Saturday, January 10, 2009

Four Horsemen of a Trauma Death

I am hardly an eschatologist in the traditional sense. However, rather than being someone who studies the end of the world, my profession puts me in a position to be around, albeit uncomfortably, the end of life. At times, that end comes violently, and to stretch an analogy a bit, I'd like to describe what I would call the Four Horsemen of the Trauma Death.

I'll start with the traditional view of what the four horsemen represent in the Bible:

A white horse, its rider holding a bow --- Pestilence
A red horse, its rider holding a sword --- War
A black horse, its rider holding a pair of scales --- Famine
A pale horse, its rider is called Death

OK. It's 1:26AM on a cold January night, and Billy Bob has had a few too many brewskis and several shots of Tequila for good measure. Rushing home on a dark, winding home, he loses his lane, overcorrects, and plows headlong into a 50 year blue spruce at a speed the local sheriff will estimate at 70mph. His last road trip just started off with a bang.

A white horse appears, its rider holding a 6 liter pitcher; this represents the average volume of blood in a typical male. The rider's name is Hemorrhage.

Billy Bob hasn't just hit a tree; the tree hit back, and inflicted a femur fracture, a fractured pelvis, a lacerated spleen, a small intracranial hemorrhage, and a pulmonary contusion. Billy Bob never was much one for wearing seatbelts, you see. Just as the realization that he is in deep kimchi hits him, Billy Bob starts bleeding --- not in a manner he is aware of, but into his thigh, abdomen, and retroperitoneum.

It is surprising how much blood loss can occur from injuries most people today would consider pretty survivable. A patient can park two units of blood into their thigh pretty quickly with a fractured femur; this happens not from laceration of a vessel, but from the bone (and bone marrow) itself. Pelvic fractures may disrupt veins in the pelvis, particularly along the sacrum, and result in substantial bleeding into the retroperitoneum. Occasionally, arterial bleeding may accompany this, along with hemorrhage directly from the bone. Splenic lacerations range from minor to overwhelming, and result in bleeding into the free abdominal cavity.

A red horse appears, its rider holding a block of dry ice; the rider's name is Hypothermia.

A typical cloudless winter night here in the Rocky Mountains is an awe-inspiring sight. The sky is clear and filled with stars not seen in most cities. It is also absolutely stinking cold. Billy Bob is trapped in the front seat of is car, which is no longer running, and the temperature outside is measured in the single digits. Even if he had had his heater on full blast before he mangled the spruce tree, it won't be long before the inside of his car starts to approximate the temperature outside.

Billy Bob, as the occupant of said vehicle, will similarly start to chill out, and not in a good way. As his core temperature drops to a state of mild hypothermia -- 95 to 90 F (35 to 32.2 C) -- he'll start to shiver uncontrollably until his glycogen stores are depleted. His body is basically trying to generate heat in any way it can. Already a little dehydrated from the diuresis caused by alcohol consumption, his volume depletion from bleeding will start to mildly worsen as his kidneys start to pump out even more urine with mild hypothermia. His blood vessels constrict in an effort to maintain core body temperature, his respiratory rate increases, and his blood pressure will mildly increase. This, however, can't go on forever.

A black horse appears, its rider holding a stopwatch; the rider's name is Time.

At this time of night, there aren't many people driving this cold county road, so nobody comes across Billy Bob for about 60 minutes. During this time, he has managed to lose not quite half his blood volume into his abdomen, pelvis, and thigh, and he is clearly hypothermic. The Good Samaritan that finds him fortunately has a cell phone, and calls for help. If he has one, he throws a blanket over Billy Bob. However, this Good Samaritan is well-informed, and has seen the execrable decision by the California Supreme Court regarding helping the injured, so he doesn't really know if he should do much more.

Tick. Tick. Tick. By the time the EMTs arrive, it's been over an hour and a half since Billy Bob deflowered the spruce tree. He's getting really cold now -- moderately hypothermic -- core temperature 90 to 82.4 F (34 to 28 C). This is not going to improve as the EMT's work as fast as they can to get him extricated and initiate treatment, as he will be exposed and may receive cold IV fluids. By the time he hits the ED in the nearest trauma center, he is thoroughly confused, and may even be showing signs of decreased heart rate and blood pressure.

