HYPOTHERMIA, FROSTBITE AND HEAT ILLNESS

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HYPOTHERMIA, FROSTBITE AND HEAT ILLNESS

• Mark Bromley PGY3

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Outline

• Heat Stroke
• Hypothermia
• Frostbite

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HEAT STROKE
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Case

• 68 M is brought into the ED for decreased LOC
• Found in bed in his apartment
• Freezer door was left open
• PMHx
• CAD, CHF, DMII
• Meds
• Metoprolol, Altace, Lipitor, ASA, NTG Patch,
  Gluconorm
• OE
• 42oC HR 65 GCS3
• What are this patients HS risk factors?
• What other diagnoses are you concerned about?
• How would you like to manage?

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Perspective

• Disease of the young and the old
• Outdoor laborers
• Athletes, children, and the elderly
• Proportional to climate
• US
• 20 cases per 100,000 people
• 240 deaths annually
• 1 cause of death among US soldiers in the 1st
  gulf war
• Heat wave in 2003 (France) caused 14,802 deaths
• Life-threatening emergency needing immediate
  treatment

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Heat Generation
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Thermoregulation
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Terminology

• Heat wave
• Three or more consecutive days during which the
  air temperature is gt32.2C
• Heat stress
• Perceived discomfort and physiological strain
  associated with exposure to a hot environment,
  especially during physical work
• Hyperthermia
• A rise in body temperature above the hypothalamic
  set point when heat-dissipating mechanisms are
  impaired (by drugs or disease) or overwhelmed by
  external (environmental or induced) or internal
  (metabolic) heat
• Heat exhaustion
• Mild-to-moderate illness due to water or salt
  depletion that results from exposure to high
  environmental heat or strenuous physical
  exercise signs and symptoms include intense
  thirst, weakness, discomfort, anxiety, dizziness,
  fainting, and headache core temperature may be
  normal, below normal, or slightly elevated (gt37C
  but lt40C)
• Heat stroke
• Severe illness characterized by a core
  temperature gt40C and central nervous system
  abnormalities such as delirium, convulsions, or
  coma resulting from exposure to environmental
  heat (classic heat stroke) or strenuous physical
  exercise (exertional heat stroke)
• Multiorgan-dysfunction syndrome
• Continuum of changes that occur in more than one
  organ system after an insult such as trauma,
  sepsis, or heat stroke

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Progression of Disease
Mild-to-moderate illness due to water or salt
depletion
Perceived discomfort and physiological strain
Changes in more than one organ system
Symptomatic
Sick
Hot Inside
Hot Outside
A rise in body temperature above the hypothalamic
set point
Severe illness characterized by a core temp gt40C
and CNS abnormalities
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Clinical and Metabolic Manifestations

• Hyperthermia
• CNS Dysfunction
• Tachycardia, Hyperventilation (CO2 lt 20)
• Respiratory Alkalosis / Metabolic Acidosis
• Hypophosphatemia / Hypokalemia
• Rhabdomyolysis (?PO4, ?K, ?Ca)
• MODS
• encephalopathy, rhabdomyolysis, acute renal
  failure, acute respiratory distress syndrome,
  myocardial injury, hepatocellular injury,
  intestinal ischemia or infarction, pancreatic
  injury, and hemorrhagic complications, DIC, with
  pronounced thrombocytopenia

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Exertional vs Classic

• Exertional Classic
• Healthy Predisposing factors/medications
• Younger Older
• Exercise Sedentary
• Sporadic Heat wave occurrence
• Diaphoresis Anhidrosis
• Hypoglycemia Normoglycemia
• DIC Mild coagulopathy
• Rhabdomyolysis Mild CPK elevation
• Acute renal failure Oliguria Marked
• Lactic acidosis Mild acidosis
• Hypocalcemia Normocalcemia

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Case

• 68 M is brought into the ED for decreased LOC
• Found in bed in his apartment
• Freezer door was left open
• PMHx
• CAD, CHF, DMII
• Meds
• Metoprolol, Altace, Lipitor, ASA, NTG Patch,
  Gluconorm
• OE
• 42oC HR 65
• What are this patients HS risk factors?
• What other diagnoses are you worried about?
• How would you like to manage?

