Temperature Abnormalities

Temperature Abnormalities – Soibhan Kelley

Hypothermia

Background

  • Core temperature <35°C (95°F)
  • Mild 32-35C (90-95F), moderate 28-32C (82-90F), or severe <28C (82F) +/- pulseless
  • 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:
    • Heat loss: Environmental, burns, iatrogenic (CRRT, cold IVF, massive transfusion protocol), vasodilatory drugs/toxins
    • Decreased heat production: endocrinopathies (hypothyroidism, adrenal insufficiency, hypopituitarism, hypoglycemia), thiamine deficiency
    • Impaired regulation: Spinal cord injury, hypothalamic lesions, other CNS insults, drugs (classes including antihyperglycemics, beta blockers, sedatives, ETOH, alpha agonists, general anesthetics)
    • Multiple mechanisms: sepsis, pancreatitis, DKA

 

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, Blood Gas (ABG preferred), CK, PT/PTT, Fibrinogen
  • EKG

 

Management

  • Treat underlying cause [see appropriate sections]
  • 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)
  • 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 CVICU
  • Identify and manage complications:  bradycardia/heart block, arrhythmias, shock, coagulopathy/DIC, rhabdo; 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 thermoregulate
  • Infectious etiologies:
    • Considerations in the ICU include central-line associated blood stream infection, catheter-associated UTI, pneumonia (including ventilator-associated), sinusitis (esp in pts with NGT or ETT), clostridium difficile, acalculous cholecystitis
  • Non-infectious etiologies:
    • Drug fever
      • Difficult to distinguish from other causes; Can begin hrs-wks after starting a drug
      • Sources: antibiotics (penicillins, cephalosporins, sulfonamides), anticonvulsants (phenytoin, carbamazepine, phenobarbital), allopurinol, heparin, dexmedetomidine
      • Drugs of abuse with sympathomimetic activity (cocaine, meth, ecstasy)
      • Anticholinergic or salicylate intoxication
    • Idiosyncratic drug reactions
      • Serotonin syndrome
      • Neuroleptic malignant syndrome
      • Malignant hyperthermia
    • Transfusion reactions
    • PE/DVT
    • Endocrine: hyperthyroidism/thyroid storm, adrenal insufficiency
    • CNS pathology (intracranial bleed/stroke, particularly hypothalamic region)
    • Malignancy
    • Heat stroke (exertional or non-exertional)
    • Other inflammatory states  Pancreatitis, gout, pericarditis, pneumonitis

 

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 [see appropriate sections]
    • 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) non-humidified nasal cannula or vent circuit
    • Avoid shivering give opiates (except in serotonin syndrome), precedex, propofol, benzos, ketamine
  • Antipyretics
    • Acetaminophen, NSAIDs
    • Block prostaglandin-mediated temperature elevations
    • 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
  • Monitor for complications
    • Rhabdo, DIC, arrhythmias
  • If high suspicion for infection and not improving on antibiotics, consider other infectious etiologies including fungal (ex: candida)