DROWNING AND NEAR DROWNING

Drowning is defined as 'death within 24 hours of submersion in a water body', while survival or death after 24 hours is termed as near-drowning. Drowning/ near drowning in children is almost always accidental and may occur at home (bucket-drowning), swimming­pools or open water bodies, e.g.

Risk factors for drowning accidents are: (a) age - toddlers or male adolescents, (b) medical conditions, e.g. epilepsy, motor disability or mental retardation, (c) drug abuse or sedation due to therapeutic drugs, and (d) child abuse or neglect.

Pathophysiology of drowning is characterised by three major pathological events: (a) sudden hypoxic- ischemic brain injury, (b) pulmonary aspiration, and (c) hypothermia; followed by secondary disturbances, e.g. fluid/electrolyte imbalance, progressive respiratory failure, neurological abnormalities and secondary infections.

Hypoxic-ischemic brain injury is caused by—(a) sudden choking due to protective laryngospasm, (b) failure of diving reflex to sustain blood supply to the brain, and

(c) myocardial ischemia due to progressive respiratory failure. Raised intracranial pressure, seizures and altered sensorium from confusion to coma, are common features of hypoxic-ischemic brain injury.

Pulmonary aspiration occurs in ~80-90% incidents and pathological consequences depend on the amount, salinity and contaminants in aspirated water. Sea­water drowning leads to acute pulmonary edema due to its hypertonicity. Drowning also washes away the lung-surfactant, leading to alveolar collapse, ventilation­perfusion mismatch and ARDS.

Hypothermia develops due to contact with cold water (conductive heat loss) before rescue and convective/ radiative heat loss from wet body after rescue. While hypothermia is protective to some extent due to reduced metabolic demands, in most cases it accentuates hypoxia due to shivering and increased sympathetic tone.

Management of drowning/near-drowning depends on the clinical state of the child immediately after rescue, who may be asymptomatic, frightened/agitated, or unconscious. Important components of management include:

On-spot first aid with:

• Immediate clearance of airways for foreign bodies.

• Positioning in prone, head-low position with head turned on one side, to prevent aspiration.

• Basic cardiopulmonary resuscitation, including breathing assistance (mouth-to-mouth breathing).

• Gastric deflation with nasogastric tube, if available.

• Prevention of hypothermia, using blankets/sheets.

• Immediate transport to the nearest hospital.

Abdominal thirsts or thoracic compressions to remove swallowed water should be avoided in a spontaneously breathing child, unless airway obstruction or foreign body is suspected due to risk of further aspiration.

Hospital care in these cases is guided by clinical assessment of vital signs on admission and subsequent monitoring. Fully alert and breathing children may be sent home after initial assessment, as late sequelae are unlikely. Other cases require:

• Quick clinical assessment for vital signs and neurological status

Cardiopulmonary resuscitation with—(a) airway suction and endotracheal intubation, if needed, (ii) breathing support with oxygen/ventilatory assistance, and

(c) circulatory support with IV fluids and vasopressors. Re-warming in a hypothermic child needs to be done cautiously, as only surface-warming with blankets or warmers may precipitate shock due to movement of blood into dilated surface vessels. Core-warming may be achieved with warm IV infusions and warm gastric lavage.

Fluid and electrolyte correction is guided by clinical and biochemical findings. Massive sea-water aspiration leads to hypernatremia and hemoconcentration (osmotic effect); while fresh-water aspiration leads to hyponatremia, hemodilution (water intoxication), and hyperkalemia (cell lysis).

Neurological complications may require anti-edema measures, e.g. mannitol or furosemide, anticonvulsants and supportive therapy.

• Prevention of secondary infections with appropriate use of antibiotics.

• Treatment of other injuries, e.g. fractures.

• Psychiatric or psychosocial support

Outcome depends on: (a) duration of submersion, (b) effectiveness of on-spot resuscitation, and (c) clinical state on admission. Development of raised ICP and ARDS are worst prognostic indicators. Although ~80% cases survive drowning accidents, neurological residue may develop in ~10%.

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