Hematology Flashcards
What is anemia?
hematocrit value at least 2 standard deviations below the mean for age
What is the normal range of hct in newborns?
45-61%
What is the normal range of hgb in newborns?
15-20%
What are possible etiologies for EARLY anemia?
1) blood loss
2) congenital erythrocyte underproduction
3) acquired erythrocyte underproduction
4) increased destruction
What are etiologies of blood loss in the neonate?
1) sequestered blood/ internal hemorrhage
2) Fetal-maternal
3) Placental
What are potential sites for sequestered blood/ internal hemorrhage?
1) intracranial: subdural, intraventricular, subgaleal
2) organ: adrenal, ruptured liver/spleen, retroperitoneal cavity
3) integumentary: bruising, hemangiomas
What are potential causes of fetal-maternal hemorrhage?
1) fetal maternal hemorrhage
2) ABO incompatability
* in most pregnancies there are fetal cells in maternal circulation (50-75%)
What are potential causes of placentall hemorrhage?
1) abruption
2) abnormal placental insertion (velamentous)
3) placental rupture
4) tight nuchal cord
5) CSX
6) TTTS (acute and chronic)
How is Fetal-Maternal Hemorrhage diagnosed?
diagnosis is by detection of fetal RBC in maternal circulation
- done on maternal blood, adult hgb has different solubility than fetal hgb.
- K-B can calculate volume of fetal blood loss (used to estimate Rhogam dose so that it is sufficent to kill fetal cells)
What is the incidence of volume transfer in fetal maternal hemorrhage?
1 in 400 pregnancies transfer > 30mL
1 in 2000 pregnancies transfer > 100mL
What is the relative occurrence of congenital erythrocyte underproduction?
rare
What are the causes of congenital erythrocyte underproduction?
1) hypothyroidism
2) adrenal insufficiency
3) hypopituitarism
Genetic causes, including:
1) congenital hypoplastic anemia (Diamond-Blackfan)
2) constitutional aplastic anemia (fanconi’s anemia)
What are the causes of acquired erythrocyte underproduction?
1) infection
2) maternal drug ingestion
3) drugs
4) nutritional deficits
5) lead toxicity
What infections are likely to cause acquired erythrocyte underproduction?
1) Parvo B 19 (most common)
2) hepatitis
3) HIV
4) syphillis
What maternal drugs are known to cause acquired erythrocyte underproduction?
azathioprine
What drugs are known to cause acquired erythrocyte underproduction?
chloraphenicol
What nutritional deficits are known to cause acquired erythrocyte underproduction?
1) Fe
2) folic acid
3) Vitamin B 12
What are causes of increased RBC destruction?
1) isoimmunization
2) minor blood group incompatibilities
3) structural abnormalities of the cell
4) RBC biochemical defects
5) infections
What isoimmunization states can lead to increased RBC destruction?
Rh incompatibility
ABO incompatibility
What structural abnormalities of RBCs can lead to increased RBC destruction?
- spherocytosis
- eliptocytosis
What biochemical defects of RBCs can lead to increased RBC destruction?
- G6PD
- pyruvate kinase deficiency
What is the etiology of erythroblastosis fetalis?
Rh incompatibility
What is the incidence of ABO incompatibility?
approximately 3%
What is the cumulative effect of ABO incompatibility with subsequent pregnancies?
may occur in first pregnancy, no sensitization req’d, subsequent pregnancies are not more severely affected
What immunoglobulin do mother’s with type A or B blood produce?
IgM
What immunoglobulin do mother’s with type O blood produce?
IgG; crosses the placenta; reason why mothers who are O tend to have hemolysis
What other effects can be expected with a mother with type B blood and an ABO incompatible fetus?
may also have thrombocytopenia since B antigen is expressed on platelets (usually mild)
What are the laboratory findings a/w ABO incompatibility?
