Mountain Health Awareness Surg Cdr Andy Brown, Lt Col Pete Davis and Surg Cdr A Mellor

Mountain Health Awareness

Surg Cdr Andy Brown, Lt Col Pete Davis and Surg Cdr A Mellor

Definitions• Intermediate Altitude (1500m – 2500m)

Physiolgical changes occur, SpO2>90%, altitude illness possible but rare• High Altitude (2500m – 3500m)

Altitude illness common with rapid ascent• Very High Altitude (3500m – 5800m)

Altitude illness common, SpO2<90%, marked hypoxia with exercise• Extreme Altitude (>5800m)

Marked hypoxia at rest, progressive deterioration, permanent survival not possible

General• Physical Fitness

– The fitter an individual, the easier it is to perform in a mountainous environment (but will not prevent altitude illness)

• Nutrition– More than at sea level

• Water Intake– 6 to 8 litres of water

per day• Good Attitude

Heat Generation• 25% of food that we eat is used by body to

rebuild itself and 75% is used to produce heat

• Diet– Caloric intake

• 4,500 calories per day– Carbohydrate intake

• Simple carbs like sugars, bread, rice and pasta are more easily converted into energy and taste good

– Hot meals and hot wets

• The body at rest produces heat at a specific rate– Moderate exercise

• Increases heat production 5 to 6 times normal rate and can be tolerated for long periods of time

– Moderate shivering• Increases heat by 20 times normal rate but only for a

few minutes. This quickly leads to exhaustion.– Intense shivering

• Increases heat production by 50 times normal rate but exhaustion follows within 30 seconds

5 Ways the Body Loses Heat• Radiation

– Heat loss from the body to it’s surroundings• Conduction

– Heat transfer from one object in contact with a colder object

• Convection– Heat loss to a gas or liquid running over the

body

• Evaporation– Heat loss when water (sweat) on the surface of

the skin in turned into water vapour• Respiration

– Heat loss when you inhale in cold air and your body warms it up

– Heat loss when you exhale warm air from your body

Physical Responses to Heat• Blood vessels in the skin open up or dilate

– Allows more blood to the surface where the heat can more easily be transferred to the surroundings (Radiation)

• Sweating begins– Heat loss through convection and evaporation

• Heart rate and breathing increases– Pushes blood to the skin surface and brings

more air in to which more heat can be added

Physical Responses to Cold

• Blood vessels at the skin surface close down or constrict– Occurs so that body loses less heat to the

surroundings– More blood goes to the core of the body leaving

the extremities with a higher tendency to get cold

• Shivering– Body is trying to warm itself up

• Body produces more urine– Kidneys are fooled into thinking the body has

more blood than it really does due to the fact that the body is bringing in the blood to the core of the body.

– Kidneys respond by producing more urine which can contribute to dehydration

Dehydration• Defined as a deficit of

total body water• Causes

– Excessive loss• Urination• Cold, dry air• Strenuous activity• Coffee and tea??

– Inadequate intake• Thirst• Water inaccessibility

Symptoms of Dehydration

• Headache• Nausea• Dizziness• Fainting• Constipation

• Dry mouth• Weakness• Lethargy• Stomach cramps• Leg and arm cramps

Signs of Severe Dehydration

• Only show when severe!!!

• Swollen tongue• Dark urine• Low blood pressure• Rapid heart rate

– Greater than 100 per minute

Prevention of Dehydration

• Adequate intake– Drink 6 – 8 litres of water per day– Try to keep your urine light coloured– Do not rely on thirst as an indicator

Heat Cramps• Painful spasms of

skeletal muscle as a result of excessive loss of body salt

• Cause– Salt imbalance

within the body• Symptoms

– Muscle cramps in the arms, legs, or abdomen

Heat Cramps• Prevention

– Avoid overheating– Eat correctly

• No need for salt tablets as normal diet contains more than enough salt

• Field Management– Have victim stop moving– Gentle massage of effected area– Add 1 tablespoon of table salt to a litre of water

and drink. Repeat as necessary.

Heat Exhaustion

• Occurs when body salt losses and dehydration from sweating are so severe that a person can no longer maintain an adequate blood pressure.

