Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

Dogs need blood transfusions: Bite-wounds or car accidents, where massive haemorrhage has occurred; surgery with bleeding; biliary fever; liver disease; septicaemia; and if they have eaten rat poison and have clotting deficiencies.

Your dog could easily and with very little discomfort become a canine blood donor and lifesaver. Just remember that dogs are different from humans in that, although they have specific blood types, they will not react to an incompatible transfusion the first time.

If they receive a transfusion of a blood type different to their own, they will develop antibodies to this as they would to a vaccine. This process takes about three weeks. Thereafter this blood type is set in their immune system’s memory as a ‘foreign’ substance and a reaction will be mounted against it on re-exposure.

Reaction
The most severe reaction is against a specific blood type DEA1.1 and the entire transfusion is destroyed within 12 hours. This can be harmful to the patient and is wasteful. Blood donors should preferably be DEA1.1 negative. DEA negative blood can be given to any dog with very little risk of a transfusion reaction.

DEA1.1 positive blood should only be given to DEA1.1 positive dogs to prevent sensitisation. In the general dog population and in the crossbreed population about 47% of dogs are DEA1.1 positive.

If we evaluate specific breeds we do, however, see distinct differences. German Shepherds, Boxers and Dalmatians are generally DEA1.1 negative. Great Danes, Boerboels and Rottweilers are more likely to be DEA1.1 positive and thus not ideal donors.

Ideal donor
Besides being DEA1.1 negative, the ideal blood donor is a large breed dog over 27 kg. The amount of blood in a dog is about 8% of its lean body weight, so a 20 kg dog has about 1.6 litres of blood.

A unit of blood, 450 ml, is collected with each donation, and this is too much blood for a smaller dog. Dogs heavier than 50 kg can easily donate two units at a time. Dogs can safely donate every six to eight weeks and not develop any type of anaemia. The blood collection bags are the same ones used by human blood transfusion services.

Closed collection
Because the blood collected is always in a sterile container and is never exposed to the environment, this is called a closed collection system. Blood is collected from the jugular vein after clipping and surgically prepping the area.

Most dogs become used to the procedure and do not require sedation. In many cases the owners assist in keeping them recumbent. The whole process takes about five minutes and dogs do not show any ‘light headedness’ after donating.

Once the blood is collected it can undergo various processes. Whole blood is when the blood is collected in a single bag with a preservative and an anticoagulant. Blood can also be separated into red blood cells and plasma, which is a more effective way of using the product.

Uses
These red blood cells are mixed with a preservative and used for diseases such as biliary. The plasma, which contains all the proteins and clotting factors, is used in liver disease, septicaemias, parvo-virus diarrhoea and rattex poisonings. The whole blood and packed red blood cells can be stored for four weeks in the fridge whereas plasma is frozen at -20°C and can be stored for up to four years.

Cats
Cats also receive blood transfusions. Most blood donor cats are in-house practice donors as they have to be tested to be free of the FeLV and FIV viruses and because only small amounts of blood (50 ml) are collected from each cat and the blood is immediately transfused into the patient.

The collection system in cats involves needles and syringes and is classified as an ‘open collection system’ which predisposes to bacterial contamination – another reason their blood is not stored.