the iceman cometh: update on hypothermia and frostbite management david s. bullard, md, med, facep,...

The Iceman Cometh: Update on Hypothermia and Frostbite Management

David S. Bullard, MD, MEd, FACEP, FAWMAssistant Professor of Emergency Medicine,

Brown University Alpert Medical SchoolMarch 6, 2012

Disclosures

• No financial conflict of interests• Always willing to obtain some

Objectives

• Review rewarming strategies• Review resuscitation and treatment considerations• Focus on treatment for the urban & suburban ED

environment NOT the backcountry• Discuss some newer treatment modalities

Accidental Hypothermia

“Urban Outdoorsman” syndrome

• October 30, 2011: Snowfall in the Northeast• 1st case of accidental hypothermia for the season• 45 year-old male (well known to the ED staff)• Rectal temperature 32⁰ C (90⁰ F)

Epidemiology

• Hypothermia occurs in various locations and in all seasons• North American survey of 428 cases of civilian accidental

hypothermia– 69 cases occurred in Florida

• Urban settings account for the majority of cases in most industrialized countries

• About 600 annual deaths attributed to accidental hypothermia in the US– About ½ of these deaths are in patients over age 65

Danzl DF, Pozos RS, Auerbach PS, et al. Annals of Emergency Medicine. 1987;16(9):1042-55.

Hypothermia

• Definition– Core body temperature below 35⁰ C (95⁰ F)

• Mild – Core temperature 32 to 35⁰ C (90 to 95⁰ F)• Moderate – Core temperature 28 to 32⁰ C (82 to 90⁰ F)• Severe – Core temperature 20 to 28⁰ C (68 to 82⁰ F)• Profound – Core temperature below 20⁰ C (68⁰ F)

Physiologic Changes of Hypothermia

• Mild– shivering, tachycardia, increased or normal blood pressure,

ataxia, poor judgment, apathy• Moderate

– shivering stops, cardiac output ⅔ of normal, a-fib, paradoxical undressing

• Severe– hypotension, bradycardia, cardiac output ½ of normal, loss of

corneal reflexes, major acid-base disturbances, v-fib • Profound

– pulse 20% of normal, EEG silent, asystole

Osborn Waves

EKG – Osborn Waves or J-waves

“No one is dead until warm and dead.”

• Dogma we all learned• Usual markers of death are unreliable with hypothermia

– Loss of brainstem reflexes– Fixed and dilated pupils– Rigor mortis– Dependent lividity

• Death declared when the patient’s core temperature has been warmed to 32⁰ C (90⁰ F) for 30 minutes

“Some people are dead when they’re cold and dead.”

Paul S. Auerbach, MD

Auerbach PS. Some people are dead when they’re cold and dead. JAMA. 1990 10;264(14):1856-7.

Potassium

• Chart review• Group A – 9 victims from snow avalanches

– Median rectal temperature 29.6° C (85.3⁰ F)– Average potassium level 14.5 mmol / L– All group A patients were in full arrest– No saves despite aggressive rewarming

• Group B – 15 patients with hypothermia following acute drug intoxication and / or cold exposure– Median rectal temperature 28.8° C (83.8⁰ F)– Average potassium level 3.5 mmol / L– All patients recovered, including 2 in full arrest

Schaller MD, Fischer AP, Perret CH. Hyperkalemia. A prognostic factor during acute severe hypothermia. JAMA. 1990 ;264(14):1842-5.

Hypothermia: Prognostic Indicators

• Retrospective Study• 22 patients rewarmed with cardiopulmonary bypass

– 10 patients with stable spontaneous circulation restored

– 2 of these patients survived long-term• Survivors

– Potassium < 9 mmol / L– pH > 6.50

Mair P, Kornberger E, Furtwaengler W, et al. Prognostic markers in patients with severe accidental hypothermia and cardiocirculatory arrest. Resuscitation. 1994;27(1):47-54.