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Case

• 37 F presents altered and hot
• Post-op Day 1
• PMHx
• Graves
• OE
• 135 39oC 143/62 (widened pulse pressure)
• Moist skin
• Loose stools

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Case

• 45-year-old man who had been outside mowing
  grass.
• EMS later found him unresponsive, and he arrived
  at the emergency department with a GCS of 3
• OE
• His skin was warm and dry
• Rectal temperature 42.2C HR170/min. Pupils
  are 7mm and reactive.
• Urine tox screen was positive for cocaine and
  marijuana
• He was admitted to the ICU, and rhabdomyolysis
  developed.
• He recovered with supportive care and was
  discharged 1 week later.

What are his risk factors?
Why is he dry?
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Case

• 67 F with dementia
• Increased confusion and agitation, requiring
  haloperidol 1mg at bedtime for 5 months
• Agitated in the ED
• Found on the roof of her building
• Progressively became minimally responsive, rigid,
  and incontinent, with a temp of 40.5oC

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Case

• 58 M with Hyperthermia
• Feeling unwell for the past 48h
• Shaking Chills Altered
• OE
• 40oC 120 75/52 25
• Flushed/warm peripherally

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Classic Heat Stroke (non-exertional)

• Results from exposure to high temperature
• Unable to compensate
• Thoughts?
• Approach?
• Consider
• Alternate Diagnoses
• Hepatic Transaminase elevations may be useful
• Treating presumptively (sepsis)

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Case

• 42 F collapsed just shy of the finish line
• It was her first marathon, and a hot day. But
  according to her friend she had been keeping
  pretty well hydrated.
• Brought to the ED via EMS confused
• Tonic-clonic in the trauma bay
• Risk Factors?
• Concerns?
• Management?

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Exertional Heat Stroke

• Results from strenuous exercise
• Typically young healthy people (athletes/workers)
• Thoughts?
• Consider
• Hydration
• Hyponatremia

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Treatment

• Cooling
• Active cutaneous vasodilation
• ? temperature gradient b/w skin and environment
  (conduction)
• ? gradient of water-vapor pressure b/w skin and
  environment (evaporation)
• ? velocity of air adjacent to the skin
  (convection)

HEAT
HEAT
How would you like to do it?
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Evaporation / Convection

• Cool water or wet sheets applied to the skin
• Fan
• Spritz or Mist
• This rarely causes shivering

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Conduction
Rectal lavage
Cold water immersion has been linked with
asystolic arrests Used by the military without
incident May be more significant in classic
heat stroke (14 mortality study of 28 patients
with CHS)

• Internal cooling, which has been investigated in
  animals, is infrequently used in humans. Gastric
  or peritoneal lavage with ice water may cause
  water intoxication.

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Conduction

• This may cause shivering
• How can you stop it?
• If the pt is shivering
• Vigorous massage
• spray with tepid water (40C)
• expose to hot moving air (45C)
• either at the same time as cooling methods are
  applied or in an alternating fashion

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Case

• A buddy recently back from visiting out east,
  tells us it was way hotter than anything weve
  experienced here.
• According to the Canadian Weather Services the
  average temperature was exactly the same.
• Yeah but it was a wet hot! It was way hotter!
• What do you think?
• Does humidity make a difference?

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Case

• 68 M with Heat Stroke
• You continue to cool
• His BP falls to 68/40
• How would you like to manage?

