Download Hypothermia and Frostbites

Hypothermia and Frostbites
Theoharis Sinifakoulis, MD, PhD
Physician
DIPLOMA IN MOUNTAIN MEDICINE
(UNIVERSITY OF LEICESTER-UIAA-ICAR-ISMM)
Member of International Society of Mountain Medicine
Member of MEDEX
International Commission for Mountain Emergency Medicine
(ICAR MEDCOM)
Hypothermia and Frostbites
Hypothermia
• While typically associated with regions of the world with
severe winters, hypothermia is also seen in areas with milder
climates.
• Cases of hypothermia can occur even during summer months.
Hypothermia
physiology
• Body temperature is the result of an interplay among heat
production, absorption, and dissipation.
• Physiologic mechanisms regulated primarily by the
hypothalamus (part of brain) maintain core body temperature
between 36.8˚C and 37.58˚C despite wide variations in
ambient temperature.
Hypothermia
physiology
• Heat transfer occurs in the following 4 ways: Conduction,
Convection, Radiation and Evaporation.
Hypothermia
physiology
• Of these 4 mechanisms, radiation and evaporation account
for most of the heat transfer in humans.
• Because the ability to dissipate heat via radiation decreases
as ambient temperature increases, convection gains greater
importance in preventing heat-related illness.
• Convection and evaporation are directly controlled by innate
physiologic responses, namely, circulatory dynamics and
sweating.
Hypothermia
physiology
• Heat Loss via Circulatory Changes
The skin has a large vascular supply that provides an effective
means of dissipating heat. In adults, blood flow may vary
tremendously given environmental and host conditions.
• Heat Loss via Sweating
Evaporative cooling is the most important physiologic
mechanism for dissipation of heat for humans. Eccrine sweat
glands, found throughout the body, can produce up to 1 to 2 L
of sweat per hour. If sweat does not evaporate either because
of physical barriers (eg, clothing or athletic protective
equipment) or high humidity, sweating results in fluid losses
without a cooling effect.
Hypothermia
definition
• Hypothermia is defined as a core temperature below 35ºC
and can be further classified by severity.
– Mild hypothermia – Core temperature 32 to 35ºC
– Moderate hypothermia – Core temperature 28 to 32ºC
– Severe hypothermia – Core temperature below 28ºC
Hypothermia
definition
• Classified by time of exposure.
– Acute – “cold stress” in a few mins to hrs
– Subacute– “exhaustion” in hrs
– Chronic– in elderly
Hypothermia
general
• Mild hypothermia can be well tolerated by most healthy
persons without significant morbidity or mortality
• Moderate hypothermia has a mortality up to 21%
• Severe hypothermia has a high mortality
Hypothermia
evaluation
• As counter-regulatory mechanisms are overwhelmed by cold
stimulus the clinical signs of hypothermia will appear
• Low grade reading thermometer
– Epitympanic
– Esophageal
– forehead (?)
• Clinical signs and history
Hypothermia
clinical presentation
• Swiss staging system
– Stage I: the patient is alert, shivering (core temperature 35°-32°C)
– Stage II: the patient is somnolent, not shivering (core temperature
32°-28°C)
– Stage III: the patient is unresponsive (core temperature 28°-24°C)
– Stage IV: respiratory and cardio-circulatory arrest (core temperature
24°-15°C)
Brugger H., Durrer B., Adler-Kastner L., Falk M., and Tschirky
F. Resuscitation (2001)
Hypothermia
clinical presentation
• mild hypothermia
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–
–
–
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tachypnea,
tachycardia,
initial hyperventilation,
ataxia,
dysarthria,
impaired judgment,
shivering,
"cold diuresis."
Hypothermia
clinical presentation
• Moderate hypothermia
–
–
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reductions in pulse rate and cardiac output,
hypoventilation,
central nervous system depression,
hyporeflexia,
decreased renal blood flow,
loss of shivering
Paradoxical undressing may be observed
Hypothermia
clinical presentation
• Severe hypothermia
–
–
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pulmonary edema,
oliguria,
areflexia,
coma,
hypotension,
bradycardia,
ventricular arrhythmias (including ventricular fibrillation),
asystole
Hypothermia
Hypothermia
treatment
• Basic Treatment for Hypothermia
– Prevent further heat loss:
• Insulate from the ground;
• Protect from the wind, eliminate evaporative heat loss by
removing wet clothing (once the patient has adequate shelter);
• Insulate the patient, including the head and neck;
• Cover the patient with a vapor barrier (such as a blue tarp, a large
piece of plastic, large garbage bags, etc.); and
• Move the patient to a warm environment.
