Approach to Near Drowning

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Pathophysiology of Drowning (Near-Drowning)

While the term "near-drowning" has been used historically, modern medical consensus prefers the term "drowning" to describe the entire process of experiencing respiratory impairment from submersion or immersion in liquid, regardless of whether it results in death or survival.
The primary pathogenic mechanism that dictates morbidity and mortality in a drowning victim is global hypoxic-ischemic injury.

Sequence of Drowning Events

The instinctive drowning response is triggered by actual or perceived suffocation, leading to unlearned, autonomic movements and struggles to maintain the airway above water.
The process begins with a period of voluntary breath-holding, which typically lasts $< 1 minute$ , followed by a small amount of liquid entering the hypopharynx.
This sensory stimulus triggers a protective reflex laryngospasm, temporarily preventing further fluid aspiration but concurrently halting gas exchange.
Hypoxemia rapidly develops, leading to a progressive decrease in arterial blood oxyhemoglobin saturation ( ${SaO}_{2}$ ) and subsequent loss of consciousness.
Profound hypoxia and medullary depression cause the laryngospasm to relax, leading to terminal apnea and the passive aspiration of surrounding water and stomach contents directly into the lungs.
Within $3 - 4 minutes$ , severe myocardial hypoxia initiates peripheral vasoconstriction, drastically decreased cardiac output, and abrupt circulatory failure,.
Cardiac arrhythmias evolve progressively from reflex tachycardia to severe bradycardia, ultimately resulting in pulseless electrical activity (PEA) or asystole.

Specific Organ System Pathogenesis

Organ System	Pathogenic Mechanisms and Consequences
Central Nervous System	Irreversible hypoxic-ischemic brain injury begins within $3 - 5 minutes$ of sustained anoxia. Several hours post-resuscitation, secondary cerebral edema may develop, precipitating intracranial hypertension and exacerbating ischemic damage.
Pulmonary System	Aspiration of fluid severely compromises lung compliance. Water washes out pulmonary surfactant, causing alveolar instability, profound ventilation-perfusion ( $V/Q$ ) mismatch, and severe intrapulmonary shunting. This disruption mimics an acute respiratory distress syndrome (ARDS) phenotype,.
Osmolar Fluid Shifts	While theoretical differences exist—fresh water (hypo-osmolar) causing alveolar fluid absorption, and salt water (hyperosmolar) drawing plasma into alveoli—clinical management remains identical, as victims rarely aspirate sufficient volume to cause massive systemic electrolyte shifts,.
Cardiovascular System	Hypoxia-induced myocardial depression impairs contractility, causing arterial hypotension and predisposing the myocardium to infarction and fatal arrhythmias.
Systemic/Metabolic	Global hypoperfusion induces acute kidney injury, cortical necrosis, disseminated intravascular coagulation (DIC), hemolysis, and profound gastrointestinal mucosal sloughing.

The Role of Cold Water Immersion

Immersion in icy water ( $< 15 - 20^{\circ} C$ ) induces "cold water shock," characterized by intense involuntary reflex hyperventilation and a severe reduction in breath-holding capability to $< 10 seconds$ , accelerating water aspiration,.
Severe hypothermia ( $< 28^{\circ} C$ ) directly suppresses the medullary respiratory center, impairs myocardial contractility, and makes the myocardium highly susceptible to spontaneous ventricular fibrillation or asystole.

Steps of Initial Resuscitation

Immediate resuscitation initiated at the submersion site by bystanders or first responders is the single most critical factor in improving neurological outcomes.
The fundamental goal is the rapid reversal of anoxia and mitigation of secondary hypoxic injury.

Prehospital and Airway Management

If feasible, trained personnel may initiate in-water resuscitation (providing rescue breaths) before reaching shore, though rapid extrication is usually required to deliver effective chest compressions.
The airway must be promptly cleared of vomitus, debris, or foreign material.
Abdominal thrusts (the Heimlich maneuver) are strictly contraindicated for the purpose of removing aspirated fluid, as they dangerously increase the risk of gastric regurgitation and secondary aspiration.
Routine cervical spine immobilization is not indicated for low-impact submersions. Cervical collars should only be applied if there is a strong clinical suspicion of traumatic neck injury (e.g., diving into shallow water, high-speed watercraft accidents), which is present in only $\approx 0.5$ of cases.

