IMHA

Question 1

Define hemolytic anemia

Answer 1

the abnormal destruction of RBCs

Question 2

Define Immune Mediated Hemolytic Anemia (IMHA)

Answer 2

when it is the immune system that is targeting and destroying the RBCs

Question 3

Define idiopathic IMHA

Answer 3

the underlying cause of the immune mediated destruction of RBCs cannot be found

Question 4

What happens in idiopathic IMHA (describe the disease process)

Answer 4

body identifies normal RBCs as abnormal –> creates and then coats the RBCs with antibodies (IgG or IgM) –> RBCs get eliminated via immune cells or immune organs such as the spleen and liver

Question 5

Define secondary IMHA

Answer 5

another disease process somehow alters either the immune system’s perception of RBCs or it alters the RBCs themselves and stimulates the immune system to initiate destruction

Question 6

What things can cause secondary IMHA?

Answer 6

• blood parasites (Babesia, Hemobartonella)
• certain drugs (sulfas, methimazole)
• toxins (zinc)
• neoplasia

Question 7

Define intravascular hemolysis

Answer 7

RBCs are being destroyed by the immune cells directly within the blood vessel walls; often see red urine and is often more severe

Question 8

Define extravascular hemolysis

Answer 8

RBCs are being identified by certain immune organs (usually spleen) and removed from circulation within those organs

Question 9

3 Primary effects of hemolysis on the body

Answer 9

• anemia
• destroyed RBCs release Hgb
• increased risk for clot formation

Question 10

How does the body normally get rid of Hb?

What does the release of massive amounts of Hb do to the body?

Answer 10

Normal: Hb broken down into bilirubin by the liver and is then excreted thru bile into feces and thru kidneys into urine

Too much Hb: amount of bilirubin is so great that it can’t be excreted fast enough; bilirubin concentration in serum increases and not all Hb is able to be broken down into bilirubin; whole Hb molecules (nephrotoxic) are excreted thru kidneys which can lead to acute renal failure

Question 11

Why does clot risk increase?

Answer 11

• inappropriate activity of coagulation cascade makes PTE formation more likely
• also increases risk for DIC which causes organ failure and death

Question 12

Clinical signs of IMHA

Answer 12

• Signs associated with anemia (lethargy, weakness, exercise intolerance, collapse, V/D (hypoxia of GI tract), icterus, pale MMC, heart murmur)
• red colored urine due to hemoglobinuria

Question 13

Who has the greatest risk for IMHA?

Answer 13

-Dogs > cats
(although cats more susceptible to Hemobartonella present with secondary IMHA)
-females > males
-Breeds: American Cocker Spaniel, Poodle, Old English Sheep dog

Question 14

How to tell if there truly is nonregenerative anemia present

Answer 14

even regenerative anemia may look like nonregenerative anemia for first 36-72hrs. If blood is continually evaluated following that time window and there are no signs of regeneration in the coming few days, it can be declared nonregenerative

Question 15

Changes to CBC with IHMA

Answer 15

• nonregenerative anemia
• hemolyzed serum
• spherocytes (2+ or greater)
• autoagglutiation (RBCs coated in antibodies stick to each other)
• +/- polychromasia and increased nRBCs
• significant leukocytosis

Question 16

Changes to serum chem & UA with IMHA

Answer 16

• hyperbilirubinemia
• elevated liver enzymes
• hemoglobinuria

Question 17

What does the Coomb’s test do?

Answer 17

identifies the presence of antibodies on RBCs, but can get false negatives

Question 18

What is the common approach to treating IMHA?

Answer 18

suppress the immune system to the point that it cannot target RBCs and destroy them

Question 19

What medications are used for immunosuppression?

Answer 19

• Corticosteroids (Pred, prednisolone, dexamethasone, Soul-delta-courte)
• Cyclophosphamide
• Cyclosporin
• Azathioprine
• Danazol

Question 20

________________ are the only meds proven to be beneficial in IMHA treatment, but no med has been proven to ___________________.

Answer 20

Corticosteroids

improve survival

Question 21

What is the main thing that is done for hospitalized IMHA patients? Why?

Answer 21

IVF to help diuresis of excessive circulating Hb and to provide volume support to the circulatory system

This is done while waiting for immunosuppressive meds to kick in and start working.

Question 22

Pros of blood transfusion

Answer 22

provides additional RBCs to give additional O2 carrying support

Question 23

Cons of blood transfusions

Answer 23

• body will quickly recognize the transfused RBCs as foreign
• RBCs won’t be available long
• May make things significantly worse by making hemolysis worse and potentially initiation a severe transfusion reaction

Question 24

Is there a common recommendation for blood transfusions in IMHA patients?

Answer 24

No; but not disputed if patient will die unless this is tried