BLOOD TRANSFUSION

HDN DUE TO RHESUS INCOMPATIBILITY

Rhesus HDN is usually caused by immune anti-D and less commonly by other Rhesus antibodies. It occurs when a Rh negative mother with circulating IgG anti-D antibody (formed from a previous Rhesus
incompatible pregnancy) becomes pregnant with a Rh positive infant and IgG anti-D passes into the fetal circulation, destroying fetal cells. The infant can
be born severely anaemic and jaundiced.

The severity of disease increases with each Rh positive pregnancy. Infants with Rhesus HDN are usually more severely affected than infants with ABO HDN.
Note: In most cases of Rhesus HDN, maternal IgG anti-D will have been detected by the laboratory during routine antenatal visits, and the strength of the antibody (titre), monitored.
When Rhesus testing is not performed routinely (due to low frequency of Rh negative persons in the population) and an infant is born severely anaemic
and jaundiced, the laboratory may be asked to investigate the possibility of Rhesus HDN.

INVESTIGATION OF HEMOLYTIC DISEASE OF NEWBORN (HDN)

1. Carry out ABO and Rh grouping of the mother and infant.
There can be no Rhesus incompatibility caused by anti-D antibody unless the mother is Rh negative and the infant is Rh positive.
occasionally, when grouping the infant’s
cells they may not appear Rh positive when antigen D receptors on the baby’s cells have been coated with maternal anti-D.

3. Measure the infant’s haemoglobin and serum bilirubin

2. Carry out a DAT test on the infant’s cord cells. The DAT will be positive in Rhesus HDN.

4. Examine a Romanowsky stained blood film for the features of HDN, including spherocytosis which is usually less marked than in ABO HDN, polychromasia (reticulocytosis) and many nucleated red cells.

With Rhesus HDN, the infant’s haemoglo-
bin is usually below 140 g/l (14 g/dl) and the serum unconjugated bilirubin may rise to over 340 µmol/l (20 mg%). Such high levels of unconjugated bilirubin can cause irreversible brain damage (kernicterus).

5. Test also the mother’s serum for anti-D antibody when this has not been tested previously.

ABO GROUPING

ABO grouping consists of:

● Cell grouping in which the red cells are tested for antigens A and B using anti-A and anti-B sera.
● Serum grouping (reverse grouping) in which the serum is tested for anti-A and anti-B antibodies using known A and B red cells.

Why perform both cell and serum grouping ?

It greatly reduces the risk of errors in ABO grouping (serves as a double check).
There is less risk of misgrouping a group A person with weak antigen A as group O (or group AB as group B) because the error will be detected when serum grouping.
Errors due to autoagglutination will also be detected more easily.
Serum grouping using a tube will also detect the presence of anti-A and anti-B haemolysins in group O donor blood.

Grouping infants and elderly patients

Serum grouping is not performed when grouping infants below 4 months of age because naturally occurring anti-A and anti-B antibodies are only formed 3–4 months after birth.

When ABO grouping elderly people or persons with a gamma globulin deficiency, anti-A and anti-B may react weakly in the serum group and therefore cell grouping will be more reliable.

BLOOD TRANSFUSION IN VARIOUS CASES

TREATMENT OF ANAEMIA

For adults, including pregnant women, blood transfusion is indicated when:

A patient is in danger of dying of anaemic heart failure or hypoxia before specific medication can raise the haemoglobin.
Obstetric delivery is imminent and the mother’s haemoglobin is below 70 g/l (7 g/dl).
Emergency major surgery is essential and the haemoglobin is below 80 g/l (8 g/dl) with an anticipated blood loss of more than 500 ml.

In the above situations, the use of concentrated red cells (10 ml/kg body weight), is indicated to avoid cardiac overload. The transfusion should be administered slowly over 4–6 hours. When indicated, a rapidly acting diuretic should be administered. The pulse and respiratory rate should be monitored and the chest examined to detect volume overload.

.
For infants and young children, blood transfusion is indicated when:

The haemoglobin is below 50 g/l (5.0 g/dl) and is associated with respiratory distress.
The haemoglobin is below 40 g/l (4.0 g/dl) and is complicated by malaria or bacterial infection even without respiratory distress.
The haemoglobin is below 30 g/l (3.0 g/dl) without apparent infection or respiratory distress.

In the above situations, transfusion with whole blood (not packed cells), 10 ml/kg body weight, without diruretics will be tolerated.
Children with respiratory distress but not profound anaemia should be treated with intravenous colloids, and be transfused only if the haemoglobin falls later to less than 50 g/l.

TREATMENT OF ACUTE HAEMORRHAGE

● Blood transfusion is indicated when there is acute haemorrhage with a loss of more than 30% of apatient’s total blood volume, and blood pressure and oxygenation cannot be maintained by crystalloid solutions (saline or Ringers’ lactate) or colloids (e.g. 5% dextran or 5% hydroxyethylstarch).

Acute blood loss should be managed by
replacement of volume. Only when shock
persists or worsens should whole blood be transfused.

Postpartum haemorrhage: Blood transfusion is indicated when hypotension and reduced cerebral function persist
after at least 50 ml/kg of volume replacement fluid has been given intravenously and all measures have been
taken to stop blood loss.

TREATMENT OF NEONATAL JAUNDICE

For newborn infants with a serum bilirubin above 300 µmol/l, an exchange blood transfusion is indicated.