Equine Anemia Evaluation & Management Flashcards
what is the difference in the lifespan between equine and canine erythrocyte
equine cells have a longer lifespan
why is it difficult to determine if anemia is regenerative in horses
because immature red cells are not released from bone marrow to circulation
no reticulocytes in regenerative anemia
what is the average lifespan of red cells
140-150 days
what red cell parameters can help determine if there is regeneration
the MCV and MCHC
in regeneration it is likely that the cells will be larger
what type of tube should you use for an accurate platelet count
citrate tubes
they clump (rouleaux) in EDTA tubes causing the count to be lower than it is
when do band neutrophils occur
when there is an acute inflammatory problem
at what platelet value should you be concerned
below 50
what are more sensitive parameters to determine if there is inflammation present besides the white cell parameters
acute phase proteins are more sensitive
because horses can have a number of infectious conditions but the white cell count can be normal
what is a normal PCV in throughobreds
~38-45%
what is a normal PCV in standardbreds
~38-40%
what is a normal PCV in warmbloods
~33-35%
what is a normal PCV in clydesdales
~30-33%
what is a normal PCV in mixed cold blood
~33%
what effect does spenic contraction have on the PCV
30% of red cell mass
will increase PCV in exercise/fear
what causes splenic relaxation and what effect does this have on the PCV
sedation
lowers PCV to low 20s even
what evironmental factors can have significant effects on the hemotology values
exercise
feeding
travel
stress
what are the general clinical signs of anemia in horses due to acute blood loss/hemolysis (3)
- tachycardia
- tachypnea & hyperpnea (indicative of hypovolemia and hypoxemia)
- mucous membrane colour depends on severity of loss
what are the general clinical signs of anemia in horses due to chronic blood loss/hemolysis (5)
- exercise intolerance
- weight loss
- pallor of mucous membranes only clinically evident at <20-24 l/l
- adaptive tachycardia at <20 l/l
- hemic murmur due to decreased viscosity, increased turbulence
at what PO2 would you start seeing cyanosis
60 mmHg
what are the features of regeneration on blood smears and hematology (3)
- howell jolly bodies
- increase in MCV
- anisocytosis more marked
what is the arrow showing
howell jolly body
at what rate does regeneration typically occur
increase of 0.32-0.42% per day (ie ~3 days to increase by 1%)
how long does it take for albumin to recover during regenerative anemia
5-10 days
how long does it take globulins to recover in regenerative anemia
3-4 weeks
what is the best sampling site to assess if anemia is regenerative
facial venous plexus
what can occur that you shouldn’t confuse for agglutination
strong red cell rouleaux formation
add adequate drops of saline
how do you test for genuine autoagglutination
in saline agglutination test 1 drop blood + 3 drops saline –> vigorous swirl
what are the tests for IMHA
in saline agglutination test
coombs test
what are infectious diseases that can cause anemia
equine infectious anemia
equine piroplasmosis
equine ehrlichiosis
equine trypanosomosis
how is bone marrow evaluated
collected from equine sternum with jamshidi needle
local anesthesia and stab incision
multiple smears made immediately
fragments of marrow used to make impression smears
what is the myeloid:erythroid ratio
normal ratio should be 0.5-2.4
if less than 0.5 M:E ratio with >5% reticulocytes indicates adequate regenerative response to anemia
what can a bone marrow evaluation test
nonresponsive vs responsive anemias (most IMHA cases are regenerative unless precursor cells targeted)
myeloproliferative disorders
what are the 3 categories of causes of equine anemia
- acute/chronic erythrocyte loss
- increased erythrocyte breakdown
- decreased red cell production
what are the reasons for acute/chronic erythrocyte loss
internal (hemorrhage into chest, abdomen, gut, bladder)/external hemorrhage
decreased survival in anemia of chronic disease
what are the types of erythrocyte breakdown
intra-/extra-vascular hemolysis
primary vs secondary
what are the 5 areas where acute blood loss can occur
- trauma or surgery: intra-abdominal, intrathoracic, arterial laceration
- respiratory: epistaxis, exercise induced, pulmonary artery rupture
- GIT: mesenteric tear, strongylus vulgaris arteritis
- urinary: renal hemorrhage
- uterine artery rupture: foaling complications
what is the approx circulating blood volume in horses
80-100 ml/kg
how much blood can a horse loose prior to collapse
20-30%
8-12 L for 500kg horse
what are the clinical signs for acute hemorrhage that might indicate a transfusion is needed
- marked tachycardia
- variable pallor to mucous membranes
- preliminary signs of tachypnea & hyperpnea (hypoxia/hypercapnia)
what are the GIT causes that can cause chronic blood loss
- gastric ulceration (particularly of glandular mucosa)
- severe colitis
- strongylus vulgaris arteritis
what are the respiratory causes that can cause chronic blood loss
- exercise induced pulmonary hemorrhage
- epistaxis (ethmoidal hematoma)
what urinary causes can lead to chronic blood loss
- renal hemorrhage
- bladder hemorrhage
what coagulopathies can cause chronic blood loss
- thrombocytopenia
- factor VIII deficiency (heritable x-linked hemophilia, prolonged PTT, normal PT)
how would you investigate the GIT if you suspect chronic blood loss from here
- gastroscopic exam
- fecal egg count
- fecal occult blood
how would you investigate the resp system if you suspect chronic blood loss from here
- endoscopy
- cytology
how would you test the urinary system if you suspect chronic blood loss from here
urine sediment cytology
how do you assess coagulopathies
- acurate platelet count
