Altitude Cold Heat

Dr Matt Wilkes

Diploma in the Medical Care of Catastrophes

Society of Apothecaries 2019

• Why do people go?• Hypobaria and physiology• Altitude illness

• Prevention and treament

• Special circumstances• Monitoring

Contents

Why do people go?140,000,000/year go above 2500m• Agriculture/animal husbandry• Foraging• Mining• Pilgrimages• Politics• Water and power sources• Weather• Travel and tourism

You need to deploy rapidly to a natural disaster at 3,500 m in Nepal. You plan to fly to 2,500 m

then travel by jeep and foot.

How will you prepare?

Hypobaria

Blue = NitrogenGreen = Oxygen

Mod High Extreme “Deathzone”

Bartsch and Saltin (2008)

Response to AltitudeLow Oxygen

Increased minute volume

Breathe out more CO2

Respiratory Alkalosis

Reduced desire to breatheVascular changes

Oxygen levels fall again

Timescale

• Acclimatisation starts at 1500 m (ish)• Acclimatisation takes up to a week (ish)• Ascent faster than acclimatisation = illness.

Acute Mountain Sickness

• Lake Louise Score ≥ 3, plus headache• Headache• Dizziness• GI upset• Malaise/Weakness

• Benign• Reversible on descent

Hall et al. (2014)

Differential

• Migraine – usually one-sided headache. AMS headache feels different• Viral illness – often other symptoms – sore throat• Hangover – alcohol produces dehydration• Diarrhoeal illnesses • Exhaustion• Dehydration• Hypothermia

Prevention and Treatment

• Prevention• Gentle ascent profile• Acclimatisation• Rest• Fluids and calories• Acetazolamide

• Treatment• Descent• Oxygen• Acetazolamide• Dexamethasone

125mg BD for prevention

Portable Altitude Chamber

• Relieves symptoms• Bridge to evacuation• Heavy and labour intensive

Sleep Disturbance

• Common• Periodic breathing• Snoring, cold, needing to pee, tent conditions, other clients• Slow ascent, oxygen, acetazolamide, temazepam

HACE and HAPE

Everyone’s brain swells a little at altitudeEveryone’s lungs have some fluid in them

Wimalasena (2013)

High Altitude Cerebral Edema

• Thought to be a progression of AMS• Severe headache• Ataxia is the key sign• Hallucinations, confusion, vomiting, apathy• Pathophysiology uncertain

Treatment of HACE

• Do not leave patients alone• Sit upright / Head-up tilt• Give oxygen (caution with PAC) – bagging?• Dexamethasone 8mg IV, then 4mg 4x daily

• (Diamox 250mg twice daily)

• Immediate descent, do not re-ascend• Follow up with neurologist +/- CT scan

Less likely to be HACE if…

• Seizures • Cranial nerve palsies • High fever• Meningism• Lack of improvement with oxygen / descent (be patient)

• HACE unless proven otherwise.

HAPE

• Non-cardiogenic pulmonary oedema• < 5% of cases of acute mountain sickness• Life threatening• Pulmonary hypertension• Exaggerated/uneven hypoxic pulmonary vasoconstriction• Vascular leakage: stress failure of capillaries• Na+/K+ pump fails• Increasing hypoxia

Sea Level

Altitude

HAPE

HAPE

• Often 2-3 days after arrival at altitude• Tired and increasingly poor exercise tolerance• Breathless at rest• Cough (common at altitude) +/- sputum• Central and peripheral cyanosis• Mild fever <38.3C• Crepitations (may be unilateral)

HAPE Treatment

• Do not leave patients alone• Sit upright and keep warm• Oxygen• Nifedipine 30mg every 6 hours• Diamox 250mg twice daily?• Dexamethasone?• Salbutamol? CPAP? PDE-5 inhib?• NO diuretics (beware non-altitude docs)

• Descent (without exertion)

At altitude, it is HACE and HAPE unless proven otherwise.

Preexisting Conditions

• COPD – worse• Asthma – variable• HTN – variable• CAD – increased risk of ischaemia• Coagulation – altered, increased• Diabetes – change in insulin requirements• Migraine – worse• Epilepsy – same

Pregnancy at altitude

• Limited evidence• Acetazolamide contraindicated during 1st trimester (teratogenicity)

and >36 weeks (risk severe neonatal jaundice)• Suspected higher incidence spontaneous abortion 1st trimester

Children at altitude

Children at altitude

• No data, but recommended sleep altitude no higher than 3000-4000m with a pre-school child (preferably <2500m)• Children with pre-existing illness may be at increased risk of

exacerbation or altitude related illness.• Otalgia and sunburn

• Adapted Lake Louise symptoms scoring systems exist for adolescents, younger and pre-verbal children.• Confounding psychological effects of travel

Pulse oximeters

• Intuitive• Instant• Cheap

• Risks of interference• What is normal?• More useful for trends than absolute values• Integrate with clinical picture

Heat

Contents

• Thermal physiology theory

• Causes of heat illness

• Types of heat illness• Treatment

• Risk factors • Prevention

• Preparation

• Summary

Tropical animal..

