Drowning

'Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid'.   This is the definition adopted at the World Congress on Drowning, Amsterdam, 2002.

As a result, the following terms are no longer used: 'dry' v 'wet' drowning, 'active' v 'passive' v 'silent' drowning, 'secondary' drowning, 'near-drowned' and 'near drowning'. 

Drowning is the second leading cause of unintentional death globally after road traffic accidents; approximately 450,000 deaths annually.

Risk factors include: gender (predominately males), age (usually young), impairment by drugs or alcohol, lack of appropriate clothing and personal flotation.

Some of the risks in the wilderness include river crossings (on foot, on horseback, or by vehicle or ferry), kayaking, canoeing and sailing accidents, canyoning accidents, diving accidents and crossing ice.

Before entering the water, carry out a realistic assessment of the dangers - and do NOT base your estimate of swimming ability on what you can achieve in a swimming pool!   You also need to prepare properly - dress for flotation and for immersion (NOT the air temperature).

Moving water is extremely powerful and therefore dangerous - if you are not alert to, or aware of, these dangers, you need to  think really hard about whether you should be entering the water at all.   Water in spate or flood is clearly more dangerous yet.   (See the Binghamton video via the link in the reference materials section).   It is also important to be aware of the possibility of underwater hazards - leading to pinning or entrapment scenarios.

On entering cold water, your body will start to go through the first of 4 stages of response - initial, short-term, long-term and post-immersion.  

Possible initial responses (the first 3-5 mins) include uncontrollable hyperventilation, peripheral vasoconstriction and tachycardia.   These are short-lived, but of themselves can cause swim failure and thereby death.   Short-term responses (5-30 mins) involve the cooling of superficial nerves and muscles, leading to impairment of dexterity.   The body then enters the long-term response phase - the cooling of deep tissues (entering a hypothermic state).   Post-immersion (during rescue or later) responses can include the collapse of arterial pressure and continued cooling.

A way to remember the key learning points to survive the initial phase of immersion is the '1-10-1' rule: you have one minute to get your breathing under control, ten minutes of meaningful activity before your muscles seize, and (at least) one hour before you go unconscious due to the onset of hypothermia.  (45F/8C water).   So, in order to survive cold shock (and not then die from hypothermia) you need to wear a buoyancy aid (PFD) or (better) a lifejacket; to survive the short-term responses, you need to don your hood and gloves, prepare your flares and use the radio; and to survive the long-term responses, you need to be dressed for immersion.   Remember: cold shock can kill, because it leads to rapid onset of swim failure.

There are no clinically relevant differences between submersion in salt- or freshwater.

Casualties can present in any of 4 groups - asymptomatic (but can still be hypoxic), symptomatic (showing signs of hypoxia and acidosis); in arrest; and apparently dead (who may, in fact, be alive but deeply hypothermic). 

The Heimlich manoeuvre is contra-indicated as a method of expelling water from the lungs (because of the increased danger of the casualty then aspirating vomit) BUT may be necessary as a way of clearing the casualty's airway.

The initial management of a drowning victim includes: removal from the water as soon as possible (bearing in mind the safety of rescuers); initiation of rescue breathing (if feasible); protecting the C-spine; and AcBC, with attention to securing the airway and providing adequate oxygenation and ventilation.   Casualties should ideally be removed from the water in the horizontal position to lessen the possibility of hypotension as the hydrostatic pressure is released.

Fluids, if administered, must be warmed and should be Dextrose 5% (in water or saline), or Saline alone.   (Not Ringer's Lactate, as a hypothermic liver may be unable to metabolize lactate normally). 

Drowning victims are a medical emergency and consideration MUST be given to getting casualties to definitive care at the earliest opportunity.

Be aware that up to 40% of drowning incident casualties will develop Acute Respiratory Distress Syndrome (ARDS) up to 72 hrs post-incident.   All drowning incident victims should be either monitored throughout this period, or warned of the possibility of symptoms developing. 

Spinal injuries should be suspected if the mechanism of injury suggests them; if the casualty is unconscious; or if they display any neurological signs or symptoms.   The incidence of such injury is, however, relatively low at 0.5%.

Hypothermia resulting from cold water immersion can be both protective and harmful; there have been several well documented cases  of survival (particularly of children) after prolonged submersion.   Prolonged resuscitation efforts may therefore be required.   At water temperatures below 5 deg C ( 41 deg F), the diving reflex may cause the heart rate to slow.

Actions in the water may prolong survival times, with the HELP and Huddle positions being most effective.   However, it should be noted that these are only realistically achievable in reasonably calm water and when wearing a buoyancy aid (PFD) or, better, a lifejacket.   (Note that a buoyancy aid (PFD) will become ineffective at keeping the face above water when the casualty becomes unconscious, and a lifejacket will turn them to face the wind/waves (because of leg drag), at which point spray will cause drowning if a spray hood is not also worn).  

In summary, drowning is commonplace; awareness of the dangers is the best preventative; good pre-hospital care can have a big impact on the outcome.   Think - ventilation, prone removal from the water, AcBC, hypothermia, and rapid onward movement to definitive care.

Controversies and Areas of Development

(Reproduced from the Wilderness Medical Society Practice Guidelines for Wilderness Emergency Care, 5th Edition, Forgey, Ed.)

Should all victims of accidental submersion be evacuated?  

Someone who is unexpectedly submersed and who comes up coughing but never loses consciousness does not need to be evacuated unless respiratory distress continues, or hypotension, bilateral crackles, and/or other signs of distress develop.

Should the Heimlich manoeuvre be used to clear the airway of a drowning victim?

The American Heart Association unequivocally recommends an immediate start of CPR without the Heimlich manoeuvre in the case of a drowning victim.   Only utilize the Heimlich manoeuvre if foreign matter is suspected of obstructing the airway or when attempts to ventilate the patient fail due to a blocked airway.