Drowning
7th April, 2010
Amanda Diaz
Intensive Care Unit
John Hunter Hospital
Drowning in Oz
• Royal Lifesaving Society Australia (08-09)
– 302 drowning deaths
• 32 (11%) age 0 – 4 yrs
• 11 (4%) age 5 – 14 yrs
• 84 (28%) age 15 – 34 yrs
– 66 (22%) Males
• 80 (26%) age 35 – 54 yrs
• 94 (31%) age > 55 yrs
– 1.4 / 100,000 people (same as 1999 levels)
Definition of Drowning
• Confusing!
• Dictionary definition regards drowning as dying
as a result of water filling the lungs preventing
gas transfer and causing asphyxiation
• Sub-classifications based on dying (drowning) v
not (near-); primary v secondary drowning (dying
at the time or later); aspiration v non-aspiration
Definition of Drowning
• 2002 World Congress on Drowning (Amsterdam)
– Published in Circulation 2003:
• A process resulting in primary respiratory
impairment from submersion/ immersion in a
liquid medium.
• Liquid/ air interface present at the entrance of
the victim’s airway prevents them from breathing
air.
• Survival is not considered in this definition
The Drowning Process: A Continuum
• Submersion → Airway below surface
• Voluntary breath-holding
– Healthy volunteers 87s (longer with hyperventilation)
– Shorter (10-20 s) in water < 15°C
• Break-point results in involuntary ventilation
– Breath-hold can be prolonged with swallowing / active
respiratory movement
• Laryngospasm when water stimulates epiglottis
/oropharynx
The Drowning Process: A Continuum
• Respiratory movement against closed glottis
• Forced expiration against column of fluid:
acute emphysema; alveolar septal rupture
• Decrease in alveolar / arterial pO2
• Increase in alveolar / arterial pCO2
– Hypoxaemia, acidosis, hypercarbia
• Critical hypoxia – release of laryngospasm
• Aspiration
The Drowning Process: A Continuum
• Aspiration amount varies widely
– Up to 10% at autopsy have no evidence of
aspiration
– Average 7 ml/kg aspirated
– 22ml/kg considered fatal aspiration
• Electrolyte disturbance from increase blood volume
– Up to 70% of drownings aspirate foreign material
• Algae
• Mud
• Vomitus
Why is drowning so complicated?
• Primary respiratory insult relatively easy to
treat
• Major therapeutic challenge is the limitation
of brain injury
• Identifying those with poor prognosis is
extremely difficult
– No 2 drownings are alike
Factors Affecting Survival from
Drowning
• Patient Factors:
–
–
–
–
–
Age
Co-morbidities / Intoxication
Aspiration
Core Body Temp
Blood pH / Stress level during submersion
• Environmental Factors:
– Water Temperature
• Rescue Factors:
– Duration of submersion
– Time to effective BLS
– Time to return of spontaneous circulation
• No single clinical or lab value predicts morbidity or mortality
Age
• Older people tend to have more co-morbidities
– Decreased physiological reserve
• Children have a high body surface area : mass ratio
– Cool down faster
• Diving Response
– Ophthalmic division CN5
– Marked generalised vasoconstriction, apnoea, bradycardia
– Hypometabolism
• Case Reports of children surviving submersion of up to
25 min (Nordic countries)
Aspiration
• 20% of drownings have normal CXR on admission
– At risk of ALI progression
• Water aspiration:
– As little as 2.2 ml/kg impairs O2 transfer
• Freshwater aspiration:
– Affects surfactant phosphlipids leading to unstable alveoli,
collapse, atelectasis
– Increases absolute shunt
– Hypotonic fluids directly cytotoxic
• Interstitial & alveolar oedema
• Saltwater (hypertonic):
– Direct acute alveolar oedema
Aspiration
• Bronchospasm
– Increases relative shunt
• Overall effect:
– Increase V/Q mismatch
– Decreased lung compliance
– Increased work of breathing
Hypoxia
• Lowers set-point to thermoneutral zone
(normally 22-28°C)
– Worsens hypothermia in pre- & post-resuscitation
phase
• Severe acid-base disturbance
– Increase anaerobic metabolism
• Increased catecholamine release
– Myocardial arrhythmias
• Coagulopathy
• DIC (endothelial cell activation)
Core Body Temperature
• Hypothermia: core temp < 35°C
• Rate of change of core body temp dependent on:
– Physical factors: water temp, movement of water
against skin, insulation, head protection (increased
heat loss via evaporation / convection / conduction)
– Physiological factors: BSA:Mass ratio, metabolic rate
(affected by alcohol), peripheral circulation
• Cooling the fully clothed adult to < 35°C
– 1 hour in water at 5°C
– 2 hours in water at 10°C
– 3-6 hours in water at 15°C
Hypothermia: Cerebral Blood Flow
• Consciousness lost at 30°C
• Neurological protection only occurs if cerebral
hypothermia induced before hypoxic damage
occurs
• Studies done in anaesthetised humans
– Cerebral blood flow decreases in proportion to O2
requirements (autoregulation)
– 6-7% reduction in CMRO2 for each 1°C decrease in
core body temp
– Cerebral activity abolished at < 22°C
BUT...
