Carbon Monoxide Poisoning in Dogs

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Carbon Monoxide Toxicosis in Dogs

Carbon monoxide is an odorless, colorless, non-irritating gas produced by the incomplete combustion of carbon fuels. It is potentially toxic for dogs as well as humans. Common sources of carbon monoxide are unventilated kerosene or propane heaters, gasoline engines, automobile exhaust, or fumes from carbon-based fuel heating systems.

When inhaled, this gas is readily absorbed into the blood, combining with hemoglobin to form carboxyhemoglobin, reducing oxygen delivery to the body, and thereby leading to decreased utilization of oxygen in the brain and heart. Most cases of carbon monoxide toxicity in dogs occur as a result of human error, such as when a dog has been left in an enclosed area where carbon monoxide is being released. A dog left in an enclosed garage with a running automobile can be exposed to toxic levels of carbon monoxide in about ten minutes. Animals are also exposed to toxic levels of carbon monoxide when they are trapped in a building that is on fire. Prolonged exposure to carbon monoxide will lead to hypoxemia and eventually death.

Symptoms and Types

Depending upon the concentration and duration of exposure of carbon monoxide, the symptoms may be acute or chronic in nature.

  • Sleepiness
  • Cherry red skin and mucous membranes (e.g., nostrils, lips, ears, genitals), but this side-effect is usually not visible in most animals
  • Weakness
  • Lethargy
  • Difficulty in breathing
  • Seizures
  • Abortion in pregnant animals especially those in late gestation period
  • Depression
  • Deafness
  • Uncoordinated movements
  • Coma
  • Death

Symptoms with chronic exposure to carbon monoxide include:

  • Nausea
  • Abnormally high levels of acids in blood (acidosis)
  • Vomiting
  • Cough
  • Flu like symptoms
  • Loss of exercise stamina
  • Disturbances in gait


Exposure to any source of carbon monoxide, like:

  • Incomplete combustion of carbon fuels
  • Accidental enclosure of dog in garage with automobile engine turned on
  • Poorly ventilated areas with any source of carbon monoxide (e.g., fireplace, oven, barbecue grill)
  • Unventilated furnaces
  • Gas water heaters
  • Gas or kerosene heaters
  • House fires


The foremost step in carbon monoxide toxicity is to get your dog away from the source of the carbon monoxide. Carbon monoxide toxicity is a life-threatening condition requiring immediate veterinary intervention. Your veterinarian will start immediate oxygen therapy to remove the carbon monoxide from the blood and bring your dog's oxygen levels back to normal. While your dog is receiving oxygen your veterinarian will collect samples of blood for diagnostic testing. A complete blood count, biochemistry profile, urinalysis and other applicable body fluid tests will be performed. Your veterinarian will also collect samples for determination of carboxyhemoglobin levels in the blood. Establishing the levels of carbon monoxide in the blood is the most useful test for basing the initial treatment plan.

Carboxyhemoglobin levels rise in acute cases and drop within a few hours once exposure to the source of the carbon monoxide has been removed. Levels of acids in the blood will also be determined during blood testing, as acid concentrations tend to rise in response to this condition and their values will determine the appropriate diagnosis and medical response. Other diagnostic tools your veterinarian may use include an electrocardiogram (ECG) to determine whether the heart has also been affected.

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