Transfusion reactions in cats due to AB blood group incompatibility.

Blood transfusion reactions were investigated in 70 unsensitised and sensitised cats. Twenty-five compatible transfusions with respect to the AB blood group system did not result in any immediate transfusion reactions. Transfusion of B erythrocytes in 12 group A cats did not produce any severe reactions because of low anti-B titres in the A recipients. However, 30 of 50 group B cats (60 per cent) suffered severe shock reactions, characterised by marked hypotension, cessation of respiration and sometimes atrio-ventricular blocks, within two minutes of the injection of incompatible A cells (phase 1). From 35 seconds to five minutes later, markedly elevated blood pressures and extrasystoles were recorded (phase 2). The blood pressures generally stabilised within 30 minutes. Haemoconcentration and leucopenia were observed in severely reacting cats and leucopenia was also recorded in some A cats who received incompatible cells but did not exhibit transfusion reactions.