Age, Size & Rate of Transfusion
From the standpoint of physiological considerations in blood transfusion, pediatric patients are divided between those who are younger and older than 4 months of age. In general, transfusions in normally developing infants who are older than 4 months are similar to those in older children. Infants younger than 4 months of age, as well as preterm and low birthweight infants, require special consideration of their immature hemostatic and immune systems, and their limited capacities to tolerate the thermal and metabolic alterations from transfusion.[19,20]
Before ordering a RBC transfusion, the desired Hb level should be determined to estimate the required transfusion volume. This level is dependent on the patient's diagnosis, clinical assessment, anticipated blood loss associated with the procedures and expected hematopoietic recovery. Special care should be taken to minimize the child's exposure to multiple units and to maximize the use of each unit of RBCs. Children and adolescents with decompensated anemia generally receive 10–15 ml/kg of RBCs, rounded off to the nearest RBC unit to avoid wastage. In small infants, rounding off can result in overtransfusion and should be avoided. The expected increase in the Hb level is approximately 2–2.5 g/dl for each 10 ml/kg of RBCs transfused. Transfusions of over 25 ml/kg of RBCs, or more than one blood volume in 24 h, require careful attention to possible cardiovascular instability and dilutional coagulopathy, as well as metabolic and thermal alterations. During extremely large transfusions, sodium citrate anticoagulant binds ionized calcium and may result in transient hypocalcemia. Rapid transfusion of RBCs containing high concentrations of extracellular potassium can result in fatal cardiac disturbances in small infants, especially when accompanied by acidosis. Hypothermia is a concern when rapid transfusions are needed for pediatric patients owing to their large surface area:weight ratio. There are several consequences of hypothermia including decreased oxygen delivery to tissues as a result of the increased oxygen affinity of Hb, decreased tissue perfusion secondary to vasoconstriction and impaired platelet function. All of these challenges must be anticipated and managed during very large transfusions.
Storage systems improving RBC availability, safety and overall effectiveness have evolved over time, and a variety of additive solutions and combinations for the anticoagulation and storage of RBC components have been developed. RBC components used for small-volume transfusions in neonates are usually stored in an extended-storage preservative solution (additive RBCs) with a hematocrit of 55–60%. An alternative method used to improve volume and RBC mass is to centrifuge RBC components before transfusion, thus attaining a uniformly packed RBC concentrate (hard-packed RBCs) with a hematocrit of 80–90%.
The rate of RBC transfusion is determined by assessment of the absolute Hb level, acuteness and severity of blood loss, ongoing blood loss, for example, owing to bleeding or hemolysis, and a child's cardiovascular status. In general, each RBC unit should be given over 2–4 h. Patients with a Hb level of less than 5 g/dl, or those with evidence of cardiac failure, warrant a slow transfusion. Children with severe anemia of gradual onset may safely tolerate a rate of 2 ml/kg/h. If the desired post-transfusion Hb level will not be met following 4 h of transfusion, the RBCs should be divided into smaller bags in the blood bank to allow for correct storage until needed.[5,19]
Pediatr Health. 2010;4(2):201-208. © 2010 Future Medicine Ltd.
Cite this: Transfusions in the Critically Ill Pediatric Patient - Medscape - Apr 01, 2010.