Blood-component therapy in children: SAQ

SAQ 1: Per-kilogram doses, thresholds and the decision for this child

Blood-component therapy transfuses the specific component a child lacks at a weight-based dose, guided by restrictive thresholds and delivered with rigorous safety checks. The four components prepared from one donation are red cells, platelets, fresh frozen plasma and cryoprecipitate, and the paediatric doses are red cells 10 to 15 mL per kg, platelets 10 to 20 mL per kg, fresh frozen plasma 10 to 15 mL per kg and cryoprecipitate 5 to 10 mL per kg. The philosophy is patient blood management: transfuse the smallest effective dose of the correct component only when the benefit outweighs the risk. [2]

For this child, three components are indicated because he is bleeding with deficits on three axes. The platelet count of 8 times ten to the nine per litre with active bleeding falls below the therapeutic threshold, so platelets are given at 10 to 20 mL per kg to a bleeding target, and the prophylactic threshold of 10 times ten to the nine per litre is the reference for the stable child. The fibrinogen of 1.2 g per litre with bleeding is below the cryoprecipitate trigger of 1.5 g per litre, so cryoprecipitate is given at 5 to 10 mL per kg. The haemoglobin of 62 g per litre with symptomatic anaemia and bleeding justifies red cells at 10 to 15 mL per kg. [10][2]

The restrictive threshold of 70 g per litre for the haemoglobin in the stable critically ill child comes from the TRIPICU trial, which showed a restrictive strategy as safe as a liberal one. The prophylactic platelet threshold of 10 times ten to the nine per litre is endorsed by the AABB and British guidelines. The neonatal platelet threshold is lower still, at 25 rather than 50 times ten to the nine per litre, because the PlaNeT-2 MATISSE trial found the higher threshold caused more bleeding and death in preterm neonates. [1][9]

SAQ 2: Special products, safety and the management of reactions

This immunocompromised child on chemotherapy should receive irradiated cellular components to prevent transfusion-associated graft-versus-host disease, because his immune system cannot reject the donor white cells. Leucodepleted components are the default and reduce febrile reactions, cytomegalovirus transmission and alloimmunisation, and cytomegalovirus-negative components are reserved for the intrauterine, neonatal and severely immunocompromised recipient. The bedside safety rests on the two-person check of identity, compatibility label, unit integrity and expiry, and on the slow first 15 minutes with observation for fever, rash, dyspnoea or hypotension. [2]

The commonest serious transfusion reaction is transfusion-associated circulatory overload, which presents with respiratory distress and pulmonary oedema within six hours of a transfusion given too fast or too large, and it is prevented by a weight-based dose, a slow rate and a diuretic for the child at risk. The acute haemolytic reaction from ABO incompatibility presents with fever and hypotension within minutes and is prevented by the rigorous bedside check. The first step in the management of any reaction is to stop the transfusion and keep the line open with saline, support the airway, breathing and circulation, and return the unit to the laboratory for investigation. [2]