Chapter 29: Trauma Systems and Mechanism of Injury

What organs are particularly susceptible to blast injuries? What organ is the most sensitive to them?

Air-containing organs such as the middle-ear, heart, lungs, major blood vessels, and the GI tract are the most susceptible to pressure changes. Junctions between tissues of different densities and exposed tissue such as the head and neck is also at great risk of injury. The most sensitive organ to blast injures is the tympanic membrane which evolutionally developed to detect small pressure changes.

What are the limitations of an airbag in an MVA?

Airbags rapidly deflate so they function only for a first impact. Also, front airbags will not activate in a lateral or front quarter panel crash, and without use of a seatbelt, they will not prevent ejection.

Following a primary assessment on a trauma patient, what should determine whether to "load and go" or remain on scene?

An altered mental status, airway or breathing problem, multisystem trauma, or significantly compromised circulation should all indicate the need for rapid transport (i.e. an on scene time of < 10 minutes).

What is a "blast front"? What is the difference between a "positive wave pulse" and a "negative wave pulse"?

Blast front: The leading edge of an explosion. Positive wave front: The phase of an explosion in which there is a pressure front greater than atmospheric pressure (this lessens as you move further away from the center of the explosion). Negative wave front: The phase after the initial positive pressure wave when pressure is less than atmospheric pressure, typically resulting in high-velocity winds as air attempts to return to the displaced space.

What signs and symptoms are commonly seen following an intense pressure wave? Why?

Bradycardia and hypotension. This is a vagal-nerve mediated form of shock without compensatory response, similar to vasovagal syncope.

What specific injuries are associated with seatbelt use?

Cervical fractures due to flexion stresses and neck sprains due to hyperextension and deceleration. Most occur when the seatbelt is used improperly. Note, though: "All arguments against seatbelt use are unfounded."

What is the primary mechanism of penetrating trauma in the U.S.?

Gunshot wounds.

Why is there a risk to taking a reflexive deep breath before impact in an MVA?

Hyper-inflating the lungs and closing the glottis can generate pressures beyond the capabilities of the lungs when the chest is now compressed against the steering wheel or airbag. Similar to a paper bag being popped, these patients are at risk of pneumothorax.

When should a head-to-toe assessment be performed on scene versus during transport?

If the patient's injuries are critical, the heads-to-toe assessment should be part of the primary assessment. If the patient is not critical, the head-to-toe can wait until transport is initiated.

What is the formula for kinetic energy and what is its practical application for EMS?

KE = 1/2 mv^2 This means that when determining the significance of the kinetics of a trauma, the effect of velocity is squared while the effect of mass is decreased by half. In other words, an increase in speed is far worse than an equivalent increase in weight.

What is the significance of physical condition and age as it pertains to injuries sustained from a fall?

Obviously patients with osteoporosis are more prone to injury than athletes who sustain equivalent injuries. Of note, children younger than 3 have fewer injuries from falls greater than three stories than do older children and adults, largely due to their more elastic bodies.

What is the significance of area as it pertains to injuries sustained from a fall?

The greater the area of contact at the time of impact, the more dispersed the forces, meaning peak pressures will be lower.

What is "pathway expansion" with regard to gunshot wounds?

The tissue displacement that occurs as a result of low-displacement sonic pressure waves that travel through the tissue. Think of throwing a stone into a pond. As the bullet moves through tissue, sonic pressure waves push tissues in front of and lateral to the projectile resulting in cavitation and rippling injury.

What is the most important factor for the seriousness of a gunshot wound?

The type of tissue through which the bullet passes. Tissues with high elasticity (such as muscle) tolerate cavitation a lot better than tissues with low elasticity (such as the liver).

What injuries should you be concerned for in a rear-end MVA?

These are the least fatal type of MVA, largely because the rate of acceleration is a subtraction of the two vehicles' speeds. These occupants suffer from sudden forward accelerating forces, and they're at particular risk of hyperextension of the neck - especially if the head-rest is improperly adjusted. One particular concern is the frequency with which back seats collapse, causing unrestrained occupants to be propelled into the backseat.

