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PHM BSc - Trauma Science > Drowning > Flashcards

Drowning Flashcards

1
Q

Define drowning

A

respiratory impairment as a result of submersion/immersion in a liquid

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2
Q

Define submersion and immersion

A

submersion - airway under surface

immersion - airway still above water - it may be splashing over the face

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3
Q

What is a water rescue

A

where a person is rescued from submersion/immersion but has no evidence of respiratory impairment

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4
Q

Describe how a drowning victim would look whilst in the water

A 
facing the shore
"climbing ladder" type motion
head tilted back
airway only just above the water
vertical in the water
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5
Q

What can lead to drowning (i.e. why would a person not keep swimming)

A 
cold shock
cold incapacitation
trauma from the fall in to water
never learnt how to swim
medical event that perhaps lead them to falling into water eg MI or epilespy
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6
Q

Compare cold shock vs cold incapacitation

A

shock - immediate sympathetic driven reaction to cold water

incapacitation - cold leads to large muscle groups becoming weak so can’t swim

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7
Q

A person becomes submersed in water… what is the immediate reflex

A

breath holding

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8
Q

What does the breath holding reflex lead to

A

breath holding = hypercarbia = eventually inspiratory drive is too high to resist = aspiration of water = laryngospasm following cold water coming into contact with vocal cords = hypoxia = eventually hypoxia leads to unconsciousness = airways relax = water floods in = unable to exchange gas = further hypoxia = cardiac arrest

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9
Q

What causes the laryngospasm (seen in someone who inhales water) to relax

A

hypoxia leading to unconsciousness

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10
Q

Why can the cardiovascular system become compromised in a drowning victim

A

fluid shift due to hydrostatic pressures on the body.

Catecholaminergic surge on exposure to hypothermia and hypoxia leads to intense vasoconstriction and arrhythmias

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11
Q

What is the typical cardiac rhythm pattern in a drowning victim

A

tachy - brady - PEA - asystole

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12
Q

What might the CXR of a drowning victim look like

A

aspiration can mimic infection on a CXR

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13
Q

State briefly how the lung can be injured in drowning

A

surfactant washout - increased surface tension leads to collapsed alveoli which can no longer participate in gas exchange
interstital oedema - increased distances for gas exchange + poor compliance
acute emphysema - due to exertion against a closed glottis
toxin related damage eg from chlorine

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14
Q

describe the mechanism behind interstitial oedema seen in someone who drowns in salt water

A

sea water is hypertonic compared to blood so blood moves from capillary - capillary endothelium - interstitial space - respiratory epithelium - alveoli.
However some fluid remains in the interstitial space cause oedema
(The reverse happens in fresh water)

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15
Q

How does the damaged alveolar-capillary membrane clinically present (drowning)

A

massive bloodstained pulmonary oedema

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16
Q

Why could a drowning victim get acute emphysema

A

ventilation against a closed glottis

17
Q

How would you approach the evaluation of a drowning victim

A 
responsiveness
pulse
auscultate the lungs to listen for crackles
assess if the patient is coughing
check BP
18
Q

What are some general management principles for a drowning victim

A 
5 rescue breaths first
oxygen
keep horizontal 
no spinal immobilisation needed
get them on to a solid surface
no need for steroids or abx
19
Q

How would you manage a unconscious (but with a pulse) or shocked drowning victim (grade4/5)

A

definitive airway management - intubate
lung protective ventilation (carefully ventilate without much worry about optimum O2 and CO2)
cardiovascular help with fluids +/- inotropes
neuroprotect

20
Q

Why is high PEEP not used in a drowning victim

A

cardiovascular instability (reduces diastolic filling)
can cause air trapping
can end up just over inflating healthy lung and not improving consolidated lung - this leads to worse V/Q mismatch

21
Q

What is the normal cerebral blood flow rate

A

40-60ml/100g tissue/min

22
Q

How does hypothermia alter the CRMO2

A

lowers the threshold for which neurons start to become damaged i.e. ionic failure won’t occur until a lower cerebral oxygen delivery than it normally would

23
Q

describe the series of events occuring as cerebral blood flow falls and how this clinically presents

A

20-30ml: become symptomatic with syncope
15-20ml: electric failure. Patient in a deep coma
10ml: ionic failure. Neurons are dead

24
Q

What is electrical failure of neurones

A

Not enough ATP to meet the requirements of a neuron to function. They are still alive however silent as aren’t discharging electrical signals

25
Q

What is ionic failure of neurones

A

Failure of the NaKATPase leads to Na influx, water influx, cell swelling and death of the neurone

26
Q

Describe some potential mechanisms behind why drowning victims can survive

A

diving reflex - apnoea, bradycardia and centralisation of circulation leads to increased O2 delivery to essential organs and lower myocardial oxygen demand
whole body cooling - unlikely since people tend to drown before their body can cool this much
selective cerebral cooling

27
Q

What is selective cerebral cooling (drowning)

A

vessels to the head and neck travel close to the surface, trachea and oesophagus so are close to cold water outside the body and the cold water that is inhaled and swallowed

28
Q

State some complications that can occur later down the line in a drowning victim

A

sepsis
DIC
gastric aspiration

29
Q

What are the ERC guidelines for drowning

A

5 initial rescue breaths

30:2

30
Q

What is a problem with research into drowning

A

publication bias - more likely to publish a case report where a patient survives despite being in the water for 60 minutes than you would if they died or if they’d only been submersed for 5 minutes

31
Q

What nerve stimulates the diving reflex

A

Ophthalmic branch of the trigeminal nerve

32
Q

How does cold shock increase the risk of drowning

A

the sympathetic response can lead to arrhythmias and sudden cardiac death
hyperventilation means water is aspirated quicker

33
Q

Why is selective cerebral cooling neuroprotective

A

decreases metabolism so reduced O2 demand
reduces cerebral oedema
reduced glutamate release

PHM BSc - Trauma Science (15 decks)

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