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Thursday, August 26, 2010

Near Drowning

Believe it or not, the U.S. Coast Guard reports that 68 people have drowned in Lake Michigan in the summer of 2010 alone, while the average for any summer is about 30. Exceptionally warm weather is believed to be the reason.

Since Shoreline medical exists just a few miles off the shoreline, and since we occasionally have to take care of near drowning victims, I thought it would be good to review the process of taking care of these patients.

I did cover it to some degree in my post about dry drownings. Yet I'll take it a step further in this post.

In fact, according to emedicine, "Near Drowning," in children aged 1-14, drownings are the second most common cause of death, next to accidental trauma. About 1,500 kids die each year of submersion injuries. In some states, like Florida and California, drowning is the #1 cause of death in children.

The rate of drownings is 1.93 per 100,000 for all age groups.

According to "Respiratory Disease," edited by Robert L. Wilkins and James R. Dexter, chapter 10, "Near Drowning," written by David Stanton, Submersion drownings account for 150,000 deaths worldwide, and between 6,000 and 8,000 deaths in the U.S. annually. Around 80,000 near drowning episodes occur in the U.S. each year, with a high incidence in men between the ages of 10 and 18 years of age, and in children under five years of age. Drownings are the 4th leading cause of death of all age groups.

Stanton writes that "poor judgement and lack of supervision are also major contributing factors in drownings" and near drownings

So here are some definitions according to emedicine:

Drowning: Death from asphyxia within 24 hours of submersion in water. If a person dies after 24 hours, the cause is attributable to the the complications, such as brain death, kidney failure, sepsis, ARDS, or secondary cause such as trauma, ceizure, stroke, heart attack, etc.

Near drowning: Survival (even if temporary) beyond 24 hours after a submersion episode.

Warm-water drowning: Occurs at water temperatures of 20°C or higher.

Cold-water drowning: occurs at water temperatures of less than 20°C. Some references include very-cold-water drowning, which refers to submersion in water at temperatures of 5°C or less.

Salt water drowning: is hyperosmolar, increases the osmotic gradient and therefore draws fluid into the alveoli, diluting surfactant (surfactant washout). Since it's hypertonic compared to the blood (approximately 3% normal saline), Stanton writes that it causes fluid from the blood into the alveoli when aspirated. Alveolar collapse occurs as surfactant is washed out and surface tension forces increase.

Fresh water drowning: considerably hypotonic relative to plasma and causes disruption of alveolar surfactant. Since it's hypotonic compared to the blood stream, when aspirated it is quickly absorbed into the blood stream increasing preload (blood going to the heart) and increases the risk of pulmonary edema and loss of cardiac output (after load).

Submersion injury: Occurs when a person is submerged in water, attempts to breathe, and either aspirates water (wet drowning) or has laryngospasm without aspiration (dry drowning). Usually at a PO2 of 25-30 the patient will become unconscious. Wikepedia notes an unconscious patient whose airway is still sealed from larygospasm (see below) stands a good chance at recovery.

Primary injury: Injuries to the body caused by sucking in water, stomach contents and lack of oxygen to vital organs while under water.

Secondary injury: Ongoing damage to organs as a result of being submerged, sucking in water, and being hypoxic for some time. This also may lead to dry drowning.

Dry drowning: Occurs when a person's lungs are unable to inhale air as a result of laryngospasm that results from emersion in water. The patient may initially appear fine, yet "drown" on dry land within the next 24 hours. I describe this in more detail in my post, "Dry drowning: drowning on dry land."

Breathing reflex: According to Wikepedia, one can hold his breath for some time, but the breathing reflex will increase until you try to breathe, even when under water. It's related weakly to oxygen and strongly to CO2. As oxygen in the blood (PO2) decreases, and CO2 increases, the urge to breath increases up to the breath-hold break point, and you will no longer be able to hold your breath. This usually occurs when the CO2 reaches 55.

Water inhalation: Once the breath hold break point has been reached, one will make the effort to suck in air. When under water, one will suck in water. The person will then try to cough up the water, and inhale more and possibly even inhale stomach contents. This ultimately results in wet drownings (see below). About 10-15% of those who drown, however, do not inhaler any water. It's believed they die of laryngospasm. For the 85-90% who do inhale water (or other fluid), it's usually a small amount, and less than 22cc/kg.

