Enviromental Flashcards
What is the temp range for hypothermia:
1. Mild
2. Moderate
3. Severe
- 32-35 degrees
- 29-32 degrees
- < 29 degrees
Describe mild (32-35 degrees) hypothermia (6)
- thermogenesis still possible
- Shivering
- Apathy
- Ataxia
- Dysarthria
- Tachycardia
Describe moderate (29-32 degrees) hypothermia (6)
- Progressive failure thermogenesis
- No shivering
- Altered mental state
- Muscular rigidity
- Bradycardia
- Hypotension
Describe severe (<29 degrees) hypothermia (6)
- Adopt temp of surrounding enviroment
- Signs of life almost undetectable
- Coma
- Fixed/dilated pupils
- Areflexia
- Profound bradycardia and hyptension
What is a J wave
Deflection at J point
Which leads can J waves be seen the best?
Lead II
V3-6
Describe frostnip (3)
- Short lived, superficial freezing
- Rapid response to warming
- No swelling
Describe superficial frostbite (3)
- Superficial layers only
- Clear blisters 24-48 hours after injury
- Tissue below remains pliable and soft
Describe deep frostbite (4)
- Full thickness
- Blood filled blisters 1-3 weeks later
- Underlying tissue woody and stony
- Bad prognosis, loss of digits likely
How should frostbite be managed immediately? (4)
- Splint area and wrap in loose, dry clothing
- Don’t warm unless you can continue to
- Rewarm at 40-42 degrees initially
- Analgesia (re-warming very painful)
When should surgery be performed on frostbite?
Delayed
What is the most useful discriminating factor in the pre-hospital environment for the severity of heat illness?
Altered mentation after 30 mins cooling
What is:
- exertional heat illness
- non-extertional heat illness
- Increased work leads to increased heat production
- Inability to compensate for enviromental change
What is the WBGT (heat)?
Wet Bulb Globe Temperature - heat stress index
When does the American College of Sports Medicine suggest cancelling an event?
WBGT > 28 degrees C
What is the initial management of heat illness? (3)
- Cool first, transfer later
- Immersion in ice water is gold standard
- Aim to cool to 38.5 degrees - 39 degrees C to avoid hypothermia
What are the 5 types of heat illness?
What is the underlying mechanism that makes heat stroke different from heat exhuastion?
SIRS response leading to multi-organ failure with encephalopathy predominating
What biochemical abnormalities can be seen in heat stroke? (6)
What the two main groups of snakes?
- Vipers
- Elapids
Where are vipers found?
Americas/Africa/Europe
Where are elapids found?
SE Asia, Australia, PNG
How long should snake bites be observed for?
24 hours - can be delayed
What type of snake is a cobra?
Elapid
How do you treat suspected envenomation?
- pressure immobilisation (> lymph/venous pressure)
- Anti-venom
- Neostigmine if paralysis due to cobra/death adder and no anti-venom
What types of spider are poisonous? (3)
- Lactrodectus (black widow, red back spider)
- Funnel web spider
- Recluse spiders
What are the effects of venomous spider bites?
Mainly local but can be systemic
What are the effects of scorpion bites in:
- US/OZ
- N. Africa, S + C America and ME
- Local affects only
- Can lead to systemic effects resembling a cathecholamine surge
What types of jellyfish have systemic effects?
Box and Portuguese Man of War
How do you treat Jellyfish envenomation?
- Box jellyfish - rinse with vinegar + anti-venom
Other jellyfish
2. Wash in sea/saline water to remove remaining nematocysts
3. Then immerse in hot water
Describe pressure immobilisation post envenomation? (4)
- Dont remove trousers as can increase venom through bloodstream
- Pressure bandage from below wound as high as possible with minimal movement of leg
- Apply splint to immobilise joint above/below bite
- Restrict walking
What is:
1. Immersion
2. Submersion
- Airway above water
- Airway below water
Following submersion what occurs initially?
Patient will swallow water preferentially until urge to breath takes over
Following submersion how long does
1. Resp movement
2. Cardiac output
COntinue for?
- 1 min
- 2 mins
(approx)
How cold does water need to be to lead to a ‘cold shock response’?
< 15 degrees
What is the ‘cold shock response?’
