IMHA Flashcards
Define hemolytic anemia
the abnormal destruction of RBCs
Define Immune Mediated Hemolytic Anemia (IMHA)
when it is the immune system that is targeting and destroying the RBCs
Define idiopathic IMHA
the underlying cause of the immune mediated destruction of RBCs cannot be found
What happens in idiopathic IMHA (describe the disease process)
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
Define secondary IMHA
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
What things can cause secondary IMHA?
- blood parasites (Babesia, Hemobartonella)
- certain drugs (sulfas, methimazole)
- toxins (zinc)
- neoplasia
Define intravascular hemolysis
RBCs are being destroyed by the immune cells directly within the blood vessel walls; often see red urine and is often more severe
Define extravascular hemolysis
RBCs are being identified by certain immune organs (usually spleen) and removed from circulation within those organs
3 Primary effects of hemolysis on the body
- anemia
- destroyed RBCs release Hgb
- increased risk for clot formation
How does the body normally get rid of Hb?
What does the release of massive amounts of Hb do to the body?
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
Why does clot risk increase?
- inappropriate activity of coagulation cascade makes PTE formation more likely
- also increases risk for DIC which causes organ failure and death
Clinical signs of IMHA
- 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
Who has the greatest risk for IMHA?
-Dogs > cats
(although cats more susceptible to Hemobartonella present with secondary IMHA)
-females > males
-Breeds: American Cocker Spaniel, Poodle, Old English Sheep dog
How to tell if there truly is nonregenerative anemia present
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
Changes to CBC with IHMA
- nonregenerative anemia
- hemolyzed serum
- spherocytes (2+ or greater)
- autoagglutiation (RBCs coated in antibodies stick to each other)
- +/- polychromasia and increased nRBCs
- significant leukocytosis
Changes to serum chem & UA with IMHA
- hyperbilirubinemia
- elevated liver enzymes
- hemoglobinuria
What does the Coomb’s test do?
identifies the presence of antibodies on RBCs, but can get false negatives
What is the common approach to treating IMHA?
suppress the immune system to the point that it cannot target RBCs and destroy them
What medications are used for immunosuppression?
- Corticosteroids (Pred, prednisolone, dexamethasone, Soul-delta-courte)
- Cyclophosphamide
- Cyclosporin
- Azathioprine
- Danazol
________________ are the only meds proven to be beneficial in IMHA treatment, but no med has been proven to ___________________.
Corticosteroids
improve survival
What is the main thing that is done for hospitalized IMHA patients? Why?
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.
Pros of blood transfusion
provides additional RBCs to give additional O2 carrying support
Cons of blood transfusions
- 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
Is there a common recommendation for blood transfusions in IMHA patients?
No; but not disputed if patient will die unless this is tried
