Temperature Abnormalities¶

Soibhan Kelley

Hypothermia¶

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, drugs (classes including antihyperglycemics, beta blockers, sedatives, ETOH, alpha agonists, general anesthetics)
- Multiple mechanisms: sepsis, pancreatitis, DKA

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

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, rhabdomyolysis; rebound hyperkalemia/hypoglycemia with rewarming

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
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

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

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) with 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
- Rhabdomyolysis, DIC, arrhythmias
If high suspicion for infection and not improving on antibiotics, consider other infectious etiologies including fungal (ex: candida)