Blood transfusions in cats: A valuable useful resource requiring a thought of strategy

PICTURE: A blood transfusion can be a potentially life-saving procedure, but in each case the risks and benefits for the recipient and the donor cat must be carefully weighed. view More

Photo credits: Image: Samantha Taylor, BVetMed (Hons), CertSAM, DipECVIM-CA, MANZCVS, FRCVS

Blood transfusions are a common practice in medical practice in which donated blood is used to replace blood lost from injuries or surgery, or to treat serious illnesses. The procedure is not done as routinely when treating domestic cats – but it can be lifesaving as it is with humans. Donor availability has been a limitation in the primary care veterinary practice, but as blood banks grow, which allow better access to cat blood, the procedure is likely to become more general.

The International Society of Feline Medicine (ISFM) today published Consensus Guidelines in the Journal of Feline Medicine and Surgery (JFMS) to address the need for authoritative guidance not only on best practice but also on some important considerations beyond clinical procedure. 1 The authors, an international panel of veterinary experts with individual expertise in infectious diseases, anesthesia, critical care and medicine, have cumulative clinical experience in drawing blood and giving transfusions obtained from treating thousands of feline patients.

Blood is a valuable resource that is harvested for the benefit of one cat (the recipient) and of no benefit to the other (the donor). A fundamental tenet of ISFM advice is that the clinician is responsible for providing adequate care to both parties.

Treating a patient in need of a blood product is clinically challenging. Identifying the need for a blood product is only the first step. The clinician must determine a clear benefit for the recipient and critically ensure that type-compatible blood is administered. This requires a blood type for both the donor and the recipient cat. Whether an individual is Type A, B, or AB in the so-called AB blood group system that exists in cats is in part influenced by both geography and breed. Type A is the most common phenotype in the world and it is believed that, for example, Siamese cats are exclusively Type A. Type B is much less common in prevalence but is noted as not uncommon in cats with no pedigree in Australia and the UK as well. Type AB is rare.

Blood groups are created by genetically determined antigen markers (alloantigens) that are present on the surface of red blood cells. In contrast to dogs, cats have naturally occurring alloantigens against “foreign” (non-self) alloantigens. This makes the blood transfusion process difficult and can lead to potentially fatal blood transfusion reactions. While the risk of a transfusion reaction increases with subsequent transfusions, a reaction can occur with the first blood transfusion. In addition to blood typing, the guidelines discuss the benefit of “cross-matching,” where blood from the donor and recipient cats is mixed to test for a reaction prior to transfusion, and it is strongly recommended that all be cross-matched Recipients with an unknown transfusion history or previous transfusion reaction.

One of the particular challenges of blood transfusion in cats is that there are risks to the donor as well – in terms of the often required sedation, as well as venipuncture and blood collection itself. While careful technique can help reduce the risks, it does A relatively unique situation in the veterinary clinical practice as a particular intervention is of no benefit to the donor animal. An attached appendix, which discusses ethical considerations regarding blood transfusion, recognizes in the guidelines that “donors” may be inappropriate in this context as it implies consent or a “gift” that cats cannot decide on themselves . “Harvesting” may be a more accurate, if less convenient, term for drawing blood.

Often times, donor cats are owned by clinicians or other cats owned by recipient cats. Sometimes donor cats can volunteer after a public appeal. Many veterinary clinics keep a register of suitable donors who can be retrieved when needed. Unowned cats may also be used in some areas. The guidelines emphasize that the clinician’s duty of care extends to the owner or carer of the donor cat, who must be well informed about the process and the risks. To help with this, International Cat Care, the parent company of ISFM, has created a resource (available at icatcare.org/advice/cat-carer-guides) that explains what to expect when owners are considering their cat to volunteer as a blood donor or, in fact, if your cat needs a blood transfusion. When pre-collected blood products are purchased through a blood bank, the origin of the blood products and the welfare of the donors who supply the blood bank must also be verified by the clinician.

Making informed decisions about the use of blood products in cats requires that the veterinarian carefully consider the clinical benefit to the recipient cat, the suitability and welfare of the donor cat, and the ethical justification for the procedure. The aim of these new guidelines is to facilitate this process and to ensure that the health and wellbeing of recipient and donor cats are equally prioritized.

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References

1. Taylor S., Spada E., Callan MB, et al. 2021 ISFM Consensus Guidelines on Collection and Administration of Blood and Blood Products in Cats. J Feline Med Surg 2021; 23: 410-432. Available at: https://journals.sagepub.com/doi/full/ 10.1177 / 1098612X211007071

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