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The Success of Emergency Endotracheal Intubation in Trauma Patients: A 10-Year Experience at a Major Adult Trauma Referral Center

Stephens, Christopher T. MD; Kahntroff, Stephanie MD; Dutton, Richard P. MD, MBA

doi: 10.1213/ane.0b013e3181ad87b0
Critical Care and Trauma: Research Reports
Chinese Language Editions

BACKGROUND: Emergency airway management is a required skill for many anesthesiologists. We studied 10 yr of experience at a Level 1 trauma center to determine the outcomes of tracheal intubation attempts within the first 24 h of admission.

METHODS: We examined Trauma Registry, quality management, and billing system records from July 1996 to June 2006 to determine the number of patients requiring intubation within 1 h of hospital arrival and to estimate the number requiring intubation with the first 24 h. We reviewed the medical record of each patient in either cohort who underwent a surgical airway access procedure (tracheotomy or cricothyrotomy) to determine the presenting characteristics of the patients and the reason they could not be orally or nasally intubated.

RESULTS: All intubation attempts were supervised by an anesthesiologist experienced in trauma patient care. Rapid sequence intubation with direct laryngoscopy was the standard approach throughout the study period. During the first hour after admission, 6088 patients required intubation, of whom 21 (0.3%) received a surgical airway. During the first 24 h, 10 more patients, for a total of 31, received a surgical airway, during approximately 32,000 attempts (0.1%). Unanticipated difficult upper airway anatomy was the leading reason for a surgical airway. Four of the 31 patients died of their injuries but none as the result of failed intubation.

CONCLUSIONS: In the hands of experienced anesthesiologists, rapid sequence intubation followed by direct laryngoscopy is a remarkably effective approach to emergency airway management. An algorithm designed around this approach can achieve very high levels of success.

From the Division of Trauma Anesthesiology, Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland.

Accepted for publication March 30, 2009.

Address correspondence and reprint requests to Richard P. Dutton, MD, MBA, Division of Trauma Anesthesiology, University of Maryland Medical System, 22 South Greene St., Baltimore, MD 21201. Address e-mail to rdutton@anes.umm.edu.

Hemodynamic instability, time pressure, lack of patient cooperation, risk of aspiration, the need for cervical spine protection, and facial injuries all contribute to the difficulty of airway management in trauma patients. The past decades have seen the development and promulgation of standard techniques (especially the American Society of Anesthesiologists’ difficult airway algorithm1), new “rescue” devices, such as the laryngeal mask airway (LMA), and a gradual shift in the United States away from anesthesiologists and toward emergency medicine physicians as the primary airway managers in the emergency department (ED). Published reports suggest a high level of success with emergency intubation, but few studies have examined a large series of patients and none in recent years.

Endotracheal intubation is considered definitive airway management in the trauma patient,1 because it allows for deep sedation and analgesia, controlled mechanical ventilation, and protection of the airway from aspiration. A review of the literature suggests that anesthetized rapid sequence intubation (RSI) is the most common method of securing the airway.2–8 This method has been shown to result in higher rates of success in first-pass attempts, speed of placement, and fewer complications. Before 1990, trauma patients were intubated by medics in the field and in transport, by surgeons and generalist physicians in the ED, or by anesthesia providers summoned to the ED. Pharmacologic options and technology for rescuing a lost airway were limited. Rapid sequence approaches were used but led to a relatively high surgical airway rate. Harrison et al.9 reported the need for a surgical airway in 2% (6 of 302) of patients intubated during prehospital transport. In the past 2 decades, there have been substantial changes in airway management equipment. The use of intubating stylets has become more common, and rescue devices, such as the Combitube™ (Tyco-Kendall, Mansfield, MA) and the LMA™ (Vitaid, Toronto, Ontario, Canada), are now available.

The development of Emergency Medicine as a recognized specialty has meant that most emergency airway management in the United States now occurs without the involvement of an anesthesiologist. A recent study evaluated the need for a surgical airway with the use of a defined airway algorithm in a Level 1 trauma center, where emergency physicians are primarily responsible for airway management.10 This study reported a surgical airway rate of 2.6% and a complication rate of 9.8%. A European study of “anesthesia-trained” prehospital providers documented a failure rate (surgical airway) of 3.9% in a population of trauma patients.10,11

We undertook a retrospective review of emergency airway management at our center to establish our current success rate and identify risk factors associated with difficult airway management. We describe the management algorithm used, the overall success rate, and the factors associated with the need for a surgical airway.