Direct Coombs: weakly positive, or negative
Indirect Coombs: positive
What is the incidence of Rh incompatibility?
before Rhogam 1%, now 11/10,000
What is the cumulative effect of Rh incompatibility with subsequent pregnancies?
primary response (with first pregnancy) is IgM (not transmitted), followed by production of IgG (transmitted). With repeat exposure IgG response is more rapid (worse over time and with future pregnancies)
What is the effect of ABO and Rh incompatibility?
Rh incompatability may be protective; as it destroys the fetal cells before the MOB can mount an immune response
What is the effect of an Rh negative mother and a Rh positive fetus?
if the mother is Rh negative and fetus is positive, there is a transplacental hemorrhage and the MOB will produce anti-D (resulting in fetal hemolysis)
What are the minor group incompatibilities?
- other Rh antigens (c, E) are most common
- Kell (K and k), infrequent; “kell kills”
- Duffy; “duffy dies”
- Kidd
- Lewis; “Lewis lives”
What are the associated risks with an exchange transfusion?
1) blood hypersensitivity
2) multiple donor exposure
3) umbilical line
4) infection
5) bleeding
6) clots
7) air embolism
8) hypocalcemia
What is the expected volume of blood in a newborn?
80-100mL/kg; term infants are closer to 80, PT closer to 100
What are the indicated treatments for severe hemolytic disease?
- phototherapy
- ABO: IVIG (reduces need for exchange transfusion)
- Exchange transfusion
What type of blood is ordered to complete an exchange transfusion?
whole blood; request hct ~ 55%
What is the effect of citrated blood that is used in an exchange transfusion?
decreased Ca levels; entire clotting cascade is Ca dependent
What orders are indicated s/p exchange?
bili, hct, plt, maybe Rx levels
- NPO for awhile
- monitor lab work Q6h
- may require a second exchange
What is physiologic anemia?
occurs in every baby; there is a large RBC mass at birth (r/t relative hypoxic intrauterine environment). At birth and with first breathes, increases PaO2, erythropoiesis ceases (for a period of time bc it is not needed); fetal RBCs have a shorter life span
What is the physiologic nadir of a FT infant?
nadir to hgb of 9-12; 10-12 weeks
What is the physiologic nadir of a PT infant?
nadir hgb is 7-8; presents much earlier
What is one of the most limiting nutritional factors in the making of new RBCs?
protein deficiency
What are the causes of anemia of prematurity?
physiologic anemia processes, iatrogenic blood loss, disease, nutritional state, fetal-neonatal erythropoiesis
What are the physiologic contributors to anemia of prematurity?
1) low set point of O2 sensor (liver to kidney switch)
2) rapid body growth
3) shortened RBC span
4) Left shifted ODC at birth
5) low plasma EPO levels
6) cardiovascular factors: systemic and local
What are the non-physiologic contributors to anemia of prematurity?
1) laboratory blood loss
2) inadequate nutrient intake: protein, vitamins and calories
3) non laboratory blood loss and hemorrhage
4) infection/sepsis
What is the indicated treatment of anemia of prematurity?
1) minimize blood draws
2) good nutrition (protein & Fe)
3) Rh-Epo
What do RBCs of anemia of prematurity look like?
- normocytic ( normal size RBC)
- normochromic (RBC hgb concentration)
- hyporegenerative (stunted erythropoietin response)
What is the effect of Epo on anemia of prematurity look like?
- won’t limit early treatment, may limit later transfusion needs
- no proof that you’ll improve your outcomes (might just delay nadir
- may improve hgb
What is the reticulocyte count?
a measure of how quickly RBCs are being produced
How is reticulocyte count calculated?
% of RBCs in blood that are reticulocytes (# of retic divided by total hct) x 100
What are normal ranges for newborn reticulocyte count?
2.5%- 6.5% at birth, should fall by 2 weeks to 0.5%-2%
How can a reticulocyte count be helpful diagnostically?
can be used acutely in a baby that has hemolysis of chronic cases of anemia (have been retic-ing for awhile; and then production ceased in response to an O2 rich environment)
How should anemia be treated?
- biggest concern is delivery of oxygen to the tissues
treatment is based on infant’s volume status