Drowning Flashcards
What is the 2002 definition of drowning?
The process of suffering respiratory impairment from immersion/submersion in liquid
Better definition?
Submersion or immersion in water leading to obstruction of interface between airway and air -> respiratory distress
What is cold shock?
Cold water immersion: triggering a maximal inspiration, tachypnoea, tachycardia, increased BP and peripheral vasoconstriction
Who is cold shock particularly damaging to?
Those with underlying cardiac problems -> arrest
What is a rough maximal voluntary breath holding time?
10s
What 3 things can happen as a result of reduced voluntary breath holding?
Swallow water, cough/laryngospasm, bronchospasm -> hypoxia/hypercapnia
What reduces breath holding capacity?
hypoxia, hypercapnia, ^RR, ^^HR etc
How far away from a place of safety do most people drown?
3m
Define cold incapacitation
‘Swim failure’: loss of proprioception, peripheral vasoconstriction, weak muscles etc - cannot stay afloat/orientated/swim
What is important to obtain for prehosp history?
How end up in water? Alcohol/trauma/medical event?
Were they talking in water and subsequently not?
How long in?
Critical factor that affects rate of cooling?
Surface area to volume ratio
Holy trinity of prehospital history?
Eye witness, first responder and patient.
Possible difference in pathophysiology if LOC pre-entry into water?
Passive entry of water into airway: no negative pressure pulmonary oedema
What temperature are bodies cooled to for cardiac surgery?
18 degrees
Is the rate of cooling in drowning sufficient to be neuro-protective?
No
What special circumstances might it be?
Selective cerebral/carotid cooling - via airway water and swallowing water which cools internally.
Pre-existing
Fast flowing
Mammalian diving reflex: bradycardia, peripheral vasoconstriction and reduced BMR etc etc - cold water on ophthalmic distribution of trigeminal nerve.
Give three examples of deciding when to attempt resus on a ‘drowned’ person?
Warm until 32 degrees with ongoing resus efforts?
Check potassium - cut off is 10
NEJ say: any more than 60 minutes underwater, do not attempt
UK (Plymouth Group): say if water temp below 6 degrees limit search and resus efforts to 30 minutes in water and if above 6 degrees, limit search and resus efforts to 90 minutes
Define death
The irreversible loss of capacity for conscious
What pathophysiology can lead to hypoxia in drowning?
Surfactant wash out -> V/Q shunt and direct gas exchange block.
Water in interstitial space - increases time for exchange
Fresh water drowning?
Theory that RBC swell and lysis but not really true, these patients are hyperkalaemic because they are dead
Median time for survivors and non-survivors?
7 and 11 minutes
Pathophysiology of lung injury in drowning
Surfactant washout and dysfunction Osmotic disruption Interstitial oedema Impaired gas transfer Poor compliance
Potential mechanisms of survival through hypothermic drowning?
Mammalian diving reflex
Total body cooling
Selective cerebral cooling
Cut off time for no survivors?
> 25 mins
Exceptions are if history of prior cooling
