Prehospital Rapid Sequence Intubation

The use of rapid-sequence intubation (RSI) in the prehospital setting has now been researched for almost 20 years. Early data pointed toward success, but outcome research released over the last few years has called this into question. Despite this, there has been increased use of the procedure.1 As EMS systems review their airway protocols, future protocols should be evidence-based to ensure optimal outcomes.

The data on prehospital RSI has been scattered in many specialty journals, including aeromedical, prehospital, emergency medicine and trauma surgery.^{1 - 32} The goal of this review is to answer two basic questions for EMS professionals:

• Can prehospital providers perform RSI with high success rates?
• How does prehospital RSI affect patient outcomes?

Prehospital RSI has many theoretical benefits, including improved oxygenation and ventilation, aspiration protection, protection of the decompensating airway and spinal protection through sedation and paralysis. The procedure also has the potential of decreasing failed endotracheal intubations in certain situations. Wang et al. recently identified a set of factors that were associated with ETI failure in the prehospital setting.2 Factors reported that could theoretically be corrected by RSI included trismus, inability to pass the endotracheal tube through the vocal cords and intact gag reflex.

Concerns regarding the procedure include the inability to intubate and ventilate after neuromuscular blockade, prolonged scene time in trauma patients and use in inappropriate situations. More practical concerns, such as the cost of training prehospital providers to perform the procedure, are valid as well.

Aeromedical EMS Literature

Aeromedical EMS produced some of the earliest literature on the topic. Flight crews are frequently exposed to patients in need of airway management, and the teams are generally highly experienced and supervised. These characteristics make for an excellent study group. The research is often limited to small, retrospective reviews evaluating success rates and short-term outcomes.

Researchers prospectively studied the use of neuromuscular blocking agents to facilitate intubation by an MD/nurse flight team.3 Valium and succinylcholine were used to intubate patients both at accident scenes and in the emergency departments of transferring hospitals. There were a total of 71 patients, with a success rate of 96% in both settings and an equal complication rate in both groups. There were two failures in the accident scene group and one in the transferring hospital group. They all were managed with either bag-valve-mask (BVM) or cricothyrotomy.

The flight crew reported 64% of the patients would have been too dangerous to fly without chemical control. In addition, either field paramedics or the flight team had attempted to intubate 43 of the patients prior to RSI, but were only successful with three.

Similar success rates were next demonstrated to be possible by a paramedic/nurse flight team. A retrospective review of RSI by these providers demonstrated a 96% success rate by intubating 115 of 119 patients.4 Most intubations were successful on the first attempt, and all failures were managed successfully by cricothyrotomy. Further research with flight teams of different compositions have demonstrated similar success rates, usually greater than 95%.^{3 - 14} The short-term complications in these studies included multiple intubation attempts, esophageal intubation, aspiration and/or cardiac rhythm changes. These complications were reported as infrequent, not significantly different from controls, or minimal in discussions by the authors.^{3 - 14} Sing et al. looked at rates of pneumonia in patients who underwent prehospital RSI, but could not find a relationship of documented aspiration and pneumonia.^5,6 The authors felt the incidence of pneumonia was more closely related to injury severity than to the RSI procedure.⁶

Another retrospective study attempted to evaluate the outcome of patients intubated by RSI in the field, then transported by helicopter, versus those transported by ground and intubated in the emergency department.¹⁴ RSI was performed on 267 patients who were brought in by ground transport to the emergency department. The flight team performed RSI on 47 patients in the prehospital setting. Both groups had success rates greater than 97%. The prehospital aeromedical group had significantly higher trauma scores (p < .01) and rates of pneumonia (p < .001). It is unclear if the pneumonia was related to the RSI procedure in the field or to the overall severity of the patients. The study did a subanalysis of the isolated head-injured patients and did not find any difference in long-term outcomes, although the results were not statistically significant.

The long-term outcome data specific for aeromedical transport and how it relates to RSI are very limited. The literature on aeromedical transport of trauma patients reports improved outcomes of patients transported by air.^15,16 As previously mentioned, many patients are not safe for transport without being controlled with paralytics. Taking these two facts together, the value of aeromedical RSI may be found in the ability to transport patients by air.

