44 DROWNING AND NEAR-DROWNING
Harrison’s Manual of Medicine
DROWNING AND NEAR-DROWNING
Approximately 90% of drowning victims aspirate fluid into lungs. Both freshwater and saltwater aspiration lead to severe hypoxemia due to ventilation/ perfusion imbalance and significant pulmonary venous admixture, although mechanisms may differ between the two situations. In victims who do not aspirate, hypoxemia results from apnea. Contaminated water may pose additional risks, including obstruction of small bronchioles by particulate matter and infection by pathogens in the water.
Other physiologic changes occurring in drowning and near-drowning victims include changes in serum electrolytes and blood volume, although these are seen only rarely in persons successfully resuscitated. Hypotonicity may cause acute RBC lysis; however, this complication has been reported only rarely. Hypercarbia is less common than hypoxemia. Renal failure is uncommon, but when it does occur, it is secondary to hypoxemia, renal hypoperfusion, or, in extremely rare cases, significant hemoglobinuria.
TREATMENT (See Fig. 44-1)
FIGURE 44-1. Treatment of a near-drowned victim should follow a sequence of priorities. *Guidelines only; assumes victim had normal arterial blood gas values (ABGs) before near- drowning. Abbreviations/definitions: CPAP, continuous positive airway pressure; CPR, cardiopulmonary resuscitation; FIO2, fraction of inspired oxygen; intubate, endotracheal intubation; ICU, intensive care unit; NaHCO3, bicarbonate; PaO2/PaCO2, arterial oxygen/carbon dioxide tension; pHa, arterial pH. (Modified from SA Graves and AJ Layon; in TC Kravis et al (eds): Emergency Medicine: A Comprehensive Review, 3d ed. New York, Raven, 1993.)
Remove victim from water as soon as possible and stabilize head and neck if trauma is suspected. The American Heart Association recommends that an abdominal thrust not be used routinely in victims of submersion as this maneuver can lead to regurgitation and aspiration of gastric contents.
Restore airway patency, breathing, and circulation immediately. Recall that hypothermia is protective of CNS function, and victims should not be presumed to have failed resuscitation until they have also been rewarmed.
Protect airway with endotracheal intubation if the patient is unconscious or obtunded. Correct hypoxemia with supplemental oxygen and mechanical ventilation with PEEP or CPAP if needed.
Establish venous access as soon as possible.
Monitor core body temperature and rewarm if necessary.
Monitor cardiac rhythm.
If patient has cardiovascular instability, evaluate cardiac output and effective circulatory volume by invasive monitoring.
Measure and monitor serum electrolytes, renal function, ABGs. Bicarbonate administration for metabolic acidosis with a pH < 7.20 is controversial but may be indicated in severe cases.
Factors adversely affecting survival include prolonged submersion, delay in initiation of effective cardiopulmonary resuscitation, severe metabolic acidosis (pH < 7.1), asystole on arrival at a medical facility, fixed dilated pupils on presentation, and low Glasgow coma score (<5). No predictor is absolute, however, and normal survivors have been reported despite presence of all these risk factors.
Effective means of preventing drowning and near-drowning include:
Avoidance of the water or use of the buddy system by people at high risk (e.g., history of syncope or seizure)
Early swimming instruction for children and enhanced pool safety
Instruction of parents about drowning risks in the home
Public safety education regarding risks associated with water-related recreational activities and the increased risk of alcohol use in the vicinity of the water.
For a more detailed discussion, see Modell JH: Drowning and Near-Drowning, Chap. 392, p. 2581, in HPIM-15.