An update on induction agents for RSI

The primary medication choices for RSI induction are etomidate, ketamine, and propofol.

Etomidate: traditionally, the “workhorse”

  • Hemodynamics: No vasodilatory properties therefore hemodynamically stable
  • Pharmacokinetics: Fast onset (1 minute) and short duration (3-5 minutes)
  • Other benefits: There are few contraindications
  • Risks:
    • Adrenal suppression (though this is transient and has not been shown to change patient outcomes)
    • Emerging evidence suggests that etomidate may increase mortality [1]

Ketamine: a good replacement for etomidate

  • Hemodynamics: Increases the release of endogenous catecholamines. This may increase blood pressure. It may not increase blood pressure in those who are catecholamine deplete (i.e. severe septic shock) and should not be relied upon to increase blood pressure. It can also lower blood pressure by depleting catecholamines. This is not thought to be dose dependent so a reduced dose is unlikely to protect hemodynamics.
  • Pharmacokinetics: Fast onset (30-50 s) and longer duration (30-45 minutes)
  • Other benefits:
    • Has analgesic properties
    • Can be used in head trauma and hypertension and may even be neuroprotective
    • Longer duration of action makes it a good choice in patients who are receiving a longer acting paralytic
  • Best use: for the shocky patient

Propofol

  • Hemodynamics: Causes vasodilation and cardiac depression which intrinsically drops blood pressure in a dose dependent fashion
  • Pharmacokinetics: Fast onset (15-30 s) and short duration (5-10 minutes)
  • Other benefits:
    • Decreases blood pressure making it useful in hypertensive emergencies
    • Has anti-epileptic properties making it useful for post-stroke, ICH, status epilepticus, or alcohol withdrawal patients
  • Risks: Because it drops blood pressure, it is important to reduce the dose in critically ill and hypotensive patients; either slowly administer until you reach the desires dissociative effect or use 10-20% of usual dose (~10-15 mg total)
  • Best uses: In patients at risk for seizure, hypertensive patients, and for post-intubation sedation

=> Key points:

  • Emerging evidence that etomidate may increase mortality
  • Dose reductions for etomidate and ketamine are unlikely to reduce the risk of hypotension post-RSI but, reduced dose may increase awareness of paralysis
  • Propofol dose should be reduced in shocky patients or avoided completely; good in choice in hypertensive stroke, ICH, status epilepticus, alcohol withdrawal patients

The Podcast: EM Quick Hits 55: Induction Agents, Gabapentinoids, Neuroprotective Intubation, Approach to Paresthesias, Preventing Burnout