Veterinary Clinical Medicine-I (General and Systemic)

BLOOD TRANSFUSION 

                  

Rationale for therapy

• Whole blood is a mixture of cellular constituents suspended in a liquid transport medium. The cells have different functions. Erythrocytes carry oxygen and participate in host defense by surface adsorption and absorption of many materials, phagocytes control bacteria, platelets are required for hemostasis, and lymphocytes mediate immunity. The liquid medium also contains an array of dissolved substances: albumin, globulins, coagulation proteins, metabolic intermediates, electrolytes, organic anions, and trace elements. Practical techniques for separation and concentration of some of the cellular constituents of whole blood are within the capabilities of all major veterinary blood donor centers. Modern transfusion therapy should be based upon use of components to treat specific defects with concentrates of the deficient blood constituent.

Consideration of the limited resource

• The most cogent argument supporting component therapy is that blood is a precious resource considering its therapeutic potential and the logistics and costs required in obtaining and delivering blood products. Separation into components permits a single donation to meet the individual needs of more than several patients. Blood donor screening eligibility criteria should be sufficient to obtain a safe donation.

Kinetic Considerations

• Following hemorrhage, homeostatic mechanisms restore the various blood constituents at differing rates, depending on the capacity for synthesis, endogenous consumption, degradation, and distribution in various physiologic compartments. The half inactivation time of canine and feline red cells is in terms of months whereas the half-life of albumin is just three to four days. Surgical blood loss may require restoration of red cells. Albumin may not be required as it will be restored within several days. Another consideration is tolerance. Loss of fifty percent of red cell mass is well tolerated in a healthy individual whereas loss of fifty percent of blood volume can be fatal unless rapidly corrected.

Consideration of Adverse Effects

• Other rationale for supporting the use of blood components include the myriad of possible adverse effects that can result from transfusion of unnecessary blood constituents. Any transfusion reaction means that the transfusion is not doing the intended job and, importantly, has burdened a patient already burdened by the physiologic state requiring transfusion. Sensitization to blood cells can result in refractory results in subsequent transfusions. Transfusion of multiple units of whole blood sequentially in order to achieve a certain hematocrit may also produce pulmonary edema due to volume overload.

Blood Donor Screening

• All blood donors should be given thorough physical examinations at each donation and be annually screened hematologically, biochemically, and serologically. Donors should be healthy, receiving adequate nutrition, and be parasite free. All donors should be blood typed and be current on appropriate vaccinations. Female donors should not have had pups or kittens and preferably not be intact. In addition, all canine donors should be screened for brucellosis, heartworm microfilaria, ehrlichiosis, Rocky Mountain spotted fever, trypanosomiasis, and systemic mycoses. Feline donors should be house cats not allowed to roam. Cats should be screened for retroviruses, heartworm microfilaria, toxoplasmosis, and hemobartonellosis.