Drowning is a common cause of accidental death, accounting for over 100000 deaths annually worldwide. Approximately 40% of drownings occur in children under 5 years of age. Exhaustion, alcohol, drugs and hypothermia all contribute to the overall problem. In addition, drowning can also occur following an epilepticr attack or after a myocardial infarct whilst in the water.
Between 10 and 15% of drownings occur without aspiration of water into the lungs. Laryngeal spasm is thought to occur with anoxia occurring due to apnoea.
Aspiration of fresh water affects the pulmonary surfactant with alveolar collapse and ventilation-perfusion mismatch leading to hypoxaemia. Aspiration of hypertonic sea water pulls additional fluid into the lungs with further ventilation-perfusion mismatch. In practice, however, there is little difference between salt-water and freshwater drowning as in both groups severe hypoxaemia occurs leading to death in some. Severe metabolic acidosis develops in the majority of survivors. In patients who aspirate more than 22 ml kg-t of water, electrolyte and volume changes do occur, but very few of such patients have survived.
EMERGENCY TREATMENT OF NEAR DROWNING
It must be remembered that patients can survive up to 30 min underwater without suffering brain damage and if the water is near O°C this time can be much longer. The exact reasons for this are not clearly understood, but it is probably related to the protective role of the diving reflex. It has been shown experimentally that submersion
in water causes a reflex slowing of the pulse and vasoconstriction. In addition, hypothermia decreases oxygen consumption of both the heart and brain. Patients should be turned to one side and the mouth cleared of any debris. Mouth-to-mouth respiration should be immediately started together with cardiac resuscitation if this is appropriate. Mouth-to-mouth resuscitation should always be attempted, even in the absence of a pulse and the presence of fixed dilated pupils, as patients can frequently make a dramatic recovery. All patients should be subsequently admitted to hospital for intensive monitoring. Intensive care therapy may be required, and patients are liable to develop the adult respiratory distress syndrome (ARDS).
The prognosis is good if the patient is fully conscious on admission to hospital but poor if the patient is still in a coma.