1. Drowning 7 th April, 2010 Amanda Diaz Intensive Care Unit John Hunter Hospital

2. 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)

3. 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

4. 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

5. 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

6. 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 pO 2 Increase in alveolar / arterial pCO2 – Hypoxaemia, acidosis, hypercarbia Critical hypoxia – release of laryngospasm Aspiration

7. 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

8. 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

9. 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

10. 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)

11. Aspiration 20% of drownings have normal CXR on admission – At risk of ALI progression Water aspiration: – As little as 2.2 ml/kg impairs O 2 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

12. Aspiration Bronchospasm – Increases relative shunt Overall effect: – Increase V/Q mismatch – Decreased lung compliance – Increased work of breathing

13. 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)

14. 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

15. 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 O 2 requirements (autoregulation) – 6-7% reduction in CMRO2 for each 1°C decrease in core body temp – Cerebral activity abolished at < 22°C

16. BUT... If ventilating: – Shivering at < 34°C Increased O 2 requirements Increased CO 2 / lactate production If hypoxic: – Set-point of thermoneutral zone lowered Shivering impaired Vasodilation of peripheries If hypercarbic: – Cerebral vasodilation

17. 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

18. Hypothermia: Muscle Function Muscle (not core) temp < 28°C – Impaired NMJ function – Weakness – Unable to swim

19. Hypothermia: Blood Increased blood viscosity Impaired coagulation – Enzyme system

20. 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

21. 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

22. 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

23. 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

24. When to stop Resuscitation considered futile when – If core body temp 35°C – Stable cardiovascular function cannot be achieved

25. 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

26. “Cerebral Resuscitation” Many modes tried – Cooling / ICP monitoring / CPP targets None have been shown to produce improved morbidity or mortality – Horse has already bolted

27. 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 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