Environmental Flashcards
At what altitude is the ‘death zone’ start?
7500meters
At 5500meters barometric pressure is at what percentage of that at sea level?
50%
Does previous altitude exposure and physical fitness prevent AMS?
No
What percentage of individuals who ascend rapidly to 4000m suffer with AMS?
60%
Aids to acclimatisation
Limit ascent to 300-600m per day.
Incorporate rest days to allow the body to catch up
Climb high, sleep low
Acetazolamide
AMS Symptoms
Headache
Anorexia
Fatigue
Nausea
Dizziness
Disrupted sleep
Treatment of AMS
Anti-emetics
Rest
Avoid further ascent
Consider descent
What percentage of climbers have hallucinations about 7500m?
32%
Classification of altitude
High - 1500-3500m
Very high - 3500-5500m
Extreme >5500m
Essential drugs for altitude emergencies
Oxygen - AMS/HAPE/HACE
Acetazolamide - AMS/HACE
Nifedipine - HAPE
Dexamethasone - HACE
Ofloxacin - contact lens related microbial keratosis.
Atmospheric pressure
760mmHg / 101kpa
Atmospheric gasses
Nitrogen - 78.5%
Oxygen - 21%
CO2 - 0.05 %
+ Other gasses
Dalton’s law
The total pressure exerted by a gaseous mix is equal to the sum of the partial pressures of each component
Boyle’s law
For any gas at a constant temperature the volume of gas will vary inversely to the pressure.
Henry’s Law
The amount of gas which dissolves in a liquid is proportional to the pressure of the gas.
Symptoms of Nitrogen narcosis
- Light headedness
- Poor concentration
- Poor judgement
- Anxiety
- Decreased co-ordination
- Hallucinations
- Coma and death
Symptoms of Oxygen toxicity
- Tingling
- Focal or generalised seizures
- Vertigo
- Tinnitus
- Nausea and vomiting
- Tunnel vision
- Personality changes
- Anxiety
- Confusion
- Coma
The pressure increases by 1 atmosphere for each ____m of descent
10
Heat stroke mortality
10-70%
Key differentiator between heat exhaustion and heat illness
CNS dysfunction
Heat exhaustion signs & symptoms
> 38 degrees C
Sweating
Oliguria
Nausea +/- vomiting
Irritable or confused
tachycardic
tachypnoeic
Heat stroke signs & symptoms
> 40 degrees C
Hot dry skin
Decreased sweating
Anuria
Nausea and vomiting
Circulatory collapse
Delirium/seizues/coma
Encephalopathy
Renal failure, liver failure, rhabdomyolysis, DIC
2 main types of heat illness
- Exertional (young fit heavy activity - rapid onset)
- Non-exerttional (elderly and young, over a period of time - exposure to environmental conditions).
Heat illness risk factors
- Extremes of age
- Underlying chronic ill health and debility (esp. cardiac, respiratory and neurological)
- Mental illness
- Drugs (diuretics, beta-blockers, alcohol, stimulants, phenothiazines, anticholinergics)
- Lack of air-conditioning (lower socioeconomic groups)
- Occupational (miners, fire fighters, military recruits)
Methods of heat loss
Conduction
Convection
Radiation
Evaporation
The ideal environment to maximise heat loss
Cool & dry
Breeze
Body temperature to cause cell injury & cell death
Body temperatures in excess of 40oC can cause direct cellular injury.
Temperatures above 42oC can directly produce cell death.
Heat stroke - Cooling Target temperature
38.5oC.
Heat stroke management
Active cooling can be reliably performed by use of tepid water sprays and electrical fans.
Benzodiazepines play a central role in seizure control and making active cooling techniques more tolerable for the patient
Immersing the patients limbs or whole body in cool water is described but impractical.
Icepacks in the groin and axillae
Sports events should be cancelled if the WBGT is greater than_____
28oC
Envenomation symptoms
- Local tissue destruction
- Bleeding disorders
- anaphylaxis
- tissue oedema
- organ failure
- paralysis
Initial management of snake and spider bites
Compression and immobilisation
Drowning: Definition
A process of experiencing respiratory impairment from submersion/immersion in a liquid.
3 Outcomes from drowning
Death
Morbidity
No Morbidity
Good prognostic indicators for the outcome of a drowning incident
Submersion <10mins
No aspiration
Child
Water temp <10oC
Core temp <33-35oC
Neurologically in tact on arrival at hospital.
If cardiac arrest occurs, ROSC <10 mins
Time to effective BLS <10mins
Water Temperature at which selective brain cooling may occur
6 oC
Drowning: groups that should received prolonged resuscitation
Submersion less that 30 mins (Tw >6oC)
Submersion less than 90 minutes (Tw <6oC)
Possibility of air pocket
Intermittent submersion
Those showing signs of life on rescue
2 main factors determining outcome following drowning
Water temperature
Submersion time
Swiss Staging model for hypothermia - Stage I
Conscious
Shivering
32-35oC
Swiss Staging model for hypothermia - Stage II
Impaired consciousness
Not shivering
28-32oC
Swiss Staging model for hypothermia - Stage III
Unconscious
Not shivering
24-28oC
Vital signs present
Swiss Staging model for hypothermia - Stage IV
Unconscious
No vital signs
<24oC
3 Frostbite Classifications
Frostnip
Superficial Frostbite
Deep Frostbite
Frostnip
Shortlived superficial freezing
Respond rapidly to warming
Superficial frostbite
Superficial skin layers only affected
Clear blisters form 24-48 hours
Underlying tissue is pliable and soft
Deep frostbite
Full thickness
Blood filled blisters form after 1-3 weeks
Underlying tissues are woody and stony
Loss of digits
Hypothermia classifications
Mild - 32-25oC
Moderate - 29-32oC
Severe - <29oC
ECG changes in hypothermia
J Waves
Slow AF
VF
Umbles of hypothermia
Stumbles, mumbles, grumbles, jumbles
Common ECG leads showing J-waves
II
V3-V6
Hypothermia Drug dosages and intervals
30-35 oC - Double intervals
<30oC - Withhold