- measure PT and PTT times
- assess hepatic funcitons
- assay factor VIII concentration
how do you assess if chronic hemorrhage/loss has stopped
check PCV and total serum protein levels
if the PCV and TSP remain low has the chronic hemorrhage/loss stopped
no
if the PCV is stable and TSP has increased has the chronic hemorrhage/loss stopped
yes but no regeneration
if the PCV has increased and TSP has increased has the chronic hemorrhage/loss stopped
yes and regeneration
the cells might be larger than expected and howell jolly bodies will be present
should increase by a point over 3 days or so
what are the types of IMHA
primary and secondary
what is primary IMHA
antibodies against erythrocytes
what is secondary IMHA
immune complexes (external antigens) are attached to the erythrocytes
disease alters the RBC membrane
multiple causes
what are the causes of secondary IMHA
- respiratory tract infections
- streptococcal abscesses
- drug induced
- neoplasia
how can respiratory tract infections cause secondary IMHA
viruses such as EIV
deposition of antigen on erythrocyte membrane
affected cells removed by reticulo-endothelial system and continues until all affected cells are removed
subsequent regeneration
what drugs can cause secondary IMHA
- penicillins & sulphonamide antibiotics
- phenothiazine tranquilizers (acepromazine)
what neoplasia can lead to secondary IMHA
- lymphoma
- fibrosarcoma
how is IMHA treated
- identify and discontinue suspected medications
- dexamethasone if severe hemolysis
- blood transfusion if clinical evidence of requirement
what steroids can be used to treat IMHA
0.1 mg/kg IV dexamethasone daily, decreasing to 48h
then change to prednisolone 1 mg/kg SID if longer term treatment
what is neonatal isoerythrolysis
a foal is born to a mare and stallion where the stallion has a different blood group to the mare
if the mare is negative for AA and Qa but the foal is positive on AA and Qa –> the mare might produce antibodies which can damage the foals red cells
when does neonatal isoerythrolysis occur usually
most often in multiparous mares
what are the clinical signs of neonatal isoerythrolysis
anemia
icterus
weakness
increased RR, HR
pale mm’s
what is the onset of neonatal isoerythrolysis
onset/severity variable
but usually 2-3 days
how do the mares antibodies destroy the foals red cells in neonatal isoerythrolysis
through the colosutrm
how is neonatal isoerythrolysis diagnosed
- signs, hematology
- rule out DDx
- immunological testing
- foal RBCs + mare serum/colostrum to see if there is lysis
how is neonatal isoerythrolysis treated
- supportive care (stall rest, nutrition)
- blood transfusion
- suitable colostrum donor
how is neonatal isoerythrolysis prevented
- check compatibility of pairing particularly if mare is Aa/Qa negative (blood typing)
2. Aa/Qa negative stallions less likely to cause NIE in foals
- prevent nursing for 24 h (alternative source of colostrum)
what are the causes of non regenerative anemia in horses (7)
- iron deficiency
- chronic disease (infection/inflammation)
- bone marrow failure
- coagulopathies
- admin of human EPO
- chronic hepatic disease
- chronic renal disease
what bone marrow diseases can cause non regenerative anemia
- myelophthisis
- myeloproliferative disorder
- bone marrow toxins: PBZ, chloramphenicol
what can cause iron deficiency
- chronic hemorrhage
- nutritional deficiency (rare)
what would a non-regenerative anemia work up look like
- search for hemorrhage
- coagulation profile
- assess metabolic function
- is there iron deficiency?
how would you search for a hemorrhage if you suspect non regenerative anemia (6)
- gastroscopic exam
- fecal egg count
- fecal occult blood
- endoscopy + cytology
- thorax and abdominal US exam
- urine sediment cytology
what is a coagulation profile
- assess accurate platelet count
- measure PT and PTT times
- citrate blood tubes
- assay factor VIII concentration
how would you assess metabolic function to tell if non regenerative anemia (4)
- assess hepatic function
- measure renal failure
- is there an inflammatory response
- are acute phase proteins increased
how do you determine if there is an iron deficiency (4)
- low serum ferritin concentraion
- decreased % saturation of plasma transferrin
- increased total iron binding capacity (TIBC)
- increase of hypochromic erythrocytes
what is the most likely cause of iron deficiency
external blood loss
how do chronic diseases cause anemia
- shortened erythrocyte lifespan
- decreased release of iron
- decreased bone marrow response to EPO
what chronic diseases can cause anemia
- pleuropneumonia
- internal abscessation
- peritonitis
- chronic parasitism
- neoplasia
what are the causes of inadequate erythropoiesis
- nutritional deficiencies
- myelophthisic anemia
- bone marrow aplasia
what nutritional deficiencies can cause inadequate erythropoiesis
- prolonged administration of sulphonamides
- decreased folate and vit B12 production by GIT flora
how does bone marrow aplasia cause inadequate erythropoiesis
neoplastic infiltrate in bone marrow
if there is true neoplasitc problems with red cell precursors what will likely be seen
other cell lines will likely be affected
what will you likely see in bone marrow aplasia
likely to have pancytopenia with decreased neutrophils & decreased platelets if myeloid stem cell involved
what is the least common cause of non regenerative anemia
bone marrow aplasia
what are laboratory signs of acute blood loss
- low PCV
- low Hb
- low TSP
what are the labortory signs of hemolysis (5)
- low PCV
- normal TSP
- increase in unconjugated bilirubin
- increase MCH
- increased hemoglobinuria
what are the laboratory signs of chronic disease (5)
- low PCV
- low Hb
- relatively high TSP
- may be inflammatory leukogram with increased APPs
- may be reduced ferritin and high TIBC
