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Blood Transfusions Notes

Veterinary Medicine Notes > Lymphoreticular cell biology 2 Notes

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Blood transfusions

1. Introduction A transfusion is intravenous therapy with whole blood or blood products. Blood products include blood components, such as packed red blood cells or plasma. Oxyglobin is a chemically modified haemoglobin of bovine origin. The aims of blood transfusions are:?To replace what is lacking. To support patients whilst investigations are being carried out or whilst treatment is initiated. To aim for a clinical improvement rather than a normal PCV
- Post transfusion PCV of 25-30% in dogs Or 20% in cats

Indications for blood transfusion are:??Evidence for circulatory collapse. A rapid drop in PCV to <20% in dogs or <15% in cats. An absolute PCV of 15-20%, depending on historical and presenting clinical signs. A PCV of <12%. Clear evidence of reduced oxygen carrying capacity.

2. Blood and blood products It is important to select the most suitable product for transfusion based on what is required. Products available include:??

Products Products Products Products

containing containing containing containing

everything - whole blood products cells - packed RBC, platelets*, WBC*
plasma proteins - plasma and its fractions none of the above - oxygen carrying solutions.

*Currently commercially unavailable in the UK.

2.1 Fresh whole blood (FWB)

Fresh whole blood is unaltered blood from a suitable donor. It should be harvested aseptically into a closed collection system. A single unit is ~450ml. It must be transfused within 8 hours or must be refrigerated after collection (making it stored whole blood - SWB).

It contains all blood products included red blood cells, platelets, white blood cells and labile and non-labile clotting factors. It is the most common agent transfused in practice, and is appropriate for animals that are haemorrhaging as a result of coagulopathies, thrombocytopaenia or due to trauma/surgical complications.

2.2 Stored whole blood (SWB)

Fresh whole blood that is not transfused within 8 hours can be refrigerated (<4degC) and stored, becoming stored whole blood. The storage life of SWB is around 3-5 weeks depending on the anticoagulant used. SWB lacks platelets, white blood cells and labile clotting factors. Once a transfusion has begun, it must be completed within 4 hours.

2.3 Packed red cells (PRC)

Packed red cells are prepared from whole blood by centrifugation. The whole blood is collected into a system where there is an extra bag for the plasma to be separated. The red cells are then re-suspended in a small volume of plasma and nutrient such as SAG-M (sodium chloride, adenine, glucose and mannitol). PRC is concentrated relative to whole blood (with a PCV of 70-80%) and can be administered with saline, although this is no longer considered necessary. The shelf life of PRC is 3-6 weeks depending on the preservative used (SAG-M provides 6 weeks of shelf life). PRC is useful in transfusions to treat anaemia due to haemolysis, chronic disease or erythropoietic failure where patients are volume deplete. PRC can also be used in conjunction with colloidal solution in animals requiring whole blood if this is unavailable.

2.4 Autologous transfusion

There are various types of autologous transfusion, including?

Harvesting blood from the patient ready for later transfusion when anticipating haemorrhage. Harvest of blood from acute cavity haemorrhage due to trauma/coagulopathies.

The benefit of autologous transfusion is that it reduces the potential for exposure to allogenic blood, reduces the risk of new infectious disease, reduces the chance of transfusion reactions and is immediately available. Scavenging systems are available but are not essential - surgical suction catheters, dialysis catheters or needles can be used as long as sterility is in place. Cavity blood drawn into sterile syringes can be driven back into the

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