Advances in prehospital trauma care

Abstract

Prehospital trauma care developed over the last decades parallel in many countries. Most of the prehospital emergency medical systems relied on input or experiences from military medicine and were often modeled after the existing military procedures. Some systems were initially developed with the trauma patient in mind, while other systems were tailored for medical, especially cardiovascular, emergencies. The key components to successful prehospital trauma care are the well-known ABCs of trauma care: Airway, Breathing, Circulation. Establishing and securing the airway, ventilation, fluid resuscitation, and in addition, the quick transport to the best-suited trauma center represent the pillars of trauma care in the field. While ABC in trauma care has neither been challenged nor changed, new techniques, tools and procedures have been developed to make it easier for the prehospital provider to achieve these goals in the prehospital setting and thus improve the outcome of trauma patients.

INTRODUCTION

Trauma is the leading cause of death for patients in their first four decades of life.[1] It is therefore essential to optimize trauma care, not just in the hospital, but also in the field when trauma patients have their first contact with medical providers. The treatment that patients receive in the field can significantly alter their outcome. Prehospital Emergency Medical Service (EMS) systems rely on advances in therapy and management, often developed for patient care in the hospital setting, but over time, has reached prehospital care providers.

The concept of the modern prehospital care system for trauma patients goes back to the introduction of the “flying ambulances” by Napoleon's private surgeon, Dominique-Jean Larrey, in 1792. The “flying ambulances” were horse drawn carriages, bringing physicians or medical supplies to the battlefield and transporting wounded soldiers away from the front line. All modern EMS systems still follow this early idea of either bringing the physician to the patient or bringing the patient to the physician.

Civilian systems were often developed for specific patient groups such as trauma patients or patients with myocardial infarction. Nevertheless, these prehospital systems were responsible for all emergency patients and had to be staffed and equipped accordingly.

In Germany, a surgeon developed the first physician based EMS system in Heidelberg with the idea to bring not just a surgeon, but a whole operating room and its staff to the scene of an accident.[2] The system showed very early the shortcomings of a large truck with an operating room team at the scene. The trauma patients did not require surgery, but rather stabilization, at the scene. In the same year, the city of Cologne introduced a similar system. Using a much smaller vehicle driven by a firefighter, one physician attended the scene of the accident and transported the patient back to the hospital.[3] The latter system was then copied by other cities and counties in Germany with the primary focus around the care and transport of trauma patients. Consistent with this, surgeons played a large role in the initial setup of these systems.

The first ground-based paramedic systems in the US are often attributed to an article from Ireland in 1967 by Frank Pantridge and John Geddes, published in the Lancet.[4] In this article, the authors describe the use of a mobile intensive care unit equipped with routine monitoring, defibrillator, and pacing capability. The unit was staffed with personnel from the cardiac intensive care unit and a junior physician.

Following this article, physician staffed mobile intensive care units were introduced in New York and Charlottesville.[5,6] Unlike European EMS systems, physician staffed EMS systems in the US did not gain popularity and in the early seventies, paramedic staffed systems were established in Miami, Columbus, Los Angeles, Portland and Seattle.[7–12]

Most EMS systems utilize some sort of a multi-tier approach, in which basic medical providers rush to the patient, and more skilled and trained personal arrive shortly after. This setup provides first responders with very basic training to perform early simple techniques such as chest compressions, automatic defibrillation or basic airway management until advanced interventions can be performed by either paramedics or emergency physicians at the scene. Some countries like Germany and France are still using EMS systems which are based on the idea of bringing the physician to the patient. The transport to the hospital comes second in this concept, as patients often undergo prolonged treatment at the scene. On the other hand, EMS systems in the US are based on the premise of bringing paramedical providers, who are trained to perform a limited number of medical procedures in the field to the patients. The emphasis is focused on rapid transport to the hospital, after the basic rescue techniques, such as airway management and fluid resuscitation, were performed at the scene.

All EMS systems have been undergoing changes over the years. The care of trauma patients is significantly influenced by military conflicts. While the Korean and Vietnam wars saw the first airborne rescue missions by helicopters at a large scale, the civilian EMS systems quickly implemented this new concept into the rescue of civilian trauma patients. Recent changes in military field medicine, such as low volume resuscitation, the revival of tourniquets, and of blood stopping granules, will clearly influence the care of civilian trauma patients in the future. The aim of this article is to give a brief overview of the advances in military and civilian EMS systems which are currently happening and which will affect the way trauma patients are treated, both in the field and in the emergency rooms receiving these patients.