• Causes are sweating and dehydration combined with strenuous physical activity

Symptoms of Heat Exhaustion

• Headache• Nausea• Dizziness• Fatigue• Fainting

Heat Exhaustion

• Prevention– Same for heat cramps– Dress properly with adequate ventilation– Dress comfortably cool– Frequent ventilation stops

• Field Management– Lay patient down with feet higher than his head– Keep patient well ventilated– Give plenty of water to drink, or via iv if severe

Heat Stroke

• Failure of the body’s cooling mechanism that rids the body of excessive heat

• Lethal in up to 40% of cases• Those who live may suffer permanent brain

damage

Symptoms of Heat Stroke

• Headache• Nausea• Dizziness• Fatigue

Signs of Heat Stroke

• Patients are delirious or comatose• Pupils may be pinpoint• Flushed skin may or may not be present• Rectal temperature of 39 oC• Sweating is often present. It is often taught

that sweating is absent. THIS IS UNTRUE.

Preventive Measures for Heat Stroke

• Same principles as heat exhaustion

• Drink plenty of water• Stay well ventilated• When temperature and

humidity are high, physical activity must be reduced.

Field Management for Heat Stroke

• Reduce heat immediately• Maintain an open airway• Remove as much of the patient’s clothing as

possible• You may immerse the victim in a cold

stream as long as the airway is clear• Give him nothing by mouth

Field Management for Heat Stroke

• When rectal temperature is below 38 oC, you may discontinue cooling. Recheck temperature every 10 minutes. If temperature rises above 39 oC again, begin re-cooling again

• Casevac ASAP

Altitude related issues

What’s the problem?

• At high altitude atmospheric pressure reduces

• The % oxygen stays the same • The pressure of oxygen is less• This leads to hypoxia – reduced oxygen

levels

Measuring hypoxia

• Pulse oximtery• Measures how much haemoglobin is

carrying oxygen• Usual reading about 96%- 99%• At sea level readings under 94% associated

with illness• Readings less than 90% in a fit healthy

person would result in ICU admission

Measuring hypoxia

• Pulse oximtery• Measures how much haemoglobin is

carrying oxygen• Usual reading about 96%- 99%• At sea level readings under 94% associated

with illness• Readings less than 90% in a fit healthy

person would result in ICU admission

Pulse oximeter

Effect of Altitude of SpO2

3 Apr

5 Apr

8 Apr

16 Apr

20 Apr

Sleep at altitude

• Sleep is disturbed!• There is an increased rate of breathing then

a pause• Pauses in breathing can last up to 9s• Improved with acetazolamide• This will be noticed in tent partners but is

not, in itself, dangerous!

Other changes

• Breathing rate increases – a lot • Heart rate increases at rest • There is an increased need to pass urine

• ALL THESE ARE NORMAL CHANGES AND PART OF ACCLIMATISING

Altitude Related Illness

• Acute Mountain Sickness (AMS)• High Altitude Cerebral Oedema (HACE)• High Altitude Pulmonary Oedema (HAPE)

Global Incidence of AMS

Barry, P W et al. BMJ 2003;326:915-919

Predicting AMS

Positive predictorsPrevious history of high

altitude illnessExertionCo-existing infections e.g.

‘flu’Permanent residence below

900 m altitude

No influenceGenderAgePhysical fitnessCoronary artery diseaseChest disease such as asthmaDiabetesPregnancy

Acute Mountain SicknessWhat is its normal course?

Symptoms typically appear 6-12 hours afterarrival at altitudes >2500 m

Gradual onset

Resolves over 1-3 days if further ascent does not occur

Lake Louise Diagnostic Criteria for Acute Mountain Sickness

• Recent gain in altitude• At least several hours at the new altitude• Presence of headache

plus at least one of the following symptoms:– poor appetite, nausea, vomiting– fatigue or weakness– dizziness or lightheadedness– difficulty sleeping

Acute Mountain SicknessWhat else could it be?

• Viral illness• Carbon monoxide poisoning • Hangover• Exhaustion• Dehydration• Migraine• Brain tumour!!!

Principles Of Treatment Of AMS

Rest• Most cases of AMS will get better in 1-2 days without specific

treatment• Rest alone often relieves symptoms of AMS• Ascent in the presence of symptoms of AMS is contraindicated

Descent• The only definitive treatment for altitude illness• Descent to an altitude lower than where symptoms began reliably

reverses AMS

Increase Oxygenation

(1) Stop ascent

(2) Descend if no improvement or condition worsens

(3) Descend immediately if:- signs/symptoms of pulmonary oedema- loss of coordination- changes in level of consciousness

