Transcript Frostbite and Hypothermia

Cold Weather Emergencies
Victor Politi, M.D., FACP
Medical Director SVCMV-Physician Assistant Program
Frostbite
Definitions
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Primary VS Secondary
Primary
– Normal thermoregulation
– Overwhelming cold exposure
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Secondary
– Abnormal thermogenesis
– Multiple causes
Physiology: Heat dissipation
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Radiation (55-65%)
• Gradient between environement and exposed
body area.
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Conduction (2-3%)
• Direct contact with cold substance
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Convection (10-15%)
• Wind…
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Evaporation (20-35%)
Physiology…
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Above 32C:
– Vasoconstriction
– Shivering
– Basal metabolic rate
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Below 32C:
– No shivering
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Below 24C:
– No basal metabolic rate
Mild (> 32C)
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Increase metabolic rate
Maximum shivering thermogenesis
Amnesia / dysarthria / ataxia
Loss of coordination
Tachycardic, tachypneic
Normal BP
Moderate (28– 32C)
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Stupor
No shivering
Bradycardic / A.fib
 BP  RR
Pupils dilated (< 30C)
Severe (<28C )
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Coma
No corneal or oculocephalic
reflexes
 BP
V.fib (Maximum risk: 22C)
Apnea
Asystole
Areflexia / fixed pupils
Flat EEG (19C)
Osborn (J) Wave
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Mr. John J. Osborn in the
early ’50’s.
When T< 33C
25%-30% of patients
Positive-negative
deflection
Osborn JJ: Experimental hypothermia: respiratory and blood pH changes
in relation to cardiac function. Am J Physiol 1953; 175:389.
Osborne (J) Wave…
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Amplitude
proportionnal to
degree of
hypothermia
Usually V3-V6
At junction of QRS
and ST segment
Osborn JJ: Experimental hypothermia: respiratory and blood pH changes
in relation to cardiac function. Am J Physiol 1953; 175:389.
ECG in Hypothermia
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Muscle tremors artifacts
Early changes
– Bradycardia
– T wave inversion
– Prolonged PR, QRS and QT intervals
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A.fib when T < 32C
V.fib when T < 28C
Rewarming methods :
Passive rewarming
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Endogenous heat production
– Shivering, metabolic rate, TSH,
sympathetic,…
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Involves decreasing heat loss
– Remove from cold environnement
– Remove wet clothes
– Provide blanket
Rewarming methods :
Active external rewarming
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Heat to body surfaces
– Heating blankets (fluid filled)
– Air blankets
– Radiant warmers
– Immersion in hot bath
– Water bottles / Heating pads
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Less effective than internal
rewarming if vasoconstricted +++
Rewarming methods :
Active internal (core) rewarming
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Warm iv fluids
Warm, humid oxygen
Peritoneal lavage
Gastric / Esophageal lavage
Bladder / Rectal lavage
Pleural / Mediastinal lavage
Microwaves (Diathermy)
Extracorporeal circulatory
rewarming
Warm iv fluids…
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Saline…Not RL
Long tubulure = lost of heat
Can use microwave for saline (No
D5W)
– Annals of EM, 1984 and 1985
– 1L of NS to 39C : 2 minutes at high power.
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No microwave rewarming for PRBC
– Hemolysis
– Hemoglobinuria
– Transfusion reaction
Warm, humidified O2
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42C-46C
Prevent heat loss
Negligible heat gain
Very important in management of
hypothermic patient:
– Up to 30% of heat production lost through
airway.
Gastric/Oesophageal/
Bladder/Rectal lavage
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Not shown to be better than external
rewarming.
Limited surface area
Limited heat exchange
Limited utility (!)
Recommend as last resort when other
modalities not available.
Peritoneal lavage
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Fluid at 40-45C
Up to 12 L/h
KCl free
Hepatic rewarming
Renal support when dialysate is used
2C-4C / h
C.I.
– Abdominal trauma
– Acute abdomen
– Free intra-abdominal air
Extracorporeal blood
rewarming techniques
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Hemodialysis
Arteriovenous rewarming
Venovenous rewarming
Cardiopulmonary bypass
Extracorporeal blood
rewarming…
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Hemodialysis : renal dysfunction
AV depends on the pt’s BP
CPB is the « Gold Standard ».
CPB improves long term survival and
neurologic outcome.
- 15 of 32 long term survivors and none had
neurologic deficits (7 years later).
B.H. Walpoth and al. Outcome of survivors of accidental deep hypothermia and
circulatory arrest treated with extracorporeal blood warming, N Engl J Med,
1997;337:1500-5
In The ED - Prethaw
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After stabilizing core temperature and
addressing associated conditions prepare to initiate rapid thawing
Protect part
Stabilize core temperature
Hydration
No friction massage
In the ED - Thaw
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Rapid rewarming in 38-410 C circulating
water until distal flush (thermometer
monitoring)
Requires 10-30 min with active motion
of part without friction massage
Parenteral analgesia
In the ED - Postthaw
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Ibuprofen 400mg q 12h
Tetanus prophylaxis
Streptococcal prophylaxis for 48-72hr
Elevation
Sequelae
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Neuropathic
pain
– phantom
– causalgia
– “Tabes” burning
– chronic
Sequelae
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Thermal sensitivity
– heat
– cold
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Sensation
– hypesthesia
– dysesthesia
– paresthesia
– anesthesia
Conclusion
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Hypothermia is rare but treatable
Good outcome after prolonged
arrests
Include Hypothermia in your  Dx
Include T as a 5th vital sign…
Call early to organize CPB if
available if patient in cardiac arrest
Prevention is still the best
Other Causes of Hypothermia
Questions ???