Temperature Abnormalities

Cairo De Souza

Hypothermia

Classification

  • Mild, core temperature 32 - 35 C (89.6 - 95 F)
  • Moderate, 28 - 32 C (82.4 - 89.6 F)
  • Severe, <28 C (<82.4 F).

Troubleshoot: True Hypothermia?

  • Ensure thermometer is “low-reading,” standard thermometers not accurate.
  • Core temperature can be measured w/ bladder catheter probe or esophageal probe (may be falsely ↑ if heated oxygen being delivered). Rectal temp can be used but is less accurate.

Etiologies

Hypothermia conditions.

Evaluation

  • Infectious work-up
  • POC blood glucose, TSH/FT4, cortisol, lipase, UA, UDS, EtOH level, additional tox as appropriate, DKA work-up if relevant.
  • Physical exam + history for exposures and trauma.
  • CBC, CMP, Lactate, ABG, CK, PT/PTT, Fibrinogen.
  • EKG

Management

  • Treat underlying cause.
  • Mild hypothermia:
    • Passive external rewarming (PER): blankets, increase ambient temperature.
    • Note that PER requires sufficient underlying physiologic reserve to generate heat. This is often impaired in elderly pts, malnutrition, sepsis.
  • Moderate hypothermia, refractory mild hypothermia, or cardiovascular instability:
    • Active external rewarming (AER): forced warm air (ie Bair Hugger), heated blankets, heat lamps, hot packs (consider burn risk). 
    • Bair Hugger cannot be done on floor because of initial q1h temperature checks, may need stepdown v ICU bed
  • Severe hypothermia or refractory moderate hypothermia:
    • Active core rewarming: Warmed IV crystalloid (limited rewarming potential unless large volume but will decrease ongoing losses), warmed humidified inspired air, warmed bladder lavage.
    • More extreme methods such as peritoneal/thoracic lavage more likely to be used in severe environmental cases in ED.
  • Pulseless severe hypothermia (“You aren’t dead unless you are warm and dead”):
    • Continue CPR until re-warmed as severe hypothermia is neuroprotective and pts can have good neurologic outcomes despite hours of CPR.
    • ACLS medications and shocks will have poor effectiveness; prioritize circulation (i.e. chest compressions) and rewarming.
    • Consider ECMO (likely venoarterial if pulseless); would need transfer to surgical CVICU.
  • Potential complications: Bradycardia/heart block, arrhythmias, shock, coagulopathy/DIC, rhabdomyolysis; rebound hyperkalemia/hypoglycemia with rewarming.

Fever and Hyperthermia

Background

  • Fever: T >38.0°C (100.4°F) driven by hypothalamus activity in response to systemic triggers (i.e. cytokines); may use lower threshold for immunocompromised pts.
  • Hyperthermia: T >41.0 C (105.8°F) uncontrolled heat production with failure of thermoregulation.

Etiologies

Hypothermia conditions.
  • Drug fever potential culprits: antibiotics (penicillins, cephalosporins, sulfonamides), anticonvulsants (phenytoin, carbamazepine, phenobarbital), allopurinol, heparin, dexmedetomidine.

Evaluation

  • Infectious work-up +/- LP; may consider pan-scan if unable to identify source.
  • POC glucose, BMP, LFT, Mg/Phos, CBC w/diff.
  • Consider coags + fibrinogen (DIC), CK/UA (rhabdo), UDS, acetaminophen and salicylate levels, TSH/FT4, cortisol, lipase, ABG.
  • Review medication list: antibiotics, serotonergic drugs, anti-psychotics, recent sedation for OR, or recently intubated with succinylcholine, dexmedetomidine.
  • Consider CT/MRI head.

Management

  • Treat underlying etiology
    • Serotonin syndrome → stop serotonergic drugs; add cyproheptadine.
    • Malignant hyperthermia → activate malignant hyperthermia team; add dantrolene.
  • Cooling
    • Target <38.0°C (100.4°F)
    • Surface cooling: Ice (bath, or ice packs more likely in our MICU), evaporative cooling with misted lukewarm water and fan.
    • Internal cooling: Cold IV fluids, dry ventilation (evaporative) with non-humidified nasal cannula or vent circuit
    • Avoid shivering -> give opiates (except in serotonin syndrome), precedex, propofol, benzos, ketamine.
  • Antipyretics: acetaminophen, NSAID
    • Effective for most causes of fever- infection, pancreatitis, DVT/PE, pneumonitis.
    • AVOID for true hyperthermia (ineffective and potentially harmful) -> neuroleptic malignant syndrome, malignant hyperthermia, serotonin syndrome, heat stroke.
  • Antimicrobials, consider antifungals if fevering through BSA.
  • Monitor for complications: rhabdomyolysis, DIC, arrhythmias.
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