Posts Tagged ‘mass casualty incident’

Marion County MRC Set-Up. Photo by Sheila Sund.

Marion County MRC Set-Up. Photo by Sheila Sund.

Our Medical Reserve Corps team recently provided first aid and first response for 4 days at a large public event called the Great Oregon Steam-Up. Although we didn’t realize it until fairly deep in planning, this was a high hazard event with a small but real risk of mass casualties. For example, in 2001, a steam tractor exploded at the Medina County Fairgrounds in Ohio (a similar event) killing 5 people and injuring 47. Although luckily nothing happened at our Steam-Up, I prepared to run first response, including triage and initial treatment for up to 30 minutes until fire and emergency medical services arrived and took over.

It was a great impetus to learn what happens to people when things blow up. You may not worry about tractor explosions unless you’re into antique machinery, but there are plenty of others things that go boom. From natural gas to chemical factories, bombs to trains – the possibility of explosion surrounds us every day.

San Bruno Pipeline Explosion, 2010. Image by Thomas Hawk.

San Bruno Pipeline Explosion, 2010. Image by Thomas Hawk.

Bystander Role in an Explosion

What is your role if an explosion happens near you? In videos of the Boston bombing, we all saw citizens rush to help (many were actually Massachusetts Medical Reserve Corps members on scene to help with Marathon medical issues). The absolutely, positively most important thing  – do not enter any area that could be unsafe. Fire, smoke, damaged buildings, chemicals, and things that could still explode – all these could injure or kill you while you are trying to help. With any possibility of terrorism, you also have to worry about “a secondary device” – a second bomb time delayed to go off once emergency responders reach the scene. Untrained heroes often end up just increasing the victim count.

If you are trained, you might have a temporary role after an explosion – depending on when and how many official responders arrive. After scene safety, start with triage, which means sorting victims quickly to decide who needs help first. To learn more about mass casualty triage, check out my post “Triage – Who Needs Treatment”?  I’ve included potential triage colors in the discussion below. Red means urgent medical care needed to prevent death or severe harm, and yellow means medical care required but could be delayed several hours. Green patients may not need hospital level care. Black means dead (or likely to become so with available resources).

An explosion damages the human body in many ways. Experts divide injuries based on relationship to the blast. It’s a nice way to understand injury causes, but it doesn’t mean that primary injuries are worse than secondary, which are in turn worse than tertiary. In fact, secondary blast injuries kill the greatest number of people.

**Warning** – the rest of this post is definitely medical and trauma. Some find this fascinating – others think its gross and depressing! If you are in the second group, you might want to quit now.

Primary Blast Injuries

Primary blast injuries are caused by the actual blast wave passing through the body. They occur mostly with high energy explosions in enclosed spaces. Blast waves literally bounce off walls, damaging the body both coming and going. Corners are particularly bad, with blast waves reflecting back and forth –through you! Blast wave intensity drops quickly with distance from the explosion, as long as it doesn’t bounce.  The likelihood and severity of primary blast injury from an explosion is tightly tied to victim location – indoors or outside, distance from the explosion, and proximity to walls –all things a responder could take note of.

The blast wave compresses everything it goes through. Internal organs containing air are particularly vulnerable – lungs, stomach, intestines, and tympanic membrane (ear drum). Air compresses differently than tissue, causing shearing, tearing, and bleeding where the two meet. Although often rapidly fatal, primary blast injuries sometimes take hours or even a few days to develop. If someone close to a high energy explosion leaves without medical evaluation, they could develop delayed life-threatening complications. All victims of an enclosed high energy blast deserve at least a yellow tag.

Blast lung chest X-ray - all explosion victims should get one! Photo from  Textbook of Military Medicine, part I, volume 5, page 302.

Blast lung chest X-ray – all explosion victims should get one! Photo by

Blast lung causes severe lung bruising and bleeding into the air spaces – which means no oxygen exchange. Air also leaks from the lungs into the chest cavity (pneumothorax) or chest wall (subcutaneous emphysema).  Blast lung can occur without other signs of injury! Some blast lung victims have obvious respiratory distress (tagged red – or black if hospital care delayed), but others just have symptoms, including shortness of breath, chest pain, cough, or bloody sputum. Tag them red or yellow depending on severity. Blast lung can take up to 48 hours to fully develop.

Air bubbles (known as air emboli) sometimes leak into torn lung blood vessels. The bubbles float downstream, eventually blocking smaller blood vessels, causing stroke, spinal cord injury, or damage to organs like the kidneys. You have to be pretty darn clever to recognize air emboli in the field.

Primary blast injuries to intestines and stomach cause internal bleeding. Children are particularly high risk. Watch for abdominal pain, tenderness to touch, nausea and vomiting, fever, or signs of internal bleeding. Patients with abdominal symptoms are usually tagged yellow if breathing and circulation is good, but watch them closely for signs of shock or dropping blood pressure. This could signal internal bleeding and a switch to red. Abdominal blast injuries are again notorious for delayed onset, sometimes causing intestinal rupture into the abdominal cavity 2 or 3 days later.

The tympanic membrane (eardrum) is so susceptible to blast damage that an ear exam is a reasonable screening for asymptomatic explosion victims. A normal tympanic membrane rules out other significant primary blast injuries. On the other hand, a damaged tympanic membrane doesn’t predict serious injury. It occurs at lower blast pressure than other organs. By the way, everyone knows about blast related hearing loss. It is often caused by inner ear damage, and doesn’t predict tympanic membrane damage.  Another primary blast injury is a ruptured globe (the eyeball – the yuckiest injury in my mind).