Humans passively gain and lose heat from the external environmentvia a number of pathways

Heat is also actively produced internallyvia muscular activityand catabolism

Exposure - gaining heat via any of the pathways mentioned

Over-exertion - hard work in hot environments, especially if unacclimatised

Dehydration - failing to maintain fluid intake (including appropriate salts)

Containment - Excessive PPE (NBC/CBRN) or in a closed vehicle

Causes of heat illness

Types of heat illness

• Minor – Heat exhaustion

• Heat rash (“Prickly heat”)• Heat cramps• Heat syncope (fainting)

• Major – Heat stroke

• Heat stroke

• Sweat gland dysfunction• Prevention• Light cotton clothing• Cool showers

• Treatment• Control infection• Cool baths• Piriton• Prickly Heat powder

Prickly heat

• Muscle spasms in arms, abdomen and calves• Fluid and electrolyte imbalance• Poor acclimatisation• May be more likely with profuse

sweating • Treatment• Rest• Stretching• Oral rehydration solutions

Heat cramps

• Dizziness, weakness, fainting• Postural change or long periods of standing• Blood pooling in legs

• Poor acclimatisation and dehydration• Treatment• Rest, legs up• Shade• Oral fluids

Heat syncope (fainting)

Heat stroke -

• Core Temperature > 40°C• Failure of heat dissipation mechanisms• Paradoxical increase in heartrate• Permanent damage to cells > 42°C• Complications proportional to

temperature and time

what is it?

Heat stroke - Symptoms and signs

• Flushed face

• Hyperventilation

• Rapid strong pulse

• Nausea/vomiting

• Cramps

• Disturbed vision

• Agitation/confusion

• Dizziness

• Staggering

• Poor co-ordination

• Collapse

• Incontinence

• Can still be sweating

• Ambient temperature may not be very high

• Heat stroke unless proven otherwise

• Conscious?• Lie casualty down in the shade• Raise legs• Strip to underwear • Active cooling • 1-2 litres of water or ORS during first hour• Measure temperature

• Unconscious?• Recovery position, cooling and evacuate

• Anyone else in the group at risk?

Treatment

• Rapid reduction in temperature is key• Duration and temp proportional to outcome• Cold water immersion• Wrap in cold wet sheets• Ice packs to groin, armpits, neck• Running stream

• Water heat transfer co-efficient 25x > than air• Spray with water (even tepid water) to drive evaporation • Fanning encourages evaporation• Evacuate

Cooling in the field

Individual risk factors

•Obesity•Poor fitness•Dehydration•Other illness•Unacclimatised•Some medication•Alcohol use

•Smoking•Poor sleep• Inadequate diet•Air travel•Previous heat illness

Prevention -• Reduce exposure• Stay hydrated + hygienic• Don’t push too hard• Look after yourself and others

Heat illness is avoidable

• Get fit• Acclimate

• adapt via exposure to artificially induced stimuli• Acclimatise

• adapt through exposure to natural environment

Preparation

• Heat illnesses are preventable• All group members must be aware of

the risks and look out for each other• Itinerary must be flexible• Regular breaks for rest and fluids• Avoid over-exertion• Acclimatise if possible

• If heat illness suspected• Measure temperature• Cool rapidly• Evacuate

Summary

COLD

Contents

• Measuring body temperature• Hypothermia• Rewarming• Diagnosis of death• Cold water immersion• Cold injury

Measuring Temperature

• Oral• ‘Rule out’ only

• Rectal• Exposes patient• Need low reading• Lag

• Epitympanic (not infrared)• Good if adequate cardiac output• Beware blockage of ear canal• Can under-read

• Oesophageal probe• Gold standard• Specialised equipment, secure airway

Definition

• Core body temperature < 35 °C• Acute:• Minutes to hours• Avalanche victims,

crevasse falls

• Sub-acute or chronic:• Hours to days• Climber trapped in the

mountains

Heat Balance

• Heat production• Muscular activity• Catabolism

• Heat Loss• Radiation• Convection• Conduction• Evaporation

Risk Factors

• Surface area : volume • Thin males• Children

• Malnourishment, dehydration and poor fitness• Poor clothing and equipment• Injury, immobility• Wet

Tipton et al. (2015)

Field management

• Prevent further heat loss• Restore body temperature• Rewarm at same rate cooled• Think about afterdrop• Treat underlying conditions/other

injuries• Protect rest of group

Mild hypothermia

• Group shelter

• Insulate

• Warm drinks and food• External heat sources

• Axillae, chest, back• Large pads• Protect skin

• Body to body of limited use• Rewarm

• Rest

Severe Hypothermia

• Signs of life may be undetectable clinically• Pupils fixed and dilated• Check for a carotid pulse for one

minute

Pulse?

