Evidence-Based EMS: Endotracheal Intubation

From the authors: Welcome to Evidence-Based EMS, a new bi-monthly series that reviews current evidence-based articles to address compelling questions about prehospital medical care. This series began as a learning exercise for our emergency medicine residents during their EMS rotation to comprehend the complicated nature of prehospital medicine and evolved into an in-depth review that has led to engaging conversation between our faculty, residents and prehospital providers, reinforcing that what is done in the prehospital arena impacts our patient’s healthcare course in the hospital and beyond. It is our hope that this column will evoke active conversation within your EMS system and foster innovative ideas to advance the field of prehospital medicine. 

It’s 2:30 on an unusually quiet Saturday morning. You are dispatched for a pedestrian injured in a motor vehicle accident. On arrival you find your patient, a 20-year-old male covered in blood with two obviously deformed legs. Your initial assessment finds him unresponsive and covered in alcohol-scented emesis. He is difficult to arouse and only moans with a vigorous sternal rub.

Just as you start to think his airway is somewhat clear, the patient begins to vomit. You and your partner roll him on his left side, maintaining c-spine precautions, and find his pulse oximeter reads 82%. You grab the airway kit and try to bag the patient, but he vomits on the both of you. You now realize this patient needs a more secure airway.

At this point should you intubate? You quickly recall a couple of articles you just read that can help you make the best decision.

Current Evidence

Prehospital endotracheal intubation (ETI) is an area that can be controversial but is highly researched. A recent study using data from 40 states demonstrated an overall prehospital ETI success rate of 85.3%, an improvement from the rate of 77% previously reported by Henry Wang, et al.^1,2 But for a life-or-death procedure that requires absolute success, why are the success rates so variable and/or low?

Prehospital ETI is fraught with risk and failure. It has many obstacles not encountered in the hospital setting, such as small spaces, poor lighting and fewer available staff to provide expertise and assistance.³ Furthermore, a study in the early 2000s that scrutinized the safety of prehospital ETI demonstrated a 57% success rate with pediatric ETI and showed no neurological benefit over bag-valve mask (BVM) ventilation.⁴

Before jumping to any conclusions, though, let’s explore prehospital ETI further in regards to cardiac arrest, trauma, rapid sequence intubation and paramedic education.

Cardiac arrest—Concerning out-of-hospital cardiopulmonary arrest, some research has challenged the practice of early intubation. One study evaluated prehospital ETI at a level 1 trauma center and found a failure rate of 31% with no improvement in mortality with successful intubation, resulting in a recommendation that BVM in the prehospital setting is an adequate airway.⁵ However, on secondary analysis, the authors did find that prehospital ETI led to improved outcomes when compared to supraglottic airways (SGAs).

Another study reviewing the Cardiac Arrest Registry to Enhance Survival (CARES) suggested that using no advanced airway led to better outcomes than using either ETI or SGA.⁶ Furthermore, a nationwide study in Japan had similar results, suggesting that advanced airway management leads to worse neurological outcomes.⁷ However, this study did not limit cardiac arrest to a cardiac etiology (i.e., it included trauma, stroke, etc.), and significantly fewer subjects had prehospital ETI attempted compared to U.S. studies.⁶

Of note, both the Japanese and CARES studies were susceptible to unmeasured confounders.^6,8 For example, did patients requiring ETI have a worse initial prognosis compared to those managed with just BVM? Did the skill level of the provider who performed the intubation affect the outcome? Were there any anatomical or patient characteristics that discouraged the use of ETI? These factors, in addition to several other variables, may have affected the results but were not controlled for in these studies.^6,8

Trauma—Prehospital ETI in trauma research has generally been broad and contradictory. For example, one study revealed an association of prehospital ETI with worse hypotension and subsequent risk of death in trauma patients of similar age and injury severity.⁹ Worse yet, another demonstrated that prehospital ETI, when used as the only advanced airway, was associated with worsened 28-day mortality in patients with hemorrhagic shock.¹⁰

In both studies poor outcomes were attributed to underlying hypotension caused by acute blood loss compounded by rapid sequence intubation (RSI) medications and mechanics of ventilation decreasing venous return.^9,10 However, contrary to the these studies, a review of a trauma database found that in patients with a Glasgow Coma Scale score of less than 8, prehospital ETI was associated with improved mortality.¹¹ In addition, another review found that rescuer procedural experience was not linked to survival outcome in prehospital ETI.¹² The U.S. study on prehospital ETI involving 40 states found that intubation in non-arrest trauma was successful more often than with non-arrest medical and cardiac arrest patients.¹

In general, the current data regarding prehospital ETI and trauma is diverse, with variables including the type of trauma, degree of paramedic training and how outcomes are defined.