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Resuscitation
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Fever vs Hyperthermia

• Fever does not cause primary pathologic or
  physiologic damage
• Fever does not require therapeutic intervention
• unless the patient has limited physiologic
  reserve

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Infectious agents / Toxins / Mediators of inflammation(Pyrogens) Infectious agents / Toxins / Mediators of inflammation(Pyrogens)
stimulate
Monocytes / Macrophages / Endothelial cells / Other cell types Monocytes / Macrophages / Endothelial cells / Other cell types
release
Pyrogenic cytokines - IL- 1, TNF, IL- 6, IFNs Pyrogenic cytokines - IL- 1, TNF, IL- 6, IFNs
stimulate
Anterior hypothalamus (Mediated by PGE2) Anterior hypothalamus (Mediated by PGE2)
results in
Elevated thermoregulatory set point Elevated thermoregulatory set point
leads to
Increased Heat conservation (Vasoconstriction/ behaviour changes)Increased Heat production(involuntary muscular contractions) Increased Heat conservation (Vasoconstriction/ behaviour changes)Increased Heat production(involuntary muscular contractions)
result in
F E V E R F E V E R

(Antipyretics/ NSAIDs act here) 
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Decreasing the Set Point

• Antipyretics
• Not useful in true Heat Shock
• May be useful in mixed presentations (ie.
  Sepsis/Heatshock)

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Prevention

• Acclimatize yourself to heat
• Schedule outdoor activities during cooler times
• ? level of physical activity
• Drink additional fluids
• Consume salty foods
• ? amount of time spent in air-conditioning
• Automobiles should be locked, and children should
  never be left unattended in an automobile during
  hot weather

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Acclimatization

• Successive exposures over weeks
• Enhanced CV performance
• Activation of Renin-Angiotensin-Aldosterone Axis
• Salt conservation by sweat glands
• Increased capacity to secrete sweat
• Expansion of plasma volume
• Increase in GFR
• Increase in ability to resist rhabdomyolysis

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HYPOTHERMIA
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Case

• 48 F presents with decreased LOC
• Found outside by police talking strangely to
  passers-by
• Complaining about her bulky coat
• Undressing despite the cold
• What is your approach?
• Differential Diagnosis?
• Why is this lady at risk?
• How is she losing heat?

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Pathophysiology

• Evaporation
• Vaporization of water through both insensible
  loss and sweat
• Radiation
• Emission of infrared electromagnetic energy
• Conduction
• Direct transfer of heat to an adjacent, cooler
  object
• Convection
• Direct transfer of heat to convective air currents

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Pathophysiology

• Cell membrane dysfunction
• Efflux of intracellular fluid
• Enzymatic dysfunction
• Electrolyte imbalances

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Case

• OE
• 48 10 110/62 34oC
• CNS Depression (GCS 5) No focal findings
• Reflexes globally reduced
• Not shivering
• But she feels cold!
• What would you like to do?

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Assessment

• Thermometer
• Need a low reading thermometer
• Oral temps influenced by respiration
• Tympanic temps unreliable
• Rectal Probe
• Core temp
• Altered if adjacent to cold/frozen stool
• Esophageal Probe
• Next to the Aorta
• Bladder Probe

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Case

• OE
• Repeat temperature via rectal probe 28oC
• Whats going on Doctor?
• Is Hypothermia a diagnosis?
• How would you classify?

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Clasification

• Mild 32-35oC
• tachypnea, tachycardia, ataxia, dysarthria,
  impaired judgement, shivering, cold diuresis
• Moderate 28-32oC
• decreased heart rate, hypoventilation, CNS
  depression, hyporeflexia, decreased renal blood
  flow, loss of shivering, paradoxical undressing,
  AFIB, junctional bradycardias
• Severe lt28oC
• pulmonary edema, oliguria, areflexia, coma,
  hypotension, bradycardia, ventricular
  arrhythmias, asystole

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Differential Diagnosis
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Differential Diagnosis
Why is this patient hypothermic?
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Case

• What investigations would you like to order?

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Investigations

• C/S (hypoglycemia)
• CBC, Lytes, INR/PTT
• ABG
• EKG
• Anything else youd like?

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Coagulopathy

• Clotting factors are temperature dependant
• they dont work when theyre cold
• Coags are performed in the lab at 37C
• ...thus, clinical coagulopathy ? N INR and PTT

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ABG

• Lactate
• Metabolic screen
• pH, pCO2, pO2
• Gas tension and H decline with the temperature
• Use uncorrected values

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EKG

• Rhythm abnormalities
• AFIB/Sinus Bradycardia
• Intervals
• PR/QRS/QTc prolonged
• Osborn J waves

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Case

• How would you like to manage this patient?

