Which medications are used for induction prior to rapid sequence intubation (RSI)?

Updated: Apr 07, 2020
  • Author: Keith A Lafferty, MD; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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Answer

Induction agents provide a rapid loss of consciousness that facilitates ease of intubation and avoids psychic harm to the patient.

Etomidate (Amidate) (0.3 mg/kg IV) has a rapid onset, a short duration, is cerebroprotective, and is not associated with a significant drop in blood pressure. It is hemodynamically neutral compared with other agents, such as sodium thiopental. It induces a transient decrease in cortisol levels as high as 86% in some studies. However, properly powered prospective studies are needed to validate this more theoretical phenomenon. Note cortisol levels are affected by severe illness independently of the induction agent used. Critical illness‒related corticosteroid insufficiency occurs in 10-20% of critically ill medical patients and as high as 60% in severe sepsis and septic shock. [39, 40] It is the most common agent used in the United States.

Ketamine (Ketalar) (1-2 mg/kg IV) produces a "dissociative" state, has analgesic properties, is a bronchodilator, and may decrease rather than increase intracranial pressure. Consider it for patients with asthma or anaphylactic shock; possibly avoid it in patients with suspected or known aortic dissection or abdominal aortic aneurysm and in patients with acute myocardial infarction. The general teaching has also been to avoid use of ketamine in patients in whom increased ICP is a concern; in particular, trauma patients with evidence of head injury. However, a review of the literature supports its use in this scenario as the hemodynamic stimulation induced by ketamine may, in fact, improve cerebral perfusion and prevent secondary penumbra ischemia. Furthermore, in the laboratory, ketamine seems to have neuroprotective properties. [41, 42, 43] Because of its positive hemodynamic effects and etomidate’s known tendency to transiently decrease cortisol levels, ketamine is being used more frequently as an induction agent.

Propofol (Diprivan) (2 mg/kg IV) has a rapid onset, a short duration, and is cerebral protective. However, propofol is a myocardial depressant and it decreases systemic vascular resistance.

Midazolam (Versed) (0.3 mg/kg IV) has a slower onset (2-3 min without opioid pretreatment) and longer duration (up to several hours) than etomidate. A study by Sagarin et al from a national airway registry demonstrated that midazolam is usually underdosed when used for RSI, presumably because of the concern for hypotension. [3] Note that the induction dose is about 20 mg for a 70-kg person. Use of midazolam as an induction agent is not recommended because of its delayed time to induction, predilection for hypotension at induction doses, and prolonged duration of action.


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