Methodology for cross-matching feline blood
1. Assemble the required equipment:
• Personal protective equipment( PPE): gloves and apron
• Centrifuge, saline solution, pipette, syringe, plain tubes, EDTA and plain blood sampling pots.
2. Put on the PPE.
3. You will need blood samples from both the donor and the recipient – 1 ml of blood collected into an EDTA tube and 1 ml of blood in a plain tube.
4. Centrifuge all the samples for 5 min at 3,000 rpm and then pipette the serum and plasma into separate tubes. The plasma will not be used( unless it is required for further tests).
5. Add 2 – 3 ml of saline solution to the red blood cells( RBCs) and gently mix, then centrifuge for 1 min at 3,400 rpm. Remove the supernatant saline and repeat the process two more times. Remove the supernatant.
6. Mix 0.2 ml of the RBCs with 4.8 ml of saline to make a 4 % suspension. Do this for both the recipient and donor RBC samples.
7. Label four tubes and place the following in each:
• One drop of recipient serum and one drop of donor RBC suspension( major cross-match)
• One drop of donor serum and one drop of recipient RBC suspension( minor cross-match)
• One drop of recipient serum and one drop of recipient RBC suspension( recipient control)
• One drop of donor serum and one drop of donor RBC suspension( optional control).
8. Incubate the tubes at 37 ° C for 15 min. 9. Centrifuge the tubes at 3,400 rpm for 15 seconds.
10. Observe the tubes macroscopically for reactions( Figure 1, page 31).
11. Add one drop of the RBC / serum mixture to a microscope slide and cover with a cover slip. Examine under a light microscope at × 40 magnification. Incompatible samples will show clumps of RBCs( agglutination).
Calculating volumes
When administering blood transfusions, the main aim is to increase the recipient ' s packed cell volume( PCV) by 20 – 25 %. As a general rule, 2 ml / kg of whole blood is likely to increase the PCV by 1 % and 1 ml / kg of pRBCs will increase PCV by 1 % [ 8 ]. Alternatively, the following simplified calculation can be used [ 11 ]:
Desired increase in PCV(%) × 2 × bodyweight( kg) = volume to be infused( ml)
Blood transfusions can be uncertain procedures for both the recipient and the donor cat. As circulating volume is taken from the donor, this can result in reduced oxygenation of tissues and may result in long-term health complications.
Calculating specific blood volumes to transfuse will reduce the risk of excessive depletion of the donor ' s circulating blood volume.
As mentioned earlier, the amount of blood considered safe to be collected from a donor is 20 % of their blood volume every 4 weeks [ 11 ]. This is taking into consideration that the circulating volume of cats is 50 – 60 ml / kg so the recommended volume limit for collection is 10 – 12 ml / kg [ 11 ].
Monitoring the patient
VNs should monitor transfusion patients closely for, at a minimum, the first 30 min of the transfusion [ 11 ]. Ideally, transfusion patients should be monitored through close 1:1 nursing observations throughout the procedure; however, if this is not viable, then the patient should be checked every 15 – 30 min after the initial 30 min.
Blood transfusions are usually delivered over a period of 4 hours; this is to reduce the risk of bacterial contamination and the risk of erythrocytes becoming non-viable. Patient monitoring within this time frame is a critical nursing consideration to ensure prompt patient intervention if needed.
As part of monitoring, the patient ' s demeanour, heart rate, heart sounds / murmurs, electrocardiogram trace, respiratory rate and effort, body temperature and blood pressure should be constantly assessed to look for any abnormalities or parameters outside the normal ranges for cats.
The patient parameters should be recorded with accurate times on the transfusion records. These records should also include details of the recipient and of the donor blood. Any abnormal behaviours or signs such as shivering, vomiting or diarrhoea, hives, swelling or any signs of anaphylaxis [ 16 ] should be reported to the overseeing veterinary surgeon and addressed as necessary under their direction [ 2 ].
32 Veterinary Nursing Journal