Drowning

　　Drowners without self-rescue ability, or those who are not familiar with the water flow and terrain of rivers and ponds and mistakenly enter dangerous areas, as well as suicide by drowning or accidental incidents, can all lead to drowning. In the early stages of drowning, there is a reflexive hold of breath, laryngospasm, and tracheobronchospasm, as well as the obstruction of the mouth and nose by mud and grass, which aggravates asphyxia. Therefore, about 20% of drowners do not have water in their lungs or only have a small amount of water in the throat, which causes a respiratory tract obstructive laryngospasm that can last for 3 to 5 minutes. Subsequently, the larynx relaxes, causing water to enter the respiratory tract and alveoli, and the surfactant in the alveoli is damaged, leading to insufficient function, resulting in dysfunctions of pulmonary ventilation and gas exchange, causing hypoxia and carbon dioxide retention, and dysfunction of various organs due to hypoxia.

　　When a person is submerged in water, they instinctively cause a reflexive hold of breath to prevent water from entering the respiratory tract. Due to hypoxia, they cannot hold their breath and are forced to take a deep breath, causing a large amount of water to enter the respiratory tract and alveoli, blocking gas exchange, and causing systemic hypoxia and carbon dioxide retention. The water in the respiratory tract is rapidly absorbed into the blood circulation by the alveoli. Due to the different components of the water in drowning, the lesions caused also vary.

　　The pathophysiology of freshwater and seawater drowning is different. Freshwater, due to its low osmolarity, can enter the blood circulation from the alveoli, causing an increase in blood volume and leading to pulmonary edema, reduced V/Q ratio, and heart failure. At the same time, hyponatremia occurs, leading to red blood cell destruction, hemolysis, hyperkalemia, and edema of the tissue cells in organs, as well as dysfunction. In addition, hyperkalemia can cause arrhythmias, ventricular fibrillation, and acute renal failure caused by the栓塞 of hemoglobin in the renal tubules due to hemolysis. At the same time, water damage to the epithelial cells of the alveoli results in a decrease in surfactant, forming atelectasis of the alveoli, further aggravating the V/Q ratio reduction, causing severe hypoxia. Seawater, due to its high osmolarity (35% salt), when inhaled, causes water to渗入 the alveoli from the blood vessels, leading to acute pulmonary edema and a decrease in blood water, resulting in blood concentration, hypernatremia, and insufficient blood volume, poor tissue perfusion. At the same time, seawater often contains calcium salts and magnesium salts, leading to hypercalcemia, bradycardia, conduction block, and even cardiac arrest. Hypermagnesemia has the effects of inhibiting the central nervous system, dilating blood vessels, and lowering blood pressure.

　　What complications can drowning easily lead to?

　　Drowning patients may lose consciousness, stop breathing, and disappear the pulse of the great arteries, and be in a clinical death state. The clinical manifestations of near-drowning patients are quite different, and are related to the duration of drowning, the amount of water inhaled, the nature of the inhaled water, and the extent of organ damage.

　　1. Symptoms

　　Near-drowning victims may have headaches or visual disturbances, severe cough, chest pain, difficulty breathing, coughing up pink frothy sputum. Drowning in seawater can cause a strong thirst, and chills and fever may occur in the first few hours.

　　2. Signs

　　The skin turns blue, the face swells, the conjunctiva of the eyes becomes congested, the mouth and nose are filled with foam or mud, and there are often changes in mental state, restlessness, convulsions, drowsiness, coma, and increased muscle tone, and shallow, rapid, or stopped breathing. The lungs can hear dry and wet rales, and occasionally wheezing sounds; arrhythmia, weak or absent heart sounds; abdominal distension, cold extremities, and sometimes head and neck injuries can be found.

　　The main preventive measures for drowning are as follows:

　　1. When drowning occurs, if you are not familiar with swimming, you can take self-rescue measures. In addition to calling for help, lie on your back, turn your head back, so that the nose can breathe out of the water. Exhale lightly, inhale deeply.

　　2. Do not panic, do not raise your arms and flail wildly, which will make the body sink faster. Swimmers, if they have a cramp in the lower legs, should remain calm, adopt the backstroke position, and use your hand to bend the toes of the cramping leg towards the back, which can relax the spasm, and then swim slowly towards the shore.

　　3. When rescuing a drowning victim, swim quickly to the vicinity of the drowning victim, observe the position clearly, and reach out for rescue from behind. Or throw in wood, lifebuoys, long poles, etc., so that the person who fell into the water can climb onto the shore.

　　4. After the drowning victim is rescued to the shore, first clean the mud and sputum in the mouth and nose, remove the dentures, and then perform water control treatment. The rescuer bends one leg and kneels, placing the drowning victim prone on the rescuer's thigh, using the body position to let the water in the drowning victim's body be discharged from the trachea and mouth.

　　5. If the breathing and heartbeat of the drowning victim have stopped, perform mouth-to-mouth artificial respiration immediately, and at the same time, perform external cardiac massage.

　　6. For normal breathing and pulse drowning victims, after water pouring, gargle at home after returning, drink some ginger soup or hot tea, and pay attention to keeping warm, let the child sleep quietly; pay attention to go to the hospital for treatment if there is coughing or fever.

　　7. Strengthen the publicity of swimming safety knowledge, prepare warm-up exercises before swimming to avoid cramps in the gastrocnemius muscle, and swim in pairs. Strengthen the safety and first aid knowledge education for marine workers.

