Practicing emergency medicine in the prehospital setting is rife with opportunities, special considerations, and perils not encountered routinely in the hospital emergency department. EMS physicians transport themselves to the scene, rather than the scene being brought to them as in standard medical practice. They many times initially perform the functions their triage nurse otherwise would, in a deliberate and expedited fashion. Patients in the field are seen at first in parallel rather than in series. The physician is given the opportunity to see the scene as a reflection of the general health of the patient, or as a first-hand account of mechanism of injury. Consequently, the physician is subject to the unique environmental dangers associated with patient care in the field that often contributed to, or are a result of, the patient’s injury or illness. A successful EMS physician in active field operations assesses the scene, acts on this assessment, and mitigates danger prior to the provision of any patient care or evaluation.

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  Describe the unique dangers inherent to practicing medicine in the prehospital environment and list some specific potential threats.

  
  
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  Define size-up and discuss the various stages.

  
  
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  Define staging and give examples of when it is necessary to stage.

  
  
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  Discuss potential additional dangers for EMS physicians responding to the scene alone.

  
  
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  Describe some situational awareness tactics.

  
  
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  Describe some ways to assist yourself and other providers in escaping a suddenly dangerous scene.

  
  
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  Describe how to “take cover” on an EMS scene in case of gun fire.

Scene size-up is a multifaceted process that occurs before and immediately upon arrival at the scene, prior to executing any other activities. The purpose of scene size-up is to expeditiously ensure that there is a safe scene on which to provide care, and that the proper resources are summoned to the scene according to the number of patients and their specific care needs. Many scenes evolve even after the first unit has arrived, and various specialty units have different perspectives on the size-up of the same scene. The hazardous materials team will have a different focus and perspective during size-up than the first arriving advanced life support unit. Just as a scene is dynamic, aspects of the size-up should be reevaluated over the course of an incident. The components of scene size-up require simultaneous assessment and include the review of dispatch information, identification of the number of patients, identification of mechanism of injury or nature of illness, resource determination, standard precautions determination, and assessment of scene safety. These components of size-up can initially be assessed from the relatively safety of the emergency response vehicle (Box 30-1).

Reviewing and giving consideration to the clues given in the dispatch information should occur en route to the scene. Professional emergency medical dispatchers (EMDs) are trained to extract crucial information from the caller that will help determine response priority, numbers of units needed, safety concerns, and even what entrance to use to reach the patient most efficiently (Box 30-2). They will communicate if there is a known presence of weapons or violent persons. When considering the dispatch information en route to the scene responders should be prepared for the worst case scenario differential diagnosis. The relevant differential based on the dispatch information can provide clues as to what equipment should be brought to the patient, and those pieces that might be left in the vehicle. Dispatch information may prompt the physician to bring specialized equipment such as a mechanical resuscitation device, an obstetrics kit, or a bariatric stretcher with plenty of manpower to utilize it. Dispatch information may also prompt a responder to request certain resources to scene before they even arrive (Box 30-3). Many dispatch centers have the capability to dispatch these resources automatically based on call criteria.¹

Scene physical locations as dispatched can be vitally important in performing a size-up, and forming a mental framework for patient injuries or illness. A motor vehicle crash dispatched as “in front of the post office on Smith Street downtown” may prompt a completely different approach, response level, and injury differential diagnosis as compared to a motor vehicle crash at “mile marker 132 on Interstate 4.” A dispatch to a “­person down” at a cardiologist’s office may evoke different concerns than a “person down” at a pediatrics office or at a drug rehabilitation facility. The location may also be associated with common circumstances and/or patient complaints/conditions. Experienced providers within the system might be able to anticipate these conditions based on the usual modus operandi of the patient or persons living there, know the best approach to the scene, and also anticipate specific hazards.

Mobile wireless Internet connectivity and electronic charting permit additional uses of dispatch information in scene size-up. En route to a scene, a savvy emergency medical services provider or EMS physician could search the address in the electronic charting database, and for patients residing or transported from there in the past, the past medical histories, medications, and allergies, as well as prior reasons for emergency response could be immediately available. Scanned ECGs and patterns of emergency medical services utilization may also be available. There may be a different index of suspicion for illness regarding a patient who has been transported numerous times per year to all different area hospitals, as compared to someone who, despite their advanced age, has never before utilized emergency medical services.

Emergency medical dispatchers (or call taker) continue to gather additional information as the caller remains on the line, and will update responders to this pertinent new information. The review of dispatch information, as in all components of scene size-up, is ongoing.

Expeditious assessment and reporting of the number of patients at the scene is crucial, as resources from outlying areas may need to be mobilized quickly. Identifying the number of patients and an attempt at quantifying the number requiring advanced life support or basic life support is key.

