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Drowning

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Drowning

- alcohol consumption and epilepsy are prominent factors in deaths by drowning
- death may be caused by laryngeal spasm, lung reflexes and vagal cardiac effects (ie "immersion") rather than true drowning with aspiration of fluid
- can occur in very shallow water and volume inhaled may be relatively small

Near drowning

- def: at least temporary survival following asphyxia while immersed in liquid

Pathophysiology

- initial period of voluntary apnoea which reaches a "breakpoint" when involuntary inspiration occurs (Hyperventilation before diving increases risk of death by drowning. Resultant hypocarbia suppresses central drive to breathe, even in presence of severe hypoxaemia from prolonged voluntary breath holding. Consciousness is lost before spontaneous central respiratory efforts resume)
- water enters lungs and at same time gasping occurs. Laryngeal spasm may follow
- airway resistance increased, reflex pulmonary vasoconstriction occurs, surfactant is diminished and lung compliance is decreased
- water shifts from alveoli into circulation
- swallowing, vomiting and aspiration of vomit is likely
- phase of secondary apnoea occurs followed by further involuntary gasping and loss of consciousness
- respiratory arrest and cardiac arrhythmias occur several minutes later

Nature of inhaled fluid

- fresh water: water quickly absorbed into circulation. May cause haemolysis. Surfactant denatured
- chlorine and soap in fresh water does not appear to be of any adverse consequence for lungs
- sea water: hypertonic fluid promotes rapid fluxes of water and plasma proteins into alveoli and interstitium, dilutes or washes out surfactant and disrupts alveolar-capillary membrane
- both fresh and salt water produce an inflammatory reaction in alveolar-capillary membrane leading to an outpouring of plasma-rich fluid into alveoli. Inhaled gastric contents may contribute to this reaction
- fresh water results in a greater increase in alveolar surface tension than salt water near drowning
- fluid fluxes through lungs can lead to hyper/hypovolaemia. Latter is more common, even in fresh water drowning. Changes rarely sufficient to be life-threatening

Lung injury

- widespread atelectasis
- pulmonary oedema
- severe intrapulmonary shunting
- gross ventilation-perfusion mismatch
- increased pulmonary vasoconstriction
- decreased compliance
- marked hypoxaemia
- infection
- ARDS

Dry drowning

- 10-20% of drowned patients
- little or no fluid found in lungs
- death probably due to profound laryngospasm. This is followed immediately by outpouring of thick mucus, which with bronchospasm, may prevent entry of water when spasm relaxes shortly before death by asphyxiation occurs
- more common in adults
- ? lung reflexes facilitated by raised blood alcohol levels

Superimposed hypothermia

- cold water impairs motor activity and even strong swimers with life jackets drown within minutes if water is very cold (4oC)
- uncontrolled involuntary hyperventilation occurs in immersion in a cold medium
- consciousness may be impaired in hypothermia

Cardiovascular effects

- remarkable CVS stability in most cases
- blood volume changes rarely of life threatening significance and hence changes in Hb and Hct usually not marked

Management

- CPR. Lung drainage procedures and the Heimlich manouever controversial: may induce vomiting
- remember risk of head and spinal injury, particularly in diving or surfing accidents
- CPAP/PEEP: intubate if patient comatose
- inotropes and fluids to restore circulation
- correct acidosis by correcting underlying causes. Sodium bicarbonate if metabolic acidosis significant (pH < 7)
- rewarming: if core temperature >30oC rapid rewarming unnecessary. Use warm IV fluids, heated blankets, warm humidified gases. Important not to cause shivering, which will increase oxygen demand
- cerebral protection: control of hyperglycaemia, ICP, fits, fever. No evidence that deliberate hypothermia or barbiturates lead to an improved clinical outcome
- prophylactic antibiotics not useful
- NG tube

Investigation and monitoring

- ECG
- direct BP
- CVP/PAWP

- ABG
- pulse oximetry
- body temperature
- urea and electrolytes: gross changes rare
- FBC: may be affected by absorbed water
- urinary Hb
- plasma haptoglobin
- plasma Hb
- CXR (patients with normal CXR on admission usually survive)
- ± SXR, cervical spine XR, CT
- drug assays
- cultures of aspirated water, tracheal swabs, sputum may be indicated in severely polluted water immersion

Prognosis

- 80% of children survive without neurological dysfunction
- 12% mortality overall
- "dry" near drowning: complete recovery usual if resuscitation started early
- with aspiration of water outlook less predictable. Surf immersion, cold water, short immersion times, skilled administration of CPR are favourable factors
- prognosis good if first gasp within 30 min of rescue and there is continuing improvement, especially in children
- mortality related to level of consciousness on admission with 34% mortality in comatose patients. 1/5 survivors had neurological impairment. 90% survival in alert or rousable patients
- hypothermia protective, but only if it occurs at the time of near drowning
- continued need for CPR after arrival in hospital and need for CPR for > 25 mins associated with poor prognosis
- in ICU following features suggest poor prognosis:

  • absence of spontaneous, purposeful movements and abnormal brainstem function 24 h after immersion
  • abnormal CT within 36 h of immersion (Normal CT on admission poor predictor)
  • low CMRO2 and low AVDO2 difference

Further reading

Modell JH, Drowning. N Eng J Med, 1993; 328: 253-6

Oh TE. Near drowning. In Oh TE (ed), Intensive Care Manual, 4th Ed., Butterworth Heinemann, Oxford, 1997, pp 617-21.


© Charles Gomersall December 1999


©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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