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Management

• Passive External Rewarming
• remove wet clothing
• blankets
• Active External Rewarming
• warmed humidified O2
• forced air warming systems
• Active Internal Rewarming
• warmed IV fluids (42oC)
• pleural/peritoneal/bladder irrigation
• Extracorporeal (dialysis/bypass/continuous
  venous)

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Case

• You begin Initially by covering the patient in
  warmed blankets while someone sets up the Bair
  Hugger.
• Patient goes into VFIB
• How would you like to proceed?

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• Modifications of BLS for Hypothermia
• If not in cardiac arrest,
• warm the patient
• Handle the victim gently for all procedures
• Physical manipulation may precipitate VF
• If in cardiac arrest,
• Assess pulse/respirations for 30-45s (may be
  difficult)
• Bag with warmed O2
• If shockable (ie. VF) shock once them resume CPR
  defer further attempts till warm

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• Hypothermic heart may be unresponsive to
  cardiovascular drugs, pacemaker stimulation, and
  defibrillation. Drug metabolism is reduced.
• Modifications of ACLS for Hypothermia
• Intubation
• ventilation with warm, humidified oxygen
• isolate the airway to reduce the likelihood of
  aspiration
• Difibrilation
• try initial shock
• if unsuccessful, defer until core temperature gt
  30C
• IV meds
• may accumulate to toxic levels (decreased
  metabolism)
• lt 30C hold
• gt 30C give at increased intervals
• Re-warming
• as discussed above
• Volume
• patients who have been hypothermic for 45-60 min
  are likely to require volume because the vascular
  space expands with vasodilation
• Routine use of steroids, barbiturates, and
  antibiotics has not been shown to increase
  survival or decrease post-resuscitation damage.
• Severe hypothermia is often preceded by other
  disorders (eg, drug overdose, alcohol use, or
  trauma). The clinician must look for and treat
  these underlying conditions while simultaneously
  treating the hypothermia.

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Case

• Initial shock converts briefly to sinus then pt
  becomes asystolic
• Continue CPR for 30 minutes with no ROS
• When do you stop?

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• Withholding and Cessation of Resuscitative
  Efforts
• In the field
• resuscitation may be withheld if the victim has
  obvious lethal injuries or if the body is frozen
  so that nose and mouth are blocked by ice and
  chest compression is impossible
• youre not dead until youre warm and dead
• hypothermia may exert a protective effect on the
  brain and organs if the hypothermia develops
  rapidly in victims of cardiac arrest.
• it may be impossible to distinguish 1o from 2o
  hypothermia
• stabilize the patient with CPR
• basic maneuvers to limit heat loss
• rewarming interventions
• Once the patient is in the hospital, physicians
  should use their clinical judgment to decide when
  resuscitative efforts should cease in a victim of
  hypothermic arrest.

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FROSTBITE
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Case

• 16-year-old male attempted to "get high" by
  inhaling airbrush propellant which contained a
  fluorinated hydrocarbon
• The patient lost consciousness and upon waking
  his lips and tongue were frozen
• His main complaints on presentation were dyspnoea
  and pain in the oral/peri-oral areas

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Case

• OE 159/94 101 24 37.1oC
• Alert and Appropriate
• Severe edema of the tongue and lips, with
  blisters on the lips and frozen saliva in the
  oral cavity
• What else would you like to know?
• Initial management/approach?

