Physiological and Medical Considerations in the

Winter Alpine Environment

Taken from various internet and published sources.

Heat Lossroom temperature

• Radiation:60%

• Evaporation: 25%

• Convection: 12%

• Conduction: 3%

Heat Gain• Metabolic heat production

• Exercise

• Sympathetic stimulation

• Thyroid hormone

• Shivering

• Radiation, Conduction, Convection

• Food

COLD STRESS

Types of cold Injury:Non-freezing

Trench Foot

Hypothermia: exhaustion hypothermia immersion hypothermia

COLD STRESS

Freezing Frostbite

-Extremities are at risk: nose, ears, fingers,

toes, penis, etc.-Never warm tissue if the potential for

re-freezing exists.

COLD INJURY PREVENTIONEat frequently to maintain energyEat frequently to maintain energy.Drink plenty of waterDrink plenty of water.Avoid tobacco.Avoid tobacco.Avoid alcoholAvoid alcohol:

Reduces self-protectionReduces self-protectionReduces shiveringReduces shiveringDiureticDiuretic

COLD INJURY PREVENTIONClothing

Clean and dry (avoid cotton)

Layered, loose, and light

Wear head protection

Avoid restriction of blood to extremities

Typical Conditions

Hypothermia98.6° Normal function

95° Distorted/slowed biomechanical reactions

90° Decreased cerebral blood flow

Myocardial irritability, atrial fibrillation

82° Ventricular fibrillation

77° Changes in CV autoregulation, decreased HR

65° Asystole

61° Lowest reported adult hypothermia survival

59° Lowest reported infant hypothermia survival

Central Nervous System EffectsHypothermia

• Most apparent system affected• Slowing of speech, thinking, sensation• Apathetic, listlessness• Similar to stroke, head injury, or intoxication

Cardio-Respiratory Effects Hypothermia

• Peripheral vasoconstriction• Increased blood viscosity• Decreased respiratory rate and volume• SA node dysfunction leads to lower cardiac

output• Arrhythmias, V-fib• Death can result from cardiac arrest

(most common cause)

Muscular System Effects Hypothermia

– Decreased function– Decreased nerve conduction velocity

• Weak/slow contractions– Shivering can result in hypoglycemia

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Types of Hypothermia

• Mild– Rectal Temp 90° - 94°F– Pale, cool– Varying degrees of confusion,

disorientation, incoherence, and ataxic gait– May shiver uncontrollably– Fine movements of the hand effected– Tachycardia, tachypnea, cold diuresis

Types of Hypothermia

• Moderate– Rectal Temp 82° - 90°F– Impaired judgment– Dilated pupils– Muscle rigidity (shivering reflex is lost)– Decreased BP, HR, respirations– Cardiac arrhythmia

– MUST BE WARMED

Types of Hypothermia

• Severe– Rectal Temp < 82°F– Patient appears dead– Comatose– Muscles are unreflexive– Slow respirations, pulse– BP undiscernible– Arrhythmia leading to V-fib

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Mild to Moderate Treatment

• Passive Rewarming– Prevent further heat loss!!!

• Remove from cold/wind environment• Remove wet clothing• Insulate the body

• Keep patient supine

Mild to Moderate Treatment• Active rewarming

– Best to provide heat internally• Warm humidified air or oxygen (112°F max)• Warm IV (104°F max) [?]• Give warm fluids with sugar orally

– External sources• Heating blankets, heat lamps, hot packs• Apply to trunk only• Use caution, “Rewarming Shock”

• Check for frostbite

Severe Hypothermia Treatment

• Passive rewarming• Be gentle, the heart is fragile• Maintain airway• CPR can cause a lethal arrhythmia

– Assess pulse for 45-60 seconds

• Defibrillation is usually ineffective < 86°F• Not dead until warm and dead

Severe HypothermiaDo Nots

• Do not try to actively rewarm (rewarming shock)

• Do not use direct heat• Do not let them consume alcohol

Rewarming Shock

• When the shell warms before the core• Vasodilation can increase stress on heart• Blood pressure can decrease• Ventricular Fibrillation due to rapid return of

cold blood to the heart

Frostbite• Ice crystals form in extracellular space• Most commonly effects

– Feet and toes– Hand and fingers– Face and ears– Scrotum and penis can be affected

• 3 degrees of frostbite– frostnip– superficial frostbite– deep frostbite

Predisposed to Frostbite• Constrictive clothing• Fatigue• Alcohol• Smoking

• Medications• Atherosclerosis• Diabetes• Peripheral neuropathy• Raynaud’s Phenomenon

