Lange Anesthesiology > Section IV. Physiology, Pathophysiology, & Anesthetic Management > Chapter 29. Fluid Management & Transfusion

Transfusion

"Human red cell membranes are estimated to contain at least 300 different antigenic determinants. At least 20 separate blood group antigen systems are known; the expression of each is under genetic control from separate chromosomal loci. Fortunately, only the ABO and the Rh systems are important in the majority of blood transfusions. Individuals often produce antibodies (alloantibodies) to the alleles they lack within each system. Such antibodies are responsible for the most serious reactions to transfusions. Antibodies may occur "naturally" or in response to sensitization from a previous transfusion or pregnancy.Simplistically, the chromosomal locus for this system produces two alleles: A and B. Each represents an enzyme that modifies a cell surface glycoprotein, producing a different antigen. (Actually, there are multiple variants of A and B.) Almost all individuals not having A or B "naturally" produce antibodies (mainly immunoglobulin M (IgM) against those antigens (Table 29–7) within the first year of life. The H antigen is the structural precursor of the ABO system but is produced by a different chromosomal locus. Absence of the H antigen (hh genotype, also called the Bombay phenotype) prevents expression of the A or B genes; individuals with this very rare condition will have anti-A, anti-B, and anti-H antibodies. Blood transfusions should be given as packed red blood cells, which allows optimal utilization of blood bank resources. Packed red blood cells are ideal for patients..."