RSI—RSI in the prehospital setting has to be weighed in terms of the benefit of a more relaxed patient for ETI versus the risk of paralyzing a patient and possibility of losing the airway. Older data suggested that prehospital RSI was associated with longer on-scene times and neurological outcomes that were unimproved if not worse.^1,13 Contrary to that belief, though, evidence from more recent years suggests that with proper training and supervision, paramedics performing prehospital ETI have had excellent outcomes. Notably, a prospective randomized controlled trial in Australia demonstrated that prehospital ETI by critical care-trained paramedics improved survival rates and functional outcomes versus delayed intubation in the ED.¹⁴

Paramedic training—The current evidence suggests that increased experience with ETI attempts leads to more successful intubations. Notwithstanding, a paramedic needs to perform five intubations for independent practice in the United States.^17–19 While some results have shown that prehospital ETI success isn’t totally dependent on experience, national data from local EMS services reported to state authorities showed a prehospital ETI success rate of 77%.² A review of paramedic programs found the median number of intubations by students was seven and that 20–25 ETIs are needed for a success rate above 90%.¹⁸

Despite this data, there are regions where EMS providers only perform one ETI a year.² However, in EMS systems like the Seattle Fire Department’s, paramedics require 2,200 hours of didactic, lab and field experience for certification. Their training includes ETI performed on manikins, then in the OR with anesthesiologists, and lastly in the field with senior paramedic supervision under orders from medical control. A total of 12 intubations are required a year, RSI can be used with supervision, and their success rate has been 88%–97%.^17,19 Additionally, a review of a multistate air-transport EMS team reported a prehospital ETI success rate of 96.6% and no deaths from loss of an airway.²⁰

Of note, the results were similar when isolated to just pediatric patients.²¹ These crews consist of paramedics and nurses who have an average of 12 years’ experience, are rigorously trained in RSI protocols, and perform approximately 25 intubations a year with prehospital ETI and simulation combined.

Bottom Line

It is imperative to remember that the best airway is the one that is ventilating and oxygenating the patient, and that more advanced techniques can be attempted if and when they are indicated. The paramedic and/or medical director must have a respect for the nuances of airway management, and a conservative approach is warranted. However, despite the risks and complications associated with prehospital intubation, the absence or sudden loss of an airway will lead to imminent death if no other option is available.

At this time literature suggests that more training is correlated with greater ETI success in paramedics.^14–22 Thus, improving skills should be the goal. Remember, anybody can learn to intubate a patient. However, it’s your ability to know when and when not to intubate that makes you a prehospital medical professional. Use the most appropriate airway, respect the procedure and know your limitations.

References

_{1. Diggs LA, Yusuf JE, De Leo G. An update on out-of-hospital airway management practices in the United States. Resuscitation, 2014 Jul; 85(7): 885-92.} 

_{2. Wang HE, Mann NC, Mears G, Jacobson K, Yealy D. Out-of-hospital airway management in the United States. Resuscitation, 2011; 82: 378–85.} 

_{3. Gaither JB, Spaite DW, Stolz U, Ennis J, Mosier J, Sakles JJ. Prevalence of difficult airway predictors in cases of failed prehospital endotracheal intubation. J Emerg Med, 2014 Sep; 47(3): 294–300.}

_{4. Gausche M, Lewis RJ, Stratton SJ, et al. Effect of out-of-hospital pediatric endotracheal intubation on survival and neurological outcome: a controlled clinical trial. JAMA, 2000 Feb 9; 283(6): 783–90.}

_{5. Wang HE, Szydlo D, Stouffer JA, et al; ROC Investigators. Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest. Resuscitation, 2012 Sep; 83(9): 1,061–6.}

_{6. McMullan J, Gerecht R, Bonomo J, Robb R, McNally B, Donnelly J, Wang HE; CARES Surveillance Group. Airway management and out-of-hospital cardiac arrest outcome in the CARES registry. Resuscitation, 2014 May; 85(5): 617–22.}

