylcholine remains the traditional gold standard because of its fastest onset and shortest duration — if intubation fails, paralysis wears off and the patient may resume spontaneous ventilation. Standard RSI uses thiopentone + succinylcholine.

Rocuronium at high dose (1.2 mg/kg) gives intubating conditions comparable to succinylcholine and is the choice when succinylcholine is contraindicated. Its long duration was historically a drawback, but sugammadex 16 mg/kg can reverse a profound rocuronium block within ~3 minutes, restoring the "can wake the patient up" safety net.

High-yield — contraindications to succinylcholine (hyperkalaemia risk via up-regulated extrajunctional ACh receptors): burns (after ~24–48 h, peak risk 1–8 weeks), crush injury / rhabdomyolysis, denervation injuries (spinal cord injury, stroke, prolonged immobility), neuromuscular disease (Duchenne, Guillain–Barré), and pre-existing hyperkalaemia/renal failure. Also avoid in known malignant hyperthermia susceptibility. In these patients use rocuronium.

Mnemonic for sux contraindications — "BURNS": Burns, Up-regulation/neuromuscular disease, Rhabdomyolysis/crush, Nerve (denervation, SCI, stroke), Serum potassium high / renal failure.

Cricoid pressure (Sellick manoeuvre)

Described by Brian Sellick in 1961. Backward pressure on the cricoid cartilage (the only complete tracheal ring) compresses the oesophagus against the C6 vertebral body, theoretically preventing passive regurgitation of gastric contents.

• Force: ~10 Newton (≈1 kg) while awake, increasing to ~30 N (≈3 kg) once consciousness is lost.
• Applied by an assistant, maintained continuously until after cuff inflation and confirmation of correct placement.

The controversy (NEET PG relevant)

High-yield: Cricoid pressure is now controversial. Evidence that it reliably prevents aspiration is weak; it may worsen the laryngoscopic view, impede mask ventilation and tube passage, and does not reliably occlude the oesophagus (which often lies lateral to the cricoid on imaging). It should be released immediately if it impedes intubation or if active vomiting occurs (continued pressure during active vomiting risks oesophageal rupture).

Many modern guidelines have downgraded it from mandatory to optional. Knowing both the classical rationale and the current scepticism is the examinable point.

Modified / controlled RSI

A pragmatic deviation from the "no ventilation" rule used when desaturation is dangerous (children, pregnancy, obese, critically ill):

• Gentle bag-mask ventilation with low airway pressures (< 15–20 cmH₂O, below the LES opening pressure) is permitted to maintain oxygenation while cricoid pressure is held.
• High-dose rocuronium is often substituted for succinylcholine.
• This trades a tiny theoretical rise in aspiration risk for a real reduction in life-threatening hypoxia.

High-yield: In paediatric RSI, the classical breath-holding "no ventilation" rule is frequently abandoned (children desaturate fast) — gentle ventilation is acceptable. Atropine 0.02 mg/kg pre-treatment is often given to children to prevent succinylcholine-induced bradycardia.

Confirmation of tube placement

Waveform capnography (continuous EtCO₂) is the gold standard for confirming endotracheal (vs oesophageal) placement — a sustained CO₂ waveform over several breaths confirms tracheal intubation. Supplementary signs: bilateral chest rise, equal breath sounds, absence of epigastric gurgling, misting of the tube, and oxygen saturation. Chest X-ray confirms depth, not tracheal placement.

Complications

• Pulmonary aspiration (the very event RSI aims to prevent) — Mendelson's syndrome (chemical aspiration pneumonitis from acidic gastric contents).
• Failed/difficult intubation and hypoxia — the most immediately lethal complication; follow a difficult airway algorithm.
• Cardiovascular: hypotension from induction agents; hypertension/tachycardia from laryngoscopy (dangerous in raised ICP, ischaemic heart disease).
• Succinylcholine-specific: hyperkalaemic cardiac arrest, malignant hyperthermia, bradycardia (esp. repeat doses/children), myalgia, raised ICP/IOP/intragastric pressure.
• Oesophageal intubation (undetected = fatal) — prevented by capnography.
• Awareness if relaxant outlasts inadequate hypnosis.
• Trauma: dental, laryngeal, oesophageal rupture (from cricoid + vomiting).

Key differentials / decision points

These are the "what would you do" decision nodes examiners probe:

• Stable fasted elective patient → standard induction with bag-mask ventilation, not RSI.
• Full stomach / emergency → RSI.
• Anticipated difficult airway + full stomach → consider awake fibreoptic intubation rather than RSI (don't paralyse a patient you may not be able to intubate or ventilate).
• Hyperkalaemia risk → rocuronium-based RSI, not succinylcholine.
• Haemodynamic instability → ketamine or etomidate induction.

Recently asked / exam angle

• Most common single-best-answer: "Drug used in RSI for rapid onset of relaxation" → Succinylcholine (and its dose 1–1.5 mg/kg). Conversely, "alternative when succinylcholine is contraindicated" → Rocuronium (1.2 mg/kg).
• Reversal of rocuronium → Sugammadex; high dose 16 mg/kg for immediate reversal of a profound block in a can't-intubate scenario.
• Sellick manoeuvre → pressure on the cricoid cartilage; force ~30 N when unconscious; rationale = occlude oesophagus.
• Best confirmation of intubation → capnography / EtCO₂.
• Pre-oxygenation target → EtO₂ ≥ 90%; methods (3 min tidal breathing or 8 deep breaths).
• Full-stomach scenarios (obstetrics, intestinal obstruction, trauma, diabetic gastroparesis) repeatedly tested as "which technique?" → RSI.
• Contraindications to succinylcholine (burns, crush, denervation, neuromuscular disease, hyperkalaemia) — very common image/clinical vignette.
• Mendelson's syndrome linked to aspiration of acidic gastric contents.
• Trend toward asking the controversy of cricoid pressure (when to release it: poor view or active vomiting).

Rapid revision

1. RSI = simultaneous induction + fast relaxant, no routine bag-mask ventilation, to secure a full-stomach airway fast.
2. Classic combo = thiopentone + succinylcholine; succinylcholine has the fastest onset and shortest duration.
3. Succinylcholine RSI dose = 1–1.5 mg/kg; rocuronium RSI dose = 1.2 mg/kg.
4. Succinylcholine contraindicated → use rocuronium; reverse rocuronium with sugammadex (16 mg/kg).
5. Succinylcholine danger = hyperkalaemia (burns, crush, denervation, neuromuscular disease) and malignant hyperthermia.
6. Sellick manoeuvre = cricoid pressure (~30 N unconscious) to occlude the oesophagus; release if it impairs view or during active vomiting.
7. Pre-oxygenate to EtO₂ ≥ 90% — 3 min tidal breathing or 8 vital-capacity breaths; add apnoeic nasal O₂ (NO DESAT).
8. Confirm tube with waveform capnography — the gold standard.
9. Haemodynamically unstable / trauma induction agents = ketamine or etomidate; etomidate causes adrenal suppression.
10. Pregnancy = full stomach → RSI is standard for GA caesarean.
11. Modified RSI = gentle low-pressure ventilation (children, obese, critically ill, pregnant) when desaturation risk is high.
12. Anticipated difficult airway + full stomach → favour awake fibreoptic intubation over standard RSI.