There are basically only two induction agents commonly used for rapid sequence intubation: etomidate and ketamine.
“The dosing of induction agents in nonobese adults should be based on ideal body weight (IBW) in kilograms. In clinical practice, the actual body weight is a reasonable enough approximation to IBW for the purposes of dosing these agents.” (1)
The dosing for obese patients is more complex and is discussed in upcoming article on this site, Dosing Induction Agents For Rapid Sequence Intubation. Dosing for obese patients is discussed in detail in the Airway Management book. (2)
The dose of induction agents in the elderly should be reduced to about one-half to three-fourths of the dose that would be used younger, healthier patients. (3)
“Etomidate has become the induction agent of choice for most emergent RSIs because of its rapid onset, its hemodynamic stability, its positive effect on CMRO2 and cerebral perfusion pressure, and its rapid recovery.” (4) Etomidate is an FDA Category C drug in pregnancy.
The usual emergency induction dose is 0.3 mg per kilogram.
The onset is 15 to 45 seconds.
The duration is 3 to 12 minutes.
“In euvolemic and hemodynamically stable patients, the normal induction dose of etomidate is 0.3 mg per kilogram IV push. In compromised patients, the dose should be reduced commensorate with the patient’s clinical status; reduction to 0.2 mg per kilogram is usually sufficient. In morbidly obese patients, the induction dose should be based on lean body weight, by using IBW and adding a correction of 30% of the weight.
Etomidate reversibly blocks an adrenal enzyme that leads to a decrease in serum cortisol and serum aldosterone levels. This effect has generated much controversy about whether or not the drug is appropriate in sepsis. This controversy is well discussed in the Airway book. (5)
“Ketamine is the induction agent of choice for patients with reactive airways disease who require tracheal intubation. Ketamine is an excellent induction agent for patients who are hypovolemic, hypotensive, or hemodynamically unstable, including those with sepsis.” (6)
The usual emergency induction dose is 1.5 mg per killogram.
The onset is 45 to 60 seconds.
The duration is 10 to 30 minutes.
Although emergent hallucinations can occur with ketamine (more commonly in adults than children), they are infrequent in RSI because practically all the patients will receive follow-up sedation after the intubation. (7)
(1) Manual of Emergency Airway Management, 4th ed, 2012. RM Walls and MF Murphy, p 242.
(2) Ibid., p 243 and Chapter 39, The Morbidly Obese Patient, pp 410-417.
(3) Ibid., p 243.
(5) Ibid., pp 249 + 250.
(6) Ibid., p 244
(7) Ibid., p 245