FETAL HEMOGLOBIN OF TRANSFUSED NEONATES AND SPECTROPHOTOMETRICMEASUREMENTS OF OXYHEMOGLOBIN AND CARBOXYHEMOGLOBIN JohnJ. Mahoney, BA, ~ RonaldJ. Wong, BS, ~ Hendrik J. Vreman, PhD,~- and David K. Stevenson, MD~" MahoneyJJ, Wong RJ, Vreman HJ, Stevenson DK. Fetal hemoglobin of transfused neonates and spectrophotometric measurements of oxy- hemoglobin and carboxyhemoglobin. J Clin Monit 1991;7:154-160 ABSTRACT. The records of 32 neonates in an intensive care unit were examined retrospectively to determine if fetal hemoglo- bin concentrations could be predicted on the basis of gesta- tional or postnatal age, or on the volume of red blood cell transfusions. In nontransfused neonates, the correlation be- tween measured concentrations of fetal hemoglobin and post- natal age was r = 0.53 with a 17.2 standard error of pre- diction. In these same neonates, the correlation between measured fetal hemoglobin divided by birth weight and gesta- tional age was r = 0.70, with a 9.6 standard error of predic- tion. A three-variable regression equation (the latter two vari- ables plus calculated fetal hemoglobin) was found to have a high correlation with data for measured fetal hemoglobin (r = 0.97) and a relatively low 8.4 standard error of predic- tion. In transfused neonates, however, measured hemoglobin concentrations divided by birth weight correlated poorly with gestational age (r = 0.30 and a 12.4 standard error of predic- tion). In addition, the transfused neonates had low correlations when fetal hemoglobin concentrations alone were compared with the total volume of red blood cell transfusions (r = 0.35) and with postnatal age (r = 0.18) and the standard errors of prediction were all-approximately 17. The correlations found between concentrations of fetal hemoglobin and age in trans- fused neonates were poorer than those reported in earlier non- transfused infant studies. Previous studies have also shown that neonatal blood containing fetal hemoglobin interferes with the spectrophotometric measurements of carboxyhemo- globin and oxyhemoglobin. Because of the imprecision in the predictions of fetal hemoglobin using age, weight, or the vol- ume of transfusion, we conclude that fetal hemoglobin should be measured if accurate spectrophotometric determinations of carboxyhemoglobin and oxyhemoglobin are desired. KEY WORDS, Blood: hemoglobin; oxygen; carbon monoxide. Measurement techniques: spectrophotometry. Transfusion: blood. From the Departments of *Pulmonary Physiology and tPediatrics, Stanford University School of Medicine, Stanford, CA. Received Dec 13, 1989, and in revised form May 4, 1990. Accepted for publication May 14, 1990. Address correspondence to Dr Stevenson, Dept of Pediatrics, Stan- ford University School of Medicine, Stanford, CA 94305. Fetal hemoglobin (HbF) has been shown to inter- fere with the spectrophotometric measurements of both carboxyhemoglobin (COHb) [1] and oxyhemoglobin (O2Hb). This interference can be corrected by a built- in algorithm [2] in the IL 482 CO-Oximeter (Instru- mentation Laboratory, Inc, Lexington, MA), a clinical spectrophotometer, once the HbF concentrafon has been measured by a dedicated assay or estimated by standard tables. For the purpose of HbF estimation, In- strumentation Laboratory includes, in the instruments' operator's manual, a table based on postnatal age. This table was generated from the results of a study with normal neonates [3]. However, for neonates in the intensive care nursery, HbF concentrations may not be predictable on the basis of postnatal age alone. These patients not only may be abnormal in both weight and gestational age, but also 154 Copyright © 1991 by Little, Brown and Company