Involuntary gasp (2-3L) and uncontrollable hyperventilation for around 90 secs
Therefore decreased time to aspirate lethal amount of water
What is the lethal amount of water aspirated in:
1. Sea water
2. Fresh water
- 1.5L
- 3 L
What is the consequence of submersion in water < 6 degrees C?
- Selective brain cooling from aspiration
- successful resus can increase from after 30mins to 90 mins
What are the good prognostic indicators in drowning (9)?
- Submersion <10mins
- Tw (water temp) < 10 degrees and patient temp <33-35 degrees
- Time to BLS < 10 mins
- Early ROSC
- Child
- No aspiration
- Spontaenously breathing
- PH > 7.1 and blood glucose < 11.2
- Neurologically intact at hospital
What is the strongest predictor of prognosis in drowning?
Submersion > 10 mins
> 25 mins nearly 100% mortality (unless very cold water)
Describe the 3 zones in water rescue and the PPE that should be worn
- Hot = in/on water + full PPE
- Warm = < 3m from waters edge + full PPE
- Cold = safe
What is the recommendation for non-specialist water rescue options? (3)
Talk
Reach
Throw
In drownings what should trigger prolonged resus? (4)
- Submersion < 30mins (Tw >6 degrees) or <90mins (Tw <6 degrees)
- Possibility of air pocket
- Intermittently submerged ie. life jacket
- Signs of life
In prolonged immersion what should the initial management be? (3)
- conscious, encourage patients to continue fighting for survival
- if semi/un conscious then remove horizontal from water to avoid circum-rescue collapse
- prioritise oxygenation ( <10% shockable) how AED not c/i in wet enviroments
What should we consider in ALS following a drowning? (5)
- 5 rescue breaths and ALS if no response
- I+V
- OG tube
- May need high PEEP
- Consider ECMO
What considerations should be made with post drowning patients? (4)
- Ignore ‘foam at mouth; and give oxygen
- Consider PHEA and PEEP 10-15cmH20
- Vasopressors and cautious fluids
- Treat as ‘wet head injury’ i.e. neuroprotection
What 3 criteria need to be met to discharge a drowning from scene?
- No foam at mouth
- No resp distress and normal resp exam
- Safety net
What does SCUBA stand for?
Self Contained Underwater Breathing Apparatus
What does a SCUBA kit consist of?
Cylinder with up to 300atm compressed gas delivered via a pressure regulator
What is Daltons Law?
Total pressure exerted by gaseous mixture is equal to the sum of the partial pressure of each gas
What is the real world consequences of Daltons law?
At sea level air subject to 1 atmosphere pressure, however as you descend that pressure increases and therefore so does the partial pressure of the component gases (o2/nitrogen in particular)
Converse true as you ascend
What is Boyles Law?
At a constant temperature the volume of gas will vary inversely with pressure
e.g.
0 m = 1atm = 1.0 (volume) x 1 (density)
10m = 2 atm = 1/2 = x 2
20m = 3 atm = 1/3 = x 3
How much descent is needed to increase pressure by 1 atmosphere?
10m
What is Henrys Law?
Amount of gas dissolved in a liquid is proportional to pressure of gas
What is the conequence of Henrys Law in diving?
As partial pressure of each component increases more gas dissolves in divers tissues/blood
Ascent = reverse of this
Slow ascent means bubbles filtered by lungs
What is nitrogen narcosis?
Breathing nitrogen at increased partial pressure (usually >4atm or 30m) leads to symptoms like being drunk. If do not resolve on ascent then alternative diagnosis likely
What is oxygen toxicity in diving?
At depth partial pressure of oxygen means free radicals may accumulate in brain
What are the symptoms of oxygen toxicity? (7)
- Tingling
- Vertgio/tinnitus
- Personality change
- n/v
- tunnel vision
- Seizure and likely death (underwater)
- Coma
What is management of oxygen toxicity?
Abort dive
What is the safe partial pressure of oxygen for recreational dive and what depth is this with compressed air?
- 1.4 atm
- 57m
What are the 3 parts of decompression illness?
- DCS
- AGE
- Barotrauma
What do the nitrogen bubbles in decompression illness cause disease? (4)
Fast reforming expanding nitrogen bubbles damage cells causing:
- mechanical compression
- stretch of blood vessels/nerves
- act as emboli
- activate inflam/coag pathways
When does type 1 (mild) DCS normally present?
