Near Drowning Syndrome
This refers to situations in which the affected dog has inhaled water in an insufficient quantity to cause drowning and death. It occurs when the dog has been drinking water from a hose or its mouth is washed out to remove undesirable materials (e.g. poisons), has been swimming and inhaled water, or has inhaled salt water. As little as 1 to 3 ml per kg body weight of water inhaled by the dog will interfere with gasous exchange in the lungs, whilst 4 ml per kg body weight or more aspirated may cause drowning and death.
How Does the Inhalation of Water Affect Dogs?
The main effect of water inhalation is compromising the functioning of the respiratory system. There are two main ways to cause this effect.
Firstly, the inhaled water dilutes the surfactant (i.e. fluid lining) in the lungs which leads to instability and subsequently collapse of the alveoli (i.e. distal airways). As alveoli are the sites where oxygen exchange takes place, such events will reduce the oxygen level in the blood circulation. The situation will continue until the surfactant is replaced.
Secondly, the inhaled water directly contributes to the presence of excessive fluid in the alveoli.
Reduction of oxygen exchange in the lungs may lead to a lack of oxygen reaching the brain. This may result in nerve induced construction of the blood vessels in the lungs and an increase in blood pressure which in turn can cause rupture of the lining of the capillaries supplying the lungs. All such changes eventually lead to a more severe building up of fluid in the lungs.
In the case of salt water inhalation, the salt osmotically draws fluid into the alveoli over several hours, further contributing to the fluid build up in the alveoli, and further contributing to the reduced oxygen exchange from the lungs to the blood vessels.
As pure fresh water inhaled, the fluid diffuses into the tissue lining the airways in the lungs which in turn causes profound dilution of the surfactant.
How to Manage the Near Drowning Syndrome?
It should be noted that the clinical signs of near drowning syndrome may not show until up to 24 hours later.
Initially as an owner of a dog that has inhaled water, he or she should clear the airways of any debris and conduct mouth to nose breathing should the dog not breathe properly.
On presentation to the veterinary clinic oxygen therapy is provided,and this is indicated until blood oxygen level is returned to normal. If unsuccessful, the dog needs to be placed on a ventilator where oxygen is mechanically delivered to the dog.
The dog is placed on intravenous fluid therapy to replace any fluid losses and to treat shock, if any. Supplementation with electrolytes may also be required as determined by various blood tests.
In some cases dogs affected by the near drowning syndrome may develop an increase in intracranial pressure (as detected by depression, deteriorating patient responsiveness, and pinpoint or dilated poorly responsive pupils) within 24 hours of the event despite undergoing the above mentioned treatment. Mannitol may need to be administered to reduce fluid in the brain in some cases.
In addition to the treatment given, frequent monitoring of the patient is required. It includes regular clinical examinations, and monitoring of the blood oxygen levels, urine output, blood pressure and condition of the heart. Blood tests are performed daily to assess the liver and kidney functions, signs of septic infection and platelet count.
Standardly antibiotics are not given unless aspiration pneumonia develops as routine use of antibiotics may lead to colonisation of the lungs with resistant microorganisms.
What are the Chances of Survival of an Affected Dog?
It depends on a number of factors, including the status of the patient on arrival at the veterinary clinic. Prognosis is not good if, on arrival, the dog requires ventilation and circulation support, and has a blood pH of well below 7.