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Introduction
Blood products are extremely useful and can be administered to animals suffering from a variety of diseases, including anaemia following haemolysis or haemorrhage, sepsis, coagulopathies, specific factor deficiencies and disseminated intravascular coagulation. The decision to give a patient a blood transfusion depends on a number of factors, including the patients Packed Cell Volume, any patient with a PCV lower than 20% should be considered for a transfusion. Additionally the onset of the anaemia whether it is acute or chronic is important and also on the clinical picture portrayed by the animal. Signs including tachycardia, bounding peripheral pulses, tachypnoea, collapse, weakness and lethargy all suggest that a blood transfusion may be necessary.
Blood groups
The number of blood groups varies between the domestic species and are determined by the presence of antigenic components on the surface of the red blood cells. Cattle have the most complex blood group systems while cats are quite simple. Normally an animal will not have antibodies against antigens present on the surface of its own red blood cells or against blood group antigens of that species unless they have been produced following pregnancy, a previous transfusion or a vaccine reaction. In order to achieve a safe blood transfusion blood typing and sometimes crossmatching of the donor and recipient patient is required. Transfusion of the incorrect blood type can lead to haemolytic transfusion reactions which can be fatal.
Initial collection of blood gives fresh whole blood. Generally this is the product most frequently used however different blood products are available and are frequently used in referral practices. Whole blood can be stored or separated into packed red blood cells, plasma, or platelet rich plasma concentrates. Giving blood components over whole blood is advantageous as it reduces the number of transfusion reactions and also allows specific replacement therapy.