AIRWAY MANAGEMENT

Despite different trauma patterns in patients, loss of airway or breathing is the most rapid cause of death. The airways of severely injured patients need to be secured as soon as possible. Airway management in the field is often more difficult than intubations in the operating room or the emergency department. This is caused by different provider training and experience, patient location, and coexisting medical or surgical problems. Over the years, different devices used in anesthesiology have been introduced to prehospital care providers. These devices range from laryngoscopes and different laryngoscope blades to oral and nasal airways. More recently introduced devices include the Eschmann elastic bougie, and even more recently, supraglottic devices.

The Eschmann or gum elastic bougie has been used by anesthesiologists, especially in Europe, since its introduction by Macintosh in 1949.[13–17] The Eschmann gum elastic bougie showed good results when used for airway management, not just in the operating room, but also in the prehospital setting.[18] Beside its traditional use to guide endotracheal intubation (ETI), the gum elastic bougie has also been described to facilitate cricothyrotomy in the field.[19] The gum elastic bougie was further evaluated as a guide for intubation after a laryngeal mask airway (LMA) was placed. In a cadaver study, the bougie was placed through an LMA and an endotracheal tube (ETT) was then placed over the bougie. This procedure was successful in placing the ETT into the trachea in about 50% of the attempts.[20]

In 2005, the European Resuscitation Council (ERC) endorsed the use of supraglottic airway devices.[21] The supraglottic devices such as LMA^™ (LMA, the Netherlands Antilles), Combitube^™ (Nellcor, Boulder, CO, USA), Rusch EasyTube^® (Teleflex Medical Company, Reading, Pennsylvania, USA), and King LT^™ (King Systems, Noblesville, IN USA) are easier to insert when compared to ETI by providers after minimal training.[22–25] While the supraglottic airway devices are not providing a definitive airway compared to a cuffed ETT, the supraglottic devices enable the prehospital provider to establish a rescue airway after failed intubation[26] and prepare for a definitive airway such as a cricothyrotomy or rapid transport to the nearest hospital for definite airway management.

A special version of the LMA is the intubating LMA, which combines the ease of insertion of a supraglottic airway device with the security of an ETT. The intubating LMA has a shorter and wider tube, allowing for easy insertion of an ETT through the previously placed LMA. This technique shows good success rates amongst providers otherwise inefficient in intubation with direct laryngoscopy[27] as a backup intubation tool after the other intubation attempts have failed,[28,29] or in cases of difficult airways, such as limited access to the patients airway.[30,31] The LMA is easy and quick to insert and often provides the ability to ventilate when adequate mask ventilation is not possible.[32]

The more recent developments of video-assisted laryngoscopes such as the Glidescope^® (Verathon Inc., Bothell, WA, USA), the Ambu^® Pentax Airway Scope (AWS) (Ambu, Ballerup, Denmark) the C-MAC^® Video Laryngoscope (Karl Storz, Tootling, Germany) or the McGrath^® Video Laryngoscope (LMA, the Netherlands Antilles) have already started to be introduced to prehospital care providers. So far, most publications of video-assisted laryngoscopes include case reports in trauma patients[33] and mannequin simulations,[34] but not randomized trials. Nevertheless, these studies have shown that the success rate and speed of intubation with video laryngoscopy is comparable in providers, experienced with direct laryngoscopy, due to a steeper learning curve with the video laryngoscopes.[34] The usage of video-assisted laryngoscopy seems to be especially useful for cases involving suspected spine injury where neck movement needs to be reduced or eliminated. Video-assisted devices have shown to reduce cervical spine movement in comparison to direct laryngoscopy.[35] In the near future, with a paucity of manufacturers positioning their product in this expanding market, we can expect more competitive pricing and aggressive advertising of these products to prehospital care providers. While the video-assisted laryngoscopes offer advantages over direct laryngoscopy for difficult airways and for providers with minimal training or experience, they also provide the disadvantage of providers losing their skills in direct laryngoscopy, therefore giving up a time-honored and proven technique to intubate a patient. Nevertheless, given the low national requirement of intubation for new paramedics, we will very likely see a widespread use of video-assisted devices in the prehospital systems. This will hopefully reverse the current trend of abandoning prehospital intubation due to the lack of intubation skill in some paramedics.