Fluid Resuscitation

• Viscosity of blood increases 2% per degree Celsius drop in temperature

• Most hypothermic patients are severely dehydrated• Need for glucose as well• Consider normal saline with 5% dextrose• Ringer’s lactate should be avoided

Rewarming Strategies Summary

• Passive External Rewarming– Dry blankets & environment (0.5⁰ C – 2⁰ C per hour)

• Active External Rewarming– Bair Hugger™ (0.8⁰ C – 2.4⁰ C per hour)– Warm water immersion (2⁰ C – 4⁰ C per hour)

• Active Simple Core Rewarming– Warmed IV fluids (0⁰ C – 2⁰ C per hour)

• Active Invasive Core Rewarming– Body cavity lavage (minimal, clinically insignificant)– Cardiopulmonary Bypass (6.9⁰ C – 9.8⁰ C per hour)

Negative Pressure Rewarming

• Vital Heat®• The Thermostat®

Negative Pressure Rewarming

• 7 volunteers cooled to a temperature of 34° C (93⁰ F)• Meperidine (Demerol®) given to prevent shivering• Warmed for two hours in 3 treatment arms

– Vital Heat® and Cotton Blanket– Cotton Blanket– Forced Air Rewarming

• Vital Heat® warming (1.3 ± 0.4°C)• Cotton blanket alone (1.2 ± 0.4°C)• Core temperature increased significantly more with

forced air warming (2.6 ± 0.6°C)

Taguchi A, Arkilic CF, Ahluwalia, A, et al. Negative pressure rewarming vs. forced air warming in hypothermic postanesthetic Volunteers. Anesthesia and Analgesia. 2001;92(1):261-266.

Frostbite

Napoleon’s Retreat from Moscow

The Yeti is the exception

• Humans are better designed to be tropical beings• Basal conditions

– Total cutaneous blood flow of 200 to 500 mL/min• External heating to 41⁰ C (106⁰ F)

– Total cutaneous blood flow of 7000 to 8000 mL/min• External cooling to 14⁰ C (57⁰ F)

– Total cutaneous blood flow of 20 to 50 mL/min

Cold-Induced Vasodilatation

• “Hunting Response”• Maximal vasoconstriction at 15⁰ C• At 10⁰ C, this vasoconstriction is interrupted every

5-10 minutes by vasodilatation• Exposure to cold offers some acclimatization of this

response

Frostbite Classification

• First Degree• Numbness and

erythema without tissue loss

• May have a white or yellow plaque

• Edema common

Cauchy E, Chetaille E, Marchand V, et al. Retrospective study of 70 cases of severe frostbite lesions: A proposed new classification scheme. Wilderness & Environmental Medicine. 2001;12:248-255.

Frostbite Classification

• Second Degree• Superficial skin

vesiculation• Clear or milky fluid in

blisters• Surrounding erythema

and edema

Cauchy E, Chetaille E, Marchand V, et al. Retrospective study of 70 cases of severe frostbite lesions: A proposed new classification scheme. Wilderness & Environmental Medicine. 2001;12:248-255.

Frostbite Classification

• Third Degree• Deeper hemorrhagic

blisters• Injury extends into the

reticular dermis• Beneath the dermal

vascular plexus

Cauchy E, Chetaille E, Marchand V, et al. Retrospective study of 70 cases of severe frostbite lesions: A proposed new classification scheme. Wilderness & Environmental Medicine. 2001;12:248-255.

Frostbite Classification

• Fourth Degree• Mummification• Muscle and bone

involvement

Cauchy E, Chetaille E, Marchand V, et al. Retrospective study of 70 cases of severe frostbite lesions: A proposed new classification scheme. Wilderness & Environmental Medicine. 2001;12:248-255.

Bone Scanning

Cauchy E, Chetaille E, Marchand V, et al. Retrospective study of 70 cases of severe frostbite lesions: A proposed new classification scheme. Wilderness & Environmental Medicine. 2001;12:248-255.