10-30 mins after surfacing
98% < 24 hours
What are the symptoms of type 1 DCS? (3)
- MSK joint pain (not on movement)
- Itching/burning sensation +/- faint rash
- Localised pain lymph nodes and swelling in tributary tissue which can be prolonged
When does type 2 (severe) DCS normally present?
Immediately but can be up to 36 hours
How often does pain feature with type 2 DCS?
30%
What systems does type 2 DCS affect? (4)
- Neuro
- Cardiopulmonary
- Auricular
- Skin
What are the neuro signs of type 2 DCS?
- Usually affects spine - LBP with progressive SCI symptoms
- Cerebral - headaches/visual field def/dizziness/poor co-ordination/amnesia/personality change/tremor
Whhat are the cardiopulmonary affects of type 2 DCS?
‘The chokes’
- pleuritic CP, haemoptysis, dry cough, tachypnoea
What is the treatment for ‘the chokes’ and what is an absolute c/i/
Recompression
Untreated PTX
What are the auricular affects of type 2 DCS?
‘The staggers’
Vertigo/tinnieus/ataxia/vomiting
If a patient developes only ‘inner ear’ symptoms following a dive what will be the cause?
Baratrauma if no other signs of DCS
What are the cutaneous manifestations of type 2 DCS?
Flat raised itchy rash > common shoulders/chest
Will become dark-bluish ‘cutis marmorata’
What is altitude decompression sickness ?
Flying after diving
How long after diving should you avoid flying?
12-48 hours
How should altitude decompression sickness be managed and when can recompression be avoided?
Descend to sea level and:
- if pain resolves
- -100% Fi02 for 2 hours available
- 24 hours observation available
then no need for recompression
How do arterial gas emboli form?
Leakage of air into pulmonary arterial system following alveoli rupture during ascent
At what depth can AGE form?
Any diver any at any depth
How can venous gas emboli that are relatively common in recreational dives become dangerous?
PFO/ASD/VSD
How long after a dive do symptoms caused by AGE and DCI develop?
10-30mins
What are the signs/symptoms of AGE?
Depends on site:
- coronary artery feels like ‘direct blow’ to chest and causes MI
- cerebral = CVA
etc
What are the time goals for treatment following signs/symps of AGE (3)?
< 2 hours better prognosis
>6-8 hours worse prognosis
If neuro/pulmonary/mottled skin then hyperbaric regardless of age
What is the initial management of AGE (ie. pre recompression)? (5)
- 100% Fi02
- Remove diving gear
- Keep patient supine and horizontal
- Take diving gear and ideally buddywith patient (to help with hx of dive)
- IVI - start 75/ml-100ml per hour and UO 0.5-2.0ml/hr
If having to fly a patient following AGE what should be ensured?
Fly under 300m and with cabin pressure 1atm
What should be avoided in AGE? (5)
- Trendelenburg
- High flow oxygen over 12 hours (toxicity)
- Entonox (can increase bubble size)
- Steroids/aspirin/lidocaine (no evidence)
- 5% dextrose can increase cerebral oedema
What is the physiology involved in acclimatisation?
As you ascend partial pressure oxygen decreases leading to lower SATs and exercise tolerance.
You adjust to this by initially increase plasma volume then gradual increasing red cell mass and so increase Hb concentration
What percentage of people will develop AMS?
60% over 4000m
What are the signs/symptoms of AMS?
Hangover like symptoms worse at night
How should AMS be managed?
No further ascent until symptoms improve
What is the prophx dose of acetazolamide?
125mg BD day before ascent until descending
What is the mechanism by which acetazolamide prevents altitude sickness?
Carbonic anhydrase inhibor which increases excretion of HCO3- leading to metabolic acidosis and therefore increases RR.
How much does acetazolamide reduced AMS by in percentage terms?
