ETI associated with improved outcomes?
The association between prehospital ETI and patient outcome is unclear. Most studies entail observational analyses vulnerable to confounding by indication [8, 9]. However, select randomized clincial trials comparing ETI with other airway techniques provide important data and perspectives. Gausche et al. found no differences in survival or neurological outcome between children receiving ETI and those receiving bag‐valve‐mask ventilation (BVM) [10]. Conducted in France and Belgium, the Cardiac Arrest Airway Management (CAAM) trial found no difference in survival between adult out‐of‐hospital cardiac arrests managed with ETI vs. BVM [11]. The AIRWAYS‐2 trial in the United Kingdom found no difference in survival or 30‐day functional outcome between adult out‐of‐hospital cardiac arrest (OHCA) patients receiving ETI vs. i‐gel® [12]. In the United States, the Pragmatic Airway Resuscitation Trial (PART) found improved 72‐hour survival among adult OHCA managed with the laryngeal tube vs. ETI [13].
Are adverse events common during prehospital ETI?
Several studies draw attention to previously unrecognized adverse events associated with prehospital ETI. Successful prehospital airway management strategies have placed strong emphasis on minimizing these and other adverse events. Many of these adverse events have been detected only through enhanced monitoring technology and rigorous airway management review.
Several studies describe complications of prehospital airway management including misplaced or dislodged endotracheal tubes [14–17]. Using continuous EtCO2 has reduced the incidence of the unrecognized misplaced endotracheal tube. Prehospital ETI may distract from other important resuscitation tasks. For example, hyperventilation after successful ETI of cardiac arrest patients can compromise coronary perfusion during CPR chest compressions [18, 19]. Furthermore, conventional ETI efforts may increase CPR “hands‐off” or no‐flow time (pauses in CPR to facilitate endotracheal intubation) compared with other airway devices [20]. Models of high‐performance CPR now teach rescuers to defer airway management in favor of providing uninterupted compressions.
Prehospital intubation has been associated with increased exposure to hypoxia, hypotension, and hypocapnia [21, 22]. Iatrogenic oxygen desaturation or braydcardia is common during intubation attempts [23]. Advanced age, preprocedural hypotension, and hypoxia are associated with peri‐intubation hypotension [24]. Hypoxia and bradycardia may be prevented by continuous monitoring of pulse oxymetry and provision of oxygen during apneia or supplemental ventilation [25, 26]. Postprocedure hypocapnia may be mitigated by flow‐limiting bag ventilation, timing devices for respiration, or mechanical ventilation. EMS medical directors should anticipate these events and promulgate protocols that direct resuscitation prior to intubation and limit exposure to hypotension, hypoxia, and hypocarbia through continuous monitoring and appropriate intervention.
Should EMTs perform ETI?
The prior national EMT curriculum included ETI as an optional module [27]. However, the ability of EMTs to acquire and maintain clinical ETI skills remains unclear. Two independent studies of EMT ETI found suboptimal success rates (<50%) [28, 29]. However, several series describe the ability of basic EMTs to use supraglottic airways (SGA) successfully [30–32]. The current National EMS Education Standards do not list either ETI or SGA as EMT skills; SGA are listed for AEMTs.
Should EMS personnel limit the number of ETI attempts?
Many EMS medical directors emphasize the goal of achieving ETI “first‐pass success.” While many prehospital EMS personnel define an ETI “attempt” as an effort to insert the endotracheal tube, national consensus guidelines suggest that an ETI “attempt” should be defined as an insertion of the laryngoscope blade to maintain consistency with airway management definitions used in other medical disciplines. A substantial portion of prehospital ETI require multiple attempts [33]. Studies of in‐hospital ETI efforts found that multiple ETI attempts were associated with increased risk of cardiac arrest [34]. Given the low probability of success following the second attempt, some EMS medical directors advocate limiting clinicians to two attempts, followed by immediate use of SGA.
Considerations for drug‐facilitated intubation
As with ETI, EMS medical directors and clinicians considering rapid sequence intubation (RSI) must place an emphasis on clinical decision making, not just procedural technique [35]. Drug‐facilitated intubation is an advanced technique that should be practiced by only the most qualified clinicians. The National Association of EMS Physicians has published national consensus standards for drug‐facilitated intubation [35].
RSI results in rapid and complete loss of airway reflexes. The consequence of failed RSI may be a patient who cannot be intubated or ventilated, with ensuing cardiac arrest. EMS personnel, including EMS physicians, performing prehospital RSI must possess exceptional ETI skills. EMS agencies that enable RSI must use monitors capable of continuous physiological monitoring, including cardiac rhythm, heart rate, blood pressure, pulse oximetry, and waveform capnography. These measures are important to warn of physiological decompensation such as hypercapnia, oxygen desaturation, and bradycardia. Finally, there must be a plan and appropriate preparation for those times when RSI fails, including a rescue airway.
Intensive continuing training is essential for maintaining a prehospital RSI program. Some EMS medical directors require that paramedics perform at least 12 ETIs annually, either on prehospital or in‐hospital (emergency department or operating room) patients [36]. Others have integrated human simulator‐based training to provide experience with managing difficult airway scenarios [37]. Video review of airways is one method of supplementing high‐fidelity simulation to demonstrate the range of anatomic differences and technical complications that may occur during RSI. The requirement for live ETI training remains controversial, with some proponents citing the value of live airway experience and opponents citing the absence of supporting data [35].
Rapid sequence airway (RSA) is a modification of RSI that replaces ETI with placement of an SGA [38]. RSI is difficult because of the need to rapidly accomplish tracheal intubation after the administration of paralytics. The appeal of RSA is that SGA insertion is simpler and contains fewer pitfalls than ETI. RSA case reports have demonstrated the feasibility of this approach. In a simulation study, when compared to RSI, RSA reduced time to airway placement and reduced hypoxia episodes [39]. When examined in an air medical system, however, no difference was detected between the two techniques [40]. However, for EMS agencies using traditional RSI, RSA may provide an important alternate option in the face of an anticipated or unanticipated difficult airway.
Sedation‐assisted intubation with a sedative agent only, without a concurrent neuromuscular blocking agent, is discouraged [35, 41–45]. Adverse events associated with RSI (e.g., iatrogenic oxygen desaturation and bradycardia) may be at least as likely with sedation‐assisted ETI [23, 46]. Sedation‐assisted intubation with etomidate has been demonstrated to have lower success rates when compared to RSI [47]. While etomidate results in more profound sedation than benzodiazepines, a formal comparison of etomidate with midazolam for prehospital sedation‐assisted intubation identified similar ETI success rates [43]. Ketamine has been described for prehospital sedation‐assisted intubation, but high‐level evidence is lacking.
Combinations of benzodiazepines and opiates to facilitate endotracheal intubation (e.g., combinations of diazepam, morphine, or other agents) are particularly unsafe since the single or combination use of these agents has rather slow onset and unpredictable sedative effects. These agents also have the strong potential for causing hypotension. The system‐level measures necessary to ensure airway management quality with sedation‐assisted intubation are essentially equal to those required for RSI programs.
Considerations