Secondary Blast Injuries

Secondary blast injuries occur from projectiles – anything flying through the air! They cause the most deaths and the most gruesome pictures. Terrorists add junk to bombs just to increase projectile injury. Projectiles cut, penetrate, impale, and amputate. Larger projectiles (pieces of equipment or building) cause blunt trauma and fractures. Cuts and lacerations have occurred up to 2 miles away from an explosion, primarily from broken glass.  Do a wide perimeter check for victims with secondary blast injuries.

Penetrating eye wound. Image by Community Eye Health.

Penetrating eye wound. Image by Community Eye Health.

Projectiles sometimes take unusual paths after entering the body, with a small entrance wound but a large area of internal damage. After triage, trauma screening includes taking off clothing to look for subtle clues. Projectiles are another common cause of explosion eye injury.

Patients with projectile amputations or severe extremity injuries often have internal injuries as well – don’t let gore distract you from the ABCs (airway, breathing, and circulation). Not only are the ABCs your major determinants for treatment and transport (triage color), but you also save lives by focusing on them. Opening and maintaining an airway (A) in the field might keep someone breathing until CPR, oxygen or ventilator support is available.

Severe bleeding falls under C for circulation. Stopping bleeding after an explosion is the most important life-saving field intervention. Direct pressure works most of the time – just push firmly and don’t back off! Use a bandage, a t-shirt, a sock, or even your bare hand if nothing else is available. Stopping bleeding is more important than cleanliness. If a foreign object is visible in the wound, leave it there and apply pressure on either side. The foreign object might actually be blocking some blood flow.

Military tourniquet training. Photo by Army Medicine.

Military tourniquet training. Photo by Army Medicine.

If extremity bleeding cannot be stopped in any other way, tourniquets are the answer. The prolonged wars in Afghanistan and Iraq greatly improved our knowledge of field trauma. Despite old-time warnings, we now know that proper tourniquet use stops life-threatening bleeding with minimal risk to nerve or underlying tissue. The tourniquet must be several inches wide – no belts or shoelaces please! The tourniquet is applied above the injury and tightened to completely block the pulse. Write down the time it was applied, keep the tourniquet visible, and don’t take it off until the patient is in the emergency room. Our MRC purchased 8 tourniquets (a big expense for our minimal budget) for the Steam-Up.

Red tag anyone with uncontrollable severe bleeding, a tourniquet, or significant internal injury (or black tag, depending on response time). On the other hand, injuries isolated to the arms or legs may look horrible, with bone protruding or partial amputation, but if the ABCs are good, they are yellow.

Projectile injuries are contaminated wounds – they’ve basically injected dirt into the body. Not only does the wound need extensive cleaning (usually under local anesthesia), but it should not be sutured. Closing contaminated wounds leads to severe and sometimes bizarre infections. Contaminated wounds need to heal by “secondary intention” – gradually filling in on their own.

Tertiary Blast Injuries

Tertiary injuries occur from the victim being thrown against things, tumbling along the ground, or falling off things (imagine action movies!). The type and severity of tertiary injuries depends on what they hit, what body part gets the impact, and the force of their movement. Again, noticing victim location and surroundings can tell a lot! Head injuries are the biggest problem here, followed by fracture, with a variety of other dislocations, lacerations, and even amputations thrown in for good measure.

Quaternary Blast Injuries

This is the “everything but the kitchen sink” term for explosion related injuries not caused by one of the three mechanisms above. Burns, inhalation injury, carbon monoxide, and toxic exposures (dirty bombs, anyone?) all count as quaternary, as do injuries from things falling on the victim. Chronic medical issues in both victims and responders can be triggered by the explosion, including heart attack, asthma, and chronic obstructive pulmonary disease – all quaternary injuries. Even behavioral health problems resulting from explosion exposure, including post-traumatic stress disorder, are considered quaternary injuries.

Head Injury

Everyone knows about the large number of United States veterans with head injuries as a result of bomb exposure in our recent wars. Why so many head injuries? Every blast injury category can injure the brain, and many victims have multiple causes. Primary blast injuries cause brain contusion and concussion, and air emboli cause stroke like damage. Poor oxygenation from blast lung causes hypoxic brain injury. Secondary blast head injuries come from flying objects hitting or penetrating the skull. If the victim’s head hits something, closed or open brain damage occurs from impact – tertiary blast injuries. Now add toxic exposures and a little PTSD – it’s pretty amazing any blast victim ever comes out normal neurologically!

Photo by Jenn and Tony Bot.

Photo by Jenn and Tony Bot.

Take- home Lessons

So that’s your quick primer on blast injuries – may you never need this knowledge! But just in case, here are a few take home lessons.

  1. Don’t ever endanger yourself to be a hero!
  2. Once emergency medical responders arrive on the scene, step back unless they ask you to continue helping.
  3. Triage victims first – don’t just assist the nearest person. The person beyond may need help more.
  4. Focus on ABCs, not gore.
  5. Your main interventions are to open airways and control severe bleeding.
  6. Direct pressure works to stop bleeding in most cases. If it doesn’t, proper tourniquet application is appropriate, but only if you know what you are doing.

Stay safe,

Sheila Sund, M.D.

P.S. If you are interested in delving into this subject more, the CDC has a wonderful set of resources on their Blast and Bombing Injuries page.

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