Water swallowing: A majority of drownings will swallow huge amounts of water, and this often results in regurgitation and aspiration of stomach contents. Most drownings aspirate both stomach contents and other debris present in the water, and this may result in alveolitis, bronchitis and pneumonitis. Ultimately this whole process greatly increases the risk for developing ARDS due to inflammation and pulmonary edema.

Increased Airway Resistance: This is due to the inhalation of debris, and inflammatory mediators are often released and this results in vasoconstriction that impairs gas exchange.

Laryngospasm: Once one inhales water, laryngospasm occurs. It's your bodies natural way of preventing water from entering the lungs. It causes water to enter the stomach first. This happens in conscious and unconscious victims. 10-15% maintain this seal until cardiac arrest. Getting to victims before this seal is relaxed increases the chances of survival significantly.

Hypoxia and Ischemia: Hypoxia is lack of oxygen to the tissues. Ischemia is when blood flow to organs is diminished. According to Stanton the brain often becomes hypoxic before cardiac arrest occurs, and this is because the brain cells are strictly aerobic, unlike the heart which can continue to function during anaerobic metabolism for some time.

Stanton notes that blood flow can continue under anaerobic conditions for some time even after the oxygen supply has been depleted, thus keeping the heart functioning.

He notes that "most people will lose consciousness after 2 minutes or anoxia and brain damage may occur after 4-6 minutes with exceptions. Some people have their bodies trained to hold their breaths longer, and cold water conditions can create an environment where your body will conserve oxygen (see cold water near drownings below).

Calcium and Potassium transport: Active transport mechanisms slow down and eventually quit working altogether, "owing to the diminished supply of energy," Stanton writes. "Cellular integrity becomes jeopardized as potassium is lost from within the cell and calcium flood into it."

Tissue Swelling: Stanton writes that during hypoxic events, as cellular integrity becomes compromised, calcium is absorbed by cells, and through a complicated process, this results in energy depletion and this compromises cellular metabolism. Then, water follows sodium and calcium into the cell, and this results in cell and tissue swelling.

Lactic Acid: Under continues anaerobic conditions, lactic acid is produced, and this decreases body pH and alters enzyme function, leading to cell death if oxygenation and perfusion are not restored, Stanton writes.

Wet drowning: Usually larygospasm will continue until the patient is unconscious for some time, when it will relax and the person will inhale water and stomach contents and other debris, and this is called wet drowning. Asphyxia will soon result in death.

Most drowning victims aspirate both water and stomach contents, and most near drownings who inhale water do the same. Although 10-15% of near drownings do not aspirate water or stomach contents.

Emedicine notes that ingestion of greater than 11cc/kg of water may result in increase blood volume, and ingestion of greater than 22cc/kg can cause electrolyte changes that may be life threatening. Swallowing water can also cause electolyte changes.

Atelectasis: Inhalation of fluid, whether seawater or freshwater, may result in atelectasis, and this increases V/Q mismatches, functional residual capacity, and lung compliance (the lungs become stiff).

Impaired gas exchange: Even minute amounts of water can cause problems with gas exchange in the lungs. Loss of surfactant can make it almost impossible to open the alveoli, which results in atelectasis. Of course you'll also have pulmonary edema.

Hypovolemia: Emedicine notes that hypovolemia (loss of blood) results because of "increased capillary permeability" in the lungs, and this results in hypotension. Depending on length of hypoxic episode, arrythmias may be present.

Cardiac muscle damage: This is due to hypoxia may decrease cardiac output, further decreasing blood pressure, and the release of mediators of inflammation will cause vasodilation and pulmonary hypertension.

Multi organ failure: Patients should also be observed for multi organ failure, which can be monitored by creatinin levels, BUN, etc, and these will be managed accordingly.

Brain injury and death: Likewise, submersion injuries to the CNS are typically the main cause of death, especially those caued by hypoxia.

Signs of sustained brain injury include:
  • including tachycardia
  • hypertension
  • tachypnea
  • diaphoresis
  • agitation
  • muscle rigidity
Infections: Brain infection is rare, yet possible, and generally occur 30 days after the episode. Pneumonia is rare, although most near drowning victims are often treated with antibiotics. Antibiotics may also be given to prevent sepsis.

