Tisherman- Hypothermia, coming to trauma bay near you!

Clinical Pearls

Accidental Hypothermia

• Exposure hypothermia
  • Heat loss by conduction, convection, evaporation, or radiation to the environment
    • Risks: #1 Alcohol
      • Decreased shivering
      • Increased vasodilation
      • Poor nutrition → less heat generation
      • Poor judgement
    • Contributing factors:
      • Exposure, age (decreased thermoregulation), nutrition, health (neuro disease, endocrinopathies, sepsis), skin conditions (burns), medications (Benzos, TCA, barbs)
  • Need a core temperature!
  • Then you need to stage the patient for management:

• Organ systems affected by Hypothermia:
  • “Umbles”
    • Stumbles
    • Mumbles
    • Fumbles
    • Grumbles
  • CNS changes
    • Agitation → lethargy → coma
    • Decreased metabolism, 6-7% per ºC (used in TTM)
    • EEG silence at 19-20°C
    • Need to rule out other neuro pathologies (bleeds, ischemia)
  • Respiratory
    • Tachypnea → bradypnea → apnea
    • Bronchorrhea, pulmonary edema
    • Intubate! – airway protection and apnea
  • Cardiac
    • Osborne (“J”) waves
    • Arrythmia progression: a fib/flutter → v fib → asystole
      • Treat with rewarming and standard ACLS methods
      • Need to be >30ºC for cardioversion
      • Pacing: transcutaneous>transvenous
  • Renal
    • Cold diuresis
      • Vasoconstriction (pseudo-volume overload) leads to increased UO
      • ADH is decreased
        • Decreased secretion
        • Decreased tubular sensitivity
    • Capillary leak
    • Adds to “rewarming shock”
    • Consider rhabdo – CPK
  • Acid/Base
    • PaO2 decreased 7.2% per ºC
    • PaCO2 decreases 4.4% per ºC
    • pH increases 0.015 per ºC
      • “pH stat” – correct pH with CO2; where “alpha stat” has no correction
  • Electrolytes are an issue
    • K will shift into cells, and will be released with rewarming!
  • Coagulopathy
    • Plts are sequestered
    • Decreased coagulation factors
      • ?fibrinolysis
        • not significant until <34ºC
  • #1: ABCs!! and then treat the underlying cause
• Re-warming
  • Passive external rewarming
    • Blanket
  • Active external rewarming
    • Warm water
    • Heating pads
    • Heated air convection blankets
    • Afterdrop
      • As the cold blood from the extremties is shunted to the core and is associated with a drop in temperature
  • Active internal rewarming
    • Airway rewarming
    • Warm IV fluids
    • Warm irrigation of pleural, peritoneal, mediastinal spaces
      • Esophageal cooling/warming device
    • Intravascular device: Servo controlled via central line
    • VA-ECMO!

• Signs of irreversibility 
  • Injuries incompatible with life
  • Hypothermia after prolonged normothermic cardiac arrest
  • pH <6.8 or K >12 mEq/L
  • Chest wall decompression is impossible
• Miscellaneous factors associated with hypothermia:
  • Drowning
    • Risks: Male, <20yo, pre-existing conditions (sx do), alcohol, ineffective safety barriers, hyperventilation (Shallow water blackout syndrome)
    • Resuscitate if <1 hour
    • Inhalation of water (not always)
      • Pulm edema
    • Aggressive treatment until warm
  • Frostbite
    • Minimize exposure and additional trauma (no massage)
    • Warm water bath (not hot water)
    • Debride or amputate
      • Wait for demarcation

Hypothermia and trauma

• Predisposed to hypothermia due to:
  • Exposure, blood loss, infusion of cold fluids, limited heat production
  • Worry about the Triad of Death
• Hypothermia < 35°C = 3x risk of death!

Therapeutic hypothermia

• Populations:
  • Cardiac arrest
    • Aim for core temp of 32 – 36 °C for at least 24 hours after achieving target temperature
  • Head trauma/TBI
    • NABISH I: no benefit of hypothermia
    • NABISH II: earlier cooling was beneficial for SDH/EDH
    • Eurotherm study: hypothermia for elevated ICP after TBI
      • No benefit!
      • Actually: favored Normothermia
  • Spinal cord injury
    • Limited data
      • Miami project of ASIA A patients cooled + early decompression
        • Some people improved
  • CVA
    • Ongoing trials, no data yet
  • Acute myocardial infarction
    • Cooling w/in 6 hrs of STEMI, x 1.3-4.5 hours, with primary PCI
      • No benefits
  • Acute hepatic failure
    • Decreased ICP
  • ARDS/Sepsis
    • Ongoing trials, no data yet
• TTM- How to do it?
  • Same mechanisms for rewarming but used to cool
  • Treat shivering
    • Sedation
    • NMB
    • Surfaced warming
    • Medications while awake!
      • High dose Valium
      • Precedex gtt
• Emergency preservation and resuscitation (hypothermia for trauma!)
  • Animal data: the colder the animal is, the longer they can tolerate an arrest
    • Kept cooled x 36 hours = great outcomes
  • EPR-CAT Trial
    • Need to identify candidates w/in 5 minutes of pulselessness
      • 18-65 yo w/ signs of life on hospital arrival
    • Cool to 10ºC → hemostasis → CPB/Control bleeding
      • End point: survival without significant neuro deficts
    • Currently ongoing at STC