Why Scene Size-Up Is the Most Important Step
Scene size-up is the first and arguably most important phase of every EMS call. It begins before you exit the ambulance and continues as you approach the patient. A thorough scene size-up protects you from hazards, provides critical information about the patient's condition before you touch them, and sets the stage for the entire patient encounter. On the NREMT exam, scene size-up questions are heavily tested because getting this step wrong can result in provider injury or death, a missed mechanism of injury, or an inadequate response.
The components of scene size-up are: body substance isolation (BSI) and personal protective equipment, scene safety, mechanism of injury or nature of illness, number of patients, and need for additional resources. Each component must be evaluated systematically on every call, even seemingly routine ones. Complacency during scene size-up is one of the leading contributors to EMS provider injuries.
BSI and Personal Protective Equipment
Before exiting the ambulance, don appropriate PPE based on the information available. At minimum, put on gloves for every patient contact. Add eye protection and a mask when splash or spray of body fluids is anticipated (trauma, childbirth, airway management). Add a gown when extensive contamination is expected. For suspected airborne infections (tuberculosis), wear an N95 respirator. PPE decisions may need to be adjusted as the situation becomes clearer, but starting with appropriate protection is always easier than adding it later.
Scene Safety Assessment
Scene safety is evaluated continuously, not just on arrival. Scan for hazards as you approach:
- Traffic: Position the ambulance to protect the scene. Wear high-visibility clothing on roadways.
- Hazardous materials: Look for placards, unusual odors, multiple patients with similar symptoms.
- Violence: Assess the environment for weapons, aggressive individuals, signs of a crime scene. Request law enforcement if there is any concern about scene safety.
- Structural hazards: Downed power lines, unstable structures, fire, smoke, water.
- Environmental: Extreme temperatures, icy surfaces, steep terrain, darkness.
If the scene is unsafe, do not enter. Stage at a safe distance and request appropriate resources (fire, hazmat, law enforcement). An injured rescuer becomes a patient and reduces the available resources to help the original victim.
Mechanism of Injury and Nature of Illness
For trauma patients, evaluate the mechanism of injury (MOI) to predict likely injury patterns. A high-speed frontal collision suggests chest and abdominal injuries. A fall from height suggests spinal, pelvic, and lower extremity injuries. Penetrating trauma location predicts which organs may be involved. For medical patients, determine the nature of illness (NOI) from dispatch information, bystander reports, and environmental clues (medication bottles, medical equipment in the home, medical alert bracelets).
Resource Determination
Based on your initial size-up, determine what additional resources are needed. Multiple patients may require additional ambulances. Entrapment requires fire and rescue. Hazmat requires specialized teams. Critically injured or ill patients may benefit from ALS intercept or helicopter EMS. Make resource requests early; it is always easier to cancel resources you do not need than to wait for resources you should have requested immediately. The NREMT tests this decision-making process: when presented with a scenario, identify the additional resources that should be requested based on the situation described.