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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.


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

  • Define size-up and discuss the various stages.

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

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

  • Describe some situational awareness tactics.

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

  • 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).

Box 30-1 Elements of the Scene Size-Up on Arrival

  • Evaluate the scene for safety hazards (“the big picture”).

  • Take the necessary standard precautions for the situation (gloves, helmet, ballistic vest, etc).

  • Determine the mechanism of ...

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