(4) Sick persons must not be left or sent down alone

Ways of improving oxygenation

Acute Mountain SicknessSummary

• Common at altitudes >2500 m• Descent is the only definitive treatment• Further ascent is contraindicated in the presence of symptoms

of acute mountain sickness • Symptoms are shared with many other medical conditions• May progress to HACE or HAPE• Prevention includes graded ascent and drug prophylaxis• Rest, drugs and the portable hyperbaric chamber may be

beneficial

High Altitude Cerebral Oedema• Usually preceded by AMS• Symptoms of AMS leading to confusion, hallucinations

and decreased consciousness• Can progress to cause death over a few hours

High Altitude Pulmonary Oedema

• Occurs 2 or 3 days after arrival at altitude• Dry cough• Poor exercise tolerance• Frothy blood stained sputum• Coma• Death

• Pathophysiology

Probably related to capillary damage due to hypoxia and pulmonary hypertension

Prevention of altitude illness

• Slow ascent rate• Above 3000m

- increase sleeping altitude by only 300-600m per day- take one rest day for every 1000m gained

• Avoid unnecessary exertion• “Climb high sleep low”

How Can I Make Myself Feel Better When I’ve Got AMS?

• Aspirin and Paracetamol– May relieve headache, but often ineffective

• Ibuprofen– Reduces headache severity and speeds recovery time

(400 mg recommended dose)

• Sumatriptan – an anti-migraine drug• Anti-nausea drugs

Drug prophylaxis

• Acetazolamide – only proven intervention• Dose – Good evidence for 500mg bd but

smaller doses 125mg bd have been shown to work

• Should be continued for 10-14 days at altitude

• Side effects – paraesthesia, mild diuresis

Acetazolamide• Carbonic anhydrase inhibitor • Stimulates increased rate of breathing• Improves oxygenation• Reduces formation of fluid around brain and

spinal cord

Dexamethasone• Relieves symptoms of AMS• May reduce fluid leaking around brain• Exact mechanisms unknown

Who Should Receive Acetazolamide To Prevent AMS?

• Those undertaking a large rapid height gain, e.g. emergency rescue

• Those with an increased susceptibility to AMS

• Others? - e.g. military ops• JSP 950 – The Prevention and Treatment

of Acute Mountain Sickness is the military reference document

Treatment

• DESCENT – for any altitude illness any other treatment is supportive until descent can occur

Treatment of AMSPortable Hyperbaric Chamber

• Short Term Effects• Relieves symptoms of AMS *†‡§

• More effective than acetazolamide*• As effective as high flow oxygen†

• Long Term Effects• Rebound effect, especially after only 1-2 hours

treatment‡§

*J Wild Med 1991; 2: 268-73; †Ann Emerg Med 1991; 20: 1109-12; ‡Br Med J 1993; 306: 1098-101; §Br Med J 1995; 310: 1232-5

The ‘Gamow’ Bag (c. 1990)

Portable Hyperbaric Chambers

AMS

• Mild, rest at altitude consider descent if severe (Use Lake Louise Score >6 is severe AMS)

• Analgesia• Antiemetics• Acetazolamide

HAPE

Descent, evacuation, oxygen Nifedipine 10mg then 20mg SR 12 hrly Pressure bag to facilitate descent

HACE

• Descent, evacuation, oxygen• Dexamethasone 4mg 6hrly• Pressure bag to facilitate descent

Altitude Illness uncertain diagnosis

• Descent, evacuation, oxygen• Dexamethasone• Nifedipine• Pressure bag

BOTH HAPE AND HACE CAN OCCUR TOGETHER – AND ARE LIKELY TO!!

From - Davis et al, JRAMC, March 2011

Cold

Hypothermia

• Defined as the state when the body’s core temperature falls to 35 oC or less

• Be aware that oral or armpit temperature is not accurate

• Rectal temperature is the most accurate way to determine temperature

Commonplace Misconceptions

• Exposure is not used to describe hypothermia

• Extreme cold is not needed for hypothermia to occur. Most cases occur between 0 and 10 oC.

Causes of Hypothermia

• Ambient temperature• Windchill• Wet clothing• Cold water immersion• Improper clothing

Causes of Hypothermia

• Exhaustion• Alcohol intoxication, nicotine and drugs• Injuries

Signs and Symptoms of Hypothermia

• Altered mental status, esp irritability / withdrawal• Loss of consciousness and eventually coma• Shivering and the stoppage of shivering• Dead appearance with lack of breathing and lack

of pulse

Prevention of Hypothermia• Cold weather clothing

must be properly worn and cared for

• Avoid dehydration• Eat adequately• Avoid fatigue and

exhaustion• Increase levels of activity

as the temperature drops• Use of the buddy system

Treatment of Hypothermia

• Make the diagnosis• Prevent further heat

loss• Insulate the patient• Re-warm the patient• Casevac the patient

Other Points to Remember

• May be given hot drinks• Avoid excessive movement of patient• Apply first aid to wounds before re-

warming• Never give alcohol• Must constantly monitor patient

Frostbite• The actual freezing of

tissues• High risk areas are fingers,

toes, nose, cheeks and ears• Three major risk factors

– Improper clothing or improper care of clothing

– Dehydration– Poor diet or starvation

Other factors that contribute to frostbite

• Outside temperature (-10 deg C or greater)