How do closed spaces affect the damage caused by an explosion?

They significantly increase it, due to a limited dissipation environment for the forces involved in the explosion.

What injuries should you be concerned for in a rotational or quarter-panel MVA? When do these occur?

This happens when a lateral crash is off-center, which effectively causes the vehicle to be thrown across a vector. These occupants typically suffer from a combination of head-on and lateral injuries.

What are the limitations of a motorcycle helmet and motorcycle gear in an accident?

While helmets protect against impact forces to the head, they transmit energy downward into the spine. Further, leather and synthetic gear helps protect against long sliding mechanisms, but offers virtually no protection against blunt trauma and objects or other vehicles.

How should a dislocated knee be splinted in the field? What significance is there to witnessing spontaneous reduction?

A dislocated knee should be splinted in the position found if the patient has good PMS. If the knee reduces spontaneously, this must be communicated to the trauma team as there is possible vascular injury that may now be missed.

What are the four types of motorcycle impacts? What injuries are associated with each?

1. Head-on impact: The motorcycle strikes another object stopping its forward momentum while the rider is propelled forward over the motorcycle. If the rider's feet remain on the pedals, bilateral femur, tibial, and/or foot injuries can occur as the forward and upward momentum of the torso is restrained by the legs. Low-riding racing motorcycles can initially wedge the pelvis during collision, resulting in anterior-posterior compression injuries of the pelvis that can cause neuromuscular compromise and/or open pelvic fractures. This is all in addition to the injuries sustained by being thrown across the ground and potentially into other objects. 2. Angular impact: Here, the motorcycle strikes another object at an angle such that the rider sustains direct crush injuries to the lower extremities between the object and the motorcycle. Open and comminuted lower extremity injuries are often the result and traumatic amputations are possible. Further, because the impact is at an angle, thoracoabdominal torsion and lateral bending spine injuries are possible, in addition to head injury and pelvic trauma. 3. Ejection: Severe abrasion injuries (road rash) down to the bone can occur. An unpredictable number of blunt injuries can further occur from secondary crashes. 4. Laying the bike down: While abrasion injuries on the side being "laid down" by the rider should theoretically be the only injuries sustained, a rider unable to clear the motorcycle can collide into vehicles/objects with devastating results.

What are the three components of the Trauma Lethal Triad?

1. Hypothermia 2. Coagulopathy 3. Acidosis

How do adults usually fall and how do children usually fall? What injuries are associated with each?

Children tend to fall head first, largely due to their relatively heavy heads, so head injuries are common in children. Further, children often fully outstretch their arms to break their fall, so wrist and upper extremity injuries are common. Adults typically try to land on their feet but often land at a backward angle. Known as Don Juan syndrome, this results in foot and lower extremity fractures, and hip, acetabular, pelvic ring, and sacral fractures. Vertebral compression fractures are frequently seen in the T12 to L2 region. Fractures of the forearm and wrist (Colles fracture) are common. Lastly, vertical deceleration forces can damage organs such as the liver, spleen, and aorta.

What injuries should you be concerned for with regard to crush and compression injuries?

Compression head injuries: These may result in skull fractures and are often associated with spinal injury. Remember that brain tissue swells and the increased ICP can be lethal. Compression chest injuries: These often produce broken ribs which can, in turn, damage the lungs and heart. Be particularly mindful of the increased risk this poses for pneumo/hemothorax and cardiac dysrhythmia. Crush abdominal injuries: In addition to the risk of internal organ damage posed by striking an object, compression against the seatbelt can cause bowel rupture, urinary bowel rupture, diaphragm tearing, spinal injuries, and rupture of the abdominal aorta and/or inferior vena cava. Pelvic fractures: External compressive trauma can fracture the pelvis, potentially injuring the urinary bladder, vagina, rectum, lumbar plexus, and pelvic floor, leading to serious bleeding from the iliac arteries. NOTE: Additional injury patterns are those seen in down-and-under and up-and-over pathway mechanisms.

