Near drowning and drowning
Definitions
Drowning is death by suffocation from submersion in any liquid.
Drowning is a common cause of death in young people.
40% of drownings occur in children aged < 4yrs. Near drowning is survival (at least temporarily). In adults, the commonest predisposing factor is alcohol, sometimes with other drugs. A significant proportion reflect attempted suicide. In the UK, marine near drowning is usually associated with hypothermia.
Pathophysiology Wet drowning Involves significant aspiration of fluid into the lungs. This causes pulmonary vasoconstriction and hypertension with ventilation/perfusion mismatch, aggravated by surfactant destruction and washout, increase lung compliance and atelectasis. Acute respiratory failure is common. ABG shows hypoxia, hypercarbia and mixed respiratory/metabolic acidosis. The onset of symptoms can occur rapidly, but in lesser insults, symptoms may be delayed. Contamination Water contaminated with chemical waste, detergents etc, may induce further lung injury. Electrolytes Irrespective of whether aspirated water is salt, fresh or swimming pool, changes in serum electrolytes and blood volume are similar and are rarely immediately life-threatening. Gastric fluid Swallowing of fluid into the stomach, with gastric dilatation, vomiting and aspiration, is common.
Dry drowning In >10-20% of deaths from drowning, a small amount of water entering the larynx causes persistent laryngospasm, which results in asphyxia and an immediate outpouring of thick mucus, froth and foam, but without significant aspiration—this is ‘dry drowning’. Secondary drowning A deterioration in a previously apparently well patient following successful resuscitation after submersion. It may occur in 5-10% of initial survivors. The diving reflex This is probably seen only in young children, but may explain why successful resuscitation without neurological deficit can occur after prolonged immersion. Cold water stimulates facial nerve afferents, while hypoxia stimulates the carotid body chemoreceptors. These effects reflexly ↓heart rate and vasoconstrict skin, GI tract and skeletal muscle vessels redistributing blood to brain and heart. Associated hypothermia results in increased metabolic demands, delaying cerebral hypoxia.
Management Consider associated injury (eg to the cervical spine from diving into a shallow pool or surfing), and treat appropriately. Maintain the airway. Remove regurgitated fluid/debris by suction of the upper airway. It is crucial to ensure adequate ventilation and correction of hypoxia. If the patient does not have a gag reflex, or is apnoeic, ventilate with a bag and mask and proceed to early tracheal intubation with IPPV. In spontaneously breathing patients, give the highest FiO2 possible. IPPV will be required if hypoxia and/or hypercapnia are present despite O2 therapy, or there are signs of pulmonary oedema. PEEP ventilation may significantly improve oxygenation by ↓functional residual capacity, improving V/Q mismatch and enhancing fluid resorption from the pulmonary bed. However, PEEP may ↓venous return to the heart and this should be commenced under ITU guidance. Inhalation of mud/sand etc may require broncoscopy for clearance. If the patient is in cardiac arrest, commence CPR. Conventional CPR is appropriate, but defibrillation may not be successful until core T°>30°C. Appropriate rapid core rewarming techniques are required.
Remove all wet/cold clothing.
Monitor core T° and start rewarming.
Relieve gastric dilatation and water absorption from the stomach by NG tube.
Check U&E, blood glucose, ABG, FBC, CXR, ECG.
Consider the presence of alcohol, drugs of abuse or in the case of possible intentional overdose, other drugs. Alcohol and/or paracetamol blood levels may be appropriate.
Do not use ‘prophylactic’ steroids, or barbiturates.
Antibiotics may be warranted if contaminated water (eg sewage) is involved (see p229).
Outcome
Resuscitation without cerebral deficit is possible after prolonged submersion (even >60mins), particularly if associated with hypothermia. 50% of children recovered ‘apparently lifeless’ will survive, and even adults GCS 3-4/15 with fixed dilated pupils can survive unimpaired.
Respiratory effort is a sensitive prognostic sign, but in hypothermic patients its absence does not necessarily imply poor outcome. Note the time to the first spontaneous respiratory gasp.
Poor prognostic factors include extremes of age, severe acidosis, immersion >5mins and coma on admission.
Good prognostic signs are patients who are alert on admission, hypothermia, older children/adults, brief submersion time and those who receive rapid on-scene basic life support and respond to initial resuscitation measures.
Asymptomatic patients who have no abnormality on repeated clinical examination, ABG and CXR require observation for at least 4-6h prior to considering discharge. Admit all others to ITU or general ward as appropriate.
