Drowning

Question 1

What is the 2002 definition of drowning?

Answer 1

The process of suffering respiratory impairment from immersion/submersion in liquid

Question 2

Better definition?

Answer 2

Submersion or immersion in water leading to obstruction of interface between airway and air -> respiratory distress

Question 3

What is cold shock?

Answer 3

Cold water immersion: triggering a maximal inspiration, tachypnoea, tachycardia, increased BP and peripheral vasoconstriction

Question 4

Who is cold shock particularly damaging to?

Answer 4

Those with underlying cardiac problems -> arrest

Question 5

What is a rough maximal voluntary breath holding time?

Answer 5

10s

Question 6

What 3 things can happen as a result of reduced voluntary breath holding?

Answer 6

Swallow water, cough/laryngospasm, bronchospasm -> hypoxia/hypercapnia

Question 7

What reduces breath holding capacity?

Answer 7

hypoxia, hypercapnia, ^RR, ^^HR etc

Question 8

How far away from a place of safety do most people drown?

Answer 8

3m

Question 9

Define cold incapacitation

Answer 9

‘Swim failure’: loss of proprioception, peripheral vasoconstriction, weak muscles etc - cannot stay afloat/orientated/swim

Question 10

What is important to obtain for prehosp history?

Answer 10

How end up in water? Alcohol/trauma/medical event?
Were they talking in water and subsequently not?
How long in?

Question 11

Critical factor that affects rate of cooling?

Answer 11

Surface area to volume ratio

Question 12

Holy trinity of prehospital history?

Answer 12

Eye witness, first responder and patient.

Question 13

Possible difference in pathophysiology if LOC pre-entry into water?

Answer 13

Passive entry of water into airway: no negative pressure pulmonary oedema

Question 14

What temperature are bodies cooled to for cardiac surgery?

Answer 14

18 degrees

Question 15

Is the rate of cooling in drowning sufficient to be neuro-protective?

Answer 15

No

Question 16

What special circumstances might it be?

Answer 16

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.

Question 17

Give three examples of deciding when to attempt resus on a ‘drowned’ person?

Answer 17

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

Question 18

Define death

Answer 18

The irreversible loss of capacity for conscious

Question 19

What pathophysiology can lead to hypoxia in drowning?

Answer 19

Surfactant wash out -> V/Q shunt and direct gas exchange block.
Water in interstitial space - increases time for exchange

Question 20

Fresh water drowning?

Answer 20

Theory that RBC swell and lysis but not really true, these patients are hyperkalaemic because they are dead

Question 21

Median time for survivors and non-survivors?

Answer 21

7 and 11 minutes

Question 22

Pathophysiology of lung injury in drowning

Answer 22

Surfactant washout and dysfunction
Osmotic disruption
Interstitial oedema
Impaired gas transfer
Poor compliance

Question 23

Potential mechanisms of survival through hypothermic drowning?

Answer 23

Mammalian diving reflex
Total body cooling
Selective cerebral cooling

Question 24

Cut off time for no survivors?

Answer 24

> 25 mins

Exceptions are if history of prior cooling