What are the most common injuries associated with primary blasts?

Contusions and hemorrhages, usually on the side facing the explosion but possibly on the opposite side if the blast occurred in a confined area. Pain or tightness in the chest, coughing up blood, tachypnea, and other signs of respiratory distress are common. Subcutaneous emphysema of the chest can occur indicating pneumothorax. Pulmonary edema may also occur. One of the most concerning injuries are arterial air embolisms which can lead to myocardial injury and/or cerebral/neurological disturbances.

What should be assessed on the scene of a motorcycle accident to help clue you in to the significant mechanisms of injury?

Deformity to the motorcycle, the side of most damage, the distance of skid in the road, the deformity of stationary objects or other vehicles, and the extent and location of deformities in the helmet.

What are Newton's first two laws of motion?

First Law: An object at rest tends to stay at rest and an object in motion tends to stay in motion, unless acted upon by an outside force. Second Law: Force = Mass x Acceleration

What is the injury pattern typically seen in adult pedestrians struck by motor vehicles?

First impact: This occurs when a vehicle strikes an adult with its bumper, creating lower extremity injuries, particularly to the knee and leg. The injuries are usually lateral and posterior as adults tend to turn to turn away from the oncoming vehicle. The tibia is usually fractured on the side of impact, and knee dislocations are common. Second impact: This occurs as the adult is thrown onto the hood of the vehicle resulting in head, pelvis, chest, and coup-countercoup TBIs. Lateral compression pelvic fractures are common and can result in open fractures. Third impact: This occurs when the body strikes the ground or some other object after it has been subjected to a sudden acceleration by the colliding vehicle.

What is the injury pattern typically seen in pediatric pedestrians struck by motor vehicles?

Known as the Wadell triad: 1. The bumper hits the pelvis and femurs instead of the knees and tibias. 2. The chest and abdomen hit the grille or low on the hood, resulting in sternal and ring fractures as well as probable abdominal injuries. 3. The head strikes the vehicle and then the hood, resulting in skull and facial fractures, facial abrasions, and closed-head injuries. Note: Children often turn toward an oncoming vehicle (haha, tiny idiots...) rather than to the side of/away from it as adults do. As such, injuries are often anterior/posterior.

Differentiate between the limitations of care provided at the different levels of trauma center:

Level IV: Able to provide ATLS before transferring patients to a higher level trauma center. These include basic ED facilities with 24-hour labs. Level III: Able to provide prompt assessment, resuscitation, and stabilization of injured patients and emergency operations. These have 24-hour EM physician coverage and prompt availability of general surgeons and anesthesiologists. Level II: Able to initiate definitive care for all injured patients. These have 24-hour general surgeons and available orthopedic surgeons, neurosurgeons, anesthesiologists, EM physicians, radiologists, and critical care physicians. Level I: Capable of providing total care for all aspects of an injury - from prevention through rehabilitation. In addition to the Level II qualifications, these additionally have cardiac surgeons, hand surgeons, pediatric surgeons, microvascular surgeons, and hemodialysis available on site.

What is the most common causes of death secondary to blast injuries?

Neurologic injuries and head trauma.

What injuries should you be concerned for in a lateral MVA?

Of particular note, seatbelts do very little in t-bone accidents since they're not designed to prevent lateral movement. Occupants nearest the impact are at risk of direct trauma to the affected side as their heads may strike the impacting side of the vehicle. As the shoulder rotates outward and posteriorly, the chest is particularly exposed to potential trauma. Further, the lateral trauma places contralateral tension on the spine placing it at risk of fracture. Far-side occupants, while at less risk of direct trauma, nonetheless face the same lateral mechanistic injuries. Note that while lateral compression injuries are less serious than anterior compression injuries, these occupants are at risk of the femur being driven through the acetabulum of the pelvis, an injury known as pelvic ring disruption.

