presented by Dr. Vikash Mishra
911 is called for a middle-aged male found sleeping on the street by a bystander. EMS recognizes the patient as a chronic EtOH user. On arrival to ED, the pt is obtunded and only responsive to pain.
v/s: HR 60, BP 90/60, RR 18, Spo2 95%. The rectal temperature is 83 degrees (an oral temp is unable to be obtained).
Two peripherals IVs are placed, warm IV fluids are started, and a warming blanket is applied. Pt is subsequently intubated and a central line is placed.
Significant Labs: CO2 18, BUN/Cr 34/1.5, EtOH negative, Trop 0.059, CBC normal, Coags normal, CK 1676. ABG: 7.179/42/41/64% Lactate 3.27
Diagnosis: ACCIDENTAL HYPOTHERMIA
There are 650 deaths/year in the U.S. from primary hypothermia. 66% of pts are male and occurs more commonly in the elderly due to impaired thermoregulation.
Hypothermia = temp< 35 degrees C (95 degrees F) and classified by severity:
Mild 32-35 C (90-95 F), Moderate 28-35 C (82-90 F), Severe <28 C (82 F)
EtOH is the most common contributory factor to hypothermia.
DDX: Must consider anything causing altered mental status based on the history and physical. Also must consider any conditions that are due to Increased Heat Loss, Decreased Heat Production, or Impaired thermoregulation
Diagnostic Testing: Labwork is generally of little help. A variety of electrolyte derangements can be seen as well as renal failure in the severely hypothermic. Of note, the severely hypothermic can have a coagulopathy related to enzyme dysfunction from the cold and acidosis. ABG’s can be difficult to interpret in the hypothermic patient, but can demonstrate a variety of derangements, e.g. metabolic (lactic) acidosis, respiratory acidosis or alkalosis. Imaging studies are of little utility, but the pt’s presentation and the differential diagnosis of the altered mental status may necessitate a Brain CT.
EKG: Numerous EKG changes can be seen in hypothermia, including prolonged intervals, ectopy, AV blocks, bradycardia, and a variety of atrial & ventricular arrhythmias. Classic finding is an Osborn J-Wave seen in 80% of hypothermia cases (this pt’s EKG had them in leads V3-V6. The pt also had AFib, a QRS of 132, and QTc of 493)
1.) Mild Hypothermia: passive rewarming
2.) Moderate Hypothermia: passive rewarming, active external rewarming
3.) Severe Hypothermia: active external rewarming, active internal rewarming, extracorporeal blood warming
Passive external Rewarming: Remove from the environment and wet/cold clothing, blankets.
Active external Rewarming: Warm blankets, heating pads, hot water bottles
Active internal Rewarming: Warm IV Fluids, warm/humidified air
Extracorporeal Rewarming: hemodialysis/filtration, etc.
Be aware of Core Temperature Afterdrop: Continued decrease in the pt’s temp even after removed from the environment and started rewarming. One possible explanation is that peripheral extremity rewarming returns cold acidemic blood to the core, causing further temperature drop and acidosis. Another possibility is peripheral vasodilation when warming causes circulatory collapse. No consensus exists regarding how to best prevent or treat afterdrop.
Mulcahy, A. (2009). Accidental Hypothermia: An Evidence-Based Approach. Emergency Medicine Practice, 11(1).