Keeping a list of patients denoting their approximate age, sex, presenting problem, and START triage designation allocates different resources to patients based on certain physiologic parameters. Various triage algorithms designate patients into four categories: require no acute care, require urgent but not immediate care, require immediate care, and those with no hope for recovery. The first step is to survey the scene from the vehicle, then make a quick walk-through of the scene if there are no obvious hazards. Some scenes may be larger than anticipated, and some patients are not identified until well into the incident. Using clues like mechanism of injury, trajectory of a vehicle, and sounds coming from unexpected locations helps the physician piece together the scene.Utilizing bystanders’ knowledge of the number of patients is also a good tactic to estimate the number. It is important to remember that bystanders may have seen the unfolding of events that lead to the emergency, or may have taken some patients away from the scene for their safety. All nonemergency vehicles around a motor vehicle crash scene should be assessed for possible patients, even if it was dispatched as a single car crash. Emergency vehicles that arrived before you may be keeping patients safe. Many bystanders and passersby will take victims into their own vehicles to stay warm and safe. Patients may be scattered around, under, behind, and inside wreckage on the scene of a trauma and even furniture, appliances, and other belongings in their own homes.

More than one patient should be suspected especially in the following scenarios: two car motor vehicle crashes, car seats or diaper bags found in the wreckage, and twin spider webs on the windshields; if no one is inside the car check around the car and in front of it for ejected occupants. Exposures to the elements and environmental toxins often produce multiple patients.

Any scene should be approached with the questions, “Could there be other patients involved in this incident?” and “Are there more patients here than the responding units can transport?” If the answer is yes, multiple casualty protocols need to be initiated. Depending on location and system status, even incidents with just a few patients may require the simultaneous dispatch of units from over an hour travel time from the scene, and can overwhelm a rural emergency medical services system with few resources, or even an urban one which is already operating at full capacity. The term multiple casualty incident has replaced mass casualty incident in many jurisdictions, to encourage incident command processes in all incidents requiring more than one transporting unit, even when there are not dozens of patients. Arrival of multiple units from potentially different directions adds hazard as well as needed assistance and the EMS physician should keep this in mind when maneuvering on the scene.

In order to proceed with the appropriate evaluation and treatment plan, it is necessary to quickly identify the mechanism of the patient’s injury or the nature of their illness. Is the patient dispatched as a “man down on the sidewalk” someone who is lying next to a mangled bicycle in a puddle of blood next to a patch of roadway with skid marks, or an older person wearing a jogging head band, MedicAlert tag indicating diabetes, and uninjured at first glance? One patient will require a rapid trauma assessment and law enforcement notification, while the other will require a primary medical survey and workup.

Mechanism of injury has traditionally been taught as an indicator of patient outcome and expected injury patterns. In 2008 in Victoria, Australia, researchers performed a retrospective analysis of 4571 cases which met the established criteria for high-risk traumatic mechanism of injury, but without evidence of injury on initial evaluation.² Forty five patients (1%) were considered to have major trauma requiring admission. The authors concluded that mechanism of injury alone is a poor indicator of major trauma, with the exception of entrapment greater than 30 minutes or fall greater than 5 meters. Although its application to patients without obvious signs of injury is questionable, traumatic mechanisms can be evaluated to guide the provider’s history and examination.

Upon arrival at a motor vehicle crash scene, attention should be paid to evidence of impacts or rollovers such as bent wheels, blown-out windows, crushed roofs, and damaged trees, telephone poles, and guard rails. Rollovers and airbag deployment can indicate the speed of the crash, as well as the potential for secondary impacts. A bent steering wheel or dashboard may increase suspicion for certain thoracoabdominal injuries, and shattered glass increases the likelihood of bleeding wounds and foreign bodies. Windshield “spider webbing” usually indicates an unrestrained passenger with a head strike on the windshield. Items strewn about the vehicle should be considered projectiles of secondary impact to your patient. Nature of illness is the medical corollary to the traumatic mechanism of injury. Just as the condition of a motor vehicle can suggest an injury pattern in a patient, the scene of a medical patient offers many clues to the disease process before patient contact is even made. Patients may be in extremis or have communication barriers that prevent them from providing you history, but the scene can provide valuable clues.

During each phase of the call certain questions about the scene may be considered: Is there garbage piling up on the porch, or a driveway that has not been shoveled for days in the dead of a snowy winter? Does the house smell of human waste? Is there a significant odor of tobacco smoke as the door is opened? These conditions often reflect poor health of the occupants of the dwelling, and a social support structure that is not effective or existent. A home with the windows open in subzero temperatures and human waste in the living space may reflect acute mental illness or delirium. An empty refrigerator or thermostat set where air conditioning and heating are at an absolute minimum might suggest socioeconomic difficulties, which are a reflection of, and contribute to, morbidity. Medications that can foretell medical history might be present in cabinets or in the refrigerator, and drug paraphernalia may be strewn about the house. There may be old hospital wrist bands or bills from hospitals in the home, suggesting recurring illness. The presence of oxygen, nebulizers, and other medical equipment may also paint a picture of the conditions afflicting the patient.