02.06 Crush Injuries

Compartment syndrome is a buildup of pressure in a fascial compartment. As the pressure increases, it restricts blood flow and can eventually lead tyo nerve damage, and muscle and tissue death.

The most common sites for compartment syndrome are the lower leg and the forearm. The amount of damage that occurs is dependent on the time that the pressure in the compartment is increased.

When it comes to assessing compartment syndrome, we look for the 5 Ps.

Pain, we look for pain that is out of proportion to the injury. If the person has a small hematoma on his arm but he is screaming bloody murder...red flag.

Pressure, the compartment, or the extremity will feel tight when you press it. The skin will also appear more taut than usual….red flag

Pallor - as blood flow is compromised, skin color and temperature will begin to decrease...red flag. 

Parasthesias or paralysis - as the nerves are compressed, numbness, tingling, loss of sensation and paralysis can occur….red flag!

Pulses - weak or absent pulses in the distal extremity are a late sign of increasing compartment pressures and a major red flag.

If we suspect compartment syndrome, we want to measure the actual pressure in the compartment and to do that we use a device with a manometer attached to tell us the pressure. A very common type of these devices is the stryker needle...google it. I have worked in several trauma centers and the stryker needle is always there. Your facility may use a different branded device but the purpose is always the same.

We want to make sure the pressure reading is less than 30. Normal readings are from 0-8 mmHg. 30-40 usually indicates ischemia.

The treatment of compartment syndrome, if we're getting those 30-40 readings without meter, is usually a procedure called a fasciotomy. This is when an incision is made through the skin down to the compartment to relieve the pressure. It is not closed right away as to let the pressure decrease and remain that way. Many fasciotomy cases, like to one in the picture, require skin grafts after some time as the wound can not be closed with simple sutures.

One very important note when dealing with suspected compartment syndrome. Its common with injuries for us to want to raise the affected limb above the heart to reduce bleeding...do not do this. We want to keep the affected limb at the level of the heart. Too high and we will drive all those loose byproducts of the crush straight towards the heart (we kind of want to avoid that hotshot of potassium, right). Too low and we risk increasing the pressure. This being the case, keep the limb level with the heart.

Now when we talk about rhabdo, there are a number of things than can cause it. There is a great lesson in the musculoskeletal section on NRSNG if you guys want to learn more but for today we are going to talk about rhabdo that follows a trauma. 

Rhabdo is caused when the stuff that is in the cell leaks into the bloodstream, usually because the cells are broken or have exploded. just think of the trauma behind it. One of the big byproducts of this cellular destruction is the release of myoglobin. Myoglobin is excreted by the kidneys  but too much of it and the kidneys start to die. The myoglobin causes a decreased flow of oxygen to the kidneys and the end result is renal failure. One of the textbook signs of rhabdo is really dark or absent urine. Im gonna talk a little about myoglobin more on the next slide. 

So with the kidneys shutting down, the body can't process the toxins and they build up in the bloodstream. Another result of this is acute confusion. So in our trauma patient, we have to put the puzzle together. Dark urine, acute confusion, traumatic crush injury = rhabdo!

So how do we treat it...we need to flush out the toxins and get those kidneys clean. Normal saline to the rescue. 2 large bore IV’s wide open with several liters going. We want to increase urinary output and improve their mental status. if we monitor both of those things, it will give us a good idea if our treatment is effective. 

So when it comes to metabolic acidosis in trauma, its usually because something is leaking. Think of like a tomato, or an orange, if we squeeze it, it leaks right. Thats kind of the same thing here, but insteat of disgusting tomato guts, the body is leaking things like lactic acid, and potassium, and Oh, MyoGlobin (get it OMG, Oh MyoGlobin...sorry)

So when hypoperfusion occurs, in this case, because of the tissue being compressed in our crush injury, che cells start to produce lactic acid as a byproduct of anaerobic metabolism, and the body becomes acidotic. (Again, NRSNG has a great lesson on metabolic acidosis, were just covering the basics here as it relates to trauma). 

This cell destruction also releases myoglobin, which is excreted by the kidneys. The presence of myoglobin can sometimes help us diagnose as it turns the urine a very dark brown. If you see that your multi trauma guy is peeing something that looks like iced tea, he is probably spilling myoglobin and you need to treat it. 

Along with that lactic acid and myoglobin,  the destruction of cells also causes the leak of large amounts of potassium into the body., This level usually peaks around 12 hours after injury. 

So how do we restore balance, well its actually not that hard, froma first line perspecvtive. If we realize that all of these things, lactic acid, myoglobin, potassium, are all spilling into the bloodstream, we would want to flush them out, right. Get some IV’s started and start running fluids wide open, these patient need several liters of fluids simply to begin to restore balance. with fluids up you can then go about correcting their acidosis or their hyperkalemia with other methods in addition to the fluid resuscitation. 

So you are in the trauma bay and your guy comes in with a suspected crush injury..what do you do..well you have to use what you got.

Look at your patient, does he have any visible signs of a crush injury? and by that, i mean, does it look like any part of his body is squished more than it should be?

Use your ears, is your guy screaming in pain even though you don't see too many visible injuries. Is the pain out of proportion to the suspected injury.

Use your brain guys. Here is where we actually have to think a little. Look at those vital signs, look at hs skin, is he showing signs of shock. We now know the signs of compartment syndrome, do you notice any. Look at the urine, check his mental status, do you think he is going into rhabdo. This is where we start putting together really fast puzzles as we stand in our trauma bay.

And of course, while we may suspect all these things, we need our labs. We need that CMP, the ABG, and we need them quick.

We talked about fluids….lots of them….like really….bag after bag.

If they are bleeding….stop it, control it.

If there is a wound that looks dirty, like if there is glass or gravel or dirt, try to clean it out gently, as best you can. This is not the time to pull our tweezers and remove each individual piece of dust, but a little flush with some saline might help a little.

Get those labs! Check your compartment pressures. And if the diagnosis is confirmed, prep them for a fasciotomy and in turn, the OR.

We talked alot about lactic acid and potassium and myoglobin. It's important with crush injuries to remember your acid base balances and your basic electrolyte values.

As with any trauma, we want to have a solid foundation of anatomy in order to think of the injuries we cannot see.