48%
What are the common side effects of acetazolamide? (3)
- Polyuria
- Parasthesia
- Altered taste
Describe te pathophysiology of High Altitude Cerebral Oedema (HACE)
Cerebral blood flow increases with altitude - combination of capillary leakage and decreased cerebral autoregulation on acute exposure to hypoxia
What are the signs/symptoms of HACE? (3)
- Progressive personality change/confusion
- Worsening co-ordination (test heel/toe and sharpened Rombergs)
- Coma/death within 12 hours
How should HACE be treated? (3)
- Descend/portable altitude chamber (head up slope)
- If unable to descend dexamethasone can by time by decreasing cerebral oedema
- High flow oxygen
What is the dose of dexamethasone used to tx HACE?
8mg STAT PO followed by 4mg TDS
What is the pathophysiology involved in HAPE?
Non cardiogenic pulmonary oedema caused by exaggerated hypoxic pulmonary artery vasoconstriction.
Lead to increased pulmonary artery pressure which causes a transudative capillary leak and mild alveolar haemorrhage + mild SIRS
What is the treatment of HAPE? (4)
- Descend
- Nifedipine SR 20-30mg QDS (sildenafil if not available)
- Acetazolamide 250mg QDS
- CPAP
How do calcium channel blockers tx HAPE?
Decrease pulmonary artery pressure by increasing NO levels in pulmonary vasculature causing smooth muscle relaxation
To what pressure is a portable altitude chamber pressurised?
2 psi = 2000m
What should be considered when using portable altitude chambers? (2)
- Will need to keep pumping
- Think what they will need in chamber as can’t leave ie. PU, warmth, meds, pen and paper to communicate
How common is HAPE?
2% >4000M
What is the main cause of decompression sickness?
Ascending too quickly
What does the FPHC define exertional heat illness as?
A syndrome associated with a raised core temperature and disordered thermoregulation which occurs on a spectrum of severity, during or immediately after physical activity
What does FPHC require alongside a raised temperature during or immediately after exercise to diagnose EHI?
Symptoms
What does FPHC define as mild EHI?
core body temperature from 38.5°C to 40°C associated with signs or symptoms of heat illness other than CNS during or immediately after exercise
What does FPHC define as severe EHI?
A life-threatening condition of disordered
thermoregulation with central nervous system dysfunction, associated with a core body temperature above 40°C during or immediately after physical activity
What are the signs/symptoms of severe EHI? (12)
Temp > 40 degrees + CNS dysfunction (less than A on AVPU) +/-
- Confusion
- Agitation or aggression
- Behavioural changes
- Stumbling gait/ataxia
- Seizures
- LOC + coma
- Vomiting
- Urinary/faecal incontinence
- Flushed/pale skin
- Collapse
- Hypotension
- Arrhythmias
What does FPHC recommend with regards to temperature measurement in EHI? (5)
- Core temperature should be measured with flexible rectal probe (rigid can cause injury)
- Oesophageal temp probe acceptable if I+V
- Core body temperature measurement should not be delayed, priority
- Peripheral temprature measurement is unreliable and may lead to false reassurance, not recommended
- Cooling recommended if not able to measure core body temp if EHI suspected until core temp can be measured
What does FPHC state about transfer before cooling in EHI?
Shown increase mortality, transfer should be delayed until cooling
How quickly should we aim to cool patients with EHI?
0.15 degrees C / min
What does FPHC recommend for cooling in EHI?
Cold Water Immersion (CWI) up to neck with continous core temp monitoring
What are the main relative contraindications to cold water immersion in EHI? (2)
- Hypotension
- Arrhythmia
If cold water immersion is c/i or not available in severe EHI what does FPHC recommend?
Shade, strip and spray
What temperature should we aim for in cold water immersion post EHI and why?
38.5 to 39 degrees to prevent hypothermia
How long should patients core temp be measured following cold water immersion ?
30 mins
What should be done if patients become hypothermic post cold water immersion?
Gentle rewarming with coretemp measurement
What patients with EHI should be 1. conveyed and 2. who can be discharged?
- Anyone with severe EHI (will need bloods)
- Mild EHI with resolution of symptoms post cooling wth robust safety netting
How and to what temp should patients with mild EHI be cooled?
- Shade, strip and spray
- 37.5 degrees as low risk of hypothermia post cooling
What does FPHC not recommend in management of EHI in pre-hospital setting? (6)
- Anti-pyretics
- Dantrolene
- Steroids
- Depolarising neuromuscular blockers
- Abx
- IV fluids unless clinically indicated (caution with ? hyponatreamia)