CIRCULATORY ACCESS

Paramedics and other prehospital providers have been placing intravenous access as a standard treatment since the beginning of prehospital care. The need to administer fluids and medication makes circulatory access essential. The “gold standard” in the field has been the peripheral intravenous access. In certain patients such as hypovolemic patients, intravenous drug abusers, burn patients, and children, peripheral intravenous access may not be possible.

While the concept of intraosseous access is quite old and has been used for pediatric patients for a long time, only recently this technique was introduced to the adult patients. The technique is supported by the European Resuscitation Council and has shown comparable plasma concentrations of injected drugs, similar to injection through a central venous catheter.[36,37] Besides mechanical intraosseous devices, the FDA approved three mechanical devices: The FAST1^® (Ping Medical, Vancouver, British Columbia, Canada), the EZ-IO^® (Vidacare, San Antonio, TX, USA), and the Bone Injection Gun^® (Wayside, Yokneam, Israel). The mechanical devices (Bone Injection Gun, FAST 1) showed to be equivalent in terms of success rates as compared to standard intraosseous needles, but differed in the time required to secure circulatory access.[38,39]

The downside to intraosseous access is the increased infection risk and, even more, the fact that blood products cannot be given through this access. This means that once at the hospital, the patient still requires intravenous access and the intraosseous needle (or needles) needs to be removed. For this reason, intraosseous access is often used as a last resort when peripheral IV access can not be established and central venous access is not possible either.

Central venous access has been used in some prehospital systems, but has a higher risk of serious side effects and complications compared to peripheral IV access. The most common risks are pneumothorax, vascular injury, and infection. For reasons of infection control, all the lines placed in the field need to be considered contaminated and should be replaced at the earliest possible time.

BLEEDING CONTROL

Tourniquets are experiencing a revival after they were all but eliminated in the early 80s when the fear of extended soft tissue damage, nerve damage and the potential loss of the extremity was feared if the tourniquet was used for too long or was not indicated in the first place. The different injury pattern experienced by the US military in the latest conflicts in Iraq and Afghanistan showed that tourniquets save lives in cases of severe blast injuries to the extremities. These findings even translated into tourniquets built into tactical gear by some manufacturers. While these types of injuries are less frequently encountered in the civilian EMS systems, there has been a change of policy regarding tourniquet use in many civilian EMS systems. The different types of tourniquets (rubber, cloth, and windlass) are successful in eliminating distal pulses when applied above and below the knee or elbow.[40] The location of the tourniquet may allow a lower amputation with preservation of the joint. Accurate documentation regarding time of tourniquet application is necessary with their use.

Other forms of hemorrhage control include advanced hemostatic dressings (where a clotting agent is impregnated into the dressing) and granular agents. Examples of hemostatic dressings are: HemCon^® bandages (HemCon Medical Technologies Inc., Portland, OR, USA) and QuickClot^® ACS+ (Z-Medica Corperation, Wallingford, CT, USA). Two examples of granular agents are Celox and WoundStat. HemCon is a positively charged chitin-based wafer which bonds strongly with negatively charged blood cells upon contact. QuikClot ACS+ dressings contain zeolite particles which rapidly absorb water upon contact with blood, thereby concentrating platelets and clotting factors at the bleeding site. Celox^™ (Medtrade Products Ltd., Crewe, United Kingdom) works like HemCon (chitin based), but the granules are packed in the wound. Lastly, WoundStat is made from smectite, absorbs water (like QuikClot ACS+) and forms a clay-like seal in the wound. Military comparisons of these agents show better control of hemorrhage in swine models.[41]

MONITORING

In recent years, end-tidal capnography or capnometry has been introduced in many EMS systems and the emergency room as a way to verify tracheal position of an ETT.[42] Capnography is also useful in guiding mechanical ventilation, especially when transport ventilators are used in which the minute volume can be better controlled than in manual bag ventilation. But the success is limited in critically ill or unstable patients. A further indication is the assessment of effectiveness of cardio pulmonary resuscitation (CPR), as larger volumes of end-tidal CO₂ indicate not only effective ventilation but also better cardiac output.