Frostnip

• 1st stage of frostbite

• Slow onset

• Sometimes unrecognized

• Skin color initially red, then turns white

• Pain or numbness in area of discoloration

• Skin surface and underlying tissue are still soft

• No freezing of tissue

Treatment for Frostnip

• Warm the affected area– Warm air– Warm water– Warmth from other body areas

• May experience tingling or burning sensation during rewarming

Superficial Frostbite (2nd degree)

• Skin and subcutaneous tissue is involved• White waxy appearance to mottled blue color• Skin surface is hard, but underlying tissue is still

soft• Edema• Numbness or dull pain lasting for days

Superficial Frostbite Treatment

• Transport as soon as possible• Rewarm the area

– warm water (100 - 105°F) • Insulate the area and maintain warm

environment • Cover blisters with dressing• Do not put pressure on the area

• Pain during rewarming is a good sign

Deep Frostbite (3rd degree)

• Deeper structures are affected• Skin becomes white, then grayish yellow,

and finally grayish blue• All sensation lost• Skin and underlying tissues become hard

Deep Frostbite Treatment

• If frozen– Leave frozen and pad area to protect from heat– Notify hospital

• If partially thawed or hours away from hospital– Rewarm before transport (100 - 105°F) – Insulate the area and maintain warm environment– Cover blisters with dry sterile dressing

Deep Frostbite Treatment

• Transport as soon as possible• Limit movement even when thawed• Do not put pressure on affected area• If conscious - ok to give warm fluids• Late management might require debridement

of necrotic tissue or amputation

FrostbiteDo Nots

• Do not rub the area– ice crystals can cause damage

• Do not thaw a frozen limb if there is a chance it will be refrozen– Refreezing causes more damage than extended

freezing

• Do not use direct heat such as a hair dryer or heating pad

• Do not disturb blisters• Do not allow the person to smoke or use alcohol

Human Body and Fluids

Fluid Requirements

• Rest: 1 ½ liters a day

• Normal activities: 2 ½ liters a day

• Mountaineering: 6 liters a day

Dehydration

• Symptoms– headache– dark urine– dizziness, nausea– weakness– dry mouth, tongue,

throat, lips– lack of appetite– stomach cramps or

vomiting

– irritability– decreased amount of

urine being produced– mental sluggishness– increased or rapid

heartbeat– lethargic– unconsciousness

• What is the universal symptom of dehydration?

Headache

Dehydration

• Prevention– Start the day with 1-2 liters– Drink minimum of 3-6 liters of fluid per day– Do not wait until you are thirsty– Monitor urine color– Avoid sweating, alcohol, caffeine

Dehydration

• Treatment– drink water or other warm liquids– do not eat snow– rest

Some Nutrition Facts

• All forms of fuel are stored in the body and eventually broken down into glucose as needed– Carbohydrates: Rapid, fuels stored in cells– Muscle: protein broken down when

carbohydrate stores are low• i.e. Carbohydrates will help prevent muscle loss

– Fats: mobilized for fuel when carbohydrates are low

• will last for days to weeks

Nutritional Requirements

• Basal: 1400-2000 calories a day

• Cold weather mountaineering: 5000 calories a day

Nutrition

• Long-term– “Grazing” diet– 40/30/30

• Short-term– Carbs

• Poorly tolerated– Fats

Altitude & Fitness

Factors Affecting Acclimatization

• Age

• Fitness

• Medical conditions

General Fitness

• It helps to be fit• After acclimatization,

the fit at low altitude will be fit at high altitude

but will be less fit than at low altitude

Normal Acclimatization

• Heart rate • Respiratory rate • Breathless on

exercise• Hungry• Urine output • Sleepy• Headache

• All symptoms should disappear or get better after rest, food and water

Humm…..what if the person doesn’t get better?

Cardiovascular Fitness Training

• Aerobic training– Exercise at 60-70% of maximum heart rate– Max HR=220-age

• Anaerobic training– Exercise at 100% of max HR for a couple

minutes a few times a week

General Training

• Strength– Free weight or machine work out– All major muscle groups twice a week

• Flexibility– End with stretching, e.g., Yoga

• Balance

Altitude Illness

Barometric pressure and altitude

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Everest

AMS

Mechanisms of AMS

• AMS is not directly caused by hypoxia• Oxygen levels throughout the body drop within

minutes of exposure but AMS takes several hours to develop.

Mechanisms of AMS

• High intracranial pressure due to increased leakage of fluid may possibly cause AMS

Mechanisms of AMS

• General fluid retention possibly via the renin-angiotensin-aldosterone system or antidiuretic hormone

What are the Predictors of AMS?

