Phototherapy has been shown to cause
hemolysis of fetal red cells and a shift to the right in the neonatal
oxygen dissociation curve (deltaP50) in vitro. To determine if these parameters act similarly in vivo, we have studied 16 icteric infants before and after
phototherapy and compared them with eight control infants studied at birth and at 3 days of age, measuring the change in P50,
2,3-diphosphoglycerate (2,3-DPG), serum
bilirubin, the percent of
bilirubin/
albumin saturation, and the
hemoglobin concentration in the two groups. Following
phototherapy, in the icteric infants there was a shift to the right in the O2 dissociation curve of + 1.7 mm Hg, a rise in
2,3-DPG of 2.26 micronmol/gm Hb, a fall in serum
bilirubin of 4.3 mg/100 ml, a decrease in percent
bilirubin/
albumin saturation of 12.4%, and a drop in
hemoglobin of 1.1 gm/100 ml. The control group showed a deltaP50 of + 2.0 mm Hg, a rise in
2,3-DPG of 3.67 micronmol/gm Hb, an increase in serum
bilirubin of 3.2 mg/100 ml, an increase in percent
bilirubin/
albumin saturation of 9.3%, and a fall in
hemoglobin of 0.3 gm/100 ml. Significant differences between the groups were seen only in the changes in
bilirubin concentration and percent
bilirubin/
albumin satruation. The magnitude of changes in P50,
2,3-DPG, and
hemoglobin concentration was similar in the
phototherapy and control groups and was related to the expected changes with reference to postnatal age. These results suggest that
phototherapy in vivo neither affects (fetal erythrocytic affinity for
oxygen nor causes
hemolysis. Pediatrics, 59:1027-1031, 1977
PHOTOTHERAPY,
2,3-DIPHOSPHOGLYCERATE,
HEMOLYSIS, NEWBORN INFANT.