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The Emergency Airway: Three Phases of Airway Management: Machiavellian, Renaissance, and Enlightenment

Braude, Darren MD, EMT-P

doi: 10.1097/01.EEM.0000419518.58349.b6
The Emergency Airway

Dr. Braudeis an associate professor of emergency medicine and anesthesiology and the director of the EMS Fellowship, the Physician Field Response Program, and Airway911 at the University of New Mexico School of Medicine, and the author of Rapid Sequence Intubation and Rapid Sequence Airway, 2nd Edition: An Airway Guide. (See FastLinks.) He is also the associate medical director of the Difficult Airway Course-EMS.





Let's start with some history. A case series on rapid sequence intubation (RSI) in the emergency department by Thompson and colleagues found that 10 percent of their 48 cases required surgical airways. (Ann Emerg Med 1982;11[10]:526.)

That was 30 years ago. I remember watching an anesthesiologist in a Los Angeles trauma center in 1985 struggle with a nasal intubation for 30 minutes, finally emerging victorious but covered in blood, as was the ceiling. Even an anesthesiologist thought this barbaric approach was more appropriate than administering paralytics outside the OR in 1985. When I went through residency in the 1990s, we used RSI routinely though we still had some attendings who would not let the residents push a paralytic until they had first given an induction agent and visualized the cords. Needless to say, we had many cases of aspiration before we all saw the RSI light.

Ron Walls and colleagues in 2011 reported on 8,937 ED airways in which RSI was used in 84 percent of intubations that required medication; overall success was 99 percent, and surgical airways occurred in less than one percent of cases. (J Emerg Med 2011;41[4]:347.) It is now safe to say that emergency medicine as a specialty has conquered the first hurdle: proving that we can administer paralytics in the ED and place a tube in the vast majority of the cases. The weight of evidence, however, demonstrates that a tube placed in the trachea at the cost of hypoxemia, hypo- or hypercarbia, hypotension or other complications has done little for the patient, and perhaps may have been worse than no tube at all, at least if that tube was only placed to ward off aspiration that might never have occurred.

We must move past this Machiavellian phase where we intubate because we can, where the endpoint of a tube through the cords justifies the means. I would argue that the next phase of ED airway management that we are entering is the Renaissance, where we will focus more on the prevention of complications — those surrogate markers of good patient outcome — than on any specific technique or device.

Hypoxemia is potentially very destructive to any patient in the peri-intubation period, particularly for patients at risk for CNS injury. Davis has demonstrated that patients whose oxygen saturation after pre-oxygenation is less than or equal to 93 percent have a high likelihood of desaturation during intubation. (Prehosp Emerg Care 2008;12[1]:46.) It is not a matter of just going quickly through a rote RSI procedure for any such patient and hoping that critical hypoxemia will not occur; instead we must plan ahead and make appropriate modifications. Everyone, please, please, please read the recent article by Scott Weingart and Richard Levitan,“Preoxygenation and Prevention of Desaturation during Emergency Airway Management.” (Ann Emerg Med 2012;59[3]:165.)

The flip side of hypoxemia is hyperoxemia. Remarkably, it may turn out that hyperoxemia is even more damaging than hypoxemia, at least after the initial intubation procedure. New evidence has shown this to be the case for patients with major head trauma and post-cardiac arrest. (J Neurotrauma 2009;26[12]:2217; JAMA 2010;303[21]:2165.) We will likely tease out exactly what oxygen level is most important for which patients, and when, over the next decade. We should get the patient through the intubation itself for now, without critical hypoxemia and then titrate the oxygen down quickly.

Hypocarbia and hypercarbia have been shown to be especially destructive in patients with severe head trauma, one of the most common indications for ED intubation. (J Neurotrauma 2010;27[7]:1233; Crit Care Med 2006;34[4]:1202.)

Hypotension also can be extremely destructive. Many patients hardly notice brief profound hypotension, but patients with cardiovascular and cerebrovascular disease with potential for watershed injury and patients with CNS injury may do quite poorly, even with pressures below 120. (J Trauma Acute Care Surg 2012;72[5]:1135.) We should be able to anticipate which patients are at risk for hypotension from medications and positive pressure ventilation and subsequent poor outcomes, and take appropriate measures to prevent or mitigate the hypotensive episode. This may include delaying the procedure until after fluid resuscitation or initiation of appropriate vasopressors, or the use of bolus dose pressors such as phenylephrine in the peri-intubation period.

One study was able to show that complications including hypoxemia, aspiration, and cardiac arrest all go up as the number of intubation attempts go up for anesthesiologists performing emergency intubations outside the OR. (Anest Analg 2004;99[2]:607.) This will soon be shown to be true for ED intubations as well in an upcoming paper so we should focus on making the first intubation attempt as successful as possible. This will likely entail greater use of video laryngoscopy and more attention to patient positioning.

Perhaps, during our Renaissance, we will see the disappearance of “successful intubation within three attempts” as an appropriate outcome measure in papers or quality assurance programs. Instead we will track success on the first airway attempt without any complications. An intubation that occurs on the first attempt at the cost of hypoxemia in a stroke patient, for example, is considered less successful than an intubation that occurs on the third attempt without any complications.

Hopefully we are not far away from the age of enlightenment when we will have teased out all these little details that affect different patient subgroups and report actual patient outcomes rather than these surrogate markers. We must focus in the meantime on what we do know. The devil is in the details. Be vigilant!

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