Haematology Flashcards
What are the main causes of Neonatal Anaemia?
- Physiological anaemia
- Anaemia of Prematurity
- Haemorrhage
APH, twin -twin transfusion - Haemolysis
- Hypoplasia/Aplasia eg. Blackfan Diamond
Symptoms of Neonatal Anaemia?
Hydrops Fetalis in severe disease
Pallor, tachycardia, respiratory distress, hepatosplenomegaly
Petechiae, purpura
Jaundice develops within first 24hrs
- Amniotic fluid/umbilical cord may be bili stained
- high risk of kernicterus
Describe Physiological Anaemia and the precipitating factors.
A physiological drop in Hb which happens in the 1st few weeks after birth - lowest around 3 months (Hb 90-100)
Factors causing the drop:
Temporary cessation of erythropoiesis
Reduced RBC survival time
Reduced production of erythropoietin
Exaggerated in preterm infants - occurs earlier and lasts longer.
Other factors - repeated blood sampling
- increased risk of iron deficiency
Common causes of Hydrops Fetalis?
Immune Hydrops:
RBC alloimmunisation diseases
Non-immune Hydrops: Cardio abnormalities - heart failure Arrythmias Chromosomal abnormalities Genetic/Metabolic abnormalities Anaemia - thallasemias Congenital (TORCH) infections
What can be done to prevent sensitisation in Rhesus -ve mothers?
ANTI-D GAMMAGLOBULIN for all non-immunised mothers
Routine administrations at 28weeks + within 72 hours of delivery
- Anti-D needed after sensitising events eg. Miscarriage, termination etc
Standard dose is 300micrograms - may need increased dose if large volume of blood transfused
- quantified by KLEIHAUER TEST
How do we identify a high risk pregnancy and how would they be managed antenatally?
Rhesus -ve mothers are screened for anti-D antibodies
Antibody titre >64 =significant haemolytic disease
- Regular USS to monitor for Fetal Hydrops
- Amniocentesis can assess haemolysis
- PUBS (percutaneous umbilical blood sample)
- Fetal Hb, allows transfusion in severe anaemia
Indications for delivery:
- > 35 weeks gestation or pulmonary maturity
- Fetal distress
- Complications of PUBS
What would be the indication for a fetal transfusion antenatally?
And what blood products would be used?
Evidence of Hydrops Fetalis on USS or haematocrit < 30% on PUBS
CMV negative leukodepleted, irradiated RBC
- aiming Hct 45-55%
What are the indications for early and immediate Exchange Transfusion?
Immediate exchange transfusion:
- Hydrops Fetalis
Early exchange transfusion:
- Cord bilirubin > 85
- Cord Hb <100
- Very high/rapidly rising SBR
ABO incompatibility is now the most common cause of heamolytic disease of the newborn.
What is the pathogenesis?
Anti-A or Anti-B antibodies are naturally occurring in A/B/O blood groups.
- form mainly IgM (do not cross placenta)
- small amounts of IgG produced
- can occur in 1st pregnancy
- more common in O blood group mothers
More mild than Rhesus disease as ABO has relatively low antigenicity (A1 >A2)
What are the clinical features of ABO incompatibility?
Jaundice within 24 hours
Anaemia uncommon
Hepatomegaly + Hydrops is RARE
DACT is weakly positive
Spherocytes on blood smear
Pathogenesis of Rhesus Disease?
- Mother Rh negative, Fetus Rh positive
- Maternal immune system sensitised by contact with Rh+ cells
- Produces IgM then IgG against D antigen
- Crosses placenta causing HAEMOLYSIS
- Sensitisation caused by miscarriage, amniocentesis, terminations, delivery or Rhesus incompatible transfusions
Postnatal investigations in a neonate with Rhesus Disease?
Hb and Haematocrit
Platelets
Coombs test
Bilirubin
What is G6PD deficiency?
Glucose 6-phosphate dehydrogenase deficiency within RBCs causing increased susceptibility to haemolysis
X-linked recessive inheritance - MALES only
More common in Black African/Americans, Chinese populations
How does G6PD present?
Can cause spontaneous jaundice + anaemia.
More commonly precipitated by medications:
- Anti-malarials
- Nitrofurantoin/Sulfonamides
- Chloramphenicol
Blood film - spherocytes, HEINZ BODIES
Reticulocytes
How do you diagnose polycythaemia in the neonate?
What are the common causes?
Free flowing blood sample with a Hct >65% or Hb > 220.
Common causes: Chronic intrauterine hypoxia eg. SGA or post maturity Delayed cord clamping, Twin- Twin transfusion Infants of diabetic mothers Neonatal Thyrotoxicosis Congenital Adrenal Hyperplasia Beckwith-Wiedemann Syndrome
Many infants with polycythaemia are asymptomatic.
If symptoms do develop, how would they present?
Plethora, irritability, lethargy, tachyonoea
Raised SBR
Hypoglycaemia
Can present with signs of hyperviscosity:
- Apnoeas
- Tremors, seizures
- Pulmonary Hypertension
- NEC
What is Haemorrhagic Disease of the Newborn and how does it present?
Vitamin K deficiency leading to a deficiency of the Vit K dependent clotting factors
- Factor 2, 7, 9 and 10
Neonates have an absence of gut flora which is involved in the production of Vit K.
Presents with spontaneous bleeding
- Can be early or late onset
What are the common bleeding sites and the risk factors for early onset disease?
Early onset is within 24 hrs of birth. Common bleeding sites: -Cephalohaematoma - Subgaleal - Intracranial - umbilical
Maternal medications main risk factor
Anticonvulsants eg. Phenytoin, phenobarb
Warfarin
Isoniazid
Late onset disease tends to present at 1-6months and can cause more severe bleeding.
What are the characteristics of this late onset disease?
Common sites of bleeding:
- Intra cranial
- Gastrointestinal
- ENT mucosa
- Injection sites
Increased risk with :
- Cholestasis eg. CF, biliary atresia, hepatitis
- Exclusively breast fed infants
What can cause Thrombocytopenia in the neonate?
Alloimmune thrombocytopenia
- Similar pathogenesis to haemolytic disease, much rarer
- usually transient fall in platelets
- Can cause intra-cranial bleeds
Neonatal autoimmune ITP
- In mothers with ITP
- Maternal antibodies cross the placenta
- High titres of maternal antibodies can indicate severity
