Xenotransfusion refers to the administration of blood products between species. In a clinical veterinary context, this often means administering canine red blood cells to feline patients. This situation may arise due to the differential availability of canine and feline blood products; a lack of access to type B feline blood; or insufficient time to blood type a patient prior to the need for blood product administration. It has been previously demonstrated in case reports and retrospective series that the one-time administration of dog blood to a cat is tolerated, however it has been suggested that the half life of these transfused cells is low, and that major and minor cross matches almost invariably occur in vitro. There is, however, a lack of well-designed prospective literature on the subject of xenotransfusion.
This study was designed as a prospective observational study of cats presenting to two veterinary teaching hospitals over a ~2y period. Cats who required an urgent transfusion (ie the clinician felt there was a high risk of death within 6h without transfusion) where the appropriate feline blood product was not available, the transfusion medicine service deemed the situation appropriate, and informed consent was present where eligible to receive canine blood if no previous xenotransfusion had occurred.
A standard transfusion protocol was applied that involved screening the donor for blood type (A/B and DEA 1), measuring standard lab values, and performing a cross match (though due to urgency this did not always occur prior to transfusion). Cats were generally transfused with 1mL/kg pRBC with a transfusion goal of 25% at clinician’s discretion. Standard transfusion monitoring occurred.
Forty-nine cats received a xenotransfusion and were included in the study. 34.7% of transfusions were due to surgical blood loss, 28.6% IMHA, and 28.6% neoplasia. There was one case each of IBD, AKI, coagulopathy, and oral ulcers (presumable Menrath’s ulcers but not specified as such). 61% of cats were type A, 28% type B, 6% type AB, and two were not typed. Crossmatches were performed in 29 cats with major incompatibilities in 69% and minor in 31%, with only 24% compatible for both.
Six cats (12.2) experienced febrile non hemolytic reactions during transfusion, which prompted stopping and restarting in 2 cases. There was no difference in reaction rate based on cross match compatibility. Five cats died during transfusion; one was undergoing CPR at the time of transfusion; two were euthanized due to diagnostics performed during transfusion; and two did not stabilize. Three were euthanized during the first 12 hours due to poor prognosis associated with primary disease. No animal died as a result of transfusion reactions. No acute reactions other than febrile-non-hemolytic occurred.
Of the surviving patients, a delayed hemolytic reaction occurred in 64% with a median onset of two days. No cat died as a result of this reaction.
There are some limitations present to this study. Among these are the relatively small sample size (though larger than most previous publications on the subject) and the lack of a control group (ie matched patients receiving feline blood). The design of the trial meant that enrolled animals may have represented a different population than the general transfusion population, as they were screened as requiring a xenotransfusion. The authors may also have under reported the onset of delayed transfusion reactions due to discharge or euthanasia of patients.
Overall, this paper suggests that there may be a place for xenotransfusion in veterinary medicine. Feline blood is obviously the preferred option when type-matched product is available. However, in situations where this is not practical or attainable a single xenotransfusion will have a low risk of serious transfusion reactions and, while the increase in hematocrit is not durable, it will allow a few days to stabilize the patient and/or attain appropriate blood products. (MRK)
Euler CC., Raj K, Mizukami K., et al. (2016) Xenotransfusion of anemic cats with blood compatibility issues: pre- and posttransfusion laboratory diagnostic and crossmatching studies. Veterinary Clinical Pathology 45, 244-253