title: Tc-99m-labeled red blood cells for the measurement of red cell mass in newborn infants: concise communication.
abstract: In vitro and in vivo investigations were performed to examine the binding of Tc-99m to neonatal red blood cells (RBC). Labeling efficiency was about 90%, and unbound Tc-99m less than 3% after one washing, in premature and full-term newborns and in children. Thus presence of high percentages of fetal hemoglobin (Hb F) did not influence the labeling of RBCs with Tc-99m. RBCs of 11 newborns were hemolysed and the distribution of Tc-99m on RBC components was analyzed. Although Hb F percentage averaged (60.0 +/- 8.1)% (s.d.), only (11.9 +/- 3.7)% of Tc-99m was bound by Hb F, whereas (45.0 +/- 6.1)% was associated with Hb A. RBC membranes bound (13.7 +/- 4.3)% and (29.3 +/- 4.0)% were found unbound in hemolysates. These results indicate that Tc-99m preferentially binds to beta chains. In vivo equilibration of Tc-99m RBCs and of albumin labeled with Evans blue was investigated in five newborn infants. Tc-99m RBCs were stable in each case during the first hour after injection. Elution of Tc-99m from RBCs was (3.4 +/- 1.5)% per hour. Body-to-venous hematocrit ratio averaged 0.86 +/- 0.03.
mesh_terms: D002648:Child; D002675:Child, Preschool; D004911:Erythrocyte Volume; D004912:Erythrocytes; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000097:blood*; D007553:Isotope Labeling; D013667:Technetium
chemical_list: D013667:Technetium