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METHODS

With the approval of the IRB, we conducted a retrospective review of all patients who underwent attempted intubation within 24 h of arrival between July 1, 1996, and June 30, 2006, a period of 10 yr. We chose to focus on the first hour of care to capture those patients intubated on an emergent basis. We excluded patients transferred from other hospitals, many of whom were already intubated. We also examined outcomes in the broader group of patients intubated within the first 24 h after admission, on the assumption that, although less time pressured, these cases would still require the elements of an emergent RSI, including cricoid pressure and manual in-line cervical stabilization.

The R Adams Cowley Shock Trauma Center (STC) of the University of Maryland Medical System, located in downtown Baltimore, is the primary adult resource center for trauma in the state of Maryland and annually receives more than 5500 primary admissions and another 1000 patients transferred from other hospitals with critical injuries. Patients arriving at the STC are assessed by a multidisciplinary team. Initial airway assessment and management is the responsibility of the attending anesthesiologist, a trauma specialist, who is typically supervising one or more residents (anesthesia or emergency medicine).

The emergency airway management algorithm in use at the STC for the period of study is shown in Figure 1.12 This is a simplification of the standard American Society of Anesthesiologists algorithm1 adopted for use in this specialized setting, where the option to reverse the anesthetic and awaken the patient is seldom practical. This algorithm is followed at the discretion of the attending anesthesiologist, in accordance with the circumstances of the case. Intermittent positive pressure ventilation via facemask is used to support the patient if desaturation occurs, and cricoid pressure and in-line cervical stabilization may be relaxed if they are preventing successful intubation. Failure in three attempts at direct laryngoscopy leads to preparations for a surgical airway and an attempt to manage the situation with placement of a LMA, with continued cricoid pressure. If LMA placement allows acceptable oxygenation and ventilation, then a variety of options are available at the discretion of the anesthesiologist. These include renewed attempts at intubation with different equipment or positioning, fiberoptic intubation through the LMA, or a surgical airway under semicontrolled conditions (cricothyrotomy or tracheotomy). If LMA placement is not successful, then a cricothyrotomy or tracheotomy is performed immediately by the surgical team.

Figure 1

Figure 1

Trauma anesthesiology billing records, quality management (QM) records, and the Trauma Registry database were used to identify patients who underwent emergency airway management during the study period. Maintenance of a Trauma Registry is a requirement for certification as a trauma center in the United States. Data are entered during daily review of each patient’s records by a specialty-trained and certified group of registrars (who also enter billing information), and information is periodically updated and reviewed by supervisors, before our reporting it to the state Trauma System. The quality of Registry data is audited internally, and again by the state certifying authority, as part of the trauma center designation process. Billing records are similarly scrutinized by both insurers and the state rate-setting commission. Billing records were used to approximate the number of patients intubated within 24 h of admission. Because electronic billing records could not identify patients presenting to the operating room (OR) for general anesthesia who had a definitive airway already in place, this number is necessarily an estimate. Trauma Registry and anesthesia QM records were then used to identify all patients who had a cricothyrotomy or tracheotomy performed within 24 h of admission. These medical records were reviewed in detail. Figures 2a–c show the distribution of patients under study. Nine patients were intubated successfully (three within 1 h and an additional six within 24 h), but then underwent tracheotomy for long-term management of severe facial injuries or brain trauma. These patients were considered “successful” airway management cases and were excluded from further analysis.

Figure 2

Figure 2

Computerized medical records, paper records, and QM files were reviewed to elicit more detailed information regarding each case. These data included the mechanism of injury, the indication for intubation, the cause of difficulties, and the patient’s ultimate outcome. Need for a surgical airway was a designated QM indicator throughout the study period, meaning that each of these cases was reviewed by an uninvolved anesthesia provider and discussed by the Divisional Quality Management (QM) Committee. Minutes of these discussions were available for review. All surgical airway cases identified had original medical records and most had available QM documentation. We also examined all QM records during this decade for evidence of morbidities associated with emergency intubation that did not result in a surgical airway: specifically, worsened neurologic injury or evidence of anoxic injury.

