Mechanism of Injury Motor Vehicle Accidents

Developing an understanding of the mechanism of injury in a motor vehicle accident is paramount to being a good paramedic. Attending motor vehicle accidents are a common occurrence for paramedics but usually one that requires more interventions and considerations by the attending paramedics than medical cases alone.

On top of the usual need for managing areas of concern, such as scene safety, multiple victims, multi-agency responses, communications/organisation, it is vital for the treating paramedics to recognise the mechanism of injury relating to each specific motor vehicle accident. (I acknowledge that motor vehicle accident and motor vehicle crashes have become synonymous).

In order to understand the mechanism of injury in motor vehicle accidents it is important to have a basic understanding of kinetic energy. Kinetic energy can be defined as the energy built up in an object in motion. When an object collides with another object the kinetic energy must be dispersed or the original object will continue to move in the same direction. The amount of kinetic energy required to be dispersed will depend on the mass of the objects in motion and the velocity (speed) in which the object is travelling. It is our understanding of how this kinetic energy is dispersed that allows us, as experienced paramedics, to make educated guesses relating to the type of injuries a patient may have based on the mechanism of injury in a motor vehicle accident.

How to Determine the Mechanism of Injury in a Motor Vehicle Accident

When you arrive at a motor vehicle accident (MVA) as a paramedic, what are your first thoughts about the potential mechanism of injury (MOI)?

When I arrive at an MVA I like to take a few extra seconds as I approach to “take in the accident” and consider the likely injuries that the occupants will have based on the mechanism of injury. This doesn’t mean that I dawdle over towards the vehicles involved, just that I want to look at them and grasp the likely mechanisms.

As a paramedic, these are the main thought processes that I consider when I approach an MVA in relation to the occupant’s mechanism of injury:

1. What type of MVA is it? Is it a head on collision, T-bone/lateral collision, rear collision, or vehicle roll over?  

2. Does the MVA involve one, two or multiple vehicles?

3. What type of vehicles are involved? Are they new vehicles, with built in crash zones (designed to absorb the kinetic energy during impact), or older vehicles, without crash zones? Are the vehicles of similar mass? For example, two sedans. Or, is there a large mass inequality, such as a sedan versus truck, in which I know the sedan is going to absorb much more of the kinetic energy than the truck.

4. What is the damage to the vehicle? In the many years gone past, when cars were made of built like tanks, paramedics looked at the damage to the overall vehicle to consider potential exchange of kinetic energy. Of course, these days, cars are designed to crush and absorb the kinetic energy. Consequently, outside vehicular damage is a relatively useless determinant of the occupant’s potential injuries. What is particularly relevant these days is the deformation that causes intrusion to the inside compartment of the vehicle, such as the driver’s or passenger’s compartment. Is the steering wheel intact? How about the windshield? Dashboard?

5. Where are the three collisions in the crash? These include: the vehicle impact, the occupant’s body impact, and the occupant’s organ’s impact.

6. What safety devices might have affected the exchange of kinetic energy? For example, were the airbags deployed? What type of restraints were the occupants using (if they were restrained at all)? For example, a 2 point (lap seatbelt), 3 point standard seatbelt (lap/and sash), 4,5,6  and 7  point racing harness, or a 5 point child seatbelt? Were the seatbelts worn correctly? Many people will try to loosen their seatbelt to allow them to sleep while another person drives. Was the person sitting normally, or did they have their feet on the dashboard when the airbag deployed?

A the end of the day, although the mechanism of injury in motor vehicles accidents is a good clue to paramedics about the potential injuries obtained by the occupants, they are only a guideline, and paramedics should treat the patients based on a thorough clinical assessment including vital signs and a thorough secondary survey.

Remember to always stay on the side of caution with a motor vehicle accident and stay safe.

Paramedic Assessment and Treatment at an MVA

These are the basic steps that I follow when I attend an MVA:

1. Look for the danger (there’s going to be a lot of it out there).

2. Try to mitigate the dangers. This will include wearing appropriate PPE, such as a reflective vest, helmet, gloves, and goggles (you may look silly but you will go home more comfortable).

3. Park the Ambulance in such a way that you provide the greatest amount of protection to yourself and the patient. This normally requires you to block at least one lane. If you need to, block the whole road and stop all traffic until you extricate the patient. It doesn’t matter if people get to work 20 minutes late because you inconvenienced them. If you end up hit by another car while trying to do your job, no one is going to be better off.

4. Work out how many patients you have and what you are likely to require. An early report to dispatch following an ETHANE report will make it easier for you to get the resources that you require early. ETHANE stands for Exact location, Type of Accident, Hazards, Access and Egress, Number of Patients, and Emergency Services on scene and still required. Determine if the patient is already out of the vehical or still sitting in it. Most people who can will get themselves out of the vehicle.

5. Ask the patient these basic questions:

– What happened? (You can tell early on if they had an LOC or not by their answer to this question).

– Where does it hurt?

– Can you take a deep breath?

6. If possible, perform a Head to Toes – if you can’t get to the patient’s entire body, go as far as you can.

7. Check vital signs.

8. Provide analgesia.

9. Provide spinal immobilisation if concerned about the patient’s spine. This includes: cervical collar, mannual head support, and extrication using a KED and/or spine board. Consider an antiemetic if there is a high suspicious of a spinal injury.

10. Provide basic supporting measures and transport to hospital.