End-tidal capnography in the prehospital setting can reduce the incidence of severe inadvertent hyperventilation by over 50%.[43]

In intubated patients with traumatic brain injury, the survival rate was increased twofold when the arrival pCO₂ was between 30 and 49 mm Hg,[44] and in another study patients with severe traumatic brain injury were less likely to die when the pCO₂ on arrival was between 30 and 35 mm Hg.[45]

To take advantage of end-tidal CO₂ monitoring, additional teaching of prehospital providers about the correlation of end-tidal to arterial pCO₂ (PaCO₂) and the limitation of end-tidal CO₂ in trauma patients is required. Furthermore, correlation withPaCO₂ should be obtained as soon as possible, which usually occurs shortly after arrival at the receiving hospital. Other devices, such as the single use colorimetric end-tidal CO₂ detectors, are still used frequently. One must remember that these devices are of single use and early exposure to ambient air prior to their use can render them useless. These devices can be removed from the breathing circuit as soon as confirmation of tube placement is made.

A new development in patient monitoring is the transcutaneous measurement of tissue hemoglobin oxygenation. Unlike other monitoring devices, the tissue hemoglobin oxygenation measurement has already found access to the prehospital field and seems to give the prehospital provider a tool to assess hypoperfusion in the field.[46]

The future may see other monitoring modalities being introduced and used, such as a point-of-care lactate monitor (much like a glucometer), but their utility in the field and efficacy must be determined.

TRAINING

Trauma management has a “language” which all providers understand if they participate in a trauma assessment and management course. There are trauma courses for medics (including firefighters), nurses, and physicians. Some trauma courses conducted in North America are as follows: International Trauma Life Support (ITLS) for all-comers, Advanced Trauma Life Support (ATLS) for physicians, and Trauma Nurses Core Courses (TNCC) for nurses. Although different governing bodies provide and teach these courses, the “language” of trauma management remains the same. It is very important in trauma management systems for all participants to be fluent in order to provide the best care for patients.

The use of muscle relaxants in patients undergoing ETI facilities and improves the suc cess rate of intubation.[47] Depolarizing and non-depolarizing muscle relaxants have been used by anesthesiologists as a regular adjunct for ETI. In the prehospital setting, the use of muscle relaxants for rapid sequence intubation (RSI) was first described by Hedges in 1988.[48] The increased success rate of ETI using RSI compared to intubation attempts without medication or without muscle relaxants has been reported[49–51] although it is still questioned by some if muscle relaxants should be used by paramedics or flight nurses. To safely use these potentially dangerous medications, advanced airway training is needed and has been proven to be effective in improving intubation success and decreasing cricothyroidotomy rates when implemented.[52] Besides additional training, protocols, quality improvement and strong medical oversight are required.

The training of new students or medical residents has been undergoing numerous changes over the last years. The most recent development is the use of simulation programs in which the student is exposed to real-life scenarios and realistic time constrictions. The idea of the simulation is to give the student not just vital parameters or other physiologic data, but also to mimic real scenarios including interaction with patients and other team members. These simulations were first used in the training of anesthesiology residents and first described in 1987.[53]

Since then, these simulations have become more sophisticated. Other medical specialties and paramedic training programs have been using simulation-based learning. Simulation is a means where difficult, and sometimes rare, events can be reproduced in a safe setting. Participants can then get multiple exposures to scenarios which occur infrequently. Studies indicate that simulation-based learning programs improve crisis management skills, especially behavioral skills, necessary in the team approach to injured patients.[54]

Airway management and RSI can safely and effectively be performed in the field when resources for prehospital airway management are focused on a small, highly trained, highly experienced and proficient group of paramedics, thereby maximizing their exposure and experience.[55] In a paramedic training program, the odds of successful ETI increase with each cumulative training exposure to ETI. This training requires substantial resources and clinical opportunities, which may not be available to many training programs.[56,57]

SCORING SYSTEMS

There have been a number of prehospital scoring systems. The purpose of these scores is to predict and identify the most critical of patients and guide with patient transport to the appropriate hospital. It has been shown that organizing a prehospital advanced live support system in combination with the transport of the patient to the most suitable hospital decreases the mortality of trauma patients. This result is attributed to improved quality of care and reduced time to definite treatment.[58,59]