• Place in recovery position, keep horizontal• Gently remove wet clothes in shelter• Evacuate or:• Rewarm slowly in field until core T >33°C• Passive and active external rewarming

• Rest

No Pulse?

• Confirm no fatal injuries• Evacuate• CPR until hospital?

Hospital Options

• Transfer to hospital with facilities• Forced air rewarming• Warm intravenous fluids• Warm humidified oxygen• Bladder and peritoneal lavage• Haemofiltration• ECMO (or cardiac bypass)

Diagnosis of Death

• Obviously fatal injuries• Chest not compressible• Abdominal muscles not kneadable• Core Temperature < 9°C• (Potassium > 12mmol/L in avalanche victim without asphyxia)

Cold water immersion

• Cold shock response (1 min)• Gasp, hyperventilation, vasoconstriction• Life jacket and slow immersion

• Cold incapacitation (5-15 min)• Loss of muscle power• Life jacket

• Hypothermia (> 30 min)• Don’t panic!

• Circumrescue Collapse

Circumrescue Collapse

• Syncope or sudden death• Before, during, after removal from water• Low blood pressure or VF

• Loss of hydrostatic pressure• Neurohumeral changes• Afterdrop• Work of rescue and mechanical stimulation

• Prevention• Roll over gunwales• Keep flat• Be gentle

Peripheral cold injury

Feeling cold

Holmer et al. 2011

Risk Factors

• Immobility• Inadequate or wet clothing• Constricting boots and clothing• Inadequate fluid or caloric intake• Fatigue and stress• Associated injuries / underlying circulatory problems• Beta-blockers and nicotine• Smoking / older age / ethnicity

Holmer et al. 2011

Field treatment 1

• Treat hypothermia• Protect frozen tissue from further damage• Remove jewellery• Do not rub or apply ice or snow• Keep frozen rather than thaw-freeze • Adequate hydration• Give ibuprofen or aspirin

Field treatment 2

• Dressings – bulky dressings• Frozen feet – Avoid weight-bearing / minimise trauma if unavoidable• Field rewarming – water at 37-39 degrees, about 30 minutes• Slow rewarming if above unavailable• Do not drain blisters unless likely to burst• Aloe vera (reduces prostaglandin/thromboxane production)• Oxygen, esp. if at altitude• Analgesia• Photographs

Hospital Treatment

• Expert advice• Bone scans• Analgesia• tPA / Ilioprost treatment• Wound care• Infection prevention / Tetanus

prophylaxis• Delay surgical management

Non-Freezing Cold Injury

• Chillblains (pernio)• Cold urticaria• Trench foot / Immersion

foot

• Cold and wet (0-15 °C)

Pathogenesis

1. Prehyperaemia:• Blanched, yellowish/white• No blisters

2. Hyperaemia• Hot, erythematous and swollen• Hyperalgesia

3. Post-hyperaemia• Altered sensation “coolness”• Hyperhidrosis

(Imray 2011)

(Vale et al. 2017)

Treatment

• Treat hypothermia• Don’t rewarm an isolated NFCI

• Control pain during hyperaemia• Ibuprofen• Neuropathic agents• Cool air on the feet?

• Follow-up• CPRS?• Fungal infection• Occupational considerations

SPOT GEN 340 Globalstar satellites and base stationsNo polar / SSA coverage, trees and valleys

• Smallest and lightest• AA batteries• Tracking• Two custom messages and SOS• Subscription• GEOS and SAR insurance for some activities=• SPOT Connect/customer service problematic• 160 pounds• New two-way version available

Garmin DeLorme84 Iridium Satellites and satellite to satellite commsWhole earth coverage

• Bigger and heavier• Micro USB charge and shorter battery life• Tracking• 2-way communication, SOS and maps• Subscription• GEOS and SAR insurance for some activities• 350-450 pounds• “Mini” version available that connects to phone

EPIRB / PLBGPS via COSPAS / SARSAT, 121.5 MHz radio freqComplete coverage

• Marine/military origins• Small but quite heavy• 5 year battery life• Waterproof• No subscription• No comms: nothing or everything!• High power, most likely to be found• 250 pounds

• Largest and heaviest• Shortest battery life• Variable ruggedness• Delay for geostationary but higher BW• Like a phone plan – subscription and call/data

charges• Allow voice, text and data (VOIP) • 400-2000 pounds• May be restricted in various countries

Satellite PhoneMany networks: LEO and Geostationary Variable coverage

Talk?

Yes?Sat Phone or

RadioNo?

Two-way commsQuite portableQuite reliable

DeLorme InReach

‘All or nothing’Quite portableMost reliable

EPIRB

One-way commsMost portableLeast reliable

SPOT