Drowning

Drowning is respiratory impairment following submersion in liquid, resulting in:

• Breath holding
  Occurs due to the mammalian dive reflex, and followed by:
  • Laryngospasm
    Occurs due to airway immersion, and leads to:
    • Hypoxia and hypercarbia
  • Breaking of laryngospasm
    Due to prolonged hypoxia.
    • Glottic opening and aspiration
  • Secondary apnoea
    Following aspiration.
    • Loss of consciousness
• Hypothermia
  Rapid hypothermia in water <5°C may provide some protection for hypoxic brain injury.

Fatal aspiration volume is ~22mL/kg.

Aspiration of icy water may be protective, as this may cause protective hypothermia prior to significant hypoxia.

Epidemiology and Risk Factors

Drowning is the third most common cause of unintentional traumatic death; risk factors include:

• Youth
  Leading cause of death in Australians aged 1-3.
• Male
• Lack of adult supervision
• Intoxiciation
• Hyperventilation
  ↓ Respiratory drive by lowering PaCO₂, which may precipitate hypoxic blackout.
• Readily available body of water
  • Pools
  • Natural bodies of water
  • Domestic
    • Bath tubs
    • Fish tanks
    • Buckets
• Disease
  • Epilepsy
  • Cardiopulmonary disease

Cold shock response occurs following submersion in icy water:

• ‘Gasp’
• Hyperventilation
• ↓ Maximal breath hold time
• Vasoconstriction
• Tachycardia
• Hypertension
• ↑ Myocardial oxygen consumption

Pathophysiology

The diving reflex occurs in response to cold-water stimulation of the opthalmic division of the trigeminal nerve, and triggers:

• Apnoea
• Generalised vasoconstriction
• Bradycardia

There was traditionally believed to be a difference between salt and fresh water drowning due to tonicity of the aspirated salt water drawing in interstitial volume, whilst free water was absorbed into circulation.

More recent data indicates no difference in the pattern of lung injury, which pokes holes in this physiologically-pleasing explanation.

Aetiology

Clinical Features

Assessment

History

• Time and duration of submersion
• Water source
  • Pollution
  • Contamination
• Resuscitation attempts
• Intoxication
  • Alcohol
  • Drug

Investigations

Bedside:

• ABG
• ECG

Laboratory:

Haemolysis screen consists of:

• Reticulocyte count
  ↑ Due to ↑ marrow turnover.
• Blood film
  • Schistocytes
    Mechanically fragmented erythrocyte, favours intravascular mechanical haemolysis.
• LDH
  Present in many cells and so not specific for haemolysis (as opoposed to other cellular destruction). Substantial ↑ (4-5× ULN) favours intravascular over extravascular haemolysis.
• Haptoglobin
  Binds free haemoglobin, and is non-specific for intravascular vs. extravascular haemolysis. Acute phase reactant and so result may be equivocal in inflammatory states.
• Free Hb
  ↑ Due to cellular destruction.
• Bilirubin
  ↑ Due to haemoglobin metabolism. Classically ↑ conjugated bilirubin, although unconjugated may ↑ in concurrent hepatic impairment.

• Blood
  • FBE
  • Haemolysis screen
  • UEC
  • CK

Imaging:

• CXR

Other:

Diagnostic Approach and DDx

Management

• Retrieve from water
  No role for cervical spine immobilisation whilst in water.
• Respiratory support
  Any arrest is likely from hypoxia.

Resuscitation:

• A
  • Intubation if required
    High aspiration risk.
• B
  • 5 rescue breaths
    Lung compliance may be poor.
  • Supplemental oxygen
• C
  • Cautious volume resuscitation

Specific therapy:

• Pharmacological
  • Bronchodilators
  • Inhaled pulmonary vasodilators
    Consider for refractory hypoxaemia.
• Procedural
• Physical
  • Lung protective ventilation if intubation required

Supportive care:

• E
  • Active rewarming
• G
  • Nasogastric decompression

Disposition:

Preventative:

Marginal and Ineffective Therapies

• Corticosteroids
• Prophylactic antibiotics

Anaesthetic Considerations

Complications

• Death
• B
  • Aspiration
  • Pneumonia
    >15%. Organisms vary depending on the fluid aspirated:
    • Natural water sources have much greater variety of microbial life
    • Common aetiologies include:
      • Assorted Gram negatives
      • Anaerobes
      • Staphylococcus spp.
      • Aeromonas spp.
      • Fungi
      • Algae
      • Protozoa
  • ARDS
    ↑ Risk with chemical pollutants:
    • Kerosene
    • Chlorine
    • Sand
  • Pulmonary oedema
• D
• E
  • Rhabdomyolysis
• H
  • Haemolytic anaemia

Prognosis

For patients with cardiac arrest:

• Survival to hospital discharge is ~44%
• Moderate-severe brain injury is 33%
• Similar outcomes seen in children

Poor prognostic signs:

• Warm-water immersion
• Immersion >5 minutes
• CPR delay >10 minutes

Good prognostic signs:

• Lower initial core temperature, unless this occurs after rescue

Key Studies

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References

1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.