Despite multiple studies documenting the adverse effects of hypoxia on outcome in patients with severe traumatic brain injury, there is a paucity of evidence to suggest that an aggressive approach to airway management leads to improvements in mortality. Here we document a mortality increase in patients undergoing paramedic RSI when compared with matched historical controls from the same prehospital system. This increase was most profound in patients with higher Head/Neck AIS scores, with mortality of 41.1% in the RSI cohort versus 30.3% in controls. In addition, there was a corresponding decrease in “good outcomes” for the RSI cohort, defined as discharge to home, rehabilitation, psychiatric facility, jail, or signing out against medical advice.
The critical challenge in interpreting these results is to determine whether the mortality increase in the RSI cohort is an unanticipated consequence of the procedure itself or instead represents some inequity between the trial patients and their matched controls. The two cohorts appeared to be equivalent on all parameters we measured, including age, sex, AIS values for each body system, ISS, arrival SBP, head injury diagnoses, and incidence of invasive procedures. Absent from our matching criteria, however, was GCS score, which can be predictive of outcome in head-injured patients. Before the trial, field GCS was not consistently calculated and when obtained reflected arrival GCS rather than immediately upon arrival. Admission GCS values were available for the control cohort but were recorded as a value of 3 or omitted from most trial patients, as they were paralyzed and intubated. We felt that the use of individual body system AIS scores provided more consistent and accurate matching. In addition, the head injury diagnoses and incidence of invasive procedures were similar between the two groups.
We excluded patients intubated in the field without RSI medications from both the trial and control cohorts. If a higher percentage of these patients existed before the trial, this would create a selection bias toward more neurologically intact patients in the pool of patients from which we selected the controls. Our previous analysis reveals the opposite to be true, however, with a higher percentage of patients intubated without RSI medications during the trial. 21 This would have selected more neurologically intact patients for inclusion in the trial, although the impact is likely small. We also considered whether the RSI procedure and early intubation merely prolonged life for a few hours in patients who otherwise might have died in the field or the resuscitation suite and been excluded from analysis. Figure 1 demonstrates that the hospital day of death was similar between the two cohorts, with no increase in deaths on hospital days 1 and 2 observed in the RSI cohort.
If the differences in outcome represent a true negative effect of paramedic RSI, then it is imperative that factors potentially responsible for the increase in mortality be thoroughly investigated. One possibility concerns the incidence of inadvertent hyperventilation, which was significantly higher in the RSI group. This phenomenon has been documented previously with both paramedics and aeromedical crews, but the impact on outcome is unknown. 23 While hyperventilated and nonhyperventilated patients appeared to be equivalent on all parameters measured, the mortality was higher for RSI patients with lower arrival pCO2 values versus their predicted outcomes as compared with those with higher pCO2 values. The introduction of ETCO2 monitors may allow more accurate control of ventilation and avoid potential complications related to hyperventilation.
The introduction of ETCO2 monitors also allowed pulse oximetry data to be recorded and stored for later analysis. Using these data, we documented transient hypoxia in over half of patients undergoing ETCO2 monitoring, with many of these developing concurrent bradycardia. 24 This is substantially higher than the 15–20% incidence of hypoxia reported for trauma intubations performed in the resuscitation suite. 25 While the impact of transient hypoxemia on head injury is unknown, the concurrent hemodynamic instability we observed suggests a systemic effect that may be even more significant to the injured brain.
Patients with multiple intubation attempts appeared to do slightly better than those intubated on the first attempt. While this may seem counterintuitive, patients undergoing multiple attempts at intubation may have been monitored more closely, with paramedics quickly abandoning an attempt at the first sign of desaturation or hemodynamic instability. This is difficult to extract from these data, and further analysis of the ETCO2 recordings may lead to a better understanding of this phenomenon. Patients undergoing CTI appeared to have slightly poorer outcomes; however, these patients appeared to have more severe injuries. Nevertheless, the effect of CTI on hemodynamics, cerebral perfusion, and ICP has not been documented.