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RESULTS

Approximately 32,000 trauma patients required intubation within 24 h of admission during the study period. Of the 6088 patients in whom intubation was attempted within 1 h, 6008 received orotracheal airways, 59 received nasotracheal airways, and 21 received surgical airways. Of the 21 emergency surgical airways, 17 were cricothyrotomies and 4 were tracheotomies (Fig. 2b). The rate of surgical airway access in emergencies was 0.3%. For patients requiring airway management between 1 and 24 h of admission, there were 10 additional surgical airways placed in approximately 26,000 attempts (estimated from OR billing records as described above), for a surgical airway rate of approximately 0.04% in these less urgent cases. The 31 patients receiving surgical airways within 24 h of admission are enumerated in Table 1. The study methodology did not permit us to identify how often an intubating stylet (gum elastic bougie) was used to facilitate intubation (anecdotally, this is common) or an LMA was placed and then followed by successful oral intubation (a rare event).

Table 1

Table 1

Overall this cohort included 26 men and 5 women, which is consistent with the demographics of trauma patients. Seven different mechanisms of injury were identified in this cohort: gunshot wound, motorcycle collision, motor vehicle collision, chemical explosion, pedestrian struck, fall from a height, and struck by a falling object. The average age was 44.7 yr (range, 18–86 yr). In the 25 patients for whom an admission Glasgow Coma Scale score was available, the median score was 13 (range, 3–15). The majority of patients were suffering from severe, multisystem injury.

Five different causes for failed endotracheal intubation were identified: foreign material in the pharynx or larynx, direct injury to the head or neck with loss of normal upper airway anatomy and airway edema, a pharyngeal mass, laryngospasm, and difficult premorbid anatomy. The distribution of causes is shown in Figure 3. Emesis, blood, and broken teeth were the identified foreign materials preventing intubation. Three patients had disruption of airway anatomy because of gunshot wounds to the face or neck; one patient who was a pedestrian struck by a motor vehicle had massive facial distortion. Edema preventing intubation was at the supraglottic, laryngeal, or subglottic level and was the result of airway burns, facial fractures, or chemical toxicity. “Anatomic variation” was noted as the primary cause of difficulty in patients who were found to have difficult laryngoscopic views without obvious injury to the head or neck. This category included variations such as obesity, limited mouth opening, short thyromental distance, limited neck mobility, and anterior larynx. In five of these cases, no specific variation was noted, and the inability to visualize the larynx was described as “surprising” by the attending anesthesiologist.

Figure 3

Figure 3

Remarkably, 87% (27/31) of the patients requiring a surgical airway survived to hospital discharge, and none of the four deaths appeared to be the primary result of failed airway management. Two of the four deaths had already suffered cardiac arrest at the scene of injury, with subsequent transient recovery of circulation but ongoing hemodynamic instability, and one other was brought to the trauma resuscitation unit in full arrest. These three patients were all judged by the QM review process to have died of exsanguinating hemorrhage that was not preventable, although an exacerbating effect of hypoxia cannot be excluded. The fourth death occurred 3 days after admission in a patient who sustained a gunshot wound to the face resulting in a carotid artery dissection and middle cerebral artery stroke.

A review of QM records revealed only one patient with the suggestion of exacerbation of an occult cervical spine injury during intubation, although focused review of this case suggested that the neurologic deficit identified after intubation may have been present earlier, but inadequately documented. No new changes in neurologic status as the result of hypoxia during intubation efforts were identified, although the impact of transient hypoxia on patients with traumatic brain injury cannot be excluded. No patients died of a hypoxic cardiac arrest during airway management efforts.

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DISCUSSION

Risk factors for poor outcome from airway management include the potential for aspiration of gastric contents, exacerbation of occult cervical spine injuries, hemodynamic instability, and traumatic brain injury. This retrospective study describes outcomes of emergency airway management in a group of 32,000 adult trauma patients during the decade from July, 1996, to June, 2006. All patients were managed using a standard protocol adapted directly from the American Society of Anesthesiologists’ Difficult Airway algorithm,1,12 and all airway management occurred under the direction of an anesthesiologist with specialty expertise in trauma. Our aim was to review our experience with emergency airway management in trauma patients, to assess the effectiveness of the protocol used, and to categorize our “failed” efforts in an attempt to better predict potentially difficult airways.