　　The main clinical examination methods for drowning include urinalysis, arterial blood gas analysis, and chest X-ray examination, as follows:

　　1. Urinalysis

　　Drowning victims often have a slight increase in white blood cells. When more freshwater is inhaled, hemodilution may occur, even red blood cell lysis, with increased blood potassium, free hemoglobin in blood and urine. When more seawater is inhaled, transient blood concentration occurs, with mild hypernatremia or hyperchloremia. Survivors usually recover normal blood volume and electrolyte concentration within 10-30 minutes. Whether it is freshwater or seawater drowning, it is rare to have fatal electrolyte disorders, but serious hyperkalemia may occur with hemolysis or acute renal failure. Severe cases may show abnormal laboratory indicators of disseminated intravascular coagulation.

　　2. Arterial blood gas analysis

　　About 75% of cases show significant mixed acidosis; almost all patients have varying degrees of hypoxemia.

　　3. Chest X-ray examination

　　It often shows patchy infiltration, and sometimes typical signs of pulmonary edema appear. Improvement or deterioration is observed within 12-24 hours of hospitalization. About 20% of cases have no abnormalities on chest X-ray. If there is a suspicion of cervical spine injury, a cervical spine X-ray examination should be performed.

　　Drowning victims should consume easily digestible, high-calorie, high-plant protein, and drying foods with a strong diuretic effect. They should avoid eating heavy, dry, difficult-to-digest, and moldy foods. The diet of the patient should be light and easy to digest, with an emphasis on vegetables and fruits, a reasonable diet, and attention to adequate nutrition. In addition, patients should also avoid spicy, greasy, and cold foods.

　　To rescue drowning victims, every second counts. Immediate on-site rescue is essential, clearing mud and grass from the mouth and nose, pulling out the tongue to ensure the airway is clear, and if necessary, performing bronchoscopy to remove airway foreign bodies. The patient should be placed on the rescuer's lap for drainage, stopping at the right time to save rescue time. For those with respiratory arrest, atropine is injected to inhibit vagal reflexes, allowing the lungs to expand, and performing mouth-to-mouth resuscitation or prone back breathing, with the former being superior due to positive pressure ventilation that expands alveoli, improving ventilation and gas exchange. Intravenous nicotinum bromatum (Kallikreolin) and doxapram are administered, and blood gas analysis is monitored to adjust ventilation volume and oxygen concentration. Dopamine and metaraminol are administered for low blood pressure and oliguria, with dexamethasone given in appropriate doses to correct shock and restore tissue perfusion. Attention is paid to fluid balance, and a right heart pulmonary artery catheter may be used to guide fluid resuscitation if needed. Furosemide 40-80mg may be administered intravenously for renal insufficiency. For those with cardiac arrest, the chest is struck with closed fists 3-5 times. If cardiac arrest persists for more than 1-2 minutes, external cardiac massage is performed. For ventricular fibrillation, defibrillation with non-synchronous 200-300WS is used, and if the fibrillation is fine, epinephrine 0.5-1mg is administered intravenously to thicken the fibrillation waves for easier defibrillation. Artificial respiration and oxygenation, as well as external cardiac massage, are essential for defibrillation. If ventricular tachycardia occurs, epinephrine or atropine or insertion of a temporary pacing catheter may be used. Tracheal intubation is performed for positive pressure ventilation with oxygen, and positive end-expiratory pressure (PEEP) may be added for pulmonary edema. Once breathing and heartbeat are restored, the head is cooled. During rescue, wet clothes should be removed, and the body should be dried with a dry towel and wrapped in dry clothing for warmth.

　　Generally, the brain recovers after cardiopulmonary resuscitation, otherwise, if consciousness does not recover, brain function should be protected. Brain function can be protected using ice caps, hypothermia therapy (25mg of chlorpromazine and promethazine in 250ml of 5% glucose for intravenous drip), and 250ml of 20% mannitol and 10mg of dexamethasone, once every 8 hours, as well as furosemide (Lasix) 20-40mg, administered intravenously several times a day as needed for dehydration therapy to reduce intracranial pressure. In cases of freshwater drowning, hyponatremia may occur, and 3% saline (which contains 513 millimoles of Na and Cl per 100ml) can be administered. The amount to be supplemented can be calculated using the formula: the amount to be supplemented plasma milliosmols = 300 - patient plasma osmotic pressure (mOsm/L) × body weight (kg) × 0.2, and the correction can take several days. In cases of hemolysis and anemia, whole blood can be administered in appropriate amounts. In cases of seawater drowning, 5% glucose solution should be used for fluid replacement. All drowning patients should have their fluid intake and output recorded, and corrections should be made to water and electrolyte imbalances based on the condition. Penicillin 6.4 million units and piperacillin (oxacillin) 6g should be administered intravenously every 12 hours to prevent lung infection. In cases of consciousness impairment, 0.75-1.125g of nikethamide (cyclophosphamide) can be administered intravenously in 250ml of solution, and the dose should be adjusted according to the patient's level of consciousness. Continuous low-flow oxygen therapy through a nasogastric tube should maintain SO2 ≥ 90%. Wheezing in both lungs can be treated with 80mg of methylprednisolone or 0.25g of aminophylline, twice or three times a day as needed. In addition, dexamethasone 10-20mg can be administered intravenously for pulmonary edema and brain edema, once a day. About 80-90% of near-drowning victims survive without sequelae after in-hospital treatment. The shorter the time from rescue from the water to the appearance of spontaneous respiration, the better the prognosis.