It is that time of the year again. You know that time of the year when everyone goes, “Oh my god its cold outside!” Which begs the question; how accurate is your hypothermia treatment information? Hopefully, you have corrected it as guidance changes. Even something as simple as treating hypothermia has updates to keep up with. The biggest thing to remember about hypothermia is that it kills our patients in so many ways. We need to be aggressive and proactive in treating it.
The human body attempts to maintain a core temperature at or near 98.6°F. Hypothermia is defined as a core body temperature < 95°F. The thermoregulatory control center in the hypothalamus receives input from central and peripheral thermal receptors. The integrated thermal signal triggers autonomic reflexes that control the initiation of cooling responses such as vasodilation or sweating (heat loss) or warming responses such as vasoconstriction (heat retention) or shivering (heat production). The body is fairly efficient at both.
However, things such as prolonged exposure, trauma, getting wet, and most importantly blood loss, stops the body from adequately protecting itself and can cause more profound hypothermia. Even at 86°F outside, which feels warm to us, our patients are unable to protect themselves and we can easily cause moderate to severe hypothermia in our patients if we do not treat them appropriately.
The standard classification of hypothermia by core temperature:
- From 89.6 to 95°F (mild hypothermia), thermoregulatory shivering control is functional and increases as core temperature decreases.
- Below 89.6°F (moderate hypothermia), thermoregulation becomes less effective and rewarming is possible only with addition of exogenous heat. As the core temperature decreases below 89.6°F, level of consciousness decreases.
- Below 82.4°F (profound/severe hypothermia), most patients are unconscious and not shivering, and the risk of VF or asystole is high.
The Lethal Triad
The lethal triad of hypothermia, acidosis and coagulopathy has been recognized as a significant cause of death in patients with traumatic injuries. Left untreated, hypothermia, acidosis and coagulopathy bring about and propagate each other, eventually resulting in a predictable but irreversible progression toward death. In one study, it was found that almost half of EMS-transported trauma patients had a temperature < 96.8°F on arrival to the ED. It’s important to note that this study also did not show any difference in incidence due to the time of the year or season.
The coagulation system is a temperature- and pH-dependent series of complex enzymatic reactions that result in the formation of blood clots. It’s been repeatedly demonstrated that as a patient’s core temperature decreases, so does the body’s ability to stop bleeding. This is a result of impaired platelet function, inhibition of the clotting factors, and inappropriate activation of clot breakdown. A core body temperature of < 93.2°F is associated with a 50% increase in mortality in a trauma patient. A core body temp of < 89.6°F is nearly 100% fatal in a trauma patient. That doesn’t leave much wiggle room for us.
With all of this in mind here are a few things we can do to combat this:
- Remember that the triad starts and ends with bleeding. Stop all bleeding as effectively as possible. Then anticipate and expect internal hemorrhage if no external bleeding is noted.
- Always assume your patient’s temperature is dropping right before your eyes, because it is, and much faster than you’d expect.
- Patients can and will become hypothermic in conditions you consider warm. Prioritize limiting a patient’s exposure to the environment, especially during prolonged extrications.
- We don’t bleed normal saline, so limit crystalloid infusion as much as possible. It contributes to the patient’s acidosis and dilutes the remaining clotting factors in your patient’s blood. IV fluids may improve a number but may actually hurt your patient in the long run.
- Aggressively warm the patient. Use blankets, hypothermia kits, warm blankets, etc.
- Administration of TXA if possible. This will help stabilize the clots that are currently formed and slow the breakdown of them.
There are many things that we do in the field that have long term patient outcomes. The aggressive treatment of shock, specifically the hypothermia portion, is one that has real effects for our patients. It is very easy to forget that the patient is cold when we are warm and sweating. With that in mind we need to be aggressive and treat every patient for hypothermia. Talk to your patient and ask if they feel cold. Take a temperature on them, especially our trauma patients. Hypothermia is listed in each and every life threat list. There is a good reason for it, so don’t take it lightly.
Jason Tartalone, NRP, FAWM, WEMT-P, TP-C, EMPF
Sergeant Rescue Training & Consulting