Neonatal anaemia, polycythaemia and thrombocytopenia: Viva

Opening question

Describe your immediate approach to this infant. [2]

This infant has life-threatening acute anaemia with signs of haemodynamic compromise: tachycardia, prolonged capillary refill, and desaturation. The immediate approach follows the airway, breathing, circulation framework, with establishment of intravenous access, a bedside glucose check, and emergency red cell transfusion of 10 to 20 mL per kg of cytomegalovirus-negative packed red cells over 2 to 4 hours. [2]

Branch 1: Resuscitation

The tachycardia at 175, capillary refill of 4 seconds, and oxygen saturation of 94 per cent indicate compensated shock progressing toward decompensation. Uncrossmatched O-negative blood may be used while a full crossmatch is performed, as the speed of correction determines outcome. [2]

The blood product should be cytomegalovirus-negative, irradiated, and leucodeduced packed red cells at a dose of 10 to 20 mL per kg over 2 to 4 hours, with a post-transfusion haoglobin check. [2]

Branch 2: Differential diagnosis

The three broad mechanisms of neonatal anaemia are haemolysis, blood loss, and decreased production. Given the rhesus-negative mother with a positive antibody screen and failed anti-D prophylaxis, rhesus haemolytic disease is the most likely cause here. [1]

Rhesus haemolytic disease produces progressive extravascular haemolysis via immunoglobulin G antibodies binding fetal red cells, potentially causing hydrops fetalis, while ABO incompatibility is milder and predominantly intravascular with spherocytes on the blood film. [1]

Anti-D prophylaxis prevents sensitisation by clearing fetal red cells from the maternal circulation, but it must be given in every at-risk pregnancy; failure to administer it in this pregnancy allowed sensitisation and antibody formation. [1]

Branch 3: Investigation

A direct antiglobulin test confirms antibody-coated red cells in immune haemolysis, serum bilirubin quantifies the haemolytic rate, and a peripheral blood film provides morphological clues. A Kleihauer-Betke test or flow cytometry detects fetomaternal haemorrhage, which is important when blood loss rather than haemolysis is suspected. [3]

Branch 4: Definitive management and counselling

Double-volume exchange transfusion is indicated when bilirubin approaches exchange levels or the anaemia is severe and progressive; its purpose is to remove antibody-coated red cells, antibody, and bilirubin while replacing them with compatible donor cells. Intravenous immunoglobulin at 0.5 to 1 g per kg blocks Fc receptors in the reticuloendothelial system and reduces haemolysis. [1]

The mother should be counselled that anti-D prophylaxis must be given in every at-risk pregnancy, that the severity may increase in subsequent pregnancies, and that antenatal monitoring with middle cerebral artery peak systolic velocity measurement will guide the need for intrauterine transfusion. [1]

Closing question

Summarise the key principles of neonatal red cell transfusion thresholds, including how they differ between term and preterm infants and the trial evidence supporting restrictive strategies. [2]

Restrictive red cell transfusion thresholds for preterm infants are supported by the multicentre trial comparing higher versus lower haemoglobin thresholds, which found no significant difference in death or major morbidity. Typical thresholds are a haemoglobin of 110 g per litre for ventilated infants on day 1, decreasing to 97 to 100 g per litre for stable preterm infants. Term infants are transfused when symptomatic with a haemoglobin below 70 to 80 g per litre or for acute blood loss. [2]

Examiner notes

This viva assesses the candidate's ability to recognise and manage a neonatal haematological emergency, distinguish immune haemolysis from other causes, apply evidence-based transfusion thresholds, and counsel families about prevention. The key teaching points are the resuscitation sequence with emergency red cell transfusion, the role of the direct antiglobulin test and blood film in confirming haemolysis, the role of anti-D prophylaxis in prevention, and the restrictive transfusion strategy supported by the multicentre threshold trials. [3]