Rhesus incompatability

Question 1

what does a patient’s rhesus status signify? (physiologically)

Answer 1

rhesus group signifies the proteins present on the RBCs of an individual

Question 2

which rhesus antigen is actually important clinically?

Answer 2

rhesus D

Question 3

which patients will never require anti-D?

Answer 3

rhesus D +ve patients (they will never recognise rhesus D as an antigen)

Question 4

what is the relevance of rhesus factor in pregnancy?

Answer 4

rhesus negative mothers (who have previously been sensitised) with rhesus positive foetuses can produce antibodies against the foetus’s blood

Question 5

suggest some sensitising events

Answer 5

childbirth

surgical TOP

organ transplant from a rhesus positive donor

antepartum haemorrhage (any bleeding from 24 weeks gestation)

amniocentesis

abdominal trauma

Question 6

how does anti-D work?

Answer 6

it attaches to and destroys the foetal blood that has made its way into the mother’s circulation before the mother has a chance to mount an immune response

Question 7

2 occasions when anti-D is given routinely (in any rhesus -ve mother)

Answer 7

28 weeks gestation

birth

Question 8

how quickly should anti-D be given to ensure that it is effective?

Answer 8

within 72 hours of any sensitisation event

Question 9

suggest how the extent of foetal blood reaching maternal circulation can be determined

Answer 9

using the Kleinhauer test

maternal blood sample is exposed to acid

• • foetal Hb is resistant to acid
• • examine to see how much Hb is left
• • – more Hb = more foetal Hb