Another factor that may play a role in outcome is the delay in transport associated with RSI, especially when the procedure was performed on scene rather than en route. The impact of this delay is unclear, especially since the incidence of significant chest or abdominal trauma that might lead to hemorrhagic shock was relatively low. Nevertheless, rapid transport to a designated trauma center has been demonstrated to improve outcome, and the impact of additional prehospital delays cannot be discounted. We observed slightly worse outcomes in patients undergoing RSI en route. The initial SBP was lower in this group, possibly explaining the decision to transport sooner and potentially accounting for some of the increase in mortality. There may also have been additional challenges and complications with the RSI procedure performed in the back of a moving ambulance.
It is important to note the relatively high number of trial patients (n = 67) ultimately determined to have either a minor concussion or no head injury. A small number of these had significant nontraumatic disease that might also have benefited from aggressive airway management, including hemorrhagic stroke and cardiac dysrhythmia; however, most of these had normal neurologic examinations upon arrival at the trauma center. Fortunately, none had complications related to the RSI procedure or early intubation, but their existence underscores the need to consider the impact of RSI protocols on patient selection. Ultimately, additional variables, such as hypoxia or the absence of airway reflexes, may need to be incorporated into the decision regarding the use of RSI. It is also interesting to note that the mean arrival pO2 value for nonintubated controls was 216 mm Hg, which is well into the therapeutic range.
It is important to consider the limitations of this analysis in interpreting these results. While the RSI and control cohorts appeared to be identically matched, there may have been other parameters we did not consider that could account for the increase in mortality in the RSI cohort. Ultimately, a randomized trial is warranted to further investigate the impact of prehospital RSI on outcome in head-injured patients. Based on these data, the San Diego Paramedic RSI Trial was suspended until an avoidable cause for the increase in mortality could be determined.
Several important factors were identified that warrant further attention in other prehospital systems considering paramedic RSI. The high incidence of inadvertent hyperventilation and transient hypoxia and their potentially detrimental effect on outcome suggest that the procedure should be performed only after intensive training and with use of sophisticated monitoring devices. In addition, the use of GCS alone as indication for RSI may be too limited, and other factors, such as loss of airway reflexes or hypoxia despite supplemental oxygen, deserve further investigation as indictors of the need for invasive airway management. Finally, the experience of the paramedics performing RSI should be considered. The paramedics in our prehospital system have significant experience with advanced airway skills; however, performing RSI every one or two years may lead to a decay in familiarity with the RSI procedure. Ultimately, a small group of specially trained paramedics with significant airway experience and ongoing training may be safer and more efficient in applying RSI to the prehospital environment.
Paramedic RSI improves intubation success rates but is associated with an increase in mortality and decrease in “good outcomes” when compared with hand-matched controls. These differences may reflect inherent inequities between the two groups, although they appeared similar on all parameters we measured. Alternatively, the increase in mortality may be related to inadvertent hyperventilation, transient hypoxic episodes, and prolonged scene times associated with the RSI procedure.
Dr. David H. Livingston (Newark, New Jersey): This excellently written study covers an important topic—does allowing field paramedics to perform RSI in the field improve outcome with patients with traumatic brain injury? There is really little to offer these patients other than removing mass lesions and avoiding hypotension and hypoxia and probably hypercapnia. Thus, it would seem logical that intubating them in the field would be beneficial. However, despite really a very nice, elegant study and an analysis that tortured the data until it would confess, the authors could not show a benefit of RSI in patients with RSI who did worse no matter how they cut the data.
As this argument is currently played out in my own home state of New Jersey and elsewhere, I can assure the audience that I used this data to try to quash paramedic RSI in my own state.
The authors began to articulate some of the issues here—unrecognized hypoxia during the intubation and over aggressive ventilation that resulted in some of the respiratory parameters. Clearly, this study also shows that the time in the field was increased in patients undergoing RSI. In the argument between the scoop and run and stay and play, scoop and run once again wins out.
