Hematology Flashcards
What is hemolytic anemia?
Accelerated destruction of red blood cells (RBCs)
Hemolysis shortens the life of RBCs, usually leading to increased reticulocyte count except in cases of bone marrow suppression.
What are the causes of alloimmune hemolytic anemia?
Destruction of fetal or neonatal RBCs by maternal immunoglobulin G (IgG) antibodies
This occurs when maternal antibodies target the fetal RBCs.
What is the definition of thrombocytopenia?
Platelet count < 120,000
Slightly lower in preterm infants.
What is the normal lifespan of platelets?
7-10 days
Most patients with thrombocytopenia are asymptomatic.
What are the clinical presentations of polycythemia?
- May be asymptomatic
- Plethora
- Cyanosis
- Respiratory distress
- Lethargy, jitteriness, seizures
- Congestive heart failure
Excess red cell mass leads to increased blood viscosity and decreased blood flow to organs.
What is the definition of hemorrhagic disease of the newborn?
Acquired hemorrhagic condition caused by a deficiency of vitamin K-dependent clotting factors
This disease can present with pallor, localized or diffuse bleeding, and jaundice.
What are the treatments for thrombocytopenia?
- Conservative management with hydration
- Maintenance of glucose levels
- Normal saline bolus
- Partial plasma exchange
Treatment is controversial in the absence of symptoms.
What is the risk of transfusion in neonates?
- Infection
- Transfusion reactions
- Metabolic complications
Rare in neonates but can result from errors in cross-matching.
What is the pathophysiology of disseminated intravascular coagulation (DIC)?
Uncontrolled activation of coagulation and fibrinolysis initiated by release of thromboplastic material from damaged tissue
This leads to consumption of clotting factors and formation of microthrombi.
What is the treatment for Rh disease?
RhoGAM to destroy Rh positive fetal cells in the mother’s bloodstream
Passive immunity that wears off after about 4-6 weeks.
What are the common enzymatic defects causing hemolytic anemia?
- G6PD deficiency
- Sickle cell disease
G6PD deficiency weakens red cell walls, making them more susceptible to destruction.
What are the laboratory studies for diagnosing thrombocytopenia?
- Platelet count
- Peripheral blood smear
Additional tests may include reticulocyte count and hemoglobin levels.
What is the incidence of vitamin K deficiency in newborns?
0.4 – 1.7 per 100 live births
Seen at 2 to 6 days after birth if no vitamin K is given.
What are the components of hemostasis?
- Blood vessels
- Platelets
- Procoagulant and anticoagulant proteins
- Fibrinolytic system
An abnormality in any component can disrupt the balance and result in excessive thrombosis or bleeding.
What are the clinical presentations of anemia in neonates?
- Pallor
- Shallow, rapid, irregular respirations
- Tachycardia
- Weak, absent pulses
- Hypotension
- Apnea and bradycardia
Acute anemia can lead to congestive heart failure and hydrops.
What is the goal of treatment for polycythemia?
Reduce hematocrit to less than 60%
This can be calculated using blood volume and desired hematocrit.
What is the definition of hemoglobin?
Major iron-carrying component of red blood cells, measuring the oxygen-carrying capacity of the blood
Normal values vary by gestational age.
What is the role of vitamin K in coagulation?
Required for activation of factors II, VII, IX, and X
Intestinal flora are required for synthesis of vitamin K, which is minimal in newborns until feedings are established.
What is the purpose of the direct coombs test?
To test for anti-A or anti-B antigens on the newborn RBCs
False negatives can occur depending on antigen load.
What is the clinical significance of fetal-maternal hemorrhage?
Can lead to anemia in the fetus due to blood loss
Causes of hemorrhage may include placental abruption, previa, or cord accidents.
What is the definition of reticulocytes?
Measures immature red blood cells, indicating red cell production
Normal values vary by gestational age.
What is the treatment for hemorrhagic disease of the newborn?
- Prophylactic vitamin K at delivery
- PRBC transfusion
- Fresh frozen plasma (FFP)
Repeated doses of vitamin K may also be administered.
What are the normal hematocrit values for preterm and term infants?
Preterm: 45% - 50%
Term: 50% - 60%
Hematocrit gradually decreases during the first 6 weeks of life due to rapid growth, increased oxygenation, and decreased production.
What does hematocrit after birth not reflect?
Volume changes from things like delayed cord clamping
Approximately 48 hours required for redistribution of plasma volume after birth.
