Section: Overview
Carbon monoxide is an odorless, colorless, nonirritating gas, that when absorbed into the bloodstream, forms a compound that causes hypoxia (reduced oxygen supply) of the heart and brain. Some pets are predisposed to toxicity due to preexisting heart or lung disease. Dogs are more susceptible than cats but all cats are at risk.
The most common causes for exposure include:
Automobile exhaust in a closed garage
Faulty exhaust system
Non-vented furnace, gas water heater, or gas/kerosene space heater
Smoke inhalation (for example, in burning buildings)
Airplane cargo areas (may accumulate carbon monoxide)
What to Watch For
Drowsiness
Lethargy
Weakness and/or incoordination
Bright red color to the skin and gums
Dyspnea (difficulty breathing)
Coma
Abrupt death
Occasionally, chronic (low-grade, long-term) exposure may cause exercise intolerance, changes in gait (walking), and disturbances of normal reflexes.
Diagnosis
Diagnosis is based on possible exposure to carbon monoxide, physical exam findings and supporting laboratory results:
Routine baseline blood tests, to include a complete blood count, biochemical profile and urinalysis are generally within normal limits, with the exception of an elevated creatine kinase (muscle enzyme).
Blood gas analysis usually reveals acidosis (low pH), related to poor oxygenation of tissues.
Carboxyhemoglobin (hemoglobin with carbon monoxide attached) concentration in the blood is high. Blood samples can be transported to and evaluated in human hospitals. This test is not available for all veterinary clinics.
Treatment
Oxygen supplementation is essential. Ideally, delivering 100 percent oxygen is best, although any amount of oxygen will be of benefit.
Respiratory support with a mechanical ventilator may be indicated in those severely effected.
Supportive fluid therapy, electrolyte, and nutritional therapy may be indicated.
The patient's cardiac (heart) and neurologic status should be monitored with electrocardiograms and serial neurologic examinations.
Following the patient's clinical signs and ideally, decreasing carboxyhemoglobin concentrations, are helpful in monitoring response to therapy.
Home Care and Prevention
Be aware that if the source of poisoning still exists, both you and your dog are at risk. Affected pets should limit physical activity for several weeks.
Prevent toxicity by minimizing exposure and using carbon monoxide detectors around your home.
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