• If ventilating:
– Shivering at < 34°C
• Increased O2 requirements
• Increased CO2 / lactate production
• If hypoxic:
– Set-point of thermoneutral zone lowered
• Shivering impaired
• Vasodilation of peripheries
• If hypercarbic:
– Cerebral vasodilation
Hypothermia: CV Function
• Arrhythmias occur – any are possible
• Core temp < 28°C
– VF
• Core temp 24-26°C
– Asystole
• Why?
– At < 30°C Purkinje fibres lose conduction
advantage over other ventricular muscle fibres
Hypothermia: Muscle Function
• Muscle (not core) temp < 28°C
– Impaired NMJ function
– Weakness
– Unable to swim
Hypothermia: Blood
• Increased blood viscosity
• Impaired coagulation
– Enzyme system
You’re Not Dead til You’re Warm &
Dead
• Hypothermia has profound effects
• A & B – if you’re thinking the above – ETT
• C: Fluid resuscitation – in water, hydrostatic
pressure increases vascular volume →
baroreceptor activation → natiuresis &
diuresis
– 2-3 L deficit on entering ED
You’re Not Dead til You’re Warm &
Dead
• C: CPR - <28°C core body temp
– Manual compression CPR must be continued until
core temp > 33°C
• Case reports of 4.5hrs manual compression CPR with
successful neurological outcome
• Case reports of 6hrs with ‘Thumper’ device
– Try defibrillation
• If not immediately successful, do not retry til > 29°C
– If successful, bear in mind reversion to VF is
common until > 30°C
You’re Not Dead Til You’re Warm &
Dead
Warming: If core temp > 28°C, aim for 1°C/hr rewarming
• Active Re-warming (1-2°C/hr)
– Forced-air warming device (Bair hugger)
– Warmed fluid
– Warmed humidified gases
• Aggressive Re-warming (temp < 28°C)
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–
–
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Bladder irrigation
Gastric/pleural lavage
Peritoneal Dialysis
Haemofiltration
Re-warming
• Cardio-pulmonary bypass
– Fem-fem (partial) most common
• Shown to be beneficial with core temp < 25°C,
regardless of rhythm
• Core temp 25-28°C is no benefit of CPB v conventional
re-warming
– Can perform aorto-caval CPB
• Increases core body temp by 10°C/hr
When to stop
• Resuscitation considered futile when
– If core body temp 35°C
– Stable cardiovascular function cannot be achieved
Neurological Outcome
• Of those who arrive ‘comatose’
– ⅓ survived intact
– ⅓ survived with minor neurological deficit
– ⅓ died or survived in a persistent vegetative state
• The only predictor proposed is regarding
avalanche:
– K > 10 mmol/l indicates asphyxial cardiac arrest
• Not compatible with successful resuscitation
“Cerebral Resuscitation”
• Many modes tried
– Cooling / ICP monitoring / CPP targets
• None have been shown to produce improved
morbidity or mortality
– Horse has already bolted
References
• 2009. Royal Life Saving Society – Australia. The
National Drowning Report 2009.
http://www.royallifesaving.com.au//resources/d
ocuments/2009_RLSSA_National_Drowning_Rep
ort_Web.pdf
• Layon, J et al. Drowning: Update 2009.
Anesthesiol. 2009; 110:1390.
• Hasibeder, WR. Drowning. Curr Op Anaesthesiol.
2003; 16:139
• Golden, F St C et al. Immersion, near-drowning &
drowning. BJA. 1997; 79:214