The Abbreviated Injury Score (AIS) is an anatomical scoring system introduced in 1971 by the Association for the Advancement of Automotive Medicine (AAAM).[60] It was originally designed to stratify victims of motor vehicle crashes and to provide researchers with a simple numeric scale. The AIS forms the basis of the Injury Severity Score (ISS). The AIS underwent a total of six revisions. The current AIS (2001) dictionary lists approximately 1300 injuries. The AIS is commonly used to assign monetary values to injuries for cost-benefit analysis.[61]

Many of these scoring systems, such as the ISS and New Injury Severity Score (NISS) require knowledge of all injuries, some of which are not identified in the prehospital setting. More current scores such as the Revised Trauma Score (RTS) look at physiologic data, but are often cumbersome to calculate.

Raum et al. developed a scoring system that is fairly easy to calculate using variables, some of which are easily obtainable in the prehospital setting. Their system called Emergency Trauma Score (EMTRAS) identified the following as the major predictors in mortality: age, prehospital Glasgow Coma Scale (GCS), base excess, and prothrombin time.[62]

In Germany, Huber-Wagner developed a similar score called The Sequential Trauma Score (STS) which allows prognosis of patient outcome at several early stages. This scoring system looks at variables in the following settings: patient data, the prehospital phase, early trauma room phase and late trauma room phase. Logistic regression of these variables showed that in the prehospital phase, age, blood pressure (BP), heart rate (HR), GCS, and anisocoria were the significant survival predictors.[63] The authors identified peripheral oxygen saturation, GCS, anisocoria, base excess, and thromboplastin as the major predictors for patients‘ outcome in the early trauma phase, and cardiac massage, AIS of the head, the maximum AIS, and the need for transfusion or massive transfusion to be the most important predictors of survival in the late trauma phase. Compared to other trauma score systems, the STS is collecting data from numerous data points to predict patient survival at different stages.

PREHOSPITAL PROVIDER SUPPORT

It is now fairly well known and understood that experiencing stressful situations can be detrimental to a provider's well-being. Sometimes called Post Traumatic Stress Disorder (PTSD), its signs and symptoms vary and each person can be affected differently. Prehospital providers are identified as a group at greater risk of PTSD.

In order to maintain the well-being of its employees, EMS systems have developed Critical Incident Stress Debriefings or Meetings. These meetings are interventions meant to manage stress, mitigate the impact of the traumatic event, and to accelerate the recovery process.[64] As with many other aspects of trauma care, the military has performed investigations into this area and applied treatment guidelines early. The Israeli Defense Forces have been using team discussions conducted by mental health professionals, after treating inured patients for many years and have developed guidelines for conducting these debriefings.[65]

A good support system should be readily available to all providers. During debriefing sessions, open channels of communication are vital and acknowledgement of feelings and fears must be validated. Furthermore, more than one session may be required. It is imperative that workers at risk be identified and treated early. In recent scenarios, support systems for prehospital providers were established at the scene, shortly after the traumatic event. In this particular case, voluntary and employed emergency responders were debriefed on the same day, following a panic in a large crowd during an open air festival where several attendees suffocated or were crushed to death.[66]

CONCLUSION

Prehospital trauma care is an important component of all trauma care systems and definite care of trauma patients needs to start early in the field. The training of prehospital care providers ranges from minimally trained first responders to attending physicians trained in trauma surgery or trauma anesthesia. Because of these discrepancies in training and experience, the prehospital system needs to carefully review and, if appropriate, adopt new technologies, techniques and tools to improve patient care of trauma patients in the field. Many of these techniques were developed by the military, while other technologies were first established in the operating room or the intensive care units. Besides the use of modern techniques and tools, it has become important to introduce scoring systems in prehospital trauma care. These scoring systems can not only aid in the care of trauma patients, but are also a requirement for many research projects to allow comparative studies of different treatment modalities or the comparison of different prehospital care systems. Last but not the least, the need to help medical providers coping with traumatic experiences and reduce the loss of experienced providers due to burn out or posttraumatic stress is of utmost importance.