Rapid Sequence Intubation (RSI)

Definition

RSI is the near-simultaneous administration of a potent sedative/induction agent and a neuromuscular blocking agent (NMBA), after a period of preoxygenation and cardiopulmonary optimization, to produce optimal conditions for tracheal intubation without interposed bag-mask ventilation - Rosen's Emergency Medicine, p. 30. It is the default technique for emergency intubation in patients without predicted difficult-airway features, and registry data show it is used in roughly 85% of all ED intubations - Rosen's Emergency Medicine, p. 30.

The rationale: taking a patient from consciousness/spontaneous breathing straight to unconsciousness with complete paralysis, then intubating without bagging, avoids gastric insufflation and theoretically reduces regurgitation/aspiration risk (though Rosen's notes the aspiration-reduction benefit is not strongly proven by evidence). Preoxygenation before paralysis is what buys the "safe apnea time" needed to intubate without ventilating in between.

The Steps ("P's" of RSI)

Different texts describe 6-7 P's; Roberts and Hedges' Clinical Procedures in Emergency Medicine frames it as six:

Preparation - assess for a difficult airway, get IV access, attach cardiac/pulse-ox/end-tidal CO2 monitoring, draw up all drugs, and set out primary and backup airway equipment (bougie, video laryngoscope, supraglottic device, cricothyrotomy kit).
Preoxygenation - 100% oxygen for ~3 minutes of tidal breathing, or 4 vital-capacity breaths, to displace nitrogen and build an oxygen reserve; this can maintain saturation for several minutes of apnea in a healthy patient. The "NO DESAT" technique (nasal cannula at 5 L/min under the non-rebreather mask, increased to 15 L/min after induction) can prolong safe apnea time and is left on during laryngoscopy - Pfenninger and Fowler's Procedures for Primary Care, p. 166.
Pretreatment - drugs given 2-5 minutes before induction to blunt reflex responses to intubation (e.g., historically lidocaine/opioids to blunt ICP or sympathetic surge). Note: the evidence supporting routine pretreatment for patient-oriented outcomes has been increasingly questioned, and many modern protocols have dropped it.
Paralysis with induction - a sedative-induction agent is pushed immediately followed by a paralytic, given essentially back-to-back.
Positioning/Placement of the tube - proper head positioning (ramped/sniffing position), laryngoscopy, and confirmation of tube placement (waveform capnography is the gold standard).
Postintubation management - sedation/analgesia, ventilator setup, confirming tube depth, and hemodynamic monitoring.

Common Drugs

Induction agents

Etomidate (~0.3 mg/kg IV) - hemodynamically stable, favored in trauma/shock, but causes transient adrenal suppression; clinical significance of this in single-dose RSI remains debated.
Ketamine (~1-2 mg/kg IV) - preserves airway reflexes and blood pressure, useful in hypotensive/shock patients and reactive airway disease/asthma.
Propofol (~1.5-2 mg/kg IV) - rapid onset, but causes dose-dependent hypotension; used cautiously in unstable patients.

Paralytics (NMBAs)

Succinylcholine (~1-1.5 mg/kg IV) - fastest onset/shortest duration; contraindicated in hyperkalemia risk states (burns, crush injury, neuromuscular disease, renal failure) and known malignant hyperthermia susceptibility.
Rocuronium (~1-1.2 mg/kg IV) - slightly slower onset, longer duration, no hyperkalemia risk; increasingly preferred, and studies comparing the two show succinylcholine may offer marginally better intubating conditions in some trials - Morgan and Mikhail's Clinical Anesthesiology, p. 1281.

Both etomidate and ketamine are considered reasonable induction choices in critically ill patients; recent meta-analyses (below) have specifically compared them for hemodynamic stability, adrenal suppression, and mortality outcomes.

Indications and Contraindications

Indications overlap with general emergency airway needs: impending respiratory failure, inability to protect the airway, need for hyperventilation/sedation in critically ill patients, and as the default approach unless a difficult airway is anticipated.

RSI is relatively contraindicated (favor an awake or alternative technique instead) when a difficult airway is anticipated and awake intubation, cannot-intubate/cannot-ventilate risk, or anatomic distortion make paralysis before securing the airway dangerous - Tintinalli's Emergency Medicine, p. 3466. Escalation pathways after a failed RSI attempt include supraglottic airway, video laryngoscopy, or surgical airway (cricothyrotomy) - Roberts and Hedges' Clinical Procedures, p. 859.

Recent Evidence (last 2 years)

Three recent systematic reviews/meta-analyses have compared etomidate vs ketamine for RSI, since this is currently the most actively studied controversy in the field:

Readdressing RSI with ketamine or etomidate - meta-analysis of RCTs, 2025 (PMID: 40355221)
Etomidate vs ketamine for in-hospital RSI - systematic review and meta-analysis, 2025 (PMID: 40239104)
Impact of ketamine on emergency RSI - systematic review and meta-analysis, 2024 (PMID: 39333918)

These generally reinforce that both agents are viable, with etomidate causing more transient adrenal suppression (of uncertain clinical significance) and ketamine offering more hemodynamic stability in shock states, without a clear mortality difference between them. If you want, I can pull the specific outcome data (mortality, vasopressor use, first-pass success) from any of these papers in detail.

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