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Case

• 4 hours after presentation develops acute
  respiratory distress
• Nasally intubated stabilized
• - admitted (ICU)
• Endoscopy showed 1st and 2nd degree burns of the
  larynx with vocal cord involvement and 1st degree
  burns of the trachea, main stem bronchi, and
  esophagus.
• The oral cavity had 2nd and 3rd degree burns
  which required debridement

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Pathophysiology
Cold
Cold
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Classification
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Classification
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Classification

• 1st Degree
• Central pallor and anesthesia of the skin
• Surrounding edema
• 2nd Degree
• Blisters containing clear/milky fluid
• Surrounding edema/erythema
• 3rd Degree
• Deeper injury
• Hemorrhagic blisters progressing to black eschar
• 4th Degree
• Injury extends to muscle/bone
• Involves complete tissue necrosis

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• Who is at risk for frostbite?
• Behavioural
• Physiologic

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Risk Factors

• Increased Conductive Heat Loss
• Contact with metal or water
• Increased Convective Heat Loss
• Exposure to wind
• Alcohol
• Behavioural Changes
• Vasodilation
• Smoking
• Hx of Frostbite
• African Americans / Women
• Ice Packs (iatrogenic)

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Diagnosis

• Clinical
• Numbness (sensory deficit)
• Distal extremeties
• Plain Radiographs
• Coincidental fractures
• Soft tissue swelling
• Technetium (Tc)-99 scintigraphy
• Predicts long-term tissue viability
• Allows early debridement
• MRI/MRA
• Predicts tissue variability
• Visualize occluded vessels demarcate ischemic
  tissue

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• Management?

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Treatment

• Prehospital
• Transport the patient to a warm environment
• Remove wet clothing
• Insulate affected areas
• Avoid walking on frostbitten feet
• ...Dont
• re-warm if there is a possibility of re-freezing
• use of stoves (tissue is insensate)
• use friction

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Treatment

• Hospital
• Re-warming
• Immerse affected area in water bath (40-42oC)
• 30 min tissue is purple and soft
• Analgesia - opiods
• Analgesia
• Dressing
• Bulky dressing to decrease oedema
• Splint to prevent contractures
• Tetanus (consider)
• Rehydration
• Cold diuresis increases blood viscosity and
  sludging
• Thrombolysis

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• Design Single institution retrospective review
  of clinical outcomes and resource use.
• Setting Burn unit of a tertiary academic
  referral center.
• Patients 2001-2006, patients with severe
  frostbite admitted within 48 hours of injury
  underwent digital angiography and treatment with
  intra-arterial tPA if abnormal perfusion was
  demonstrated. These patients were compared with
  those treated from 1995 to 2006 who did not
  receive tPA.
• Interventions tPA vs traditional management of
  frostbite injury.
• Main Outcome Measures Number and type of surgery
  were recorded, along with amputations of digits
  (fingers or toes) and more proximal (ray,
  transmetatarsal, or below-knee) amputations.
  Resource utilization including length of stay,
  total costs, cost per involved digit, and cost
  per saved digit were analyzed.
• Results 32 patients with digital involvement
  (hands, 19 feet, 62 both, 19) were
  identified. 7 patients received tPA, 6 within
  24 h of injury. The incidence of digital
  amputation in patients who did not receive tPA
  was 41. In those patients who received tPA
  within 24 hours of injury, the incidence of
  amputation was reduced to 10 (P.05).
• Conclusions tPA improved tissue perfusion and
  reduced amputations when administered within 24
  hours of injury. This modality represents the
  first clinically significant advancement in the
  treatment of frostbite in more than 25 years.

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Treatment of experimental frostbite with
pentoxifylline and aloe vera cream
Miller MB, Koltai PJ

• OBJECTIVE To compare the therapeutic effects of
  systemic pentoxifylline and topical aloe vera
  cream in the treatment of frostbite.
• DESIGN The frostbitten ears of 10 New Zealand
  white rabbits were assigned to one of four
  treatment groups untreated controls, those
  treated with aloe vera cream, those treated with
  pentoxifylline, and those treated with aloe vera
  cream and pentoxifylline.
• MAIN OUTCOME MEASURES Tissue survival was
  calculated as the percent of total frostbite area
  that remained after 2 weeks.
• RESULTS The control group had a 6 tissue
  survival. Tissue survival was notably improved
  with pentoxifylline (20), better with aloe vera
  cream (24), and the best with the combination
  therapy (30).
• CONCLUSION Pentoxifylline is as effective as
  aloe vera cream in improving tissue survival
  after frostbite injury.

Arch Otolaryngol Head Neck Surg 1995 121678
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Thank you