The Hot Topic of Hypothermia in Trauma
Arthur Hsieh // April 1, 2012
Article updated December 27, 2017
Trauma is the leading cause of death in humans from age 1 through 441. As EMS providers, we are trained to assess and manage severely injured patients.
Hypothermic trauma patients are less likely to survive their injuries (Photo Greg Friese)
Ongoing research has refined the way we treat trauma, such as minimizing the use of spinal immobilization, reducing the amount of intravenous fluids in hypovolemia and reducing the use of an advanced airway when ventilating a brain injured patient.
One area of trauma resuscitation receiving increasing scrutiny is the control of body temperature when a patient is severely injured. Unintentional hypothermia is one leg of the so-called "lethal triad" of conditions that can cause death to occur in the weeks after the initial insult:
- Metabolic acidosis: When the body's tissues are underoxygenated, normal aerobic metabolism that produces enough energy (ATP) to power itself switches to a much less efficient anaerobic metabolism. Like a fire that doesn't get enough oxygen, anaerobic metabolism releases toxic byproducts such as lactic acid. This raises the pH of the fluids surrounding the tissues, making metabolism even worse.
- Coagulopathy: The ability for blood to form clots worsens when bleeding becomes significant.
- Hypothermia: Body temperatures below 36 degrees Celsius (96.8 degrees Fahrenheit) causes the body to shiver as a homeostatic mechanism. Shivering in trauma will cause the body to burn through precious ATP unnecessarily. Hypothermia also worsens coagulopathy.
When we talk about shock in trauma patients, what we are really referring to is this lethal triad of acidosis, coagulopathy and hypothermia. The best way to reduce this condition is to prevent it from happening in the first place. This is why we look immediately for the initial signs of shock:
- Anxiety, restlessness
- Pale skin signs, especially at fingernail beds and oral mucosa
Recall that a falling or low blood pressure is a very late sign. In fact, in the initial phases of shock, blood pressure may actually rise briefly. A French study looked at the causes of hypothermia in trauma patients. The researchers found that hypothermia occurred in 14 percent of the study population. While the severity of the injury was the primary cause, the temperature of the transport unit as well as the temperature of the fluid used during resuscitation also played a major part in cooling the patient's core temperature2.
Further analysis shows that while the ambient temperature of the environment plays a small part in hypothermia, having the clothes removed on scene is a significant factor.
Trauma patient care
What does this mean for EMS providers in the management of trauma patients? Consider the following tips:
- Maintain a high suspicion. As discussed earlier, determine whether the patient is in the early phases of shock as soon as possible. Your primary assessment findings, integrated with a rapid understanding of the mechanism of injury, should trigger a presumptive impression of early shock. This in turn should push your team to rapidly extricate the patient off the scene and enroute to a trauma center.
- Time is not the trauma patient's friend. While the "golden hour" has long been questioned as to its precision, the concept of minimizing time on scene is not3. Patients with internal hemorrhage must be treated by a surgeon as early as possible. This means that EMS must perform only the procedures necessary to preserve airway, breathing and circulation on scene. In the vast majority of cases, these are basic life support procedures. Advanced airways and intravenous access have not been demonstrated to be helpful, and in many cases, have been found harmful4.
- Cover up what you expose. While we are trained to "strip and flip" the trauma patient to thoroughly examine the body, recognize that heat loss accelerates dramatically. If the patient begins to shiver, consider this a dangerous sign. While there is no evidence to actively warm the patient, it is clear that keeping them covered with sheets, blankets or reflective covers is essential.
- Chilled liquids may be good for cocktails, but not for trauma situations. A liter of intravenous fluid at room temperature can drop core temperature by 0.25 to 1 degree Celsius in a healthy patient, although it may be worse in trauma patients5. If you must deliver intravenous crystalloid solution to raise dangerously low blood pressure, use fluids that have been warmed prior to administration.
- Keep the ambulance hot. In another words, raise the temperature of the patient compartment of your unit so it's uncomfortably warm for you. It'll likely be better for the trauma patient in reducing heat loss through radiation. Similarly, consider padding or covering your backboard to reduce heat loss through conduction. If your patient is trapped and requires extended extrication, cover the patient as completely as possible to maintain body temperature. Consider bringing a portable heater onto the scene.
Critically injured patients require the utmost of care in the initial resuscitation phase. EMS providers can promote better outcomes by keeping in mind the dangers of hypothermia in trauma patients. Simple interventions can go a long way in preventing such deadly heat loss.
1. Centers for Disease Control. "10 Leading Causes of Death by Age Group, United States – 2010." http://www.cdc.gov/injury/wisqars/pdf/10LCID_All_Deaths_By_Age_Group_2010-a.pdf. Accessed 12 March 2013.
2. Lapostolle, F et al. Risk factors for onset of hypothermia in trauma victims: The HypoTraum study. EPub. Critical Care. 2012 Jul 31;16(4):R142. http://ccforum.com/content/16/4/R142. Retrieved 12 March 2013.
3. Newgard CD, Schmicker RH, et al. Emergency medical services intervals and survival in trauma: assessment of the "golden hour" in a North American prospective cohort. Ann Emerg Med. 2010 Mar;55(3):235-246.e4.
4. Stockinger ZT, McSwain NE. Prehospital endotracheal intubation for trauma does not improve survival over bag-valve-mask ventilation. J Trauma 2004;56:531–536.
5. Gentilello LM, Cortes V, Moujaes S, et al. Continuous arteriovenous rewarming: experimental results and thermodynamic model simulation of treatment for hypothermia. J Trauma 1990; 30:1436-49.