Exam 3 - Polycythemia, Splenic Disorders, & Lymphadenopathies Flashcards
what is relative polycythemia?
artificial increase in Hct but a normal RBC count – increase in Hct from loss of plasma volume
seen with dehydration & exudative wounds (burns), may seen increased Na, TS, & pre-renal azotemia
what is absolute polycythemia?
true increase in Hct/PCV – classified as primary or secondary
what values define polycythemia in dogs? cats?
dogs – PCV >55%, hemoglobin > 18 g/dL
cats - >50%, hemoglobin > 14 g/dL
how is primary polycythemia defined?
bone marrow is producing too much – NOT driven by EPO
how is secondary polycythemia defined?
driven by increased EPO – either appropriate or inappropriate
what are the end target organs in polycythemia & how are they affected?
CNS – ataxia, mentation changes, & seizures
ocular - +/- retinal hemorrhage, retinal detachment, blindness
nasal – epistaxis
what does ‘sludgy’ blood indicate?
hyperviscosity
what clinical signs are associated with polycythemia?
sludgy blood, hypercoagulability, PU/PD, & caudal cyanosis (right to left shunt)
what is the purpose of phlebotomy in patients with polycythemia?
removing a certain % of blood volume to decrease hyperviscosity
what is the target PCVs when performing a phlebotomy?
dogs – 55%
cats – 50%
goal is to remove 10-20 ml/kg
T/F: phlebotomy may not be ideal for all cases, but it should be performed in patients exhibiting clinical signs of polycythemia
true
what is the mechanism of primary absolute polycythemia?
marrow is producing too much erythrocyte lineage
peripheral EPO levels are low
bone marrow shows same as if EPO levels are high
can’t use bone marrow to differentiate primary from secondary
T/F: bone marrow examination can be used to differentiate primary from secondary polycythemia
false - not ideal
what is the mechanism of appropriate secondary polycythemia?
primary trigger – body needs more PaO2 (hypoxemia), such as pulmonary disease, increased altitude, or right to left cardiac shunting
T/F: for appropriate secondary polycythemia, the most important therapy long-term is phlebotomy
false – find the underlying cause & treat that
what is the mechanism of inappropriate secondary polycythemia?
secondary source of EPO being produced independent of O2 need – normal PaO2 – diseases such as renal EPO producing tumor, or rare other tumors such as nasal
how is secondary inappropriate polycythemia treated?
must find mass & if possible, & remove
what diagnostics are typically used for polycythemia?
thoracic & abdominal imaging – tumor hunt!!!
history/clinical signs are very important!!!
PaO2 levels, history of respiratory or cardiac disease
EPO levels are ideal – but very hard to do & often unavailable
what is the therapy used for polycythemia?
find the underlying cause!!!!
phlebotomize as necessary & pharmacologic management
what is the mechanism of action of hydroxyurea for patients with polycythemia?
erythropoiesis suppressant
why is clopidogrel used for patients with polycythemia?
anti-coagulant
what are the 3 general functions of the spleen?
- immune system – main defense against intracellular & cell surface pathogens affecting RBC/WBC, cleans up expired RBC
- reservoir – platelets, lymphocytes, & RBCs, extramedullary hematopoiesis
- iron metabolism
what happens with splenic contraction?
increases RBC – can see with bone marrow failure, anemia, & contraction can increase PCV substantially
why is the spleen important for iron metabolism?
storage, metabolism, & delivery of iron to the bone marrow
splenectomized patients have low iron – but other cells eventually take over this process
what specific organisms do we care about in relation to the spleen?
babesia, mycoplasma, & rickettsial bugs