MD Notes

creation date: 2026-11-02 09:09
tags: Pharmacology

Rapid Sequence Intubation Agents

Background

Rapid sequence intubation (RSI) agents are used for induction and paralysis prior to intubation attempts. This page discusses dosing used for a typical adult - dosing will likely require to be adjusted for hypotension/shock patients.

Intubation is discussed separately.

Induction Agents

Induction agents are used to amnestatize and sedate the patient.

Ketamine

  • Dose: 1.5 mg/kg IV (4mg/kg IM)
  • Onset: 60-90 sec
  • Duration: 10-20 min
  • Use:
    • Any RSI, especially if hemodynamically unstable
    • OK in TBI, does not increase ICP despite traditional dogma
    • Reactive airways disease (causes bronchodilation)
  • Drawbacks:
    • Increased secretions
    • Caution in cardiovascular disease (hypertension, tachycardia)
    • Laryngospasm (rare)
    • Raised intra-ocular pressure

Thiopentone

  • Dose: 3-5 mg/kg TBW IV
  • Onset: 30-45 sec
  • Duration: 5-10 min
  • Use:
    • Any RSI if haemodynamically stable
    • Status epilepticus
  • Drawbacks:
    • Histamine release
    • Myocardial depression
    • Vasodilation
    • Hypotension
    • Must NOT be injected intra-arterially due to risk of distal ischaemia
    • Contra-indicated in porphyria (disease of enzyme deficiency for heme production)

Propofol

  • Dose: 1-2.5 mg/kg IBW + (0.4 x TBW) IV
    • Can use 1.5-2.5 mg/kg x TBW as the general guide
  • Onset: 15-45 seconds
  • Duration: 5-10 minutes
  • Use:
    • Haemodynamically stable patients
    • Reactive airways disease
    • Status epilepticus
  • Drawbacks:
    • Hypotension
    • Myocardial depression
    • Reduced cerebral perfusion
    • Pain on injection
    • Variable response
    • Very short acting

Fentanyl

  • Dose: 2-10 mcg/kg TBW IV
  • Onset: <60 seconds (maximal at ~5 min)
  • Duration: dose dependent (30 minutes for 1-2 mcg/kg, 6h for 100 mcg/kg)
  • Use:
    • Used low dose as a sympatholytic premedication (e.g. TBI, SAH, vascular emergencies)
    • Used in a “modified” RSI approach in low doses or titrated to effect in cardiogenic shock and other hemodynamically unstable conditions
  • Drawbacks:
    • Respiratory depression
    • Apnea
    • Hypotension, bradycardia
    • Slow onset
    • Nausea and vomiting
    • Muscular rigidity in high induction doses
    • Tissue saturation at high doses

Midazolam

  • Dose: 0.3mg/kg TBW IV
  • Onset: 60-90 sec
  • Duration: 15-30 min
  • Use: not usually recommended for RSI, some practitioners use low doses of midazolam and fentanyl for RSI of shocked patients
  • Drawbacks:
    • Respiratory depression
    • Apnea
    • Hypotension
    • Paradoxical agitation
    • Slow onset
    • Variable response

Etomidate

  • Dose: 0.3mg/kg IV
  • Onset: 10-15 seconds
  • Use:
    • Most situations including hemodynamically unstable, other than sepsis or seizures
  • Drawbacks:
    • Adrenal suppression
    • Myoclonus
    • Pain on injection

Paralytic Agents

Paralytic agents are neuromuscular blockers used to paralyze the patient to aid intubation. They do not sedate the patient and as such should always be paired with an induction agent.

Succinylcholine

  • Dose:
    • 1.5 mg/kg IV
    • 4 mg/kg IM (in extremis)
    • 2 mg/kg IV if myasthenia gravis
  • Onset: 45-60 seconds
  • Duration: 6-10 minutes
  • Use: widely used unless CI
  • Drawbacks:
    • Numerous contra-indications (hyperkalemia, malignant hyperthermia, >5d after burns/ crush injury/ neuromuscular disorder)
    • Bradycardia (especially after repeat doses)
    • Hyperkalemia
    • Fasciculations (depolarizing blocker causes intiail spasm)
    • Elevated intra-ocular pressure
    • Will not wear off fast enough to prevent harm in “cannot intubate, cannot ventilate” (CICV) situations

Rocuronium

  • Dose: 1.2 mg/kg IV IBW
  • Onset: 60 seconds
  • Use:
    • Any RSI unless contra-indication
    • Situations that require rapid recovery for extubation after elective procedure or neurological assessment (ensures persistent ideal conditions in CICV situation (i.e. immobile patient for cricothyroidotomy))
    • Can be reversed by sugammadex
  • Drawbacks: allergy (rare)

Vecuronium

  • Dose: 0.15 mg/kg IV (may be preceded by a 0.01 mg/kg IV priming dose 3 minutes earlier)
  • Onset: 120-180 seconds
  • Duration: 45-60 minutes
  • Use: not recommended for RSI, unless no suxamethonium or rocuronium cannot be used; can be reversed by sugammadex
  • Drawbacks: allergy (rare), slow onset, long duration

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