Drowning

Introduction

Drowning is the process of respiratory impairment from submersion or immersion in liquid. Drowning is the third most common cause of unintentional death world-wide – and accounts for 7% of all injury related deaths. In most developed countries it is the second most common cause of accidental death in children – behind road traffic accidents. The highest incidence is in toddlers and teenage boys.

Submersion is defined as the airway being below the level of the liquid, whereas immersion is where a liquid is splashed across the face. For a diagnosis of drowning, there must be respiratory impairment.

Drowning results in hypoxaemia, which can rapidly cause irreversible brain damage, cardiac arrest and death. In survivors, the degree of long-term neurological impairment is related to the period of hypoxaemia.

It is common for drowning patients to be submerged for a prolonged period of time. Physiologically – most drownings occur quickly – within seconds to minutes. However, in situations where patients become cold, individuals may survive for much longer periods (several case reports of an hour or longer). This is because as the body cools – the brain in particular – its oxygen (and metabolic) demand falls. For each degree of temperature loss between 37 and 20 degrees centigrade the metabolic demand reduces by about 5% – thus that a “cold” patient can have <50% of the oxygen demand of a ‘warm’ (i.e. physiologically ‘normal’ temperature) patient. This is important in resuscitation – you should actively warm the patient as quickly as possible, and any ongoing CPR should not cease until the patient is at least 34 degrees centigrade. Be aware this can take a long time (hours!).

Management includes prompt removal from the water and commencement of CPR. Rewarming the patient by removing wet clothes and applying warm blankets and active warming techniques should also be considered. Management of arrhythmia and decreased level of consciousness may also be indicated – such as intubation and ventilation and transfer to ICU.

Be aware of delayed pulmonary oedema several hours after the drowning event.

Pathophysiology

• The initial response to to expel water from the mouth – by spitting or coughing
• Next, a patient will breath-hold. This can last up to 1 minute or so. Eventually the hypoxic drive kicks in and patients begin to hyperventilate – inhaling large quantities of liquid (aspiration) and this also causes laryngospasm
• This leads to hypoxia and loss of consciousness and subsequently cardiac arrest
• Young children immersed in cold water may stimulate a protective “diving reflex’ which causes:
  • Apnoea
  • Bradycardia
  • Shunting of blood to the brain and heart
  • These factors can increase survival in this circumstance
  • Also be aware that cold water immersion is more likely to lead to dangerous cardiac arrhythmias – most commonly VF.

In the lungs

• Surfactant is washed away – which can cause atelectasis (collapsing of the alveoli)
• Pulmonary oedema is common. This can be delayed – and in drowning survivors can be dangerous as it continues to develop hours after the drowning event.
  • Fluid shifts into the alveolar spaces as a result of increased intravascular pressure, and due to the effects of the different osmolarity of the circulation and the fluid in the lungs.
  • It doesn’t seem to make much difference if the drowning is in saltwater or freshwater as to the degree of pulmonary oedema
• Haemolysis can also occur. This is thought to be due to the swelling and hurting of red blood cells due to absorption of water from the lungs. This can lead to hyperkalaemia which may subsequently cause arrhythmias and cardiac arrest

Pathological sequelae of drowning:

• Aspiration pneumonitis
• Pulmonary oedema (often bloodstained)
• ARDS
• Ischaemic cardiomyopathy
• Hypothermia
• Electrolyte disturbance (especially hyperkalaemia)
• Trauma (beware of c-spine injury)

Causes

• Unattended bodies of water – mainly in children under 5
  • Buckets of water
  • Bath
  • Swimming pools
• Misadventure
  • Mainly in teenagers and adults
• Intoxication
  • Often in combination with misadventure
• Underliyng medical conditions
  • Epilepsy
  • Cardiac arrest
  • Hypoglycaemia
  • Elicit drug use / abuse
• Water temperature and hypothermia
  • Very cold water inhibits the ability to swim due to hypothermia
  • Water <4 degrees centigrade is particularly dangerous, and the average time to drowning s around 4 minutes
  • Water below 15 degrees centigrade is associated with hypothermia, but body fat levels and activity can affect this

History

• Mechanism of immersion
• Duration of immersion
• Time to CPR
• Time to first breath
• Time to return of spontaneous cardiac output (ROSC)
• Precipitating factors – e.g. MI, seizure

Examination

• Temp
• Pulse oximetry
• Other vital signs
  • Respiratory rate and pattern
  • HR and rhythm
  • BP
• ECG
• Evidence of pulmonary oedema
  • Crackles and wheeze on auscultation
  • May have cough productive of bloodstained fluid
• Examine for internal injuries – e.g. if fell from a height
  • Abdominal examination
  • Head to toe to look for spine, limb and chest injuries
• GCS

Investigations

• ECG
• Bloods
  • Blood gas
  • Electrolytes
  • U+E
  • Glucose
  • Blood alcohol
  • FBC
  • LFT
  • Consider blood cultures
• CXR
• CTB and C-spine if any chance of trauma

Prognosis

Predictors of poor prognosis include:

• Immersion >10 mins
• Delayed CPR (e.g. no bystander CPR)
• CPR >25 minutes
• Time to first breath
• Higher water temperature
• Cardiac arrest – especially asystole
• Precipitating cause (e.g. MI)
• High lactate
• Dilated non-reactive pupils
• pH <7.0
• GCS <5

Management

Immediate Action – Prehospital

• Remove the patient from water as quickly as possible
  • Beware of c-spine injury!
• Do NOT attempt CPR in the water, although rescue breaths may be appropriate
  • CPR in the water is associated with relay of rescue and aspiration
  • It may occasionally be performed over a short distance by well-trained professionals
• Start CPR as soon as possible – as per BLS protocol
• Remove wet clothing
• Wrap in warm blankets
• Maintain c-spine precautions if indicated
• Transfer to medical facility as soon as possible – continue resuscitation / CPR as per ALS protocol

Hospital management

• ABCs
• Rewarm to 34 degrees
  • May take up to 24 hours
  • Remove wet clothes
  • Use warm blankets
  • Consider active re-warming – e.g. with bear hugger device, warmed IVF fluids, warmed, humidified inspired gasses
• Oxygen
• NG tube for stomach decompression
• Intubation and ventilation if unconscious (commonly defined as GCS <8)
• Neurological
  • Head up position
  • Aim for MAP of 80mmHg
  • Treat seizures – e.g. benzodiazepines
• Cardiovascular
  • Monitor for arrhythmia (VF common in hypothermia)
  • Continue CPR until patient is >34 degrees centrigrade
  • Consider ECMO (cardiopulmonary bypass) – this is especially useful in those with asystole who are cold
• Renal
  • Renal failure can occur and dialysis may be required
• Infection
  • Conisder antibiotics – depending on immersion liquid and time of immersion. Freshwater tends to have more pathogens than saltwater. Household water or winning pool likely to be lower risk for subsequent infection
  • Efficiacy of prophylactic antibiotics is unproven and should one be given if fever develops or water is considered to be grossly contaminated. Unusual organisms may be causes of subsequent pneumonia
• Observe for at least 6 hours in apparently well patients to monitor for delayed onset pulmonary oedema
• It is not possible to predict neurological outcomes. Children in particular often have good outcomes. Aggressive resuscitation should be given to all drowning victims

 

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