Cord blood red cell osmotic fragility: a comparison between preterm and full-term newborn infants.
BACKGROUND
The osmotic fragility of red blood cells reflects their membrane ability to maintain structural integrity. The osmolality at which the cells lyse is related to their shape, deformability, surface area/volume ratio and intrinsic membrane properties. In cord blood, there may be differences between premature and term infants, and be influenced by maternal medication and other factors. There have been no definitive findings on possible differences between preterm and full-term infant osmotic fragility.


OBJECTIVE
To determine if cord blood erythrocyte osmotic fragility differs between premature and full-term newborn infants, using two parallel techniques.


METHODS
Cord blood samples were obtained from preterm singletons (N=11), preterm multiple births (N=10), full-term infants (N=24), as well as adults (N=22), for comparison. An osmotic fragility test was used to determine the NaCl concentration at which 20%, 50% and 80% of hemolysis occurred using individual logistic curves. A glycerol lysis test determined the time needed to lyse 50% of red blood cells.


RESULTS
Cord blood red cells of multiple birth premature infants were more hemolysis-resistant than erythrocytes from full-term infants or adults. Another index of osmotic fragility, the difference in NaCl concentration for 80% and 20% red cell hemolysis showed that premature infants had greater differences than full-term infants or adults. Glycerol lysis time revealed that both preterm and full-term infants had an erythrocyte subpopulation that took longer than adult blood to attain 50% hemolysis. Correlation between both tests was very significant (r=-0.603, P<0.0001, N=67).


CONCLUSIONS
This study shows that erythrocytes of premature infants, although, in average, less osmotically fragile than those of healthy full-term infants, contain a more hemolysis-susceptible cell subpopulation.
Bautista
Maria L G
ML
Division of Neonatal/Perinatal Medicine, Schneider Children's Hospital at North Shore, North Shore-Long Island Jewish Health System, 300 Community Drive, Manhasset, NY 11030, USA.
Altaf
Waseem
W
Lall
Ritu
R
Wapnir
Raul A
RA
D000328:Adult; D004912:Erythrocytes / Q000502:physiology*; D005260:Female; D005312:Fetal Blood / Q000166:cytology*; D005990:Glycerol / Q000494:pharmacology; D006461:Hemolysis / Q000502:physiology; D006801:Humans; D007231:Infant, Newborn / Q000097:blood*; D007234:Infant, Premature / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009996:Osmotic Fragility; D011247:Pregnancy; D011272:Pregnancy, Multiple; D012965:Sodium Chloride / Q000494:pharmacology; D018709:Statistics, Nonparametric
D012965:Sodium Chloride; D005990:Glycerol