How should oxygen therapy and fluid administration be integrated into the treatment of blast injury patients?

Oxygen should be administered to any patient suspected of having a pulmonary injury. That said, be careful using positive pressure since these patients are prone to developing a pneumothorax. Similarly, be careful with fluid administration as they're prone to pulmonary edema.

What are the 5 phases of progressive deceleration as pertains to motor vehicle collisions?

Phase 1: Deceleration of the vehicle; occurs when the vehicle strikes another object and is brought to an abrupt stop, converting the kinetic energy of the vehicle into mechanical energy seen as deformation of the vehicle. Phase 2: Deceleration of the occupants; starts during breaking and continues until the occupants' forward motion is stopped by the vehicle, resulting in deceleration, compression, and shear trauma injuries. Phase 3: Deceleration of internal organs; the body's supporting structures and internal organs continue their forward momentum until stopped, resulting in tears and shearing injuries to internal organs. Phase 4: Secondary collisions; occur when an occupant inside a vehicle is struck by unsecured objects inside the vehicle, often resulting in head and spinal injuries. Phase 5: Additional impacts; all additional impacts the vehicle may receive, such as if it is now struck by another vehicle.

Identify and describe the different categories of blast injuries:

Primary blast injuries: Injuries due to the compression wave generated by the explosion. Air-filled cavities, such as the lungs, eardrums, and other compressible organs, are most prone to these injuries. The closer in proximity to the blast, the greater the compression wave and the greater the injuries. Note that in water, blasts have a 3x greater range due to water's relative incompressibility. Secondary blast injuries: Injuries sustained by being struck by flying debris and shrapnel. Note that a "blast wind" occurs immediately following an explosion - less powerful but longer lasting than the compression wave and due to the force applied to nearby air molecules - which is also capable of flinging debris at high rates of speed. Tertiary blast injuries: Injuries that occur from an individual being thrown by the compression wave into the ground and/or surrounding objects. This can result in a number of blunt and penetrating injuries. Quaternary blast injuries: Miscellaneous additional injuries such as burns caused by the explosion, respiratory injuries from inhaled toxins, and crush injuries from collapsing structures. Quinary blast injuries: Injuries specific to "dirty bombs" which expose individuals to biological, chemical, or radioactive contaminants.

What type of injuries pose the greatest risk of lethal injuries?

Roll-overs. Of particular note, ejection increases odds of death by 800%.

What is the Revised Trauma Score and what was it designed for? How does the scoring system work and what factors are integrated into the score?

The RTS is a physiologic scoring system used to assess injury severity in patients with head trauma. The scale scores patients from 0 - 12 and factors in GCS, systolic blood pressure, and respiratory rate.

What is the significance of height as it pertains to injuries sustained from a fall?

Since gravity is increased for every second squared, one falls from a two-story building 72% faster than one falls from from a single-story building. Since velocity is a squared function of kinetic energy, injuries sustained exponentially worsen from increased heights. As such, falls greater than 15 feet or 2.5 - 3 times the height of an individual are correlated to increased morbidity and mortality.

What is the significance of surface as it pertains to injuries sustained from a fall?

Surfaces such as deep snow that have more plasticity dissipate forces of deceleration, thereby lessening injuries. Surfaces without plasticity, such as asphalt, leave nearly all of the mechanical forces dissipated into the individual.

What injuries should you be concerned for in a head-on MVA?

This injury mechanism results particularly in deceleration injuries which often result in shearing, avulsing, or rupturing organs and their respective fascia, vasculature, nerves, and soft tissues. Of note, be mindful of the following: Brain injuries: The brain is particularly prone to striking the skull resulting in cerebral bleeding and bruising. Aortic injury: The aorta is the most common site of deceleration injury in the chest, and it's easily sheared away from its point of fixation in these mechanisms. Abdominal organ damage: Blunt trauma can cause tearing at their points of attachment, shearing injuries, and/or tearing of the abdominal wall. The liver, kidneys, pancreas, spleen, and large and small intestines are particularly vulnerable. Kidney injury: The forward motion produces tears to the organ and points of attachment with the abdominal aorta and renal arteries. Bowel injury: While motion of the large bowel is restrained, the small bowel can tear and dump its contents into the abdominal cavity. NOTE: Additional injury patterns are those seen by crush and compression injuries at the time of impact.