Frostbite Rewarming

• When to rewarm in the field?• Immersion in circulating water• 40 – 42° C (104 – 107.6° F)• Avoid physical trauma• Pain control

Blister Care

• Debridement of clear blisters (2nd degree frostbite)– Prevention of further contact of PGF2α and TXA2

• NO debridement of hemorrhagic blisters (3rd degree frostbite)– Prevent desiccation of the deep dermis– May be helpful to aspirate the fluid

Ibuprofen

• Inhibits the arachidonic acid cascade• Decreases prostaglandin synthesis• Decreases systemic levels of thromboxane• Ibuprofen recommendations

– Based on a single animal study showing a 23% tissue survival with aspirin vs. control

– Theoretically aspirin blocks the production of certain prostaglandins that are beneficial to wound healing

• Starting dose of 400 mg• Continue dose at 12 mg / kg / day

McIntosh SE, Hamonko M, Freer L, et al. Wilderness Medical Society practice guidelines for the prevention and treatment of frostbite. Wilderness & Environmental Medicine. 2011;22:156-166.

Aloe Vera

• Ten frostbitten rabbit ears assigned to 4 groups:– untreated controls– aloe vera cream– Pentoxifylline (Trental®)– aloe vera cream and pentoxifylline

• Results– control group – 6% tissue survival– Aloe vera cream – 24% tissue survival– Pentoxifylline – 20% tissue survival– combination therapy 30% – tissue survival

Miller MB, Koltai PJ. Treatment of experimental frostbite with pentoxifylline and aloe vera cream. Archives of Otolaryngology and Head Neck Surg. 1995;121(6):678-680.

Thrombolytics

• Retrospective, single-center review• 32 patients with digital involvement of frostbite

– All patients got digital angiography• 7 patients received tPA (6 within 24 hours of injury)• The incidence of digital amputation in patients who

did not receive tPA was 41%• In those patients who received tPA, the incidence of

amputation was reduced to 10% (P<.05)

Bruen KJ, Ballard JR, Morris SE, et al. Reduction of the incidence of amputation in frostbite injury with thrombolytic therapy. Archives of Surgery. 2007;142:546-553.

Vasodilators

• Iloprost– Prostaglandin E₁

• Reserpine– Inhibits uptake of norepinephrine

• Pentoxifylline– Phosphodiesterase inhibitor

• Buflomedil– Inhibition of α-receptors

Vasodilators / Thrombolytics

• Open-label study• Randomly assigned 47 patients with severe frostbite to

3 different treatment arms• All patients got rapid rewarming, plus aspirin and

buflomedil• Randomized to receive one of three regimens for 8

days– Group 1 – aspirin and buflomedil– Group 2– aspirin plus iloprost– Group 3 – aspirin, iloprost and rt-PA (day 1 only)

Cauchy E, Cheguillaume B, Chetaille E. A Controlled Trial of a Prostacyclin and rt-PA in the Treatment of Severe Frostbite. New England Journal of Medicine. 2011; 364:189-190.

Results

• Group 1 – aspirin and buflomedil– Risk of amputation was 60% (9 of 15 patients)

• Group 2– aspirin plus iloprost– Risk of amputation was 0% (0 of 16 patients)

• Group 3 – aspirin, iloprost and rt-PA (day 1 only)– Risk of amputation was 19% (3 of 16 patients)

• Authors maintain a role for rt-PA in select patients

Cauchy E, Cheguillaume B, Chetaille E. A Controlled Trial of a Prostacyclin and rt-PA in the Treatment of Severe Frostbite. New England Journal of Medicine. 2011; 364:189-190.

Summary

Hypothermia• Remove wet clothing• Dry environment• Accurate temperature• Hyperkalemia / Acidosis• Dehydration• Caloric needs• Rewarming

– Mild– Severe

Frostbite• Rewarming• Pain control• Ibuprofen• Blisters

– Clear– Hemorrhagic

• Aloe vera• Tetanus status• Consultants for long-term

sequelae

Prevention