A recent review provides a good summary of goals an aeromedical program should aim to meet and suggestions on how to achieve them.17 These goals include success rates comparable with in-hospital rates, limiting multiple attempts, early recognition of misplaced endotracheal tubes, and avoidance of hypoxia, hyperventilation and hypotension. Among other things, the authors promote strict medical oversight, quality improvement and a planned stepwise approach to RSI to help achieve these goals.

Ground EMS Literature

Paramedics working in ground EMS are often confronted with difficult airway situations that have the potential to be mitigated by RSI. Some EMS providers may be transporting patients long distances, in which case airway management becomes even more important. The aeromedical literature demonstrates that paramedics can be trained to perform the procedure with high success rates. Therefore, it is reasonable that the same can be accomplished with paramedics in ground EMS. By 1988, it was shown that small, highly trained paramedic groups could achieve RSI success rates similar to the aeromedical rates.¹⁸ In this first report, the paramedics intubated 95 patients with RSI and had a success rate of 96%. These paramedics were required to perform three intubations per quarter and had monthly operating room time to practice intubation and review medication administration. Run reports were also reviewed on a weekly basis, with feedback provided to paramedics by the physician supervisor as needed.

A larger retrospective review covering 20 years of prehospital RSI also demonstrated high success rates.19 The procedure was performed by paramedics serving a county of 175,000 residents. The paramedics were reported to have extensive classroom training, followed by a minimum of 20 intubations in the operating room under the supervision of an anesthesiologist before they were certified. They were also required to intubate one patient monthly for three years post-certification, followed by one patient per quarter. They performed RSI on 1,657 patients during that time period, with a success rate of 95.5%. Most of the patients were trauma patients. All 74 RSI failures were managed either by bag-valve-mask, Combitube (The Kendall Company, Mansfield, MA) or surgical airway. There were six unrecognized esophageal intubations, but only one after instituting end-tidal CO2 detectors. One patient who had undiagnosed amyotrophic lateral sclerosis died after succinylcholine was administered.

A retrospective review of a ground EMS system serving a county population of 600,000 was published in 2000. Paramedics were required to successfully intubate 12 patients in their first three years of practice; recertification required four successful intubations per year. They received a two-hour training session on RSI, with a test prior to starting the study. The paramedics demonstrated a success rate of 92%. There was a 5% rate of cardiac complications.²⁰ Four patients had cardiac arrest, and three developed bradycardia and hypotension. The authors raised the concern for event-related hypoxia as a possible cause of the complications.

The first prospective attempt at RSI in a large urban system was the San Diego RSI Trial, which involved 813 paramedics, including 12 agencies, and five medical centers serving a population of 2.79 million.21,35,36 The trial evaluated RSI in head-injured patients with a GCS less than 8 who could not be intubated by standard technique and were farther than 10 minutes from a hospital. The paramedics received a seven-hour training course in the procedure. Three attempts were allowed prior to mandatory insertion of a Combitube.

The first data published from this trial reported success rates and short-term complications.21 Paramedics attempted RSI on 114 patients and were successful 96 times (84.2%). Seventeen failures were managed with Combitube; one patient was undergoing RSI en route and was intubated in the ED. Most intubations were successful with the first attempt, and there was only one protocol violation for excessive attempts. Twenty-six esophageal intubations were all recognized and removed in the field. Scene times were 13.3 minutes higher when RSI was done on scene compared with en route (95% CI, 10.1 to 16.6 minutes). The paramedics’ rate of intubation in the San Diego trial was reported successful in 84%, but the validity of claiming success was called into question by some.²² Researchers cite this rate as an improvement over the 39% of patients they could intubate before RSI. Critics point to aeromedical literature with success rates as high as 98%.