What is the "down-and-under" pathway with regard to MVA injury mechanism? What injuries are typically associated with this?

This pathway is experienced by sliding under the steering column or dash. The knees hit the dashboard, transmitting the energy of the deceleration up the femurs to the pelvis. If the feet are not locked by the brake pedal or floorboard, the energy along the tibia is transferred into the lower leg with no immediate injury. If, however, the feet are locked in place, femur fracture and/or dislocation can occur. Also watch out for possible knee fractures/dislocations. Meanwhile, the torso continues forward until it impacts the steering wheel, dash, seatbelt, or airbag system. As such, look for rib fractures and cardiopulmonary injuries secondary to compression mechanisms.

What is a multisystem trauma?

Trauma that affects several body systems.

What is the "up-and-over" pathway with regard to MVA injury mechanism? What injuries are typically associated with this?

Typically seen by unrestrained occupants, the lead point here is the head. Rotation occurs around the ankles with the occupant impacting the windshield, roof, mirror, or dashboard, causing serious compression and deceleration injuries, particularly to the head and spine. Keep in mind that if the patient ejects, secondary injuries will be sustained from striking the ground and/or objects that now strike the patient.

What physiologic criteria necessitate transport to a trauma center?

a. A GCS score ≤ 13 b. A systolic blood pressure < 90 mmHg c. A respiratory rate < 10 or >29 breaths/min, or the need for ventilator support

What mechanism of injury criteria necessitate transport to a trauma center?

a. An adult fall from > 20 feet, or a pediatric fall from > 10 feet or 2 - 3x the height of the child. b. An MVC with > 12" intrusion into the passenger compartment or > 18" intrusion anywhere. c. An MVC with partial or complete ejection. d. An MVC with the death of another occupant in the same passenger compartment. e. An MVC with vehicle telemetry data that suggests a high mechanism of injury. f. Pedestrians or bicyclists struck by a vehicle at > 20 mph. g. Motorcycle crashes at > 20 mph.

What anatomic criteria necessitate transport to a trauma center?

a. Any penetrating trauma to the head, neck, torso, or or extremities proximal to the elbow or knee. b. Chest wall instability or deformity. c. Two or more proximal long bone fractures. d. A crushed, degloved, mangled, or pulseless extremity. e. Amputation proximal to the wrist or ankle. f. A pelvic fracture. g. An open or depressed skull fracture. h. Paralysis.

In addition to the formal trauma criteria, what additional factors should be taken into account when deciding whether to transport a patient to a trauma center?

a. Patients > 55 years of age. b. Adults > 65 years with a systolic blood pressure < 110 mmHg. c. Patients on anticoagulants or who have bleeding disorders. d. Women > 20 weeks pregnant. e. Low-impact mechanisms in older adults. f. Patients with burns in addition to other trauma should be considered for transport to a burn unit. g. Children should be considered for treatment to a pediatric-capable trauma center. h. EMS provider judgement.

According to the Association of Air Medical Services, in what circumstances should air transport be considered?

a. There is an extended time required to access or extricate a remote site or trapped patient, thereby depleting the ideal time frame to get the patient to a trauma center by ground. b. The nearest trauma center is > 20 - 25 miles away. c. The patient requires ALS care and there is no sufficiently near ALS ground unit. d. Traffic conditions or hospital availability make it unlikely that the patient will make it to the nearest trauma center within an appropriate time frame. e. There are multiple patients who would overwhelm the resources of nearby trauma centers. f. Local EMS systems require that patients be brought to the nearest facility for stabilization before being shipped out, thereby delaying the time to definitive care. g. There is a multiple casualty incident.