Drowning

Question 1

Define drowning

Answer 1

Primary respiratory impairment following submersion or immersion in a liquid medium

Can be classified according to clinical findings at the scene:

Class 1: No evidence of aspiration
Class 2: Evidence of aspiration but with adequate ventilation
Class 3: Evidence of aspiration with inadequate ventilation
Class 4: Absent ventilation and circulation

Question 2

What are the pathophysiological changes that occur during drowning?

Answer 2

1. Respiratory:
   - panic, breath holding, laryngospasm
   - eventually hypoxia leads to relaxation of laryngeal muscles and acidosis with hypercapnia leads to stimulation of respiration.
   - Aspiration leads to: surfactant washout, bronchospasm, direct alveolar toxicity.
   - Pulmonary oedema and atelectasis leads to V/Q mismatch and ARDS.
2. Cardiovascular:
   - Diving reflex (aims to conserve O2) stimulated by CNV1 results in bradycardia and vasoconstriction
   - Catecholamine surge leads to further vasoconstriction, arrhythmias and pulmonary oedema
   - progressive hypoxia leads to bradycardia and cardiac failure.
3. Neurological:
   - hypoxic brain injury
4. Metabolic:
   - hypothermia
5. Infection:
   - from aspiration
   - usually gram +ve organisms
   - Gram -ve organisms more likely in fresh water

Question 3

What are the risk factors for drowning?

Answer 3

• children
• male gender
• intoxication
• occupation/hobbies - fishing, scuba diving
• medical conditions e.g epilepsy
• open water conditions e.g. sea

Question 4

What is the immediate management of a drowning victim?

Answer 4

Pre-hospital:

1. Removal from water - spinal injury risk in water is low
2. Five rescue breaths prior to CPR

In Hospital:
1. Resuscitation following ATLS protocol
A&B:
- secure airway
- LPV
- bronchoscopy
C:
- fluid resuscitation and vasopressors
D:
- Neuroprotection
E:
- temperature control to 34oC
- empirical ABx

Consider ECMO as improved survival for patients who arrest and those who didn’t.

Question 5

What are poor prognostic indicators in drowning?

Answer 5

1. Submersion >5 mins
2. pH <7.10 on arrival
3. Cardiac arrest
4. Delayed CPR
5. Prolonged CPR

Question 6

Define hypothermia

Answer 6

Core body temp < 35oC:

• mild 32-35
• moderate 28-32
• severe <28

Question 7

How is heat lost from the body?

Answer 7

5 routes:

1. Radiation (40%)
2. Convection (30%)
3. Evaporation (15%)
4. Conduction (5%)
5. Respiration (10%)

Question 8

What may make a person become hypothermic?

Answer 8

1. Increased heat loss:
   - Surgery: open body cavity, skin exposure, cold table
   - trauma
   - Submersion/immersion
   - burns
2. Impaired thermogenesis/thermoregulation:
   - Surgery: muscle relaxation, GA
   - Endocrine: hypothyroid
   - elderly
   - low body fat
   - alcohol
   - CNS pathology - hypothalamic impairment

Question 9

What are the complications of hypothermia?

Answer 9

1. Cardiovascular:
   - Catecholamine surge causes vasoconstriction, hypertension and tachycardia.
   - progressive/continued hypothermia causes bradycardia/bradyarrhythmias
   - Osborn J waves
   - asystole <20oC
2. Respiratory:
   - respiratory depression
3. Neurological:
   - CNS depression
   - coma and fixed and dilated pupils < 30oC
   - EEG isoelectric <20oC
4. Endocrine/metabolic:
   - BMR drops 7% for every 1oC drop.
   - acidosis, hyperkalaemia, hypermagnesemia, hyperglycaemia.
5. Haematological:
   - thrombocytopenia
   - bone marrow suppression
   - DIC
   - increased blood viscosity
   - impaired immunity

Question 10

How would you manage a hypothermic patient?

Answer 10

Resuscitation with an A-E approach:

• Pulse check can be unreliable (echo may be required)
• CPR should not be delayed
• Up to three attempts at defibrillation for VF - delay further attempts until temp >30oC
• avoid ALS drugs until temp >30
• not dead until ward (>32oC) and dead

Manage hypothermia (reward at 2-3oC / hour):

• Passive: remove wet clothes and dry skin, increase ambient temp, blankets, encourage movement
• Active external: forced air warmers, radiant heaters
• Active internal: warm IV fluids, warm humidified gases, intravesical warm lavage, RRT, ECMO warming.
• monitoring: oesophageal temp probe
• serial ABGs

Manage complications of hypothermia (see question on complications)

Question 11

What are the complications of re-warming?

Answer 11

1. Cardiovascular:
   - dysrrhythmias
   - vasodilatation and hypotension (distributive shock & afterdrop)
   - cardiogenic shock
2. Neurological:
   - seizures
3. Metabolic/endocrine:
   - acidosis
   - hypoglycaemia
   - hyperkalaemia from reperfusion injury