Dr. Dana Brooks, an internist at Seattle Veterinary Specialists in Kirkland, answers this week's question.

Question: Dogs have a muscle layer around the spleen that can contract and push more blood back into general circulation. Is this considered an autotransfusion?

Answer: Along with it's many other functions, the spleen is a reservoir for red blood cells. Dogs have a layer of smooth muscle in the capsule of their spleen that can contract and expel stored red blood cells into the circulation. This typically happens in response to an adrenaline surge (fight or flight reflex).

Examples would be exercise, cold, low oxygen levels, bleeding, low blood pressure, fear, excitement or pain. In some studies dogs have been shown to raise their circulating red blood cell volume by as much as 10 percent.

Some other animals can do this to varying degrees -- cats, sheep, horses, and humans are able to do this to a degree as well. So although this is can be an emergency injection of red blood cells into the system when the need arises, it is not a true autotransfusion.
Autotransfusion is a process where one receives one's own blood for a transfusion rather than from a donor.

This typically occurs in one of two ways. Someone can donate their own blood before an upcoming surgery or other event where they foresee that it will be needed.

In the second case, the blood is harvested from a body cavity at the time the patient is actively bleeding (surgery or trauma). The blood is collected in a sterile manner, filtered to remove clots, and given directly back to the patient. This is the most common reason for an autotransfusion in dogs and cats.

Dr. Dana Brooks

Dana Brooks is a internal-medicine specialist at Seattle Veterinary Specialists (SVS) in Kirkland. She graduated from Mississippi State University College of Veterinary Medicine in 1991 and completed her residency at Michigan State University Veterinary Teaching Hospital in 1995. She worked in the Northeast until 2007, when she joined SVS. Her special interests include hormonal and immune-mediated diseases as well as endoscopy. She lives with two black cats named Jasper and Logan.

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