Drowning

7th April, 2010Amanda Diaz

Intensive Care UnitJohn 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 re-warming• Active Re-warming (1-2°C/hr)– Forced-air warming device (Bair hugger)– Warmed fluid– Warmed humidified gases

• Aggressive Re-warming (temp < 28°C)– 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/documents/2009_RLSSA_National_Drowning_Report_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