Veterinary Medicine - December 2008 - (Page 669)

poorer prognosis, a more recent study contradicted those ndings.12,29 Thromboembolism and anticoagulants DIC and thromboembolism are common causes of morbidity and mortality in patients with IMHA.1 The pathogenesis is largely unknown, but potential contributors include endogenous conditions such as blood ow stasis and hypercoaguability as well as exogenous factors such as repeated venipuncture, intravenous catheters, and glucocorticoid administration. Whether anticoagulant therapy is used at the time of diagnosis or added when thromboembolism is suspected is largely institution-dependent. Anticoagulants such as low-molecular-weight heparin, unfractionated heparin, warfarin, low-dose aspirin, and fresh-frozen plasma have all been used to prevent or treat this condition, although few studies have shown prolonged survival with their use.15 In one study, the use of fresh-frozen plasma (10 ml/kg) with unfractionated heparin (100 U/kg subcutaneously every six hours) failed to prevent thromboembolic complications in IMHA patients.38 Unfractionated heparin alone is generally not associated with an increased risk of bleeding, but neither is it associated with an improved outcome. Two studies failed to document increased survival with the use of unfractionated heparin.13,14 Another study demonstrated that relatively high doses of unfractionated heparin (300 to 375 U/kg subcutaneously every six hours) were needed to obtain target concentrations for anticoagulation, and even those concentrations may be inadequate in preventing thrombosis.39 If used, unfractionated heparin should be adjusted to prolong the activated partial thromboplastin time to 25% to 50% over baseline or to inhibit factor Xa to a target range of 0.35 to 0.7 U/ml. Low-molecular-weight heparin (150 to 200 U/kg subcutaneously every six to eight hours) is an alternative to unfractionated heparin and is starting to be used to treat thromboembolic disease in veterinary medicine. Low-molecular-weight heparins have better subcutaneous bioavailability, are better able to inhibit factor Xa, and likely can be given at a decreased frequency compared with unfractionated heparin. No clinical studies have been done to determine whether this drug is effective in preventing thromboembolism in patients with IMHA. Measuring antiXa activity is necessary to monitor the anticoagulant effects of this drug. The use of ultra low-dose aspirin (0.5 mg/kg orally once daily) in addition to immunosuppressive medications has shown clear promise in canine patients. The bene cial effects of aspirin are thought to be from vasodilation and modulation of platelet aggregation. One large study in dogs treated with glucocorticoids and azathioprine compared the use of ultra low-dose aspirin, unfractionated heparin, and a combination of these two medications.14 The results demonstrated that the patients treated with aspirin had signi cantly longer survival times than patients treated with unfractionated heparin alone. In this study, the use of aspirin was not associated with any adverse clinical effects, even when used with high-dose glucocorticoids. which if missed would make treatment unlikely to succeed. Finally, the quick detection of complications and the speedy removal of nonessential drugs that can cause an immune reaction can also help improve the chances of survival. Good nursing care that includes daily intravenous catheter care, proper nutrition, short walks, low-stress handling, and limited phlebotomy can also contribute to a better outcome. Peripheral intravenous catheter placement may be preferable to jugular placement in patients with the potential to develop a coagulopathy. Ancillary treatments and medications such as intravenous uids, gastric protectants, promotility drugs, and antinausea medications can all support a patient through the initial days of treatment. Intravenous uids, especially in patients with intravascular hemolysis, may help prevent hemogloblin nephrosis. Removing unnecessary indwelling catheters may reduce the risks of thromboembolism.15 LONG-TERM MANAGEMENT AND PROGNOSIS A steady or rising hematocrit, increasing reticulocytes, and decreasing spherocytes indicate a positive response to therapy.1 Medication tapering usually does not begin until the hematocrit is normal. Tailor drug tapering to the individual Supportive care Aggressive, detail-oriented supportive care is a critical factor for the successful treatment of IMHA. Timely recognition Medication tapering usually does not begin until the hematocrit is normal. and treatment of an underlying disease can allow immunosuppressive drug therapy to be tapered more quickly. Antibiotic administration while awaiting con rmation of suspected infectious disease can improve the chances of recovery. Thorough diagnostic testing can help detect underlying infectious or neoplastic causes of immune-mediated hemolysis, patient. Glucocorticoids can be tapered by about 25% every three to four weeks. If an underlying disease has been addressed or the response to treatment is rapid, drug tapering can occur more quickly. Measure the hematocrit ve to seven days after discharge and again after each decrease in drug dosage. Perform a complete blood count, reticulocyte VETERINARY MEDICINE December 2008 669

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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