Discussing: “Preoxygenation, Reoxygenation, and Delayed Sequence Intubation in the Emergency Department” (Weingart SD, J Emerg Med. 2010 Apr 7)
- Patients requiring intubation should be classified by oxygenation saturation as low risk, high risk and apneic.
- Reservoir face masks with oxygen set at the highest rate possible are the recommended sources of high FiO2 during preoxygenation.
- All patients, if possible, should be intubated with the head-elevated position to increase safe apnea time.
- Consider using CPAP masks, noninvasive positive pressure ventilation or PEEP valves on a bag-valve mask in patients who cannot achieve oxygen saturations greater than 93%-95%
- Rocuronium may provide a longer duration of a safe apneic period in patients with a high risk of desaturation.
- A nasal cannula set at 15 L/minute is effective at providing oxygenation during the apneic period.
Intubation is a vital procedure to the Emergency Physician. Yet there is more to it than just placing an endotracheal tube. There is the setup, positioning, oxygenation, sedation, checking tube placement, and more. On top of this, there is the underlying illness to consider. The truth is, the majority of patients intubated in the Emergency Department (ED) are sick. Something is very physiologically wrong, and they are not maintaining adequate oxygenation. It becomes your job to do this for them. The authors in this article did an extensive literature review on pre-intubation and peri-intubation techniques which reduce the risk of hypoxia in the adult patient requiring intubation in the ED.
The authors developed a risk-stratification approach based on patients’ pre-intubation oxygen saturation and the risk of desaturation according to the oxyhemoglobin dissociation curve. They determined that those with oxygen saturations greater than 95% are low risk, those with oxygen saturations between 91%-95% are high risk, and those with oxygen saturations of 90% or less are considered hypoxemic. That is to say, high risk and hypoxemic patients are very likely to rapidly reach critical levels of oxygen saturation (<70%) during intubation if no support is provided.
In order to support a patient, pre-oxygenation and oxygenation during the apneic period should be maximized. Begin by placing the low risk patient on a reservoir face mask with oxygen set at the highest rate possible, ie a non-rebreather face mask set at 15 L/minute. In patients with adequate respiratory drive, pre-oxygenation should last for 3 minutes or 8 breaths with maximum inhalation and exhalation. For the high risk patients consider using, and the apneic patients use CPAP masks, noninvasive positive pressure ventilation or PEEP valves on a bag-valve mask device to achieve >93%-95% oxygen saturation. For further support, be sure to place patients in a head-elevated position. For spinal injury patients, place them in reverse Trendelenburg. By using head-elevation, a safe oxygen saturation level can be maintained for roughly 100 seconds longer than placing the patient supine.
During the apneic period, all patients should be placed on nasal cannula at 15L/minute. This allows for apneic oxygenation. In optimal conditions (which do not usually exist in the ED), a PaO2 can be maintained at greater than 100 mm Hg for up to 100 minutes! Do not remove the nasal cannula until after successful intubation.
Finally, the authors noted that rocuronium may increase the safe apneic period by over 100 seconds versus succinylcholine.
Level of Evidence:
Given that this was an extensive review article that looked at the many aspects of pre-oxygenation, there is not a categorical level of evidence for this.
The biggest surprises of this article are:
- A nonrebreather face mask is effective for the majority of patients than bag-valve mask ventilation for pre-oxygenation.
- Nasal cannula oxgenation should be maintained throughout the entire procedure.
- All patients with an O2 saturation <90%, should be placed on CPAP masks, noninvasive positive pressure ventilation or PEEP valves on a bag-valve mask device.
Relevant sources and useful links: