Controversies in Emergency Medical Services

Emergency medical services (EMS) is the broad term for medical care and related services provided in the out-of-hospital environment. These services have been in existence in some form since the time of Napoleon and originally were created during times of war in an effort to treat, triage, and transfer wounded soldiers. The first civilian hospital-based ambulance system in the United States was created in 1865 in Cincinnati, OH. The ambulance was staffed by an intern in a horse-drawn carriage and carried items such as splints, brandy, morphine, and a stomach pump. Modern-day EMS has evolved significantly since that time and has paralleled the growth in emergency medicine.

The expansion in care provided in the out-of-hospital setting is based primarily on the extrapolation of therapies provided in the hospital (and, in particular, emergency department) setting. Limitations to performing high-quality research in the field include variability in EMS provider skill level, variability of EMS protocols, limitations in funding, restricted access to equipment, practice location (rural vs. urban), ability obtain patient consent, and difficulty in obtaining patient follow-up. Given these hurdles, prehospital research typically carries acknowledged limitations; in other cases, one is left to extrapolate findings from in-hospital care to the out-of-hospital environment.

This article will highlight a few of the many areas of controversy that may be found in the current EMS literature, suggest where there are gaps in existing knowledge, and make some recommendations regarding clinical application of the research.

Prehospital Hypothermia

Approximately 300,000 people in the United States suffer from out-of-hospital cardiac arrest each year.1 Despite many technical advances as well as the widespread availability of defibrillators, advanced life support medications, and trained medical personnel, many of these victims do not survive.2-4 Of those who have return of spontaneous circulation (ROSC) in the field, fewer than half leave the hospital alive. The most common cause of death in these individuals is anoxic brain injury.5

Recent studies of early cooling in post-cardiac arrest patients3,4 have shown clinical benefit, including reduced morbidity and mortality. Post-cardiac arrest hypothermia has produced benefit whether instituted in the ED or the ICU.3,4 Both overall survival and better neurologic outcome were increased. Based largely on these studies, the "2005 AHA Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care" recommended that "unconscious adult patients with ROSC after out-of-hospital cardiac arrest should be cooled to 32°C to 34°C (89.6°F to 93.2°F) for 12-24 hours when the initial rhythm was VF (Class IIa)."

Many experts believe that induced hypothermia should become standard following cardiac arrest and should be instituted in the prehospital setting. This may be based, in part, on animal studies, which have shown that the benefits of post-arrest hypothermia are maximized when initiated early and that these effects may also be time-limited.6,7

The exact mechanisms for the neuroprotective effects of hypothermia remain elusive. It is known that for every 1 degree Celsius of cooling, brain metabolism is decreased by 6%.8 It has been suggested that this leads to conservation of limited oxygen and substrate stores within neurons. It is also conjectured that part of the benefit of hypothermia comes from suppression of chemical reactions under hypoxic conditions that cause free radical release, electrolyte shifts, and amino acid release. Under normothermic conditions, these reactions ultimately lead to mitochondrial damage and cell death.9-12

Many methods of cooling have been studied. These vary greatly in equipment costs and convenience as well as in ease and speed of temperature control. One of these methods is the use of cooling blankets that cool the body with air or water that flows through the blanket. This method is limited by the size restrictions of such devices for use in the prehospital environment. Another method investigated is the use of cooled intravenous saline. This method may be more feasible in the prehospital setting. Studies have used cooled saline (4°C) with infusion rates of 60-100 mL/min.9,12-15 In these studies, the patient can be cooled between 1 and 2 degrees Celsius in the first hour of infusion. Kampmeyer et al.16 proposed an economical solution to the potential problem of keeping cooled fluids immediately available in the field. The authors concluded that at ambient temperature, a cooler with six-sided insulation and reusable ice packs is practical and can maintain a temperature of 4°C in two 1-L bags of normal saline for more than 24 hours.

One additional method17 evaluated the use of an adhesive cooling device. These devices are applied over the torso of the patient and provide cooling comparable to rates achieved using cooled saline. The average cooling achieved with the adhesive cooling pads was 3.3°C, compared to 1.4-1.7°C with cooled saline in most studies.13-15 The adhesive cooling pads provided a seamless transition to in-hospital cooling.

Most studies suggest cooling for at least 24 hours to an ideal temperature of 32-34°C.18,19 Temperature monitoring is a key component to successful use of therapeutic hypothermia. This may be challenging in the prehospital setting, especially in the post-arrest patient. In addition, the majority of studies suggest that once cooling is initiated, the patient should not be rewarmed for at least 12-24 hours. Prehospital hypothermia requires collaboration between the EMS and the accepting facility, which must have proper equipment and expertise to continue the cooling process. This may explain why few prehospital systems have adopted a prehospital hypothermia protocol.20

Several barriers exist to the implementation of therapeutic hypothermia protocols in the prehospital environment, including equipment challenges as well as difficulties in controlling the rate of temperature decline and ability to achieve the goal temperature. Cady et al.9 have specifically addressed some potential drawbacks of prehospital cooling. They mention that hypothermia may be burdensome, both in execution and time, on one- or two-person EMS crews. They further note that after completing the primary survey, there may not be much time to initiate cooling prior to arrival. In addition, they emphasize the risk of early rewarming if post-arrest cooling initiated by EMS is not sustained by the accepting hospital. Kamarainen et al.14 reviewed the literature on prehospital hypothermia and confirmed many of these findings, noting the well-described benefit.

Cooling in itself is not a benign procedure. Therapeutic hypothermia increases the risk of arrhythmias, infection, hyperglycemia, and coagulopathy. Most of the previous studies acknowledge these risks; however, such complications were rarely encountered. Additionally, cooling induces shivering, which produces heat and is therefore counterproductive to the cooling process.

Gaps in Knowledge. There is clear benefit to the use of hypothermia in survivors of ventricular fibrillation. There are limited data to support the use of hypothermia with other underlying rhythms and non-cardiac causes of cardiopulmonary arrest; however, the few studies on patients with other initial rhythms do appear to support the use of hypothermia. It remains unclear whether there is benefit to initiating post-cardiac arrest hypothermia in the field.

Recommendations. The authors support implementation of a prehospital cooling protocol in coordination with local hospitals, as such treatment may provide increased benefit to patients suffering from out-of-hospital cardiac arrest. Currently, infusion of cooled saline may be the most convenient and cost-effective method. Those being cooled should be placed on a monitor, as they are at increased risk for arrhythmias; this may limit the use of the procedure in systems without trained paramedics. In addition, while measurement of core temperature is ideal, constant core temperature monitoring is not without its limitations in terms of both cost and convenience.

Prehospital Electrocardiograms

The American Heart Association estimates that every year 1,200,000 Americans suffer an acute myocardial infarction (AMI). ST-elevation myocardial infarction (STEMI) accounts for approximately 500,000 AMIs and carries a substantial risk of death. Early revascularization of patients with STEMI has been shown to improve mortality and functional outcome.

Strategies for revascularization include early administration of fibrinolytic agents (door-to-drug time) or mechanical measures (door-to-balloon time). Obtaining a prehospital ECG in patients with STEMI has been demonstrated to be a key element of reducing revascularization times21 and is currently a Class I recommendation of the American Heart Association.22 However, the best method of implementing this strategy remains to be defined.

A study by Eckstein et al.23 demonstrated that in Los Angeles County, obtaining 12-lead ECGs in the field resulted in 90% of the patients receiving percutaneous intervention (PCI) under the goal time of 90 minutes or less. In this study, the initial read of a STEMI was based on either a computer-generated interpretation of "acute MI" or by identification of > 1 mm of ST elevation in 2 contiguous leads upon presentation to the emergency department. The full benefits of this system were limited by the fact that only 31% of the study patients were transferred by EMS directly to a center with PCI capabilities. Swor et al.24 evaluated the impact of prehospital ECG acquisition on the reduction in door-to-balloon time in their prehospital system. Here again, the ECG was interpreted by the EMS providers with assistance from the computer algorithm; however, EMS providers were able to activate the catheterization lab from the field. These authors found that door-to-balloon time was less than 90 minutes in 85.2% of cases. Here again, the authors were only able to demonstrate a successful strategy of prehospital activation of the cardiac catheterization laboratory in 31 of 164 STEMI patients (18.9%) transported during the study period. A recent study by Schull et al.25 surveying EMS providers in five provinces in Canada demonstrated that only 47% of paramedics were trained in 12-lead ECG acquisition, and 40% were trained in ECG interpretation. Since ECG acquisition and interpretation or transmission is the essential first step in activating a STEMI alert, this clearly points to a weak link in optimizing STEMI care. Finally, Brainard et al.26 conducted a meta-analysis on all studies evaluating the reduction in door-to-reperfusion time. This study identified only four studies of appropriate quality, all of which were conducted prior to the AHA's Class 1 recommendation on prehospital ECG. Nonetheless, these authors found a 22-minute reduction in door-to-reperfusion time in the patients who had a prehospital ECG. Due to the publication dates of the four studies included in this analysis (prior to 1995), it is likely that most of these patients received pharmaceutical reperfusion but not other strategies, such as pre-arrival catheterization team activation, that would take full advantage of the use of prehospital ECG.

Several possible methods are available to initiate STEMI activation using the prehospital ECG. The simplest method is an activation based on the formal interpretation of the computer algorithm built into most commercially available ECG machines. These algorithms have been shown to have a high sensitivity for detection of significant ST elevations in patients later proven to have STEMI.28 When this strategy was employed by Brown et al.,29 there was a demonstrated reduction in the door-to-balloon time (73 minutes vs. 130 minutes for non-field STEMI), an improved ejection fraction, and a lower mortality rate. The false negative activation of the cardiac catheterization laboratory was 20% in this study.

Another strategy is to train paramedics in the interpretation of the ECG independent of the computer interpretation. This approach was evaluated by Trivedi et al.,30 who evaluated 103 trained paramedics on 5 separate clinical scenarios with ECG findings of both STEMI and non-STEMI. Four months after receiving a one-hour training program, the sensitivity for diagnosing STEMI was 92.6% and the specificity was 85.4%. This confirms the findings of earlier studies.31,32 However, Vaught et al.33 evaluated the impact of paramedic interpretation on door-to-balloon time in a system with paramedic interpretation. They found that there was no improvement in door-to-balloon time.

More recently, transmission of the images to the emergency physician or cardiologist has been shown to be an effective strategy. Adams et al.36 examined the impact of transmission of the ECG image to a cardiologist's hand-held device on door-to-balloon time. Patients who received prehospital transmission of the ECG to the cardiologist demonstrated a 28-minute decrease in average door-to-balloon time when compared to those patients who presented directly to the emergency department during the study period. Similarly, Dhruva et al.37 demonstrated that using wireless technology to transmit the ECG from the scene directly to the cardiologist resulted in a 66-minute improvement in door-to-intervention time when compared to their historical control group. Finally, Sejersten et al.38 showed that the average door-to-balloon time was 74 minutes, 63 minutes shorter than historical controls.

Perhaps the most important question for patients identified in the prehospital setting is destination, particularly in urban and suburban centers with many receiving hospital options. Given the fact that early treatment of STEMI patients has demonstrated better functional recovery and improved mortality, it would seem intuitive that transport to a PCI-capable center would be most appropriate. Eckstein et al.39 showed that implementing a formal network of STEMI receiving centers within an organized EMS system produced a door-to-balloon time of less than 90 minutes in 89% of cases and an EMS contact-to-balloon time of less than 90 minutes in 62.5% of cases. The impact of an organized system was recently examined by Sivagangabalan et al.,40 who demonstrated that a direct field-to-catheterization-lab strategy based on ED interpretation of the transmitted ECG improved both functional outcome (systolic ejection fraction) and 30-day mortality when compared to patients transported to the emergency department of the interventional center or those who were first transported to a community setting. These authors also found that any delay from symptom onset to reperfusion resulted in an additional mortality risk of 0.3% per minute of delay. These findings have confirmed results from earlier studies.41-43 (See Table 1.)

Table 1: Summary of Prehospital ECGs, Transmission, Interpretation, and Outcome

Article

Prospective or Retrospective

n

EMS Level

Transmission Method

Interpreter

Activation

Outcome

Eckstein et al23

Retrospective (compared EMS vs. self transport)

238

EMTP

Call in

EMTP/ED

ED

Reduced DTB (108 to 95 min)

Swor et al24

Prospective (compared field activation vs. all other STEMIs)

164

EMTP

Call in

EMTP

ED

Reduced DTB (96 to 70 min)

Curtis et al27

Retrospective review of national MI registry (comparing patients who received a prehospital ECG to those who did not)

55647

Varied

n/a

n/a

n/a

Reduced DTB (110 to 94 min)

Brown et al29

Prospective (field vs. non-field STEMI)

78

EMTP

n/a

Computer

EMTP

Reduced DTB (130 to 73 min)

Vaught et al33

Retrospective (compare EMS DTB before and after implementing field activation)

92

EMTP

Cellular transmission

EMTP

ED

DTB time did not meet 90 min standard

Adams et al36

Prospective (field activation vs. self transport vs. prior EMS vs. failed transmission)

24

EMTP

Wireless transmission

EMTP

Cardiology

Reduced DTB (101 to 50 min)

Dhruva et al37

Prospective (EMS field activation vs previous EMS)

80

Unclear

Wireless transmission

EMTP

ED/Cardiology

Reduced DTB (145 to 80 min)

Sejersten et al38

Prospective (field activation vs. control)

565

EMTB and MD

Wireless transmission

Unclear

Cardiology

Reduced DTB (112 to 49 min)

Sivagangbalan et al40

Prospective (compared to self presentation or EMS without field activation)

1449

EMTP

Wireless transmission

ED/EMTP

ED

Reduced DTB (146/105 to 78 min)

LeMay et al42

Prospective (field activation vs. control)

333

EMTP

Call in

EMTP

EMTP/Cardiology

Reduced DTB (125 to 63 min)

Key: DTB = Door-to-balloon time; EMTP = paramedic; EMTB = EMT basic; ED = emergency department physician

Gaps in Knowledge. Prehospital 12-lead ECGs appear to be a major strategy to reduce door-to-balloon time and thus expedite transfer to definitive care for patients suffering from STEMI. However, the best strategy for obtaining an ECG and placing the data into the hands of the decision-makers remains unclear. In addition, the question of who is most appropriate to activate the catheterization lab (EMS personnel, ED physician, or cardiologist), what are appropriate under-triage and over-triage rates, and a cost/benefit analysis of STEMI systems have yet to be determined. A cost/benefit analysis must be conducted to determine the true benefits to fully implementing a regional STEMI system.

Recommendations. There is a clear benefit to obtaining a prehospital ECG and placing that information into the hands of decision-makers. Barriers, including costs of equipment, training of paramedics, and geographical disparities in the availability of advanced prehospital providers (paramedics vs. EMT-basics or intermediates) and access to PCI centers, must be addressed.

Prehospital Termination of Resuscitation

National statistics suggest that only about 5% of patients who experience out-of-hospital cardiac arrest survive to hospital discharge.45,46 In particular, those patients who do not regain a pulse in the out-of-hospital setting have a particularly dismal prognosis.47 Kellerman et al. showed that of 758 patients who did not have return of spontaneous circulation in the out-of-hospital setting, only 3 survived to hospital discharge; all had neurologic impairment.48

Many authors have suggested that criteria be developed that predict those patients with expected poor outcomes with out-of-hospital arrest. Factors including an initial rhythm of asystole or PEA (pulseless electrical activity) and no return of spontaneous circulation (ROSC) in the field have been associated with a poorer prognosis.49,50 This has led to some discussion about extending the ability of prehospital providers to terminate resuscitation efforts in the field beyond the declaration of futility in those with obvious signs of death (dependent lividity, decapitation, rigor mortis, etc.).

Termination of resuscitation (TOR) in the field for out-of-hospital cardiac arrest remains a controversial issue. Several areas must be considered when discussing this topic, including: which patients should be eligible for field termination; who is qualified to declare TOR; what are the costs and benefits to instituting such a policy in the field; if TOR is initiated in the field, who then becomes responsible for disposition the body, for supporting the family, and completion of the death certificate?

Much of the literature on terminating field resuscitation seeks to tease out the circumstances and characteristics shared by those who survive, identify those with better neurological outcomes, and integrate these characteristics into their decision-making rules. This may prove helpful, as there is a significant cost, time burden, and safety concern for the EMS providers and emergency department staff involved in the care of these patients.

Most early studies on this topic have involved systems with paramedic units that were capable of interpreting underlying ECG rhythms and utilizing advanced life support measures. As an example, Mohr et al. noted that most physician medical directors were comfortable with cessation of resuscitation efforts if no response to ACLS measures was noted after 45 minutes of resuscitation.52 The American Heart Association suggests that failure to respond to intensive resuscitation efforts of more than 10 minutes duration rarely results in a neurologically intact survivor.53 The issue becomes blurred with recent evidence that advanced life support measures actually may worsen the prognosis,54 or when the EMS provider is not able to determine the underlying rhythm and is only able to distinguish when a shockable rhythm is present.

Morrison et al. recently evaluated a prediction rule to be used by basic EMTs for terminating resuscitation efforts in the field.46 This study evaluated patients at least 18 years old with non-traumatic cardiac arrest and prospectively evaluated the validity of the rule in 1999 cardiac arrest survivors and assessed neurologic outcome of survivors. In the study, 1999 cardiac arrest victims were identified; 41 of them survived to hospital discharge. The investigators prospectively applied the TOR rule to consecutive cardiac arrest cases by assigning each patient to the "terminate" group or "transport" group, while not acting on the rule. The TOR prediction rule included the following criteria: no ROSC, no shocks administered, and the arrest is not witnessed by EMS personnel. When the TOR prediction rule was applied, 772 of these patients would have met criteria for field termination and, of the 772, 4 survived to hospital discharge. This resulted in a 0.53% false-negative rate.

Ong et al.55 reported on the use of field termination rules in a BLS system with automated external defibrillators. These authors evaluated several TOR rules that differed in criteria, such as the return of spontaneous rhythm, the advice of the AED to deliver a shock, various time intervals, and the presence of other complicating factors such as drugs, hypothermia, or drowning. The sensitivity for each of the decision rules was greater than 99%, but only the rule that included termination of resuscitation for patients with unwitnessed cardiac arrests where no shock was advised and did not have a return of spontaneous rhythm had a specificity over 50%. It should be noted, however, that three patients in whom termination of resuscitation would have been advised were discharged alive in this retrospective study. The study concluded that the rule developed by Morrison and Verbeek et al.56,57 had the largest impact on limiting transport.

The results of Morrison et al.46 have been validated by several other authors such as Richman et al.,58 Ruygrok et al.,59and Sasson et al.60 Ruygrok et al.59 compared three TOR criteria: BLS criteria, ALS criteria, and neurologic TOR criteria. (See Figure 1.) The authors made the assumption that if all of the criteria were met, resuscitation efforts would have been stopped. These three rules were then applied to a large registry of cardiac arrest patients. Each rule was analyzed with regard to patient outcomes, including survival to hospital discharge as well as neurologic function based on the Cerebral Performance Categories Scale. The authors determined that all three criteria were able to identify patients requiring continued resuscitation. Of the three rules, the BLS was the best at predicting patient survival with good neurologic outcome. The BLS criteria were also more accurate at predicting death and poor neurologic outcome. Sasson et al.60 analyzed the sensitivity and specificity of the BLS and ALS TOR rules and found the BLS rule to be 50.6% sensitive and 98.7% specific. This compared with the ALS TOR rule, which was found to be 23.3% sensitive and 100% specific.

Morrison et al.46 also commented on the cost of futile resuscitation and noted that transport and in-hospital health care costs for victims of cardiac arrest are nearly $5.1 billion annually in the United States. There was the potential to reduce hospital transport of cardiac arrest victims by about 30%.

What is highly controversial is the false-positive rate for each rule. In each of these studies, at least one patient whose resuscitation efforts would have been terminated in the field according to the prediction rule survived to discharge, many with good neurologic outcomes. This raises ethical and legal considerations in applying TOR prediction rules.

One additional concern is the issue of responsibility for the after care of the patient and the family. Delbridge et al.61 conducted a prospective study in which they interviewed family members present at the scene of unsuccessful resuscitation efforts. In this study, 96% of those interviewed were satisfied with the decision to terminate in the field. Seventeen of the 53 patients were transferred to the emergency department. Seventy-six percent of the families of these 17 patients said they would have accepted field termination. The overall conclusion of this study was that families, in general, were receptive to field termination and happy with the care provided by paramedics surrounding their family member's death. Schmidt et al.62 performed a similar study by interviewing surviving family of out-of-hospital cardiac arrest victims who were terminated in the field. Their study also found that family members thought that the EMTs were both professional and supportive.

Gaps in Knowledge. Issues that need to be considered in instituting a TOR policy include emotional support for the family, disposition of the body, and certification of death. Several systems that have implemented a TOR policy have EMS providers inform the family of the death and stay with the patient until a local coroner or public safety officer arrives to assume care of the body. This clearly does not address all of the concerns mentioned. Further clarity is needed on issues including family resistance to TOR, unsafe scenes, EMS comfort with TOR policies, and consistent training on field termination and notification of death. Such matters remain under discussion at the national level. Sasson et al.63 described the collaboration of several influential national organizations that will be able to work collaboratively to minimize these barriers so that prehospital TOR may be more widely implemented. Finally, ethical issues surrounding the implementation of TOR policies, including a threshold for false-positive terminations, must be resolved.

Recommendations. Simple TOR prediction rules have a very high sensitivity and specificity when applied to patients with out-of-hospital cardiac arrest. Some rules require information that is available even to basic emergency care providers. When applied in a prospective manner, TOR would significantly reduce health care costs associated with unnecessary transportation of cardiac arrest victims and prolonged yet futile ALS care, as well as reducing the physical burden on hospital staff. However, as mentioned, no acceptable miss rate has been established. Until these ethical and legal issues are resolved, public acceptance and global implementation of these rules are unlikely.

Prehospital Intubation

Airway remains the first priority in patient care. It has always been assumed that securing a definitive airway early leads to better patient outcomes, especially if a compromised airway is identified in the prehospital phase of care. Early studies demonstrated that paramedics could reliably be taught to perform intubation in the out-of-hospital setting. Airway management recently has emerged, however, as an area of controversy in the prehospital arena. The controversy has arisen because, while a secure airway is important, intubation is not a benign procedure. Concerns have been raised regarding skill proficiency, complication rate, and impact on patient outcome.

A primary area of concern is the high failure rates of prehospital intubation. Studies cite failure rates from 15-50% by paramedics in the prehospital setting.66-70 Prehospital failure rates are primarily derived from reviews of out-of-hospital intubations by ground paramedics, which are compared to failure rates between 3-6% in intubations done by physicians.67

A major contributing factor appears to be the low incidence of use of this complex skill by individual EMTs.71 Recent studies discuss the issue of training and experience in intubation, noting that UK paramedics average about 1 intubation per paramedic per year.68,70 Other studies note that prehospital intubation rates might increase if paramedics could have more experience and training in endotracheal intubation.73,74 Using a large statewide database, Wang et al. found that two-thirds of paramedics had two or fewer intubations during a one-year period, and 39% had no attempted intubations.75

Part of the low success rate of prehospital intubation recently has been elucidated by Garaza et al.74 These authors identified many distracting factors, such as location of intubation, bystanders, weather, unsafe scene, suboptimal lighting, and patient position. The discussion that ensued encouraged paramedics to optimize their intubation conditions by increasing available space, improving lighting, preparing the equipment, and training personnel.

As with any medical procedure, one must weigh the risk vs. benefit when evaluating the applicability of any procedure in the field of medicine. Several studies tout the benefits of early intubation,76-79 which include safety during transport, ability to oxygenate and ventilate, and the prevention of aspiration. Only recently have the true risks of performing an intubation been more clearly delineated. These risks include airway trauma following multiple failed attempts, hematoma formation, aspiration, hypoxemia, laryngospasm, and esophageal trauma/intubation.81-85

Several tools exist to help mitigate risks associated with the procedure, especially missed esophageal intubation. More objective means of confirming an endotracheal intubation are available. Capnometry, capnography, color change end-tidal CO2 detectors, and esophageal detector devices (EDD) all act as secondary confirmatory devices. Each of these methods has drawbacks and advantages, depending on the clinical situation. For example, color-change ETCO2 detectors have a higher incidence of false-negative readings (color change consistent with esophageal intubation when the tube is actually in the trachea) in patients with poor perfusion or cardiac arrest.80 Esophageal detector devices may appear to demonstrate proper tracheal placement during prolonged bag-valve-mask ventilation when the tube is actually in the esophagus.80 The American Heart Association (AHA) Guidelines propose the following algorithm for ETCO2 device use in endotracheal tube confirmation:

"If a pulse is present, rely on the colorimetric, qualitative CO2 techniques.

"If a pulse is absent, use the colorimetric CO2 device. But if the device shows no color change, add the test of the EDD. No air rush with positive suction indicates that the tracheal tube is in the esophagus — therefore reintubate. Air rush with no suction indicates that the tube is in the trachea — therefore secure the tube."80

The colorimetric device and EDD are relatively cost effective, with the color-change devices costing between $10 and $20 on average, and the esophageal detection device averaging around $5. In addition to their affordability, these devices are relatively low tech, user-friendly, and very portable, which makes them very feasible for EMS use.

Tan et al. reported that an increase in the number of attempts was associated with a delay in transport to definitive care, also resulting in an increase in complications including hypoxia, cardiac arrhythmia, airway injury, bleeding, and edema.70 The authors concluded that limiting field intubation to two attempts would decrease complications and likely reduce associated morbidity and mortality.

In addition to their conclusions regarding intubation success and complication, Cobas et al.,64 Eckstein et al.,88 and Cudnik et al.89 noted an increased mortality in patients who received prehospital intubation. This is perhaps the most important issue, as it relates specifically to prehospital intubation and is consistent with earlier work from Davis et al.90 and Wang et al.91 demonstrating a detrimental effect of prehospital intubation on patient outcome. In fact, the relative risk of death and poor outcome was 1.6 in the Davis study and 4.0 in the Wang study. Cobas et al. found no improved survival with intubation as compared to bag-valve-mask ventilation (BVM).64 Some limitations to these studies include the fact that they are focused on trauma patients who are at increased risk for having a difficult airway, compromised by blood, foreign bodies, emesis, or injury. These results were recently refuted by Bulger et al.,92 who retrospectively studied moderate to severe head-injured patients who received paralytic agents and found no difference in mortality.

Interestingly, the success rates for intubation as well as outcomes are improved in patients intubated by air medical crews. This was noted by Davis et al.,90 Wang et al.,91 and Cudnik et al.,89 who found improvement in survival in these subsets of patients. Germann et al.93 evaluated the intubation skills of air medical personnel and found that they had an out-of-hospital success rate of 92%. This may be up to 30% better than ground EMS success rates. The authors suggest that this is likely due to the strict skill performance requirements, ongoing training, and more frequent exposure to intubation that air medical crews experience. This conclusion was supported by Fakhry et al.,94 who found a 96.6% success rate for scene RSI performed by air transport paramedics. Intubation in their hands was associated with low complication rates and proper ventilation as measured by arterial pCO2. They attribute the success of their program to training, regular experience, and close monitoring of a limited group of providers, which maximizes their exposure and experience with this procedure.

Gaps in Knowledge. Most of the data on the dangers of endotracheal intubation come from large EMS systems or statewide databases. It is also known that air medical transport programs appear to have both procedural success and outcomes similar to those of physicians. The specific factors that result in high intubation success, low complications, and improved mortality require further study. The role of strict adherence to the use of secondary confirmation devices following intubation as a means of reducing esophageal intubation requires better analysis. Finally, the role of alternative airway devices in maintaining proper ventilation and oxygenation in the prehospital setting, which is not discussed here, deserves further consideration

Recommendations. Intubation is a very helpful and sometimes life-saving procedure that can be performed by paramedics. However, it should be used selectively with a full understanding of the limitations and risks associated with the procedure. Operator experience is key, and the number of previous intubations and the comfort level of the operator have an impact on the success of intubation. Thus, providers should have a system in place to train and regularly refresh their intubation skills. Systems that provide a concentrated experience in intubation with strong medical oversight appear to have the best results. The environment is an important element in success or failure of field intubations; whenever possible, one should try to minimize distractions and maximize space in addition to ensuring that all equipment is readily available. Where appropriate experience cannot be achieved, EMS should be encouraged to assist with bag-valve-mask ventilation or consider the use of alternative airway devices, which may be a safe and effective way to support ventilation and oxygenation in a patient in whom intubation would otherwise be considered.

Summary

Prehospital care is an inexact science, combining studies conducted in an uncontrolled environment along with extrapolations of in-hospital therapies and procedures. Areas such as initiation of hypothermia in the survivors of cardiac arrest, termination of futile resuscitation efforts, the role of prehospital ECG in emerging STEMI systems, and the optimal role of prehospital intubation in patient care remain controversial and will require further elucidation in the emerging EMS and emergency medicine literature.

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