– Activate the emergency medical services system to provide transport
to a medical facility.
– Do not give alcohol or permit patient to use tobacco.
Hypothermia
treatment
Nobody is dead unless re-warmed and dead
Gregory ,1974
Hypothermia
treatment
• Hypothermia I – II (responsive)
– Avoid moving the body excessively. Protection from wind. Insulation.
Hot drinks without alcohol.
• Hypothermia III (unresponsive)
– Avoid moving the victim excessively. Protection from wind. Insulation
in a stable position on one side (if the victim is not intubated). Close
observation, cardiorespiratory monitoring Core temperature
measurement (epitympanic). Supplemental oxygen. Transport by
helicopter to hospital experienced in treatment of hypothermia
• Hypothermia IV (cardio-circulatory arrest)
– Cardiopulmonary resuscitation without interruption. Transport by
helicopter to a hospital with cardiopulmonary bypass.
Hypothermia and Frostbites
Frostbites
• Frostbite results from the freezing of tissue
• It is a disease of morbidity and not of mortality
Frostbites
definitions
• Frostbite is a severe, localized cold-induced injury
• Frostnip refers to cold-induced, localized paresthesias that
resolve with rewarming
• Chilblain, is characterized by localized inflammatory lesions
that can result from acute or repetitive exposure to damp
cold above the freezing point
• Immersion foot (also referred to as Trench Foot) is a nonfreezing cold injury
Frostbites
pathophysiology
• The freezing injury of frostbite may be divided into 4
overlapping pathologic phases:
•
•
•
•
prefreeze
freeze-thaw
vascular stasis
late ischemic
Frostbites
classification
• Frostbite has been divided into 4 “degrees” of injury,
historically following the classification scheme for thermal
burn injury.
• These classifications are based on acute physical findings and
advanced imaging after rewarming.
• Severity of frostbite may vary within a single extremity.
Frostbites
classification
• First-degree frostbite
– presents with numbness and erythema. A white or yellow firm, slightly
raised plaque develops in the area of injury. No gross tissue infarction
occurs; there may be slight epidermal sloughing. Mild edema is
common.
• Second-degree frostbite
– injury results in superficial skin vesiculation; a clear or milky fluid is
present in the blisters, surrounded by erythema and edema.
Frostbites
classification
• Third-degree frostbite
– creates deeper hemorrhagic blisters, indicating that the injury has
extended into the reticular dermis and beneath the dermal vascular
plexus.
• Fourth-degree frostbite
– injury extends completely through the dermis and involves the
comparatively avas- cular subcutaneous tissues, with necrosis
extending into muscle and to the level of bone.
Frostbites
classification
• To simplify classification, either in the field or before
rewarming and/or imaging, we favor the following 2-tier
classification scheme:
– Superficial no or minimal anticipated tissue loss, corresponding to 1stand 2nd-degree injury
– Deep deeper injury and anticipated tissue loss, corresponding to 3rdand 4th-degree injury
Frostbites
classification
Frostbites
Frostbites
Frostbites
risk factors
• Anything…
– that increases localized heat loss or decreases heat production
– following direct exposure to freezing materials
• Plus..
–
–
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Smoking
Alcohol consumption
previous cold injury
Raynaud phenomenon
Frostbites
Frostbites
prevention
• “prevention is better than treatment”
• Maintaining peripheral perfusion
• Protection from cold
Frostbites
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
If a body part is frozen in the field, the frozen tissue should be protected
from further damage. Remove jewelry or other extraneous material from
the body part. Do not rub or apply ice or snow to the affected area.
