After the completion of this procedure, the patient can be paralyzed and intubated. Just as in a procedural sedation, we want patients to be calm but still spontaneously breathing and protecting their airway.

The ideal agent for this use is ketamine. This medication will not blunt patient respirations or airway reflexes. In addition, ketamine provides a dissociative state, allowing the application of preoxygenation.³

A ketamine dose of 1.0-1.5 mg/kg ­administered by slow intravenous push will produce a calmed patient within approximately 45 seconds.

Preoxygenation can then proceed in a safe, controlled fashion. This can be accomplished with an NRB, or preferably in a patient exhibiting shunt, by the use of a noninvasive mask hooked up to ventilator with a continuous positive airway pressure (CPAP) setting of 5-15 cm H2O.

After a saturation of greater than 95% is achieved, the patient is allowed to breathe the high FiO2 (fraction of inspired oxygen) oxygen for an additional 2-3 minutes in order to achieve adequate denitrogenation. A paralytic is then administered, and following the 45- to 60-second apneic period, the patient can be intubated.

In patients who have high blood pressure or tachycardia, the sympatho­mimetic effects of ketamine may be undesirable.

While these effects can be blunted with small doses of benzodiazepine and labetalol,³ a preferable sedation agent is available for these hypertensive or tachycardic patients. Dexmedetomidine is an alpha-2 agonist that provides sedation without any blunting of the respiratory drive or ­airway reflexes.^4,5

A dexmedetomidine dose of 1 mcg/kg administered to the patient over a period of 10 minutes will lead to a ­sedated patient who will accept preoxgenation after 3-5 minutes in a majority of cases.

Another advantage of this medication is that, after the sedative agent is administered and the patient is placed on noninvasive ventilation, frequently the respiratory parameters improve so dramatically that intubation can be avoided.

In these cases, we then allow the sedative to wear off, and we reassess the patient’s mental status and work of breathing.

If we deem that intubation is still necessary at this point, we can proceed with standard RSI by administering a conventional sedation agent (such as etomidate or additional ketamine) in combination with a paralytic, because the patient has already been appropriately preoxygenated.

A video demonstrating these concepts is available online at http://blog.emcrit.org/misc/preox.