IMHA

Question 1

IMHA

Answer 1

• Life threatening
• Common in dogs and rare in cats
• Characterised by type II immune reaction where RBCs coated with immunoglobulin, complement or both are removed from circulation bu direct destruction or phagocytosis

Question 2

Primary IMHA

Answer 2

• Idiopathic
• autoimmune hemolytic anemia
• true autoimmune reaction against self antigen on erythrocytes

Question 3

Secondary IMHA

Answer 3

• associated with presence of a foreign antigen
• stimulates immune system to destroy erythrocytes without a true autoantibody
• triggers: systemic infections, drugs and neoplasia
• more common than primary in cats
• non immune mediated : direct RBC destruction from disorders such as Dirofilaria immitis infection and vena-caval syndrome (hemolysis occur due to trauma to the RBCs when they circulate through parasite thrombus)

Question 4

What kind of dogs and cats are predisposed to IMHA?

Answer 4

Female dogs and male cats

Average age of 6.5years for dogs and 3 years for cats

Question 5

Signs and symptoms of IMHA

Answer 5

*Lethargy, depression, anorexia for 3 days or more, discoloured urine, vomiting, diarrhoea, dyspnea,

Question 6

Seasonal component to IMHA

Answer 6

Spring and summer

Question 7

Initial physical exam findings

Answer 7

Pallor, tachycardia, fever, icterus, cranial organomegaly, lymphadenopathy, petechiae

Cats: hypothermic

Systolic heart murmur, hyper dynamic pulse quality, dyspnea, collapse

Question 8

PCV in IMHA patient

Answer 8

Less than 25% and as low as 6%

Spherocytosis common in 85-95% of cases (difficult to identify in cats due to size)

Question 9

Signs of regeneration

Answer 9

Polychromasia, anisocytosis, macrocytosis, nucleated RBCs, reticulocytes

Question 10

Nonregenerative anaemia

Answer 10

• found in up to 50% of dogs and most cats at presentation

* dogs take 3-5 days while cats take 7 days to regenerate

Question 11

Thrombocytopenia

Answer 11

*occur in 50-70% of dogs and rare in cats

Question 12

Combination of thrombocytopenia and hemolytic anaemia

Answer 12

Evan’s syndrome

Question 13

Serum biochemical adnormalities

Answer 13

Total bilirunin elevation, hepatic transaminase and alkaline phosphatase elevation, azotemia, and hyperglobulinemia.

Urinalysis shows bilirubinuria or hemoglobinuria

Question 14

DIC

Answer 14

Prolonged coagulation times (prothrombin time, activated partial thromboplastin time) and increased fibrin degradation products and d-dimers are consistent with DIC

Question 15

What test is used to diagnose IMHA?

Answer 15

Spontaneous macroagglutination on slide agglutination test is diagnostic when rouleaux formation has been ruled out by saline washing

• Not all dogs will hav autoagglutination
• Macroagglutination is not diagnostic of IMHA in cats

Question 16

How is slide agglutination test performed ?

Answer 16

• one drop of EDTA-blood on a glass slide and gently mixing with one drop of saline
• slide is gently rocked while being observed for clumping of RBCs (macroagglutination)

Question 17

Coomb’s test

Answer 17

• direct antiglobulin test (DAT)
• used to detect anti-erythrocyte antibody or complement on the surface of RBCs
• Mixing of anticoagulated patient RBCs with rabbit or goat anti-canine (or anti-feline) immunoglobulin or complement which reacts with immunoglobulin or complement-coated RBC to result in aglgutination
• positive in 35-60% of dogs with IMHA
• can produce false positive and negative results

Question 18

Treatment for IMHA

Answer 18

• no single best treatment
• supportive care to treat anemia - IVF crystalloids
• minimise risk of secondary complications
• immunosuppresive drug therapy - Glucocorticoids: prednisolone PO, dex IV if PO not tolerated
• potentially secondary immunosuppressive drugs: azathioprine and cyclosporine
• potential blood transfusion: packed RBCs over whole blood
• less volume
• less chance of reaction to plasma proteins

Question 19

What is the risk of IV catherization in patients with IMHA?

Answer 19

It increases the risk of pulmonary thromboembolism

-the most common cause of death for dogs with IMHA

Question 20

How do you determine when to transfuse an IMHA patient?

Answer 20

Based on presence of clinical signs of weakness, tachycardia, tachypnea, rapidly decreasing PCV

Question 21

Drawbacks of transfusion therapy

Answer 21

• suppression of erythropoietin response
• prolongation of time to erythroid recovery
• possibly increased risk of pulmonary thromboembolism
• presence of autoantibodies may shorten survival of transfused red cells

Question 22

Complications of IMHA

Answer 22

• Thromboembolism
• indicative of patient in hypercoagulable state
• risk factors for development of thrombophilia and thromboembolism
• blood stasis
• hypercoagulability
• vascular endothelial injury
• hyperbilirubinemia
• hypoalbuminemia
• severe thrombocytopenia

Question 23

Where is the most common location of clinically evident thromboembolism?

Answer 23

The pulmonary system

-cerebral thromboembolism can also occur

Question 24

Clinical signs of thromboembolism in the pulmonary system?

Answer 24

Acute respiratory difficulty
Orthopnea
Profound anorexia
Acute neurologic decompensation 
Neuro-lateralizing signs 
Sudden death

Question 25

What anticoagulant therapy can you use to treat suspected hypercoagulability associated with IMHA?

Answer 25

Heparin require antithrombin to be effective and antithrombin is decreased in dogs with IMHA- hence not an effective anticoagulant