Lastly, the study again demonstrates the concept: just because you can do something, maybe you shouldn’t. During my fellowship, Dr. Richardson kept referring to this as if the only tool you have is a hammer, and everything begins to look like a nail. Thus, if we give the paramedics the ability to intubate, they will want to intubate again and again.
Who do you think really was benefiting from this procedure if there was anybody benefiting from it in the field?
In our own estimation, looking at 1,200 RSIs in our emergency department, maybe 10 to 15 or 20 percent of patients, max, would benefit; thus, a lot of people would be intubated in the field, and you’d wonder whether they should.
How much did this whole program cost? If you were going to go forward to do this, how do you keep the paramedics recurrently training, especially if they are only doing one or two a year, and how much does this cost in an ongoing program?
Lastly, given your data, I have a big question. Are you going to pull this from the paramedics in the field? Clearly, your data at a 3:1 cohort match looks pretty good that patients are doing worse.
Dr. Daniel P. Davis (San Diego, California): The principal investigators met 2 days after the data was analyzed, and they decided to suspend the trial until we could determine whether the increase in mortality was a true effect of RSI or whether there was some error in the way that we had done the matching. In continuing to analyze the data for the subsequent 6 months, we could not come up with anything to suggest that these 2 groups were inappropriately matched. Thus, we have not reinitiated the trial, and within the past month, the California State EMS Board voted to discontinue the trial.
We have discussed performing a different trial in the future that might utilize a select group of medics who undergo more specific training. That introduces the question about the cost of training. For this trial, all medics who went through the training course were eligible to perform RSI regardless of how many intubations they had accumulated. Over 500 medics went through an 8-hour training course for which they were compensated. Instructors were also paid, and course materials, including home study aids, were supplied to the medics. In addition, there were administrative costs, not to mention the cost of medication and equipment. I’m sure you can imagine that it’s a fairly substantial endeavor. Of note, specific refresher courses were not required, bringing up the issue of a decay in skills with time.
We are looking at the number of medication and protocol violations and have noticed that they appear to increase as a function of time following the initial training module. Anecdotally, medics have told me that they feel less comfortable with the procedure several years out from the training course, especially if they hadn’t been involved with an RSI in the interim. The data collection sheet also served as a cheat sheet for the medics, helping guide them through the procedure, but anybody who has performed RSI knows that it’s infinitely more complex than something that can be performed from a cookbook.
As far as who benefits from the procedure, we have not yet identified a particular RSI subgroup that does better than their matched controls. This analysis pooled all RSI patients and all controls, breaking the line between each patient and his or her matched controls. Future analyses may retain this link to investigate the role of certain parameters in determining outcome and defining patients who may benefit from RSI. I think there were many patients who were doing just fine on their own and did not require RSI, opposed to patients who were hypoxic despite supplemental oxygen or bag valve mass ventilation and likely benefitted from intubation.
Dr. Richard J. Mullins (Portland, Oregon): I think the authors have carefully examined the value of rapid sequence intubation and demonstrated that, with it, patients had improved survival in the prehospital phase in the later time period.
If you improve airway management in patients with brain injury, one consequence should be that more patients will survive to be admitted to your trauma center, but some will still expire because of their lethal brain injury. Vital statistics records regarding patients who die of unintended injury generally show that 60 to 80 percent of blunt trauma patients expire at the scene.
My question relates to your measure of survival. Would not 6-month survival be a better indicator in brain-injured patients of whether you benefited patients with your process of rapid sequence intubation?
Dr. Daniel P. Davis (San Diego, California): Originally, one arm of this study was intended to use the Glasgow Outcome Scale to determine long-term outcome, however it quickly became apparent that the only patients that we could find consistently were the dead ones, and the lack of follow-up became the fatal flaw for that part of the study. We were limited to using data available from the trauma registry, which meant that once a patient left the hospital, they were lost to follow up.
