Salt water and fresh water near-drowning vary in how they affect the lungs. Because of it’s high sodium content, salt water draws water from the bloodstream into the airways effectively flooding the airways. Fresh water inactivates a substance called surfactant, which is manufactured by the lungs and functions to keep the lungs from collapsing. Without surfactant, the airways collapse (atelectasis). Therefore, the main feature of salt water drowning is pulmonary edema (fluid in the airways) and the main feature of fresh water drowning is atelectasis (collapse of airways). Fresh water near-drowning carries a better prognosis than salt water near-drowning.
Near-drowning in cold water carries a better prognosis than warm water. Cold water protects the brain from damage due to lack of oxygen by lowering the pet’s body temperature, which subsequently decreases the body’s demand for oxygen. Cold water can also initiate the diving reflex, which causes a decrease in the pet’s heart rate and redirects blood to vital organs such as the brain and heart to delay brain damage.
Laryngospasm, spasm and closure of the airway occurs in approximately 10 percent of near-drowning victims and results in asphyxia, which is a total lack of oxygen. Laryngospasm minimizes damage to the lungs by preventing water from entering the airways. However, unless the laryngospasm is relieved, your pet will die from lack of oxygen.
Aspiration of water into the lungs causes the lungs to lose their elasticity and become stiff, which makes it more difficult to breathe. Pulmonary edema, an accumulation of water in the lungs, occurs if your pet directly aspirates the water into the lungs. However, it can also result from struggling to breathe against a closed airway as in laryngospasm or secondary to hypoxic (no oxygen) brain damage and is termed neurogenic pulmonary edema.
Cerebral edema, swelling of the brain, can occur secondary to loss of oxygen. If cerebral edema is severe, the pet may experience seizures, loss of consciousness, coma and death. Arrhythmias, or abnormal heart rhythms, may occur as a result of near-drowning and shock.
Diagnosis In-depth on Canine Near Drowning
While the diagnosis of near drowning is based on an observation of the event, certain diagnostic tests are necessary to evaluate the extent of lung or brain damage or to monitor the condition of a severely affected pet. If your pet appears normal after submersion, 24-hour hospitalization for observation may be all that is required. However, the following tests are necessary for those pets whose condition is more serious.
- Thoracic radiographs (chest X-rays) are taken to look for the presence of pulmonary edema or to see if pneumonia is present. Pulmonary edema due to near drowning may take up to 48 hours to develop so serial X-rays are often necessary.
- An arterial blood gas is obtained to assess how well a pet is able to oxygenate. A blood gas also helps the veterinarian to decide whether oxygen therapy is necessary.
- A pulse oximeter also assesses how well a pet can oxygenate. The pulse oximeter utilizes a special clip placed on the pet’s lip to measure oxygenation.
- A transtracheal aspirate (TTA) samples the fluid in the lungs if pneumonia is suspected or if the pet was submerged in contaminated water. The sample is then submitted for microscopic evaluation and culture so appropriate antibiotics can be chosen to treat the pneumonia.
- A complete blood count and biochemistry profile evaluate changes in the white blood cell count or damage to internal organs due to loss of oxygen and shock.
- Urinalysis detects the presence of hemoglobinuria (hemoglobin in the urine), which may occur as a result of damage to red blood cells from fresh water near-drowning.
- Central venous pressures are measured using an intravenous catheter placed in the jugular vein. Serial measurements are taken to determine the proper amount of IV fluids to be administered to near-drowning patients. Not all hospitals have the facilities to do this type of monitoring; however, inability to do such a test does not hinder proper care for your pet.
Treatment In-depth for Canine Near Drowning
Hospitalization and observation for the 24-hour period following a near-drowning incident is recommended regardless of how good a pet may appear initially. Difficulty breathing may develop hours after the near drowning incident. Treatment may consist of the following:
- Supplemental oxygen for pets that have difficulty breathing.
- An IV catheter for administration of IV fluids, which are used to treat shock and dehydration, and for administration of certain drugs.
- Diuretics such as furosemide (Lasix) to treat pulmonary edema. Unfortunately, diuretics do not relieve the edema secondary to near-drowning as well as in cases of pulmonary edema due to other causes like heart disease.
- Bronchodilators such as aminophylline or terbutaline to dilate the airways and improve breathing. These drugs usually have only a minor effect, as bronchoconstriction is not the main problem in near drowning patients.
- Mechanical ventilation (use of a respirator) for patients that do not respond to therapy with oxygen and IV drugs. Your pet will be fully anesthetized while your veterinarian places an endotracheal tube or tracheostomy tube, which is then attached to the ventilator. The machine will breathe for your pet. This is usually a temporary measure (24-72 hours) until your pet can breathe normally on his own.
- I.V. drugs such as mannitol or steroids to reduce cerebral edema in those pets that have severe changes in their mental status due to a prolonged period of oxygen deprivation or due to seizures following a near-drowning episode.
- Antibiotics are not indicated unless the pet was submerged in contaminated water or pneumonia is present. Antibiotics are initiated only after a culture has been obtained.