• Snow or ground temperature

• Windchill• Cold metals• Petroleum products

Other factors that contribute to frostbite

• Exhaustion• Hypothermia• Race• High altitude• Prolonged immobility• Wounds• Previous cold injury,

tobacco and drug use

Signs of Frostbite• Skin may appear red, white,

grey, blue, frosty or even normal

• Skin may feel waxy or firm• Joints may be stiff or

immobile• Affected part may feel like a

block of wood or even ice• Pulses may or may not be

present

Symptoms of Frostbite• Tingling• Burning• Aching cold• Sharp pain• Increased warmth• Decreased sensation• No sensation at all

Classification of Frostbite• Frostnip

– Affected area becomes painfully cold and white– Returns to normal with re-warming < 30 mins

• Superficial– Skin appears red, grey, or blue and had waxy

feel– Faint pulse present– Sensation of pain and light touch may be

absent, but deeper sensations such as pressure will be intact

Classification of Frostbite

• Superficial– Joints will be mobile– Movement of part by

the victim will be possible but it may be difficult

Classification of Frostbite

• Deep– Skin appears the same

as superficial– Pulse will not be

present– Skin will feel woody,

firm or even rock hard if completely frozen

Classification of Frostbite• Deep

– Tissues will feel doughy or hard

– All sensation will be absent

– Skin will not move easily or not at all

– Joints will be stiff or immobile

– Movement of the affected part will be minimal or absent

Prevention of Frostbite• Dress in layers• Keep clothes dry• Dress properly• Avoid dehydration• Avoid starvation• Buddy system• Like dehydration,

frostbite results from a failure in leadership

Field Management for Frostbite• Frostnip

– Re-warm face, nose and ears with hands– Re-warm hands in armpits, groin or belly– Re-warm feet with buddies armpits or belly– Do not massage the affected part – AND

NEVER MASSAGE WITH SNOW!!!– Do not re-warm with stove or open flame– Remove constricting clothing– Do not allow tobacco products– Use 30 minute rule i,.e. if it isn’t better in

30mins it’s frostbite

Field Management for Frostbite

• Superficial or deep– Treat frozen extremities as fractures– Treat frozen feet as stretcher cases– Prevent further freezing– Prevent freeze -- thaw -- re-freeze– Treat for hypothermia– Re-warm in bath water with temperatures

maintained at 40oC

Non-Freezing Cold Injury (NFCI)

• A cold - wet injury to the feet or hands from prolonged (generally 7 - 10 hours) exposure to water at temperatures above freezing.

• May require amputation and should not be taken lightly

• Major risk factors– Wet– Cold– Immobility

Signs and Symptoms of NFCI• Extreme pain• Classified from mild to

severe• Similar to frostbite• Other signs

– Red and purple mottled skin

– Patches of white skin– Very wrinkled skin– Severe case may leave

gangrene and blisters– Swelling

Prevention of NFCI

• Keep feet warm and dry

• Change socks• Exercise (keeps

blood flowing)

Treatment of NFCI• Casevac• While awaiting

casevac

– Feet should be dried, warmed and elevated

– Pain relief

Snow Blindness

• Sunburn of the cornea• Causes

– High Altitude• Less UV rays are filtered out

– Snow• Reflection

Signs and Symptoms of Snow Blindness

• Painful eyes• Hot, stocky, or gritty

sensation• Blurred vision• Headache• Excessive tearing• Eye muscle spasms• Bloodshot eyes

Prevention of Sun Blindness

• Wear sunglasses with UV protection at all times

Treatment of Snow Blindness• Casevac• Patch the eyes• Wet compresses• Healing should occur

within two days or a week for more severe cases

• diclofenac drops (MO only)

Personal Hygiene

• Body• Hair• Fingernails• Feet• Oral Hygiene

Water Purification• Removing or destroying enough impurities to make the

water safe to drink• Giardia cysts and amoeba are an ever present danger• DO NOT DRINK FROM STREAMS

Waste Disposal

Toilets if available

Carry toilet tissue

Take all otherwaste out with you

Questions?

SUMMARY

• Do not ignore headache, nausea or dizziness

• Use the buddy system

• Maintain good personal hygiene