INDICATIONS AND POINTERS FOR TRANSFUSION
One of the greatest quandaries is when to transfuse an anemic patient that has immune-mediated hemolytic anemia. Consensus on this is lacking, but Dr. Hohenhaus said she recommends transfusion in cases of brisk hemolysis, inadequate response to therapy, and worsening anemia.
For patients with immune-mediated thrombocytopenia (ITP), there is no set platelet number at which transfusion should be considered, but Dr. Hohenhaus noted that platelet-rich plasma should be used in patients that are actively bleeding.
In human medicine, there is also concern about dilutional coagulopathy in patients who receive multiple transfusions. Stored blood loses its clotting factors over time, so, in people, the recommendation is to give 1 unit of fresh frozen plasma for every 3 units of stored blood.
NEW RESEARCH AVENUES
Dr. Hohenhaus discussed new areas of research in veterinary transfusion medicine, such as leukoreduction of blood prior to transfusion. Reducing the number of white blood cells has been shown in some European studies in people to decrease the risk of lung injury and circulatory overload.
A recent retrospective study in dogs evaluated lactate concentrations to assess transfusion response.2 The study found that transfusion early in the course of treatment (within the first six hours of admission) corrected lactate concentrations faster and that correction of lactate concentrations was associated with an improvement in prognosis.
The utility of intravenous immunoglobulin (IVIg) for immune-mediated disease is an area of interest that warrants further research, Dr. Hohenhaus said. Some efficacy has been noted in using IVIg to treat patients with ITP; however, randomized head-to-head trials will be needed before it can be recommended as part of standard therapy.
1. Hohenhaus AE. Transfusion therapy in immune-mediated hematologic disease. Presented at the Annual Meeting of the American College of Veterinary Internal Medicine; June 2012.
2. Holahan ML, Brown AJ, Drobatz KJ. The association of blood lactate concentration with outcome in dogs with idiopathic immune-mediated hemolytic anemia: 173 cases (2003-2006). J Vet Emerg Crit Care 2010;20(4):413-420.