_{7. Hasegawa K, Hiraide A, Chang Y, Brown DF. Association of prehospital advanced airway management with neurologic outcome and survival in patients with out-of-hospital cardiac arrest. JAMA, 2013 Jan 16; 309(3): 257–66.}

_{8. Wang HE, Yealy DM. Managing the airway during cardiac arrest. JAMA, 2013 Jan 16; 309(3): 285–6.}

_{9. Shafi S, Gentilello L. Pre-hospital endotracheal intubation and positive pressure ventilation is associated with hypotension and decreased survival in hypovolemic trauma patients: an analysis of the National Trauma Data Bank. J Trauma, 2005 Nov; 59(5): 1,140–5, discussion 1,145–7.}

_{10. Wang HE, Brown SP, MacDonald RD, et al. Association of out-of-hospital advanced airway management with outcomes after traumatic brain injury and hemorrhagic shock in the ROC hypertonic saline trial. Emerg Med J, 2014 Mar; 31(3): 186–91.}

_{11. Davis DP, Koprowicz KM, Newgard CD, Daya M, Bulger EM, Stiell I, et al. The relationship between out-of-hospital airway management and outcome among trauma patients with Glasgow coma scale scores of 8 or less. Prehosp Emerg Care, 2011; 15: 184–92.}

_{12. Wang HE, Balasubramani GK, Cook LJ, Lave JR, Yealy DM. Out-of-hospital endotracheal intubation experience and patient outcomes. Ann Emerg Med, 2010 Jun; 55(6): 527–37.}

_{13. Davis DP, Hoyt DB, Ochs M, et al. The effect of paramedic rapid sequence intubation on outcome in patients with severe traumatic brain injury. J Trauma, 2003 Mar; 54(3): 444–53.}

_{14. Bernard SA, Nguyen V, Cameron P, et al. Prehospital rapid sequence intubation improves functional outcome for patients with severe traumatic brain injury: a randomized controlled trial. Ann Surg, 2010 Dec; 252(6): 959–65.}

_{15. Fakhry SM, Scanlon JM, Robinson L, et al. Prehospital rapid sequence intubation for head trauma: conditions for a successful program. J Trauma, 2006 May; 60(5): 997–1,001.}

_{16. Prekker ME, Kwok H, Shin J, Carlbom D, Grabinsky A, Rea TD. The process of prehospital airway management: challenges and solutions during paramedic endotracheal intubation. Crit Care Med, 2014 Jun; 42(6): 1,372–8.}

_{17. Warner KJ, Sharar SR, Copass MK, Bulger EM. Prehospital management of the difficult airway: A prospective cohort study. J Emerg Med, 2009; 36: 257–65.}

_{18. Wang HE, Seitz SR, Hostler D, Yealy DM. Defining the learning curve for paramedic student endotracheal intubation. Prehosp Emerg Care, 2005; 9: 156–62.}

_{19. Warner KJ, Carlbom D, Cooke CR, Bulger EM, Copass MK, Sharar SR. Paramedic training for proficient prehospital endotracheal intubation. Prehosp Emerg Care, 2010 Jan-Mar; 14(1): 103–8.}

_{20. Brown CA 3rd, Cox K, Hurwitz S, Walls RM. 4,871 Emergency Airway Encounters by Air Medical Providers: A Report of the Air Transport Emergency Airway Management (NEAR VI: “A-TEAM”) Project. West J Emerg Med, 2014 Mar;1 5(2): 188–93.}

_{21. Tollefsen WW, Brown CA 3rd, Cox KL, Walls RM. Two hundred sixty pediatric emergency airway encounters by air transport personnel: a report of the air transport emergency airway management (NEAR VI: “A-TEAM”) project. Pediatr Emerg Care, 2013 Sep; 29(9): 963–8.}

_{22. ACGME. Emergency Medicine Guidelines, guidelines for procedures and resuscitation, www.acgme.org.}

Hawnwan Philip Moy, MD, is an assistant medical director of the Saint Louis City Fire Department, emergency medicine clinical instructor and core faculty of the EMS Section of the Division of Emergency Medicine at Washington University in Saint Louis, MO. He completed his emergency medicine residency at Barnes Jewish Hospital/Washington University in Saint Louis and his EMS fellowship at the University of North Carolina in Chapel Hill.  

Aldo Andino, MD, is a second year emergency medicine resident physician at Washington University in St. Louis, and a graduate of The University of Texas Medical School at Houston. His professional interests include medical public relations, disaster preparedness and tactical EMS.