EBM: Hypothermia
Listening to the weather report on my way into work; “Cleveland will see temperatures of 90°F, but feels like 105°F today, be safe out there…” I start to prepare myself for a possible hyperthermic patient to be brought through the doors. I mentally review what I will do to resuscitate that patient should they come. But then I remember, hypothermia can also occur, even if the temperature outside is not freezing and I need to be prepared to care for the hypothermic patient as well.
Hypothermia is defined as any core body temperature less than 35°C and has varying degrees of severity. Mild is typically defined as a core body temperature between 35°C - 32°C in a patient who is awake and shivering, Moderate 32°C – 28°C with altered mental status and lack of shivering, severe <28° C with vital signs present and profound <28°C without vitals. There are multiple different causes of hypothermia that can be lumped into 2 groups: increased heat loss (e.g. environmental exposure) and decreased heat production (e.g. sepsis, inability to shiver secondary to neuromuscular disease, burns, and trauma).
Treatment of the hypothermic patient begins with obtaining vital signs and stabilization of the ABC’s. Obtaining a core temperature, ie oral or rectal, on your patients with altered mental status is a must. There are a few ways to approach the treatment of hypothermia specifically including passive external rewarming, active external rewarming, and active internal rewarming. Passive external rewarming is appropriate for the mild hypothermia and includes removing wet clothing from the patient, placing them in a warmed room and insulating them with warm blankets. With these maneuvers, you should see an increase in core body temperature of about 0.5°C – 1°C/hour. Active external rewarming is appropriate for those patients falling into the moderate severity or those patients with mild hypothermia not responding to passive rewarming. Active external rewarming includes using forced warmed air covering like a Bair Hugger or ArcticSun warmer, hot packs and warm humidified air via facemask or ET tube. Active internal rewarming should be used for any patient with a core temperature of less than 28°C and includes warmed IV fluids to 40°C, warmed water lavage of the bladder, thoracic cavity, peritoneum, and GI tract, as well as initiating ECMO, cardiac bypass or dialysis.
Disposition of the hypothermic patient depends on the severity and cause of the hypothermia and safety of discharge for the patient. For example, if the patient presented because of environmental exposure, sending them back to that environment is not safe. If the patient required active external rewarming, consider admitting for observation. If the patient required active internal rewarming, especially any form of lavage, consider admitting to the ICU for further care.
Special consideration should be paid to the patient in severe and profound hypothermia. Core body temperatures <30°C have a high likelihood for dysrhythmias including V.tach and V.Fib and a low likelihood for response to medications and electricity to fix the dysrhythmia. If you are planning to place a central line, be cautious about where your guidewire is as you do not want to trigger a PVC. Femoral lines are useful in this situation. If the patient has any organized rhythm, no matter how slow, do not initiate CPR if you feel a pulse as this can trigger ventricular rhythms. Give yourself at least 45seconds to feel for a central pulse. If the patient is in cardiac arrest with no organized rhythm, start compressions and continue while actively internally rewarming the patient. It is unlikely that normal ACLS interventions are going to work when the body is <30°C, but trying a single defibrillation with a dose of epi is advised. If this does not work, rewarm the patient by about 5°C and retry ACLS. Normal signs of death like fixed and dilated pupils, acidosis, and prolonged asystole are not useful in the patient that is >30°C. CPR must be continued until the patient is at least 32°C. If asystole persists once the core temperature has reached ~32°C, CPR can be terminated. There is also evidence that if the potassium is >12 or if the body is too frozen for the chest to compress and recoil CPR can also be terminated.
POST BY: DR. JENNIFER CAPREZ (R3)
Resources
Farkas J. “Hypothermia - EMCrit Project.” EMCrit Project. Accessed 17 June 2022.
Nickson C. “Hypothermia • LITFL • CCC.” Life in the Fast Lane • LITFL, Accessed 17 June 2022.
Swaminathan A. “Accidental Hypothermia - REBEL EM - Emergency Medicine Blog.” REBEL EM - Emergency Medicine Blog. Accessed 17 June 2022.
James A, Glauser J. Hypothermia. Crit Decisions in Emerg Med. 2011; 25(5).
“Accidental Hypothermia - WikEM.” WikEM, https://wikem.org/wiki/Accidental_hypothermia. Accessed 17 June 2022.
“UpToDate.” UpToDate – Evidence-Based Clinical Decision Support | Wolters Kluwer, https://www.uptodate.com/contents/accidental-hypothermia-in-adults#H1132136995. Accessed 17 June 2022.