Harvey Chapter 4 Evaluation of Erythrocytes PART II AKG Flashcards
Erythrocyte and Iron Assays Ddx of anemia and erythrocytosis
What causes splenic contraction in cats, dogs, hot-blooded horses, and some marine diving mammals (e.g., seals)?
- Exercise
- Hypoxia
- Hemorrhage
- Excitement
HCT in the spleen (about 80-90%) is much higher than that of peripheral blood. T/F
True
That is why splenic contraction increases HCT 1.3-1.5x above resting levels
What causes splenic enlargement and subsequent decrease in HCT?
Anesthesia (especially with barbiturates)
Why are manual reticulocyte counts recommended to be performed in cats compared to dogs?
Cats have more punctate reticulocytes than aggregate reticulocytes. In dogs, aggregate reticulocytes are present in blood for a few days and mature into punctate reticulocytes for only a very short period of time (hours?) before they become mature RBCs. In cats, punctate reticulocytes circulate in blood for up to a week before they mature. Additionally, punctate reticulocytes continue to be released from BM after HCT begins to increase and aggregate reticulcoyte release has ceased in cats. Most analyzers do not detect punctate reticulocytes because of the very small amount of ribosomal DNA present, and manual counts are required to count both aggregate and punctate reticulocytes.
What is the corrected reticulocyte count equation?
(patient’s HCT/mean normal HCT) x raw reticulocyte count%
How long does it take to reach a maximal aggregate reticulocyte response to anemia?
4 days
What are these larger cells?
Macroreticulocytes (aka ‘stress’ reticulocytes) - thought to occur during severe regenerative anemia - thought that one less mitotic division occurs during production and that large immature reticulocytes are released
The MCV is larger in the fetus or adult?
What it is compared to adults at the time of birth in dogs and cats vs horses and cattle?
Fetus
Horses and catte at birth: MCV is within adult RI
Cats and dogs at birth: MCV is higher than adult RI
Copper and pyridoxine are important in iron metabolism and heme synthesis. Deficiencies in these nutrients may result in _____ anemia.
microcytic
Which drugs interfere with heme synthesis and have the potential for causing the formation of microcytic RBCs with siderotic inclusions?
- chloramphenicol
- lead
- hydroxyzine in dogs
Which dog breeds normally have MCV values below the reference interfals established for other breeds of dogs, but they are not anemic?
Japanese breeds: akita and shiba
MCVs may be spuriously ______ in dogs with persistent hyponatremia.
MCVs may be spuriously ____ and MCHC may be spuriously ______ in dogs with persistent hypernatremia.
MCVs may be spuriously decreased in dogs with persistent hyponatremia because RBCs shrink when they are diluted in vitro with counting fluid. MCVs may be spuriously increased and MCHC may be spuriously decreased in dogs with persistent hypernatremia because RBCs swell when they are diluted in vitro.
What causes high MCHC values?
- Artifactual increases in hemoglobin: lipemia, protein precipitation (cryoprotins and paraproteins), Heinz bodies
- Artifactual decreases in HCT (via analyzer): in vitro or in vivo hemolysis, RBC agglutination
*remember MCHC = Hgb/HCT x 100
In iron deficiency, which value decreaes first:
MCV or MCHC?
MCV first, then MCHC
What would cause two separate populations like this on the histogram?
Blood transfusion of a donor that has a substantially different MCV.
May also see two populations if there is substantial fragmentation of RBCs
You have normal or increased PaO2 but arterial blood is dark-colored. What should you suspect?
Methemoglobinemia
Significant methemoglobinemia (oxidative damage) has been associated with clinical cases of which toxins (that serve as oxidants)?
- Benzocaine
- Acetominophen
- Phenazopyridine in cats
- Skunk musk in dogs
- Chlorate toxicity in cattle
- Copper toxicity in sheep and goats
- Red maple toxicity in horses and alpacas
- Nitrite (cattle eating nitrate-accumulating plants and nitrate is reduced to nitrite by ruminal microbes) - also sodium nitrite preservative
- Onions/garlic
- Naphthalene (moth repellent) in dogs
- Methylene blue in cats
- Propofol and propylene glycol in cats
- Brassica sp. (kale) in cows
Persistent methemoglobinemia resulting from RBC ______ deficiency has been recognized in many dog breeds, DSH cats, and horses.
Cytochrome B5 reductase
*animals with this deficiency, in contrast to thsoe with methemoglobinemia produced by oxidant drugs, usually exhibit few or no clinical signs of illness
Which anticoagulant causes erroneuously low iron concentrations when measuring serum/plasma iron concentrations?
EDTA
so use heparin or serum
Serum iron concentration is generally increased (hyperferremia) in animals with….
- Hemolytic anemia
- Dyserythropoiesis
- Hypoplastic or aplastic anemia
- Iron overload
- Acute iron toxicity
- Chronic hepatopathy (dogs)/acute hepatocellular necrosis
- Experimental pyridoxine deficiency (pigs)
- Administration of glucocorticoids (dogs and horses)
- Opposite effect in cattle and goats
Serum iron concentration is low in….
- Iron deficiency anemia
- Inflammation
- ~50% of dogs with PSS
- Demand for iron > iron stores: EPO administration or acute hemorrhage
- GC administration in cattle and goats (opposite in dogs and horses)
How can serum ferritin concentrations help differentiate true iron deficiency from anemia of inflammatory disease?
Because both conditions will have decreased circulating serum iron levels, but only true iron deficiency will have decreased serum ferritin. Serum ferritin will be normal to high in anemia of inflammation.
What increases serum ferritin concentrations?
- Hemolytic anemia
- Inflammation (ferritin is an APP)
- Liver damage: toxic, hepatitis
- Malignancy: HS, LSA in dogs
- Iron overload
- Transiently increased in horses after moderate to severe exercise and in foals following consumption of colostrum
Stainable iron is assessed int he bonw marrow with which stain?
Prussian blue
