Critical Care: Drowning & Near Drowning

DROWNING & NEAR DROWNING

Drowning, with or without aspiration of water, is death while submerged in water. Near-drowning, with or without aspiration, is suffocation while sub-merged with (at least temporary) survival. Survival depends on the intensity and duration of the hypoxia and on the water temperature.

Pathophysiology

Both drowning and near-drowning can occur whether or not inhalation (aspiration) of water occurs. If water does not enter the airways, the patient primarily suffers from asphyxia; however, if the patient inhales water, marked intrapulmonary shunting also takes place. Ninety percent of drown-ing patients aspirate fluid: fresh water, seawater, brackish water, or other fluids. Although the amount of liquid aspirated is generally small, marked venti-lation/perfusion mismatching can result from fluids in the airways and alveoli, reflex bronchospasm, and loss of pulmonary surfactant. Aspiration of gastric contents can also complicate drowning before or after loss of consciousness or during resuscitation.

The hypotonic water aspirated following fresh water drowning is rapidly absorbed by the pulmo-nary circulation; water cannot usually be recovered from the airways. If a significant amount is absorbed (>800 mL in a 70-kg adult), transient hemodilution, hyponatremia, and even hemolysis may occur. In contrast, aspiration of salt water, which is hypertonic, draws out water from the pulmonary circulation into the alveoli, flooding them. Thus, hemoconcen-tration and hypernatremia may occasionally occur following saltwater drowning. Hypermagnesemia and hypercalcemia have also been reported follow-ing near-drowning in salt water.

Patients who suffer from cold water drowning lose consciousness when core body temperature decreases below 32°C. Ventricular fibrillation occurs at about 28–30°C, but relative to normothermic drowning, the hypothermia has a protective effect on the brain and may improve outcome provided that resuscitation measures are successful.

Clinical Manifestations

Nearly all patients with a true near-drowning epi-sode will have hypoxemia, hypercarbia, and meta-bolic acidosis. Patients may also suffer from other injuries, such as spine fractures following diving accidents. Neurological impairment is generally related to duration of submersion and severity of asphyxia. Cerebral edema complicates prolonged asphyxia. Acute lung injury and ARDS develop in many patients following resuscitation.

Treatment

Initial treatment of near-drowning is directed at restoring ventilation, perfusion, oxygenation, and acid–base balance as quickly as possible. Imme-diate measures include establishing a clear and unobstructed airway, administering oxygen, and initiating cardiopulmonary resuscitation. In-line stabilization of the cervical spine is necessary when intubating patients who suffer from near-drowning following a dive. Although salt water can often be drained out of the lungs by gravity, this practice should not delay institution of cardiopulmonary resuscitation; abdominal thrusts may promote aspi-ration of gastric contents. Resuscitation efforts are always continued until the patient is fully assessed and under treatment in a hospital, particularly fol-lowing cold water drowning. Complete recovery is possible in such instances even after prolonged periods of asphyxia. Management includes tracheal intubation, positive-pressure ventilation, and PEEP. Bronchospasm should be treated with bronchodila-tors, electrolyte abnormalities corrected, and acute lung injury and ARDS treated as discussed above. Hypothermia should be corrected gradually over a few hours.