by: Roxanna Khorzad, DVM, DACVECC, CCRT
Amtrak, a 10 yr MN domestic short hair, presented to the emergency department for acute onset of difficulty breathing, vocalization, and blue-colored gums. On presentation, he had cyanotic gums, open mouth breathing, and increased respiratory rate and heart rate. He was placed in oxygen supplementation cage and a blood sample was obtained. The blood sampled was brown in appearance. He was successfully treated for methemoglobinemia for suspected acetaminophen toxicity with oxygen, N-acetylcysteine, Denamarin, and supportive care. A few weeks later Amtrak returned for similar signs and then subsequently 2 additional times for the exact same signs of methemoglobinemia.
Acetaminophen is a medication routinely used in human medicine to treat fever and/or pain. Signs of toxicity can develop within a few hours. Signs include depression, rapid breathing, nausea, and cyanotic mucous membranes. Cyanosis is due to methemoglobin which decreases oxygen caring capacity of hemoglobin. Blood will become brown in color instead of red.
The most common cause of methemoglobinemia in cats is toxicity or ingestion of acetaminophen. Other causes include ibuprofen ingestion, topical anesthetics such as benzocaine, or genetic disorder.
