The lethal triad of death: Made Easy!

In the realms of pre-hospital emergency medicine, there exists a nightmarish combination of conditions known to many as the “trauma triad of death.” It refers to a collection of physiological abnormalities that significantly increase mortality rates in patients with traumatic injuries. The main conditions are hypothermia, acidosis, and coagulopathy. Each condition can worsen the others, creating a positive feedback loop that can lead to death if not interrupted.

When we say traumatic injuries, we mean any injury that causes hypovolaemia. So when we talk about trauma patients, we’re talking about severe blood loss. Which makes up the epicentre of the entire problem.

For better understanding; Hypo = low and Volaemia = Volume (Low fluid volume). When our patient is bleeding heavily, they’re losing fluid, so low volume. In tern, this will lead to something called hypoperfusion which is low perfusion of the organs.

As a direct result of that reduction in volume (blood) our patients core body temperature will start to drop. This can eventually lead to hypothermia. A condition where the body’s core temperature dips below 35°C which poses a significant threat in various pre-hospital healthcare settings for first-responders.

How we hear you say?

Think about it; our blood has many known purposes. it’s more than just red liquid. It’s actually warm red liquid (Approx. 37°C actually). Aside from being warm blooded, the movement of blood going around the body actually helps regulate our bodies temperature. If you’ve lost blood, you’ve also lost warmth. That there is the first condition of the lethal triad of death!

Then What?

Hypothermia can seriously hinder our bodies coagulation system, which is a series of complex cellular reactions that result in the formation of blood clots to stop both internal and external bleeding. It makes sense right? – Even when we’re cold, we don’t work or function to the best of our abilities and it’s no different for our bodies clotting systems.

Here are some key points on how hypothermia impacts coagulation (It’s slightly heavy):

• Platelet Function: Hypothermia can disrupt platelet function, which is crucial for blood clotting. Platelets lack nuclei but perform vital functions in hemostasis and thrombosis. During hypothermia, there can be a slowing down of coagulation enzymes, disordered fibrinolysis, and disruption of platelet function¹.

• Coagulation Cascade: Very mild hypothermia (down to 35°C) generally has no effect on the coagulation cascade. However, temperatures below 35°C can induce mild platelet dysfunction and sometimes a mild decrease in platelet count. More significant effects, such as a delay in the initiation of thrombus formation and a decrease in the speed of clot creation and growth, begin at temperatures below 30°C².

Our patients are now in a worsened state of hypovolemia and hypoperfusion because the bodies ability to from clots is inhibited, which means they’re still bleeding. Now, because we’re still bleeding, we’re also loosing oxygen. this increases hypoperfusion and leads to something called acidosis.

When our trauma patients experiences significant bleeding it can lead to haemorrhagic shock. In haemorrhagic shock, there is inadequate blood flow to tissues, resulting in tissue hypoxia (insufficient oxygen supply). Because our patients can’t use oxygen rich blood for fuel, in an act of desperation, it starts burning other elements, such as glucose as a fuel source. Tissues deprived of oxygen switch to anaerobic metabolism, leading to the production of lactic acid as a by-product.

What the hell are you guys on about?

So, lets make it easy. Acidosis is when there’s too much acid in your body, and it can make you feel pretty sick. Imagine your body is like a hot tub, and for the water to be just right, it needs a good balance of chemicals. If the pool gets too much acid, it’s not going to be fun to relax in, right? Well, your body works the same way. It needs to keep a balance between acid and base (which is the opposite of acid). If there’s too much acid, your body tries to fix it, but if it can’t keep up, that’s when acidosis happens.

There are two types of acidosis and here’s a simple breakdown:

Metabolic acidosis: This happens when your body either makes too much acid, like when you exercise a lot and your muscles get tired, or when it can’t get rid of acid fast enough, like if your kidneys aren’t working right. Or, when you’ve lost loads of blood!

Respiratory acidosis: This is when your lungs can’t get rid of enough carbon dioxide (which is kind of like an acid) from your body, like if you have trouble breathing or a lung disease.

Lactic acid rapidly accumulates in our patients tissues, causing the body’s pH to drop. This drop in pH results in a severe metabolic acidosis. As already mentioned, metabolic acidosis occurs when there is an excess of acids in the body fluids. A lowered PH level is very bad for the body. it damages our tissues, organs and causes what we call decreased myocardial performance (Aka, the heart won’t function very well. Remember, the heart is a muscle and needs the right fuel (oxygen) to function).

Due to the acidosis, our patients heart is not functioning well, therefore causing a reduced cardiac output. which again, worsens hypothermia. Eventually, if this system is not corrected it will cause our patients to go into cardiac arrest and severely reduce the chance of a positive outcome.

So, in summary, Blood loss leads to a drop in our patients core temperature (amongst other things), this then leads onto the development of hypothermia. Hypothermia reduces the working capabilities of our clotting factors. Now because we can’t form any clots (And probably still bleeding) we’re also losing fuel (oxygen). In a last final stand our bodies try and burn glucose as an alternative fuel source. However this results in the creation of lactic acid which screws up the performance of our heart.