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canine immune mediated haemolytic anaemia - Coggle Diagram
canine immune mediated haemolytic anaemia
clinical presentation
mean age 6 years, uncommon under 1, but can occur at any age
non specific signs: lethargy, loss of appetite, vomiting, diarrhoea
PE
may reveal signs consistent with anaemia
tachycardia, tachypnoea, rapid heart rate, pale mm and systolic murmur
yellow to orange discolouration of faeces and red urine are consistent with haemolysis
concurrent thrombocytopenia causing petechiae reported in 2-5% of IMHA cases and may be due to immune-mediated platelet destruction (evans syndrome)
splenomegaly and hepatomegaly in up to 40% of cases
laboratory testing
anaemia (severe ht <12-14%)
usually reticulocyte numbers increase during the first days of hospitalisation as adequate time has elapsed for BM response to begin
inflammatory leukogram
pronounced leukocytosis with left shift is common and monocytosis in about 50% of dogs
decreased platelet counts common
PT and APTT may be increased
this in combination with thrombocytopenia suggests DIC
further supported by low fibrinogen concentrations (although this may be increased in acute phase response)
diagnosis
direct agglutination test (coombes test) detects erythrocyte bound immunoglobulins and complement
spherocytes from partial phagocytosis of antibody coated RBC membranes are characteristic of IMHA
differentials
secondary IMHA develops if antibodies on RBC surfaces occur during or after infection, neoplasia, administration of some medicines or possibly vaccination
treatment
immunomodulation to decrease erythrophagocytosis and suppress immunoglobulin production
if anaemia is severe and compromising tissue oxygenation, blood transfusions may be necessary
prednisolone initially 2mg/kg/day
if oral medication not appropriate --> dexamethasone (0.2-0.3mg/kg/day) IV/SC
Hct assessed daily and when stabilises, continue at initial dosage for additional 3 days, then 1.5mg/kg/day for 14 days. If dog improves, give same dosage but on alternate days for 14 days and then taper to 0.25mg/kg q 48h for 21 days
therapy effectiveness should be assessed at 4 and 10 weeks after beginning tx
if dog completely recovered, defined as Ht >36% then prednisolone protocol should be completed, if relapse revert to initial dose of 2mg/kg/day
thromboprophylaxis
most dogs with iMHA are in a hyper-coagulable state and at risk for thromboembolic events
prognosis
it is estimated that 65% of dogs with IMHA survive the first year
most deaths occur in the first 2 weeks after diagnosis
thromboembolism, renal or liver failure
haemolysis may be difficult to control in some dogs, resulting in need for blood transfusions
in some dogs with IMHA their BM is slow or fails to regenerate RBCs (non-regenerative IMHA) may be due to BM damaged by hypoxia during the initial haemolytic crisis or thromboembolism within the BM
differentiate from pure red cell aplasia, since the conditions and responses to treatment differ