Excess Carbon Dioxide in the Blood in Dogs

Carbon dioxide (CO2) is a gaseous waste product that comes from functioning cells and is carried by the blood to the lungs, where it is exhaled. CO2 is necessary in order to keep a balance of electrolytes, and of acid based PH. When the level of carbon dioxide is too high for too long, conditions arise such as respiratory acidosis (caused by abnormal breathing rate and volume). Hypoventilation, which is inadequate intake of air, is the event that will cause a state of excess carbon dioxide in the blood. If not treated, hypercapnia can lead to coma and death. This event can occur with any breed of dog, male or female and of any age.

Excess carbon dioxide in the blood is also known as hypercapnia. An abnormal rise in the arterial pressure of carbon dioxide in the blood can lead to respiratory distress that often needs mechanical ventilation as part of the treatment and recovery process.

Signs of excess carbon dioxide in the blood are very apparent once the condition reaches a critical stage.

• Dizziness
• Irregular heartbeat (arrhythmia)
• Rapid heart rate (tachycardia)
• High blood pressure (hypertension)
• Altered level of consciousness (obtundation)
• Central nervous system depression which presents as decreased rate of breath, decreased heart rate, complete loss of consciousness, coma, and death

When a dog has excess levels of carbon dioxide in the blood there can be many causes. Documentation states that the most common reason that your dog enters this state is hypoventilation (low amount of air intake in the lungs), which most often occurs when a dog is placed under anesthesia. Other instances where hypoventilation can lead to excessive carbon monoxide are listed here.

• Shock such as effects on the body after electrical shock or anaphylactic  reaction
• Infection that has become severe
• Restriction of airway
• Lung disease
• Dehydration
• Medication overdose
• Chest wall damage
• Central nervous system disease
• Trauma
• Diaphragmatic hernia
• Drugs causing respiratory depression
• Respiratory fatigue
• General anesthesia (hypercapnia is secondary to anesthetic-induced hypoventilation)
• Other problems during anesthesia like equipment malfunction or accident

Unless your dog is under anesthesia, which will provide a concrete lead as to the diagnosis, the process could be a long one. 

The symptoms that are apparent, along with a physical examination (to check for an obstruction, or to listen to lung sounds for example) and a discussion of the recent medical and behavioral history of your pet will be the starting point for the diagnosis. Complete blood count and biochemistry tests will be done to look for markers pointing to a primary cause or a secondary illness. Urinalysis is another standard procedure because it can indicate many illnesses like infection or kidney disease.

Other tests could include imaging diagnostics like radiograph or ultrasound, tools that are useful in viewing possible injury or disease. 

First and foremost is giving your dog the treatment he needs to get him breathing on his own again. Adequate ventilation is key and will most likely be provided in the form of mechanical ventilation. Of course, if your canine companion is under anesthesia, there is standard oxygenating protocol that will be followed by the veterinary team. 

Treatment will vary, depending on the underlying cause for the excess carbon dioxide. For example, dehydration can be administered to with the infusion of fluids and medication to correct electrolyte balances. After oxygen stabilization, an infection can be treated with antibiotics. An airway obstruction can be removed, sometimes by a simple endoscopy, but at times requiring surgery. Once the cause of the hypercapnia has been determined, medical care will assist in recovery for your beloved pet.

When the underlying cause of the hypercapnia is treatable and reversible, prognosis is good. Even when the situation has become a life-threatening one, as long as the air restriction and the excess of carbon dioxide have not been in effect too long, dogs can respond well to the mechanical ventilation and begin breathing on their own. If your dog cannot resume his air intake without mechanical aid the prognosis is poor.