Veterinary Medicine - December 2008 - (Page 668)

Immune-mediated hemolytic anemia PEER-REVIEWED Leﬂunomide. Le unomide (4 mg/kg orally once daily), an inhibitor of pyrimidine biosynthesis, has been used to treat rheumatoid arthritis in people and granulomatous meningoencephalomyelitis, neoplasia, and graft rejection in dogs. Limited but favorable reports exist on the use of this drug for treating IMHA. Side effects in dogs appear to be minimal but can include vomiting, lymphopenia, and anemia. The recent introduction of a generic form may make it less costly for routine treatment. The dose should be adjusted to Liposomal-encapsulated clodronate. Liposomal-encapsulated clodronate (dichloromethylene diphosphonate) is the focus of two studies, one of which is ongoing at Colorado State University.35,36 Clodronate is a bisphosphonate that, when incorporated into liposomes, is rapidly phagocytized by macrophages leading to apoptosis. Intravenous liposomalencapsulated clodronate has been shown to signi cantly reduce the number of canine splenic macrophages and dendritic cells in vitro, thereby obstructing the clearance of antibody-coated RBCs. This Consider splenectomy only in patients that have not responded to immunosuppressive medications, require high-dose and long-term medications to maintain a remission, or are experiencing severe side effects from medications. As there is a risk of developing marked infection after splenectomy, it is not recommended for patients taking multiple immunosuppressive medications.1 Treating tissue hypoxia Patients with IMHA often need oxygencarrying uids to support them through the rst few days of care until immunosuppression begins to control the disease process. Oxygen alone is rarely bene cial in severe anemia, unless a patient’s clinical signs are complicated by thromboembolism. The criteria for transfusion are not rigid but may include the presence of severe tachypnea, dyspnea, tachycardia, cold extremities, weakness, mental depression, or a hematocrit under 15%. If a patient appears comfortable when resting in a cage but becomes agitated and clinically unstable during necessary procedures (radiography or ultrasonography), give a transfusion before proceeding. The choice of administering packed RBCs, whole blood, or synthetic hemoglobin can be controversial and is often institution-dependent. Ideally, only the necessary component should be given. As transfusion reactions can occur in patients that have not had transfusions previously, crossmatching should be done before transfusion in all non-autoagglutinating patients. Also perform cross-matching in any dog that has received a prior blood transfusion. Since autoagglutination may interfere with accurate blood typing and crossmatching, packed RBCs should only be administered from universal donors (DEA 1-7 negative blood; DEA 4 can be positive) in dogs with IMHA.15 Administering puri ed polymerized bovine hemoglobin solution (Oxyglobin—Biopure) can be bene cial in cases in which crossmatching is not possible or compatible blood is not available. Although one study noted that Oxyglobin administration was associated with a Patients often need oxygencarrying uids through the rst few days of care. maintain a serum trough concentration of 20 µg/ml.31 IVIG. Intravenous human immunoglobulin (IVIG) (0.5 to 2 g/kg intravenously daily, given over six to 12 hours) has been infrequently used to treat a variety of immune-mediated diseases in dogs, including IMHA. The mechanism of action of IVIG is thought to be a blockade of the Fc receptors on macrophages, thereby reducing phagocytosis of antibody-coated RBCs, interfering with complement, and suppressing antibody production. In addition, IVIG inhibits erythrocyte phagocytosis by binding to canine monocytes and lymphocytes and possibly by an anti-idiotypic downregulation of antibody production. IVIG can be given to patients with IMHA as a single infusion or on two or three consecutive days.34 Although IVIG appears to impart short-term bene ts (re ected by a rising packed cell volume and reticulocytosis) within days of infusion, long-term bene ts were not seen. No complications have been seen with a single IVIG infusion in dogs. Unfortunately, IVIG is also costly and dif cult to obtain.30 reduction, in effect, slows the clearance of opsonized erythrocytes and allows time for the other immunosuppressive drugs to work. The initial study, involving intravenous infusion of liposomal-encapsulated clodronate in healthy dogs and in seven dogs with IMHA, found that the drug is rapid-acting and well-tolerated.35 In that study, results were favorable, and dogs treated with liposomal-encapsulated clodronate in conjunction with prednisone, azathioprine, and heparin demonstrated an improved survival. Splenectomy Splenectomy is considered one of the last-choice treatments in canine IMHA. The bene ts arise from removing one source of B cells and splenic macrophages, the primary culprits in the removal of antibody-coated erythrocytes.24 It is undetermined how effective this procedure is in routine IMHA cases, since only one recent clinical study has been done to assess it as a forerunner of treatment.37 Although this study did show increased survival with splenectomy (58% survival vs. 37.5% in the control group), the sample size was small. 668 December 2008 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - December 2008

Veterinary Medicine - December 2008 Contents Letters Thanking Our Valued Reviewers Practical Matters Idea Exchange Why Do Dogs and Cats Eat Grass? Managing Atypical and Critical Cases of Primary Hypoadrenocorticism in Dogs Behaviors Suggestive of Postoperative Pain in Cats What to Consider When Considering Digital Radiography Avoid Common Bandaging Mistakes in Dogs and Cats IMHA: Diagnosing and Treating a Complex Disease CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - December 2008

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