Veterinary Clinical Medicine-I (General and Systemic)

CROSSMATCH OF BLOOD 

• Crossmatching reveals the presence of naturally occurring isoantibodies or antibodies generated in response to a previous incompatible transfusion. Crossmatching does not prevent sensitization of the patient to future transfusions. In fact, even though a specific blood donor is crossmatch compatible with the patient, if five or more days have elapsed since the first transfusion, another crossmatch must be performed if more blood products are to be administered and especially when the same donor blood products will be used.
• Crossmatching is a simple technique that can be performed with standard laboratory equipment. A major, minor, and autocontrol crossmatch should be performed although the minor crossmatch is rarely used in dogs. The major crossmatch should always be compatible at room temperature and at 37 degrees Celsius (°C).
• The following is a simple (nonpurist) major crossmatch protocol (donor red cells and patient serum or plasma):
• Centrifuge EDTA or citrated DONOR blood at the LOWEST centrifugal rate possible on your centrifuge...for about 10 minutes.
• Remove 0.2 mLs of packed and place in 4.8 mLs of normal (0.9%) saline. Mix. (There are now 5.0 mLs in the tube; this essentially replaces washing step.)
• Place 0.1 mL of this mixture into three small test tubes.
• Place 0.1 mL of PATIENT serum or plasma into each of the three tubes described above. Each tube will now have 0.1 mL of the donor red cell-saline mixture and 0.1 mL of patient serum or plasma, a total of 0.2 mLs each.
• Incubate-for 15 minutes-one tube at 37 degrees C, one at room temperature (25 degreesC), and one at refrigerator temperature (4 degrees C).
• Centrifuge briskly for one minute.
• Examine the supernatant for any hemolysis. Any hemolysis indicates crossmatch incompatibility.
• Examine the cell button. Flick or swish the test tube. The fluid in the tube should redden as red cells disperse. If the button is agglutinated or microagglutinated (examine a drop under low microscopic power), this indicates crossmatch incompatibility. To complete the minor crossmatch, use patient red cells & donor serum or plasma. To complete the autocontrol use patent red cells and patient plasma. In dogs the minor crossmatch is useful for a patient receiving multiple plasma product transfusions.