Near & Accidental Drowning
Bridget MacDonald CVT, VTS (ECC), Nursing Shift Supervisor
Veterinary Technician Specialist
Veterinary Specialty & Emergency Center
Warm weather is here and that means pool parties and long runs on the beach with our four-legged friends. Sadly with the warm weather, we can often times see a rise in cases presenting to the Emergency room for accidental or near drowning. In some scenarios, accidental drowning may be secondary to other causes such as seizure, head trauma, hypoglycemic event, cardiac arrhythmias, and syncopal episodes (5 Minute Vet Consult -Silverstein 2007).
It is important to understand the definition of drowning and near-drowning. Drowning is described as death from asphyxia while submerged and near-drowning is described as survival within 24 hours of submersion. There are some canine (and feline) studies that have evaluated the pathophysiologic effects of saltwater versus freshwater. There is not enough research supporting whether or not chlorinated (pool) water has any effect on outcome or overall survival rates. However, one study reported by JAVMA (2006, Hofmeister, et al), looked at toxicosis associated with ingestion of quick-dissolve granulated chlorine in a dog. In this case example, the dog presented 18 hours post ingestion and had clinical signs of tachypnea, depression, dehydration, mucositis and productive cough. The dog was treated supportively in a hospital setting and was discharged after 15 days.
This suggests that while rare, subsequent disease processes are common and treatable following pool water ingestion.
What we do know is that when an animal is submerged for a length of time, carbon-dioxide levels increase in the bloodstream (CO2 >45 mmHg) which stimulates the respiratory center. In some cases, there may be laryngospasm prior to aspiration which may reduce the amount of water aspirated. When we think about the type of water aspirated, salt versus fresh, both will cause hypoxemia (PaO2 <80 mmHg) leading to ventilation perfusion mismatch with a secondary lactic acidosis. We know that fresh water aspiration will dilute pulmonary surfactant. Pulmonary surfactant are lipoproteins formed by alveolar cells that are responsible for reducing surface tension of the lungs. When surface tension is compromised, it may lead to alveolar collapse, atelectasis and (aspiration) pneumonia affecting overall lung compliance. Fresh water is less hypertonic than the body’s extracellular fluid; therefore, fresh water is rapidly absorbed from the alveoli and into the intravascular space, thereby causing hypervolemia (Goldkamp, Schaer 2008).
In cases where large volumes of water are aspirated (>22ml/kg), hemodilution, intravascular hemolysis and electrolyte imbalances may also occur leading to a dilution-induced hyponatremia.
When acute hyponatremia is severe (usually <120-130 mEq/L), CNS signs may be seen (obtundation, head pressing, seizure, coma, and death). Sodium concentration correction should not exceed a rate greater than 0.5 to 1 mEq/L per hour or no more than 10 mEq/L in the first 24hrs. Secondarily, hypovolemia may occur due to non-cardiogenic pulmonary edema as a result of the redistribution of fluids.
In contrast to freshwater, saltwater has a higher tonicity to that of the body’s extracellular fluid. Thus it has the opposite effect, drawing salt water from the intravascular space into the alveolar space (Goldkamp, Schaer 2008) causing hypernatremia. Severe hypernatremia (>180 mEq/L) due to rapid onset may be associated with CNS signs of obtundation, head pressing, seizures, coma, and death (Burkitt, 2009). Hypernatremia should be treated even if the patient is not showing clinical signs. Cautiously lowering serum levels at 1 mEq/L/hr is the recommended rate. If the levels decrease too rapidly, edema and cellular swelling may occur and therefore monitoring the patient for cerebral edema is important. Regardless of which fluid is aspirated and depending on the total volume, both saltwater and freshwater aspiration may cause serious lung damage leading to hypoxemia. The lung injury may be so severe that it ultimately may lead to acute respiratory distress syndrome, also known as ARDS, which is a life-threatening condition requiring mechanical ventilation.
A study reported by JAVMA (2008, Heffner et al) looked at the evaluation of freshwater submersion in 28 cases (25 dogs and 3 cats) from 1996-2006. The purpose was to determine clinical characteristics, treatments and outcomes in both species evaluated after submersion in fresh water. Of these animals, the cause was only determined in 16 of the animals (falling into water, breaking through ice, intentional submersion) and twelve of the animals were submerged in unclear surroundings. Eighteen of the animals survived to discharge, all cats died and nine of the ten non-survivors, respiratory tract failure was the cause of death (or reason for euthanasia).
Most diagnoses are made not just based upon clinical signs, but a thorough history is also key in these types of cases as they present to us. It is important to know what type of water submersion took place, how long the patient was submerged, and the temperature of the water. From the time of owners rescuing the patient to the time of arrival, the chances of overall survival increase if immediate steps are taken. If the owner calls prior to arrival and they feel the pet has undergone cardiovascular or respiratory collapse, mouth-to-snout resuscitation should be advised according to the current RECOVER guidelines. While the signalment and history are being obtained, triage and early interventional care should be simultaneously initiated by the medical team. This includes providing essential oxygen therapy via flow-mask, securing airway if necessary and obtaining vascular access as well as obtaining an initial database ( PCV/TS/BG/Venous Blood Gas with Electrolytes ). Arterial blood gas should be obtained if accessible. If CPR is indicated, appropriate measures should be taken right away to begin chest compressions and positive pressure ventilation as indicated by the RECOVER guidelines.
Monitoring devices should be placed on the patient to evaluate SPO2, ECG, ETO2 if intubated, NIBP, and temperature monitoring and support as needed. Radiographs are also a useful diagnostic tool in detecting aspiration pneumonia and non-cardiogenic pulmonary edema, or in some cases sand-bronchogram, however there may not be detectable changes radiographically due to a 24-48 hour lag time. Correcting electrolyte imbalances as indicated also play a key role in the treatment and recovery of near drowning cases. If cerebral edema is developing based on clinical signs or Cushing’s reflex, the use of diuretics such as Mannitol (0.5g/kg) may be indicated to help reduce intracranial pressure (ICP). Antibiotic therapy also may be necessary if aspiration pneumonia is evident. Close monitoring and nursing care in an ICU setting is critical in the treatment and outcome for these patients as severe complications may arise.
The bottom line is that prevention of these types of accidents may be reduced by awareness. Owners should be educated if their pets are elderly or have underlying conditions that may make them susceptible to accidents. The prognosis is good if the animal is conscious at presentation and treated quickly with no complications.
Bridget MacDonald is an Emergency & Critical Care Veterinary Technician Specialist at the Veterinary Specialty & Emergency Center. The Veterinary Specialty & Emergency Center operates state-of-the-art emergency and specialty veterinary hospitals that are open 24/7/365 in both Levittown PA and Philadelphia PA. For more information about our world-class emergency and specialty care, please visit VSEC on the web at www.VSECVET.com.