Risk Factors for AMS

• Rapid ascent

• Heavy exertion at altitude

• Residence at sea level

• Altitude, uncommon <7,500 ft

• Hx of prior AMS

• Young age (less common at age >50yrs)

• Physical fitness not protective

AMS Differential Diagnosis

• Dehydration

• Hypothermia

• Exhaustion

• Hangover

• Viral illness

• Sedative or hypnotic medication

• Carbon monoxide poisoning

Prevention of AMS

• Spend a day or so at base camp before starting ascent

• Once above 8,200 ft, do not climb higher than 2,000 ft in 24 hrs

• Climb high but sleep low

• If climbing to over 9,800 ft in 1 day or with Hx of prior AMS or HACE, take prophylactic medications

Symptoms of Mild AMS

• Headache• Malaise• Anorexia• Low urine output

• Nausea/vomiting• Dizziness• Dyspnea on exertion• Dry cough• Inner chill

Any symptom of AMS should be considered due to altitude unless proven otherwise.

Headache is the most common.

Natural History of Mild AMS

• Usually self-limiting

• If untreated may persist for weeks

• May progress to moderate and severe forms of AMS or to death

• Responds well to treatment

Moderate AMS

• Ataxia– Single most useful sign for deterioration

• Lassitude• Strange behavior • Confusion• Impaired judgement• Consciousness level coma• Shortness of breath

Treatment of Moderate AMS

• Stay at altitude, do NOT go further• Descend if symptoms do not improve or get worse• Water• Rest• Deep breathing every 4-6 minutes• Diamox, Dexamethasone• Give oxygen if available• Use hyperbaric bag

Prevention of AMS

• Acetazolamide 125-250 mg twice a day [?]

• Ginkgo biloba 60 mg 1-3 times a day [?]

• Dexamethasone 4 mg four times a day

• No support for nifedipine, furosemide, or codeine

HACE

High Altitude Cerebral Edema

• Symptoms include those of AMS, plus:

• Any kind of neurological disorder: ataxia, irrationality, hallucinations

• Can be accompanied by hemorrhages or thrombosis

• HACE is life threatening. Untreated, the person will fall to a coma and die within hours to one or two days.

High Altitude Cerebral EdemaTreatment

• Descend!!

• Hyperbaric chamber

• Dexamethasone

HAPE

High Altitude Pulmonary Edema (HAPE)

• Accounts for most deaths from high altitude illness but uncommon (0.1-0.4% of travelers >7,500 ft)

• Risk factors are same as from AMS

• Cold is also a risk factor (increased PAP from sympathetic response)

• More common in those with pulmonary vascular disease

Clinical Presentation of HAPE

• Usually seen on 2nd night at altitude• Dry cough, then frothy sputum, then blood-

tinged sputum• Crackly, rattlely breathing• Rapid breathing• Increased heart rate• Cyanotic lips, face, fingernails• Mild fever is common

Prevention of HAPE• Slow ascent (Climb high, sleep low)

• Above 8,200 ft limit ascent to 2,000 ft daily. Add rest day every 2,000 – 4,000 ft

• Acetazolamide, Ginko biloba, cocoa, anti-asthma

• Special precautions in climbers with Hx of HAPE– Nifedipine– Salmeterol

Treatment of HAPE

• Immediate descent mandatory

• Supplemental oxygen

• Hyperbaric therapy if available

• Medication: Nifedipine, Diamox

• Mortality without medication- 50%

Acetazolamide Diamox®

• Carbonic anhydrase inhibitor • Diuretic• Side effects:

– water loss, tingling, sulphur allergies

• Dosage – 125-250 mg twice daily [?]– start the day before the ascent– acetazolamide does not mask the symptoms

of altitude sickness

Gingko Biloba

• Might be useful

• Recent studies suggest benefit at altitude

• Possible alternative to acetazolamide for people with sulphur allergy

• Dosage: 60 mg 1-3 times/day [?]

Coca

• South American locals chew coca leaves

• Exact mechanism not known

• Seems to be useful

Anti-Asthmatic Medication

• Seems to improve ventilation

• Long term studies still pending– (what about asthmatics at altitude?)

Novel Approaches

• Levitra

• Cialis

• Viagra

PORTABLE HYPERBARIC CHAMBER

“THE GOLDEN RULES”

If you feel unwell at altitude, it is high altitude illness until proven otherwise.

Never ascend with symptoms of AMS.

If you are getting worse or have HACE or HAPE, get down immediately.

HAFE high altitude flatus expulsion

• Expanding bowel gases at altitude

• Irritating to your partners