Breathing and Circulation

Because the primary insult is respiratory, rescue breathing must be initiated immediately if the victim is apneic or displays ineffective respirations.
Providers should use positive pressure bag-valve-mask ventilation supplemented with $100$ inspired oxygen.
Endotracheal intubation is indicated for persistent apnea, profound cyanosis, severe hypoventilation, or to secure the airway in a patient with a depressed sensorium.
If the child is pulseless, exhibits severe bradycardia, or is profoundly hypotensive, full cardiopulmonary resuscitation (CPR) following the standard sequential ABCs (Airway, Breathing, Circulation) must commence.
Rescuers must promptly remove wet clothing to halt ongoing conductive and convective heat losses.

Pharmacological and Fluid Resuscitation

Intervention	Specific Actions and Dosages
Vascular Access	Establish rapid intravenous (IV) or intraosseous (IO) access for fluid and drug administration.
Epinephrine	The primary vasoactive agent for brady-asystolic arrest. IV/IO dose is $0.01 mg/kg$ ( $0.1 mL/kg$ of $1 : 10, 000$ solution) every $3 - 5 minutes$ . If no vascular access is present, an endotracheal dose of $0.1 - 0.2 mg/kg$ can be utilized.
Volume Expansion	Administer isotonic crystalloids ( $0.9$ Normal Saline or Lactated Ringer's) as rapid $10 - 20 mL/kg$ boluses to augment preload and treat hypovolemia.
Defibrillation	If a shockable rhythm (Ventricular Fibrillation/Pulseless Ventricular Tachycardia) is identified, deliver an initial shock of $2 J/kg$ , followed by $4 J/kg$ for refractory rhythms.

Subsequent Hospital Management

All pediatric drowning victims require continuous hospital observation for a minimum of $4 - 6 hours$ , even if initially asymptomatic, as delayed pulmonary edema and progressive hypoxemia can manifest during this window.

Respiratory and Systemic Support

Initial diagnostics should include arterial blood gas analysis, a complete metabolic panel, complete blood count, and chest radiography.
Patients developing ARDS require invasive mechanical ventilation with lung-protective strategies, strictly limiting tidal volumes ( $< 5 - 8 mL/kg$ ) and optimizing Positive End-Expiratory Pressure (PEEP) to overcome alveolar collapse and intrapulmonary shunting,.
Prophylactic antimicrobial therapy is not indicated, as the initial inflammatory response is chemical rather than infectious. Antibiotics should only be prescribed based on subsequent radiographic evidence or strong clinical suspicion of bacterial pneumonia,.
In cases involving profound, medically refractory ARDS or severe reversible cardiac failure, extracorporeal life support (ECMO) has been successfully utilized.
Gastrointestinal integrity must be protected; severe mucosal sloughing mandates strict bowel rest, nasogastric decompression, and gastric acid neutralization.

Neurological and Temperature Management

The cornerstone of neurocritical care following drowning is the meticulous preservation of adequate oxygenation, ventilation, and cerebral perfusion pressure.
Routine utilization of aggressive therapies to reduce intracranial pressure (ICP)—such as severe fluid restriction, prophylactic hyperventilation, neuromuscular blockade, or barbiturate coma—has not been proven beneficial in drowning victims and may paradoxically worsen neurological morbidity.
Blood glucose concentrations must be tightly regulated to avoid both hypoglycemia and hyperglycemia, as wide fluctuations exacerbate ischemic central nervous system damage.
Hyperthermia (core temperature $> {37.5}^{\circ} C$ ) is observed in nearly $50$ of victims within the first $48 hours$ and must be aggressively prevented and treated to minimize secondary anoxic brain injury.
For comatose survivors, targeted temperature management (TTM) is a standard consideration; however, findings from the THAPCA (Therapeutic Hypothermia After Pediatric Cardiac Arrest) randomized controlled trial indicate that targeting therapeutic hypothermia ( $33^{\circ} C$ ) yields no significant survival advantage compared to strict targeted normothermia ( ${36.8}^{\circ} C$ ).
If accidental severe hypothermia ( $< 30^{\circ} C$ ) is present upon admission, controlled active internal and external rewarming measures must be utilized until the core temperature reaches $32 - 34^{\circ} C$ ,.