Frostbites
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Refreezing injury
A decision must be made whether or not to thaw the tissue. If
environmental conditions are such that thawed tissue could re-freeze, it is
safer to keep the affected part frozen until a thawed state can be
maintained. Recommendation Grade: 1B
Frostbites
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Spontaneous/passive thawing
Most frostbite will thaw spontaneously and should be allowed to do so if
rapid rewarming cannot be readily achieved. Do not purpose- fully keep
tissue below freezing temperatures, as it will increase the duration that
the tissue is frozen and could easily result in more proximal freezing and
higher morbidity. If environmental and situational conditions allow for
spontaneous or slow thawing, tissue should be al- lowed to thaw.
Recommendation Grade: 1C
Frostbites
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Treatment of hypothermia
No specific studies examine concurrent hypothermia and frostbite.
Hypothermia frequently accompanies frostbite and causes peripheral
vasoconstriction that will impair blood flow to the extremities. Mild
hypothermia may be treated concurrently with the frostbite injury.
Moderate and severe hypothermia should be treated effectively prior to
treating the frostbite injury. Recommendation Grade: 1C
Frostbites
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Ambulation and protection
If at all possible, a frozen extremity should not be used for walking,
climbing, or other maneuvers until definitive care is reached. If using a
frozen extremity for locomotion or evacuation is unavoidable, the
extremity should be padded, splinted, and kept as immobile as possible to
minimize additional trauma. Measures should be taken to protect frozen
tissue to prevent further trauma. Recommendation Grade: 1C
Frostbites
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Dressings
Bulky, clean, and dry gauze or sterile cotton dressings should be applied to
the frozen part and between the toes and fingers. Recommendation
Grade: 2C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Hydration
Vascular stasis can result from frostbite injury. Recommendation Grade:
1C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Ibuprofen
If available, ibuprofen should be started in the field at a dose of 12 mg/kg
per day divided twice daily (minimum to inhibit harmful prostaglandins) to
a maximum of 2400 mg/ day divided four times daily if the patient is
experiencing pain. Recommendation Grade: 2C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Rapid field rewarming of frostbite
Field rewarming by warm water bath immersion can and should be performed if the proper equipment and methods are avail- able and
definitive care is more than 2 hours away. Other heat sources (eg, fire,
space heater, oven) should be avoided because of the risk of thermal
injury. Rapid rewarming by water bath has been shown to result in better
outcomes than slow rewarming. Recommendation Grade: 1B
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Antiseptic solution
Adding an antiseptic solution (eg, povidone-iodine, chlorhexidine) to the
rewarming water has theoretical benefits of reducing bacteria on the skin.
However, this practice is not substantiated by supporting evidence in
frostbite care. Frostbite is not an inherently infectious process and most
injuries do not become infected. If available, adding an antiseptic solution
to the water while rewarming is unlikely to be harmful and may reduce
the risk of cellulitis if severe edema is present in the affected extremity.
Recommendation Grade: 2C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Pain control
During rewarming, pain medications (eg, NSAIDs or opiate analgesics)
should be given to control symptoms as dictated by individual patient
response and medication availability. Recommendation Grade: 1C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Debridement of blisters
Debridement of blisters should not be routinely performed in the field. If a
clear, fluid-filled blister is tense and at high risk for rupture during an
evacuation, aspiration of the blister and application of a dry gauze
dressing should be performed in the field to minimize infection.
Hemorrhagic bullae should not be aspirated or debrided electively in the
field. These recommendations are common practice but lack evidence
beyond case series. Blisters should be evaluated to determine whether
they pose a risk for rupture and/or infection and aspirated according to
the above guidelines. Recommendation Grade: 2C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Elevation of extremity
If possible, the thawed extremity should be elevated above the level of
the heart, which may decrease the formation of dependent edema.
Recommendation Grade: 1C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Topical aloe vera
If available, topical aloe vera should be applied to thawed tissue prior to
applying dressings. Recommendation Grade: 2C
Frostbites
treatment
• Wilderness Medical Society Practice Guidelines for the
Prevention and Treatment of Frostbite (2011)
Surgical treatment/amputation
After frostbite occurs, complete demarcation of tissue necrosis may take 1
to 3 months. Since significant morbidity may result from unnecessary or
premature surgical intervention, a surgeon with experience evaluating
and treating frost- bite should assess the need for and the timing of any
amputations. Recommendation Grade: 1C