One limitation of our study is its retrospective nature. Although we were able to examine medical records of the patients who required surgical airways, we could not individually review all 57,000 admissions during this time period. We were thus forced to estimate the number of patients requiring intubation within 24 h of admission from OR billing records. Emergency intubations performed in the Trauma Resuscitation Unit are billed separately, with a specific time recorded in the Trauma Registry, and thus could be exactly counted. It was not possible for us to retrospectively determine intrinsic details of the successful intubations, including number of attempts, number of operators, equipment used, and lowest oxygen saturation. This detail would have allowed a closer analysis. It is possible that some of the patients in this series should have received a surgical airway sooner, for example, to mitigate the effects of hypoxia or hypercarbia on traumatic brain injury. It was also not possible to assess the contribution of micro- or macroaspiration on the development of subsequent respiratory distress in a population of patients with many risk factors for respiratory failure, including premorbid conditions, prehospital aspiration, traumatic brain injury, acute and chronic intoxication, hemorrhagic shock, transfusion, long bone fractures, and direct pulmonary injury.

Another limitation is the data collected on the need for a surgical airway. Although we can identify the causes with reasonable accuracy, because of the contemporaneous QM review of these high-profile cases, we cannot identify how often similar patients were managed successfully. We are unable to assess the specific impact of “attending discretion” in avoiding or mitigating difficult airway management. It is likely that some patients with observable risk factors for difficult intubation were managed differently than routine patients: earlier hands-on involvement of the attending anesthesiologist is one possibility; another might be the decision to use an awake fiberoptic approach in cooperative patients. This is one area in which the involvement of anesthesiologists, as opposed to emergency medicine physicians, may have played an important role.

Our success in emergent airway management (99.7%) compares favorably with previously published series. In a consensus paper from the Eastern Association for the Surgery of Trauma, Dunham et al.13 describe an overall failure to intubate with RSI in trauma centers to be 1.7% in a population of 943 patients. A review of other literature reports surgical airway rates ranging from 0.3% to 5.6% at major Level 1 trauma centers. Of these studies, the majority of institutions report a failed intubation rate of 1%–2%.14–24

Although premorbid anatomic variations were the leading cause of failed oral intubation in our series, head and neck injuries were also an important risk factor. Thirteen of our 31 patients who required surgical airways had injuries involving the head, face, neck, upper chest, or a combination. This is consistent with prior studies of emergency airway management in which many of the difficulties encountered were in patients with trauma to the face or neck. The cited report by Dunham et al.13 describes the evidence base supporting techniques for emergency intubation in trauma patients. The group reported that many patients with severe neck injury required immediate airway intervention secondary to cervical hematomas and laryngotracheal injury. Fourteen percent (3 of 21) of our failed emergency intubation group had a significant neck injury.

This retrospective survey, the largest reported, confirms an overall high rate of success in emergency airway management. Although secondary effects of hypoxia could not be assessed in this review, the fact that no patients died of acute hypoxia is encouraging. Having intubations supervised by a small group of specialist anesthesiologists is likely beneficial, as is the immediate presence of surgical support when difficulties arise. Others have reported that training is important to increase the percentage of successful airway placements.25,26 One previous study reported on senior Emergency Medicine residents rotating as the trauma airway manager for 2 mo in addition to OR training throughout their residency, with a combined experience of 70–80 intubations.6 This is comparable with the 50–80 intubations, many urgent, that an average resident performs in 1 mo in our practice. We believe that this level of experience and training contributes strongly to good outcomes.

Using a small selection of adjunctive technologies, only the intubating stylet (bougie) and the LMA keeps our protocol simple and allows for practice and familiarity for all providers. Although many other adjunctive devices have been recommended for emergency airway management, it is likely that practice and experience are important when using the device in an emergency.27 It is possible that the video laryngoscope (Glidescope®, Verathon, Bothell, WA), which has entered our practice in the past year, will further improve our experience, or that simulator training, now routine at our site, will improve performance in emergencies.

In summary, it is possible to achieve a high rate of success in emergency airway management. The need for a surgical airway in our practice is primarily the result of premorbid anatomic variation, although trauma to the face or neck also contributes. The cornerstones of effective airway management in our series were a simple protocol based on rapid sequence induction of anesthesia, judicious use of selected adjunctive devices, and an experienced anesthesia faculty present at each admission.

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