Dr. James W. Davis (Fresno, California): I, too, commend the authors on this study, however I’m wondering if the outcomes aren’t even worse than were suggested. Should the failure to intubate be part of an intent to treat analysis? In other words, you can make an airway a whole lot worse by attempting to instrument it, and then, if you don’t get that airway, those patients may, indeed, do worse. Further, you excluded all your early deaths and your scene deaths. Did any of those patients have an unrecognized or a missed intubation or an esophageal intubation?
Dr. Daniel P. Davis (San Diego, California): Those are excellent questions, and I think that those questions would have even more relevance if we had demonstrated a benefit with RSI. If we had performed an intent to treat analysis, we most likely would have observed even greater mortality in the RSI group.
Of the 7 deaths that occurred in the field or within 30 minutes of arrival, all had severe multi-system injuries that were deemed to be nonsurvivable. It was not thought to be the RSI procedure itself that lead to the death. Conversely, there were patients who did not have significant injuries but in whom the medics had difficulty establishing an airway, with hypoxic injury noted on CT scans, although none resulted in death.
Dr. Arthur L. Trask (Vienna, Virginia): The scenario that you described is a reverse of what we have done in Fairfax, Virginia, where there is only a select group, probably 10 or fewer, that are allowed to do RSI. They are all related to the helicopter services in that area. Our statistics are totally the opposite of what yours are, and that is that we don’t do RSI if they’re less than 10 minutes from the hospital, or if they can be there with the scoop and run technique. However, in those areas where we can’t get there because of the traffic and so on, the helicopter comes in, picks them up, and does RSI. The mortality statistics in those patients were significantly different, 30 percent improved mortality in our RSI group. The training of 10 people is a lot different than the training of 600, and that’s why we have kept it to that size group.
Dr. Daniel P. Davis (San Diego, California): I agree. I think that the future of prehospital RSI is going to require more intensive training for a select group of people, be they air medical teams or a small group of specially trained medics who may or may not work in every prehospital system.
Our enrollment criteria required that the transport time be an estimated 10 minutes or longer; thus “scoop and haul” was still the standard when closer to the trauma center.
Dr. Randal M. Chesnut (Portland, Oregon): This is a very nice study, and this methodology becomes quite definitely Class II when it reaches peer-reviewed publication. The question will then be when it generates a lot of discussion, to whom will this be not generalizable? In other words, San Diego is sort of a specific situation—the history of the trauma system, the set up of short transport times, etc. In what communities would this not be applicable? What does it take as a baseline to consider applying such an RSI protocol?
Dr. Daniel P. Davis (closing): In any city that was considering adding RSI to the scope of practice for all medics, I think this is going to give them significant pause. If the situation is such that a “strike team” of specially trained medics can be stationed at several locations in a particular city and quickly reach the scene to perform RSI, it may still be worth considering.
In southern California, where the cities are 50 to 100 or more miles wide, it’s not feasible to have specially trained teams of medics who will require 30 to 45 minutes to get to any particular scene. In this scenario, air medical teams are the only viable option to perform RSI.
As far as paramedic RSI is concerned, i think it must be special trained “strike teams” stationed at various points in a city where they could easily get to any scene in a timely fashion. Even in such an idealized scenario, there is not enough evidence that early intubation improves outcome in traumatic brain injury.
The authors gratefully acknowledge the contributions made by the San Diego County Base Hospital and Trauma Departments, American Medical Response, San Diego Medical Services Enterprise, Mercy Air, county flight nurses, the RSI Educational Task Force and trainers, paramedic provider agency coordinators, Palomar and Southwestern Colleges, the County of San Diego Division of EMS bio-statistical team, the California EMS Authority, and especially the paramedics throughout San Diego County whose enthusiastic support made the study possible. The authors particularly note David Bailey, RN, Ginger Ochs, RN, Gina Anderson, RN, Kelly Forman, RN, and Mark Angeloni, RN, for their training contributions.
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Keywords:© 2003 Lippincott Williams & Wilkins, Inc.
Brain injury; Head trauma; Intubation; Paramedics; RSI outcome