Key Takeaways
- Kinematics is the study of energy transfer during a traumatic event; kinetic energy = 1/2 mass x velocity squared, meaning speed has a greater impact on injury severity than weight
- Newton's First Law (inertia) explains why unrestrained occupants continue moving at vehicle speed during a sudden stop
- Blunt trauma causes injury through compression and deceleration forces, while penetrating trauma causes injury along the path of the projectile or object
- The five types of motor vehicle collisions are frontal (head-on), lateral (T-bone), rear-end, rollover, and rotational; each produces a predictable injury pattern
- Falls are assessed by three factors: height of fall, surface landed on, and body part that struck first
- Scene size-up follows the sequence: BSI/PPE, scene safety, mechanism of injury/nature of illness, number of patients, and need for additional resources
- The Golden Hour refers to the critical first 60 minutes after major trauma during which definitive surgical care should ideally begin; the Platinum 10 Minutes is the maximum on-scene time for critical trauma patients
Mechanism of Injury & Scene Assessment
Understanding how injuries occur is just as important as recognizing the injuries themselves. By evaluating the mechanism of injury (MOI), EMTs can predict injury patterns and prioritize care even before a full assessment is complete.
Kinematics of Trauma
Kinematics is the study of motion and energy transfer as it relates to traumatic injury. The fundamental principle is that energy cannot be created or destroyed - it can only change form. When a moving body comes to a sudden stop, kinetic energy is transferred to tissues, causing damage.
Kinetic Energy Formula:
KE = 1/2 x mass x velocity^2
This formula reveals a critical concept: doubling the speed quadruples the kinetic energy. A car traveling at 60 mph has four times the kinetic energy of one traveling at 30 mph. This is why speed is a far more significant factor in injury severity than weight.
Newton's Laws Applied to Trauma
| Law | Principle | Trauma Application |
|---|---|---|
| First Law (Inertia) | A body in motion stays in motion unless acted upon by an external force | An unrestrained occupant continues moving at vehicle speed during a sudden stop |
| Second Law (Force) | Force = Mass x Acceleration | Greater mass or deceleration produces greater force on tissues |
| Third Law (Action-Reaction) | Every action has an equal and opposite reaction | When a body strikes an object, the object exerts equal force back on the body |
Blunt vs. Penetrating Trauma
Blunt trauma results from an object striking the body or the body striking an object without breaking the skin. Injuries occur through:
- Compression - tissues are crushed between the impacting object and internal structures
- Deceleration - organs continue moving and tear at their points of attachment (e.g., aortic tear at the ligamentum arteriosum)
Penetrating trauma involves an object that breaks the skin and enters the body. Injury severity depends on:
- Velocity of the projectile (low, medium, or high)
- Profile (size of the frontal area)
- Fragmentation (whether the object breaks apart)
- Path through the body (what organs are in the trajectory)
Motor Vehicle Collision Patterns
Frontal (Head-On) Impact:
- Up-and-over pathway: head strikes windshield, cervical spine compression, chest/abdomen strikes steering wheel
- Down-and-under pathway: knees strike dashboard, femur fractures, hip dislocations
- Suspect: cervical spine injuries, traumatic brain injury, flail chest, myocardial contusion, aortic tears, spleen/liver lacerations
Lateral (T-Bone) Impact:
- The near-side occupant receives the most energy
- Suspect: lateral cervical spine fractures, clavicle fractures, lateral rib fractures, splenic injury (left side) or liver injury (right side), pelvic fractures
Rear-End Impact:
- The vehicle and occupant are accelerated forward; the head hyperextends over the headrest
- Suspect: cervical spine hyperextension injuries (whiplash), especially if headrest is improperly positioned
Rollover:
- Multiple impacts occur in unpredictable directions
- Highest risk for ejection if unrestrained
- Suspect: multi-system trauma; injuries may be anywhere
Ejection:
- Being ejected from a vehicle increases the risk of death by 25 times
- The body strikes the ground, other vehicles, or objects at vehicle speed
Fall Assessment
Evaluate falls using three key factors:
- Height - Falls greater than 3 times the patient's height (or >15-20 feet for adults) are considered significant
- Surface - Hard surfaces (concrete) transfer more energy than soft surfaces (grass)
- Body part - Feet-first landings cause calcaneal fractures, lumbar spine compression; head-first landings cause cervical spine and TBI
Scene Size-Up
Every trauma call begins with a structured scene size-up:
- BSI/PPE - Don appropriate personal protective equipment before approaching
- Scene safety - Identify hazards (traffic, fire, hazmat, violence, downed power lines)
- Mechanism of injury - Determine what happened and predict injuries
- Number of patients - Call for additional resources if needed
- Additional resources - Request ALS, fire, law enforcement, helicopter as needed
The Golden Hour & Platinum 10 Minutes
- Golden Hour: The concept that critically injured trauma patients have the best outcomes when they receive definitive surgical care within 60 minutes of injury
- Platinum 10 Minutes: EMTs should limit on-scene time to 10 minutes or less for critical trauma patients to maximize the Golden Hour for hospital care
- These time frames emphasize rapid assessment, essential interventions only, and expedited transport to an appropriate trauma center
According to the kinetic energy formula (KE = 1/2mv^2), what happens to kinetic energy when the speed of a vehicle doubles?
Which motor vehicle collision type is MOST commonly associated with cervical spine hyperextension injuries?
An EMT arrives at a motor vehicle crash scene. What is the FIRST step in the scene size-up?
A patient was ejected from a vehicle during a rollover crash. Being ejected increases the risk of death by approximately how many times?
The "Platinum 10 Minutes" concept refers to:
Match each motor vehicle collision type to its expected injury pattern:
Match each item on the left with the correct item on the right