The cumulative weight of time has taken its toll on my body --- my back aches, I've had several surgeries, the gray hair on my head is thinning, and I don't sleep well. For Billy Bob, the cumulative weight of time has now started to compound his problems. Not only is he severely volume depleted and hypothermic, he is starting to develop a coagulopathy. His body is trying to stop his ongoing hemorrhage, and in doing so is chewing through his available clotting factors like Ms. Pac-Man with a bad case of PMS going through a box of chocolates....and thereby gradually depleting them. Additionally, hypothermia has an adverse effect on the clotting cascade, with an approximately 10% reduction in the rate of enzyme reactions of plasma coagulation for each 1° C decrease in core temperature.

Now with a mild coagulopathy, his bleeding increases, not only in his leg, pelvis, and abdomen, but also in his contused lung. This causes worsened exchange of oxygen and CO2, making him hypoxic and acidotic. So, he's got that going for him.

Now, unlike "ER," "House," "General Hospital," and all of those other "doctor shows" that I have never seen, it takes time for the ED staff to get a trauma patient resuscitated. The stopwatch doesn't speed up in the ED, but it doesn't slow down, either. Starting IVs, examining the patient, possibly intubating him, performing an abdominal ultrasound, obtaining a chest X-Ray, obtaining blood for labs, placing a foley catheter.....all of these things take time. The problem is, Billy Bob doesn't have much time left.

A pale horse appears, its rider is called Death.

A frantic display of 21st century medical technology is unleashed on Billy Bob. The ultrasound shows free fluid (blood) in the abdomen, meaning he needs to get to the OR pronto. The unbelievably intelligent ED doc quickly surmised he needed to be intubated, and did so. The trauma bay is kept warm, and the thermostat is dialed up to "Baghdad at noon in July." A warming blanket is placed, and is frequently displaced by personnel trying to care for the patient. Large IVs are placed, and the trauma surgeon decides it's time to start transfusing Billy Bob with O-negative blood because his BP has remained in the balmy 80s despite a few liters of fluids. It doesn't help much.

Hi ho, hi ho, it's off to the OR we go. With a little luck we'll get him back. Hi ho, hi ho!

In the OR, also made as toasty as possible, the anesthesiologist starts to pour blood and factors into Billy Bob like a bartender on free drink night at a strip club. The surgeon is greeted by a large pool of blood in the abdomen, a spleen beat to a pulp and oozing tremendously, and a retroperitoneal hematoma large enough to cover a small polar bear. Out comes the spleen, and the retroperitoneal hematoma is wisely left alone with the hope that it will tamponade. The abdomen is now too tight to close, and every visible surface seems to be oozing; the abdomen is therefore left open with a VAC, which while preserving blood flow to the kidneys and gut, doesn't really help the hypothermia situation much.

By the time the orthopedic surgeon arrives in the OR to place an external fixator, the anesthesiologist is seeing bleeding from Billy Bob's nose and mouth, and there is blood in the endotracheal tube. He is also having a hard time ventilating the patient, who is persistently hypothermic (temp 92) and acidotic. A chest tube is placed first on the side of the contusion, where there is a fair amount of bloody fluid, and for completeness on the opposite side. The contused lung now has the consistency of liver, so high pressures are required to try to get some moderate degree of gas exchange.

At this point, pouring more blood products into Billy Bob is like throwing a cup of water on a burning building. It remains, however, all that can be done, so we do it. Surgeons and anesthesiologists really don't like it when patients die in the OR, so after the "ex fix" has been placed and the femur appropriately splinted, Billy Bob takes his final ride tour of the hospital, to the ICU. Cold, coagulopathic, and comatose, there is nothing else that can be done, and Billy Bob continues to hemorrhage and eventually develops cardiac dysrhythmias and dies.

This is only one of the many ways in which trauma patients meet their end. Despite everyone's best efforts, some patients arrive with injuries that overwhelm them; timeliness is desirable, but not always achievable. But it is important to remember that the original insult to Billy Bob's physiology came well before he hit the tree --- it started with that indefinable transition from sober to drunk.