Esophageal Intubation and Carbon Dioxide Monitoring

Early recognition of esophageal intubation is of paramount importance to both ground and aeromedical EMS performing RSI. Clinical assessment of proper placement, including direct visualization, auscultation, chest rise and tube condensation, cannot always confirm proper placement of the endotracheal tube.²³

End-tidal carbon dioxide (ETCO2) detection has been endorsed by most major organizations involved in airway management.^23,24 Without routine use of these devices, the rate of misplaced endotracheal tubes has recently been reported to be as high as 12% - 25%.^25,26 ETC02 can be detected by colorimetric means and capnography. Continuous waveform capnography provides both a waveform and a quantitative numeric value during transport. In a recently published study of ground EMS, the rate of misplaced intubations was zero when continuous capnography monitoring was used and 23.3% when it was not.²⁴ While both capnography and colorimetry are excellent, one study demonstrated superior ability of capnography to detect esophageal intubation.²⁷

Outcome Data in RSI and Traumatic Brain Injury

Prehospital RSI research has been increasingly focused on traumatic brain injury (TBI) and patient outcomes. TBI patients represent an excellent study group, because they may be difficult to intubate with standard technique in the prehospital setting and they represent a patient population that can easily be identified by using the Glasgow Coma Score. The population also allows for measurable outcomes such as death, discharge to home and discharge to a long-term-care facility.

In a recent review of prehospital RSI, Wang et al. discussed the evidence in favor of and against the practice of intubation in traumatic brain injury patients.²⁸ The expert panel cited animal models and historical data on aspiration that would favor the procedure. Included in their summary of evidence in favor of the procedure were two studies. One article cited had demonstrated worse outcomes for TBI patients with prehospital hypoxia and/or hypotension.29 The second article was a retrospective review of 1,092 trauma patients in which about half were intubated without RSI in the prehospital setting. The patients who were intubated in the field had a 21% absolute mortality benefit.³⁰

In the same review, the authors discussed three research papers that showed worse outcomes in TBI patients who underwent prehospital intubation.31 - 33 Since that time, more research has been published on this topic.34 A retrospective study of 4,098 TBI patients compared outcomes of those who were intubated with RSI in the prehospital setting versus in the emergency department. The results demonstrated higher adjusted odds of death for the prehospital group (OR 3.99, 95% CI, 3.21 - 4.93). The results also demonstrated increased adjusted odds of poor, moderate and severe functional impairment in the prehospital group.

The San Diego RSI trial was the first trial to look at outcomes of patients with traumatic brain injury as they relate to prehospital RSI.35 The study enrolled patients prospectively and hand-matched each patient to three historical controls from their trauma registry. Patients were matched by age, sex, mechanism of injury, trauma center and various trauma scores. The primary outcomes of the trial were mortality and good outcomes (discharge to home, discharge to jail, discharge to rehab facility, discharge to psychiatric facility and discharge against medical advice). The researchers also looked at many other secondary outcomes.

There were 209 patients enrolled, who were matched to 627 historical controls. Mortality was higher in the prehospital intubated group both for all patients (OR 1.6, 95% CI, 1.2 - 2.2) and in patients with a head and neck abbreviated injury score greater than three (OR 1.6, 95% CI, 1.1 - 2.3). Secondary data demonstrated that the prehospital group had a significant increase in scene time (p<.0001), increase in P02 (p<.0001) and decrease in PCO2 on arrival (p<.0001). The RSI patients with PC02<33 on arrival, multiple attempts at intubation, Combitube insertion and intubation attempts en route to hospital had a worse outcome, but it was not reported as significant.

The results of this trial may be related to prolonged scene time or hyperventilation of the head-injured patients. A subanalysis of the San Diego RSI trial was done to evaluate the incidence of desaturation and pulse rate reactivity during the event of RSI.36,37 One agency bought equipment capable of storing information during RSI, including pulse oximetry and heart rate. The researchers had data on 54 of the 102 patients who were enrolled in the trial after the equipment purchase. They found no difference in patient demographics or injury severity in those with these data and those without. The authors showed 57% of the patients they reviewed had desaturations during RSI with a median duration of 160 seconds and a median decrease of SpO2 of 22%. During this desaturation, 40 patients had pulse rates greater than or less than 22 beats per minute from their baseline. Furthermore, the paramedics described intubation as "easy" in 84% of the patients who experienced desaturation. The study did not compare the outcomes of those who had desaturation to those who did not.

