Vampire Veterinarian

I've had a couple of folks ask me recently about blood transfusions in dogs. We've all heard the docs on ER call out "put two units of O-neg on the rapid infuser. Type and cross-match for two more." It's actually very similar in dogs and cats (although not usually that dramatic).

Whole blood is made up of red cells, white cells, platelets, and various blood proteins. Red cells are what make blood red. Their color is the result of the hemoglobin protein that is responsible for carrying oxygen around the body. White cells are, generally speaking, your immune system workhorses. Platelets are responsible for creating clots and stopping bleeding. The blood proteins are too numerous to list, but the major ones are antibodies (globulins) and albumin (the most prevalent protein).

Just like in people, dogs and cats have specific blood types. In people, there are types O, A, AB, and B. Additionally there is the Rf factor (O+ versus O-). In dogs the blood types are called DEA (Dog Erythrocyte Antigen) and although about 10 are described, the ones we are concerned with are DEA 1.1, 1.2, and 1.7. Blood types in cats are limited to A, B, and AB. 95% of cats are type A in the U.S. Persians and British Shorthairs are most likely to be type B. That's important because giving A blood to a B cat is likely to kill them because type B cats have natural antibodies against type A blood. Donors are always typed. Universal canine donors are DEA 1.1, 1.2, and 1.7 "negative". There is no universal cat donor.

Prior to a transfusion, the recipient and donor blood is mixed together to check for compatibility (this is a simplification, but the general idea is correct). This is referred to as cross-matching. If the blood is incompatible, there is a danger that the recipient may simply reject the new cells and end up in a worse place than where they started.

When a person (or animal) donates blood, the whole blood in collected in a specially designed bag. Some blood is kept as whole blood. It has a shorter shelf-life and is less frequently used. Most blood is then spun down in these cool, huge, refrigerated centrifuge and the cells (now called packed cells) are separated from the plasma (the straw colored stuff that is now liquid gold and costs about as much). These products can be further processed to separate out things like clotting factors, specific types of cells, or special proteins. Most of the time they are simply kept as plasma (frozen and it keeps for quite a long time) or packed cells. The red cells are bathed in a mixture of electrolytes and energy that keeps the cells happy and alive for a period of weeks.

In the veterinary field, there are large blood banks that process the blood. If it is collected in a local hospital, it's usually collected as whole blood and used as whole blood on-site. I used to have one of the really groovy centrifuges where I worked in Connecticut and would process our own blood products. We were very lucky to be able to do this.

Most folks think of blood transfusions as something you do in cases of trauma and blood loss. That's what we've been exposed to on the television. Someone is shot, looses tons of blood, and then gets it replaced with some donated blood. That's only one of the reasons we may need blood. In cases where the body has been using up the red cells only (like if the immune system is inappropriately attacking the cells) then we may only need red cells. In cancer patients we may have destroyed all of their platelets or white cells and only need to supplement those particular cells and we don't want to give them whole blood.

As you can imagine, it's expensive to collect and process blood. The blood has a short shelf life and you have to spend a lot of money getting qualified donor. Blood transfusions in practice can range in price from $250 for a small dog to $1000 for plasma in a larger dog.

AMH