Other complications: Emedicine notes, "Submersion injuries that are associated with prolonged hypoxia or ischemia are likely to lead to both significant primary injury and secondary injury from reperfusion, sustained acidosis, cerebral edema, hyperglycemia, release of excitatory neurotransmitters, seizures, hypotension, and impaired cerebral autoregulation, especially in older patients who cannot rapidly achieve core hypothermia."

Initial Assessment: Stanton write that "the initial assessment of drowning victims should be rapid and directed toward the victim's level of consciousness, pulse, and breathing rate. Information from onlookers can also be very helpful in determining extend of injury.

When you get one of these patients, here are some questions to ask that might help with how you treat the patient:

1. How long was the patient submerged. In most cases, the answer is unknown.

2. Was there alcohol or drug use?

3. What was the water temperature? If cold, you'll have to rewarm patient.

4. Were rescue meneuvers attempted?

5. Was there a secondary cause of drowning?

  • Trauma (unintentional and intentional) (under 1 yr consider child abuse or poor parenting)
  • Seizures
  • Cardiac disease, dysrhythmias, and syncope
  • Exhaustion and hypothermia
  • Hypoglycemia
  • Alcohol and drug use

Signs and symptoms of near drowning:

1. Asymptomatic: especially if brief, witnessed submersions with immediate resuscitation

2. Symptomatic:

  • Cough
  • Dyspnea
  • Wheezing
  • Hypothermia
  • Bradycardia or tachycardia
  • Vomiting, diarrhea, or both
  • Anxiety
  • Altered mental status
  • Cardiopulmonary arrest
  • Cardiac arrhythmias (ventricular tachycardia, ventricular fibrillation, bradycardia)
  • Apnea
  • Death
Vital signs: (will be variable depending on how long submerged and temperature of water. This information comes from Stanton's writings in "Respiratory Disease)
  • Heart rate: Patient may be in full arrest or have normal respiratory rate and cardiac rythm. Common dysthrythmias are bradycardia or asystole.
  • Respiratory rate: May be not breathing and may have normal rate
  • Temperature: Will depend on the temperature of the water, body surface area, and duration of submersion. If hypothermic, careful rewarming techniques are required.
  • Pupils: May be dilated due to resuscitation efforts and meds used to revive patient. They may also respond slowly to light
  • Head and neck: Should be inspected for trauma
  • Auscultation: Wheezing as a result of bronchospasm, foreign body aspiration, and/or late inspiratory crackles associated with atelectasis. Coarse crackles may indicate patient aspirated and/or has pulmonary edema and is at high risk for pneumonia or ARDS.
  • Extremities: Cool to touch due to hypothermia and peripheral vasoconstriction. A slow capillary refill is resent when peripheral circulation is reduced. Cyanosis is common.
  • ABG: Hypoxemia, especially when aspiration has occurred, and metabolic acidosis. The more severe the metabolic acidosis the more severe the hypoxic episode was.
  • Other labs: Hemoglobin, hematocrit, and electrolyte concentration may decrease when large volumes of fresh water is swallowed or aspirated. This is the result of the dilution effects of the water when it enters the circulating blood volume.

Cold water near drownings: This causes the deoxyhemoglobin dissocotiation curve to shift to the left, causing the body to conserve oxygen. This also results in bradycardia and peripheral vasoconstriction to assure what oxygen is available gets to vital organs.

So those who are submerged in cold water (less than 21 degrees celcius or 70 degrees F) are able to be submerged for greater amounts of time. Stanton notes that some children have been under as long as 40 minutes and still survived.

Signs of sustained brain injury include:

  • including tachycardia
  • hypertension
  • tachypnea
  • diaphoresis
  • agitation
  • muscle rigidity
Treatment: Appropriate BLS and ACLS as appropriate. Other treatment is based on your initial assessment and x-ray and lab results. Oxygen is often necessary. Bronchodilators can be used to treat bronchospasm. Intravenous IV access is usually necessary to restore electrolyte management to normal, and to allow quick access for any other medications.

Discharge: Stanton writes that "if a patient is stable and no neurologic or pulmonary detterioration has occurred within 12-24 hours, the patient may be discharged. Physician follow up within 2-3 days after discharge is strongly recommended and may detect a developing pulmonary infection.

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