December 29, 2011 — Thresholds for transfusing children vary from those in adults, according to a 2-part review study published in the January 2012 issue of Anaesthesia & Intensive Care Medicine.
"The transfusion of a blood product into a child is associated with a greater risk of harm when compared to an adult," writes Rachel Hartrey, MBBCh, FRCA, a consultant pediatric anesthetist at Southampton University Hospital National Health Service Trust in the United Kingdom. "The younger the child, the greater these risks are: 18:100,000 in all paediatric age groups, increasing to 37:100,000 in those less than 1 year of age; this compares to 13:100,000 in adults. These calculations are based on red cell transfusion alone and do not take into account risks posed by other blood products, in particular fresh frozen plasma...and platelets."
The first part of the review describes normal hematological ranges in infants and children, lower levels of hemoglobin that can be tolerated without undue risks, and how to evaluate blood loss to ensure that blood products are not transfused unnecessarily.
The second part of the review describes strategies to avoid transfusion of blood products, and which fluids to use instead, as well as recommendations regarding how much and which blood products to use when indicated to reduce adverse effects.
Normal hemoglobin values are highest at birth (14 - 24 g/dL), decreasing to 8 to 14 g/dL at 3 months, and then gradually increasing to 10 to 14 g/dL at age 6 months to 6 years, 11 to 16 g/dL at age 7 to 12 years, and 11.5 to 18 g/dL in adulthood.
Thresholds for Red Blood Cell Transfusions
For infants younger than 4 months, thresholds for red blood cell transfusions based on hemoglobin levels are 12 g/dL for preterm infants or term infants born anemic, 11 g/dL for chronic oxygen dependency, 12 to 14 g/dL for severe pulmonary disease, 7 g/dL for late anemia in a stable infant, and 12 g/dL for acute blood loss exceeding 10% of estimated blood volume.
For infants older than 4 months, thresholds for red blood cell transfusions based on hemoglobin levels are 7 g/dL in a stable infant, 7 to 8 g/dL in a critically unwell infant or child, 8 g/dL in an infant or child with perioperative bleeding, and 9 g/dL in an infant or child with cyanotic congenital heart disease (because of increased oxygen demand). To slow bone marrow stimulation in a child with thalassaemia major, the recommended threshold is 9 g/dL.
For a child with sickle cell disease (SCD), the recommended threshold is 7 to 9 g/dL, or more than 9 g/dL if the child has previously had a stroke. When a child with SCD undergoes major surgery, the threshold should be 9 to 11 g/dL, and sickle hemoglobin should be less than 30%, or less than 20% for thoracic or neurosurgery.
Strategies to Avoid Transfusion
Strategies to avoid perioperative transfusion of allogeneic blood include:
- maximizing preoperative hemoglobin;
- preoperative autologous donation, which is associated with risks including transfusing the wrong blood unit, wasting donated blood, bacterial contamination, and preoperative anemia;
- acute normovolemic hemodilution when major blood loss is expected;
- patient position to avoid increased venous pressure;
- use of tourniquets where appropriate;
- surgical technique to achieve hemostasis, using diathermy and tissue glues;
- deliberate hypotension (at a safe level);
- hypervolemic hemodilution, although infusing large volumes of fluid may dilute clotting factors and cause interstitial edema;
- use of tranexamic acid, although there is still uncertainty as to the most effective dose;
- and intraoperative cell salvage in operations in which major blood loss is anticipated. However, reactions to the retransfused blood have been reported, which may be caused by leukocyte stimulation or a reaction to the additives.
"Blood is not only involved in the carriage of oxygen, but has many other functions including haemostasis," Dr. Hartrey writes in the second part of the review. "Therefore it is little wonder that the development of a compound that deals with only one element of this (e.g. oxygen carriage) is compromised by side effects. Several of the proposed alternatives, including haemoglobin-based oxygen carriers...and fluorocarbon-based solutions, have been associated with significant clinical side effects such as abnormal clotting."
Dr. Hartrey has disclosed no relevant financial relationships.