Discussion RSI can play a critical role in prehospital patient care. The precise fit of the procedure in a prehospital airway management protocol is still unclear.

RSI has consistently been reported to have high success rates when done by aeromedical EMS systems. Reported success of ground-based EMS systems has not had the same consistency. The reason for the disparity is unclear. The level of experience may be more variable with ground EMS than helicopter EMS, and training provided to the paramedics may explain part of this disparity, as well. The paramedics in the Wayne et al. study appeared to have more training than did paramedics in the San Diego RSI Trial.19,21 While the studies are not directly comparable because of methodology, this represents a plausible explanation. Finally, the medications and doses used across studies have not been consistent.

Overall, outcome data currently speak to limiting the procedure. Most of the clinical trials that looked at prehospital intubation and outcomes of traumatic brain injury patients showed worse outcomes for patients. Furthermore, the only trial to date of prehospital RSI of TBI patients looking at outcomes showed unfavorable results, as well. The reasons for this have not been firmly established, but may include prolonged scene time, event-related hypoxia or post-event hyperventilation. Additional circumstances, such as the need for aeromedical transport not otherwise feasible without RSI, should be considered when developing or updating an EMS airway protocol.

The suggestion in previous research that transient event-related hypoxia may worsen long-term outcomes needs to be studied. In addition, the concern about post-event-related hyperventilation might be further explored in research that makes use of portable ventilators and continuous waveform capnography.

Other aspects of outcome data need to be researched, as well. The possibility that experienced paramedics may have better outcomes with the procedure needs to be more fully explored. Outcome data for prehospital RSI and how it relates to other patient populations, such as undifferentiated trauma and medical respiratory distress, needs to be evaluated. Finally, outcome data in regard to RSI and transport time may help define a population that benefits from the procedure.

Recommendations

EMS systems that decide prehospital RSI is appropriate in their community should be cognizant that the literature has identified some areas of potential improvement regarding the procedure. These areas include:

• Rate of Success: Internal review of ongoing success rates with the procedure should be done. The success rates, at a minimum, should match those of the current aeromedical community (>95%) and have a goal of achieving rates similar to those of the hospital. Individuals who have lower success rates may benefit from additional training. If success rates across the entire system are low, the procedure should be suspended until a cause is found and an action plan is implemented to correct the problem. End-tidal CO2 detectors should be used to help recognize esophageal intubations early.
• Attention to Oxygenation: Preoxygenation should be performed prior to all RSI attempts. Patients should have continued SpO2 monitoring during the entire course of the procedure; equipment that can store data for review is ideal. Attempts at intubation should be aborted when SpO2 falls below 90%, and the patient should be oxygenated via bag-valve-mask. A set number of attempts should be established as a maximum prior to insertion of a rescue airway device.
• Attention to Post-Intubation Ventilation: Ventilation should be emphasized in training and continuing education. A portable ventilator may provide the best way to ensure reliable ventilation in some EMS systems, especially those with long transport times. Continuous waveform capnography should be used to give real-time feedback on the adequacy of the ventilations and any changes that need to be made.
• Monitoring of Outcomes: Internal review of short and/or long-term outcomes of patients that undergo prehospital RSI should be done. Outcome data may provide insight into current practice not realized by measuring success rates alone. Procedural oxygenation, post-event ventilation and scene time should be considered when outcome data conflict with success rate data.

References

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Aaron Bernard, MD, is a resident physician in the Department of Emergency Medicine at the University of Cincinnati. He is also a flight physician for University Air Care and is assistant medical director for Reading Fire and Rescue in Cincinnati, OH.

Daniel Handel, MD, is a fourth-year resident in the Department of Emergency Medicine at the University of Cincinnati Medical Center. His current research interests involve paramedic first responder systems and access to care issues.

Donald Locasto, MD, is an assistant professor in the Department of Emergency Medicine at the University of Cincinnati. He developed and is a director of the University of Cincinnati Emergency Medicine Special Operations Institute, which serves as a physician support organization for the EMS community, and is the medical director for the Cincinnati Fire Department.