Drowning Flashcards
Define drowning
respiratory impairment as a result of submersion/immersion in a liquid
Define submersion and immersion
submersion - airway under surface
immersion - airway still above water - it may be splashing over the face
What is a water rescue
where a person is rescued from submersion/immersion but has no evidence of respiratory impairment
Describe how a drowning victim would look whilst in the water
facing the shore "climbing ladder" type motion head tilted back airway only just above the water vertical in the water
What can lead to drowning (i.e. why would a person not keep swimming)
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
Compare cold shock vs cold incapacitation
shock - immediate sympathetic driven reaction to cold water
incapacitation - cold leads to large muscle groups becoming weak so can’t swim
A person becomes submersed in water… what is the immediate reflex
breath holding
What does the breath holding reflex lead to
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
What causes the laryngospasm (seen in someone who inhales water) to relax
hypoxia leading to unconsciousness
Why can the cardiovascular system become compromised in a drowning victim
fluid shift due to hydrostatic pressures on the body.
Catecholaminergic surge on exposure to hypothermia and hypoxia leads to intense vasoconstriction and arrhythmias
What is the typical cardiac rhythm pattern in a drowning victim
tachy - brady - PEA - asystole
What might the CXR of a drowning victim look like
aspiration can mimic infection on a CXR
State briefly how the lung can be injured in drowning
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
describe the mechanism behind interstitial oedema seen in someone who drowns in salt water
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)
How does the damaged alveolar-capillary membrane clinically present (drowning)
massive bloodstained pulmonary oedema
Why could a drowning victim get acute emphysema
ventilation against a closed glottis
How would you approach the evaluation of a drowning victim
responsiveness pulse auscultate the lungs to listen for crackles assess if the patient is coughing check BP
What are some general management principles for a drowning victim
5 rescue breaths first oxygen keep horizontal no spinal immobilisation needed get them on to a solid surface no need for steroids or abx
How would you manage a unconscious (but with a pulse) or shocked drowning victim (grade4/5)
definitive airway management - intubate
lung protective ventilation (carefully ventilate without much worry about optimum O2 and CO2)
cardiovascular help with fluids +/- inotropes
neuroprotect
Why is high PEEP not used in a drowning victim
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
What is the normal cerebral blood flow rate
40-60ml/100g tissue/min
How does hypothermia alter the CRMO2
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
describe the series of events occuring as cerebral blood flow falls and how this clinically presents
20-30ml: become symptomatic with syncope
15-20ml: electric failure. Patient in a deep coma
10ml: ionic failure. Neurons are dead
What is electrical failure of neurones
Not enough ATP to meet the requirements of a neuron to function. They are still alive however silent as aren’t discharging electrical signals
What is ionic failure of neurones
Failure of the NaKATPase leads to Na influx, water influx, cell swelling and death of the neurone
Describe some potential mechanisms behind why drowning victims can survive
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
What is selective cerebral cooling (drowning)
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
State some complications that can occur later down the line in a drowning victim
sepsis
DIC
gastric aspiration
What are the ERC guidelines for drowning
5 initial rescue breaths
30:2
What is a problem with research into drowning
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
What nerve stimulates the diving reflex
Ophthalmic branch of the trigeminal nerve
How does cold shock increase the risk of drowning
the sympathetic response can lead to arrhythmias and sudden cardiac death
hyperventilation means water is aspirated quicker
Why is selective cerebral cooling neuroprotective
decreases metabolism so reduced O2 demand
reduces cerebral oedema
reduced glutamate release
