Equine Anemia Flashcards
What is Anemia?
- Decrease in circulating RBC mass
- Decreased Pack Cell Volume
- Decreased RBC
- Hemoglobin decreased except with intravascular hemolysis
What sites for Bone Marrow Biopsy are used in horses?
- Rib
- Sternum
What are the (broad) causes for anemia?
- Blood loss
- Destruction/Hemolysis
- Decreased Production
How is Regenerative vs. Non-regenerative anemia determined in horses?
- Horses do NOT release immature RBC into peripheral circulation
- May see a mild increase in anisocytosis and MCV
- Only way to determine Regenerative is w/ bone marrow biopsy
- or wait 3 days to see if RBC# increases
How can Internal hemorrhage and external hemorrhage be differentiated (I.e. GI bleed into lumen vs hemothorax)
-
Internal: bleeding into the body cavity, ~⅔ of RBCs are autotransfused back into circulation w/in 24-72hrs
- rest are phagocytized back - iron is reused
- External: blood is lost to outside, iron is lost
What are the clinical signs of Blood Loss Anemia?
- Increase in HR & RR
- Pale mucous membranes
- poor venous distention
- weakness
- fainting
- Frequently have heart murmur
- changes in blood viscosity
How is Blood loss Anemia diagnosed?
- PCV and TP initially normal
- Start reduction by 4-6hrs, takes up to 24hr for complete redistribution
- Splenic Contraction - adds RBC to peripheral blood
- Regeneration of RBC should start to be evident at 3 days, max response in 7 days
- PCV will increase about 1% or less a day
What is the treatment for Blood loss anemia?
- Stop the bleed
- surgical hemostasis
- aminocaproic acid
- Yunnan Baiyo
- Formalin
- IV fluids - for severe acute hemorrhage - restore ‘volume’
- Blood transfusion -
- signs of shock (PCV from 18% to 12% depends on speed of bleed)
- Acute < 15-18%
- Chronic <12%
- signs of shock (PCV from 18% to 12% depends on speed of bleed)
What is Blood transfusion crossmatching?
- Major cross match: compatibility between donor RBC and any alloantibody in patient’s plasma
- Minor cross match: compatibility between alloantibody in donor’s plasma and patients RBC
What is a ‘universal donor’ for equine blood transfusions
- Donors that do not have Aa or Qa blood types
- also lack Aa or Qa antibodies in plasma
What are the clinical signs of Chronic Blood loss?
- Animals will tolerate a much lower PCV than with acute blood loss
- Weight loss
- ill thrift
- pale mucous membranes
- heart murmur (viscosity related)
- exercise intolerance
- signs of shock if severe enough
How is chronic blood loss diagnosed?
- Find source of blood loss
What is the treatment for chronic blood loss?
- stop bleeding
- supplement with dietary iron if necessary
what causes Chronic Blood loss?
- Immune mediated destruction
- Oxidative injury to the RBC
- Infectious agents
- may increase RBC fragility
- may induce IMHA
- Iatrogenic
- hypo or hypertonic drugs
- Liver or Renal hemolysis
How can intravascular hemolysis and extravascular hemolysis be differentiated?
- Intra:
- Hemoglobinemia (pink plasma)
- icterus
- hemoglobinuria (red/brown urine)
- Extra:
- intense icterus
What is Immune Mediated Hemolytic Anemia? (IMHA)
- Antibodies to RBC
What are the clinical signs of IMHA in Horses?
- Depend on intra/extravascular hemolysis
- Fever
What bloodwork is common in horses with IMHA?
- Anemia
- +/- pink plasma (intravascular hemorrhage)
- ⇡ total & indirect bilirubin
how is IMHA diagnosed?
- Detection of antibody on RBC
- Coomb’s test
-
Direct immunofluorescence/Flow cytometry
- IgG, IgA, IgM
- Autoagglutination
What causes false negatives on a Coomb’s test?
- Use of steroid prior to testing
- rapid hemolysis of RBC that have antibody on them
What causes IMHA in horses?
- Drugs - penicillin
- Infectious agents
- equine infectious anemia
- streptococcal
- clostridial infections
- Piroplasmosis
- Neoplasia - lymphosarcoma
- Maternal antibody - neonatal isoerythrolysis
- Idiopathic IMHA
What is the treatment for IMHA in horses?
- Stop all previously administered drugs
- remove/treat underlying disease
- immunosuppression (steroids)
- blood transfusions (if necessary - concern for reactions)
- prevention of hemoglobin induced nephrotoxicity (use of fluids)
What does oxidative injury do to RBCs?
- Heinz body formation
- oxidized, precipitated hemogglobin
- appear as round, blue-black granules on RBC membrane
- can see w/ New Methylene Blue stain
- Result in damage to RBC membrane → Invtravascular hemolysis
- methemoglobinemia
- heme iron oxidized from ferrous to ferric
- Can’t carry oxygen
- Mucus membranes will appear brown
What causes Oxidative injuries to RBCs in horses?
- Wilted Red Maple leaves (Acer rubrum)
- Wild onions - n-propyl disulfide
- phenothiazines
- Nitrate poisoning - methemoglobin only → no intravascular hemolysis
What are the clinical signs of Red Maple toxicosis?
- Rapid death
- several days of hemoglobinuria
- brown mucus membranes
- high heart rate
How is Oxidative RBC injury diagnosed?
- Rule out IMHA
- look for Heinz bodies
- Methemoglobinemia (normal <1.77%)
- Red Maple can cause up to 50%
How is RBC Oxidative Injury treated?
- Blood transfusions may be necessary
- fluids to prevent hemoglobin-induced nephrotoxicity
- Large doses of Vit C
- Supportive Care
What causes Nonregenerative Anemia in horses?
- Anemia of chronic disease - common (mild anemia)
- Iron deficiency - uncommon
- Bone Marrow Suppression - rare
- drugs or neoplasia
What does Anemia of Chronic disease look like? (on blood smear)
- Mild to moderate anemia
- Normocytic
- normochromic
- non-regenerative
- Does NOT result in clinical signs
- treatment not necessary
What is the pathophysiology of Anemia of Chronic Disease?
- Basic cause - lack of iron mobilization
- inflammation results in increased production of hepcidin (protein from the liver)
- ⇡Hepcidin → ⇣Ferroportin → iron trapped intracellularly (not available for RBC production)
- inflammation results in increased production of hepcidin (protein from the liver)
What is Ferroportin? purpose?
- Transmembrane protein present on enterocytes, macrophages, liver cells
- Transports iron out of the cell
How is Anemia of Chronic Disease Diagnosed?
- Mild anemia and chronic disease
- Bone Marrow - document non-regenerative anemia
- Serum iron conc. ⇣
- indices of iron storage are normal
What is Iron deficiency? what does it look like on blood smear? causes?
- Uncommon
- Serum iron concentrations decreased
- indices of iron storage also decreased (ferritin, bone marrow staining for iron)
- Blood Smear:
- non-regenerative
- microcytic
- hypochromic
- Cause: chronic external blood loss
What causes Bone Marrow Suppression in horses?
- Drugs:
- recombinant human erythropoietin
- autoantibodies that cross react with equine erythropoietin
- SMZ (pancytopenia)
- recombinant human erythropoietin
- Neoplasia - myelophthisis
- accumulation of abnormal cells in bone marrow
- Viral - Equine Infectious Anemia
- Chronic Renal Failure
- lack of erythropoietin production
What is Hepcidin?
- Antimicrobial peptide
- Produced in the liver secondary to inflammation
- Destroys ferroportin
