title: Circulating RBC volume, measured with biotinylated RBCs, is superior to the Hct to document the hematologic effects of delayed versus immediate umbilical cord clamping in preterm neonates.
abstract: BACKGROUND
  One problem assessing the hematologic physiology of preterm infants after delivery and/or the efficacy and toxicity of therapeutic interventions affecting RBC measurements is the inability of blood Hct values to accurately reflect circulating RBC volume-owing to changes in plasma volume that influence Hct (i.e., a fall in plasma volume concentrates RBCs to increase Hct; a rise in plasma volume dilutes RBCs to decrease Hct).
  
  
  METHODS
  As part of a randomized, clinical trial testing the hypothesis that delayed clamping of the umbilical cord at delivery expands neonatal circulating RBC volume, blood Hct was compared to circulating RBC volume results measured directly with autologous, biotinylated RBCs or estimated mathematically with neonatal body weight and Hct values in neonates after immediate or delayed (60 sec) cord clamping.
  
  
  RESULTS
  Circulating RBC volume measured directly with biotinylated RBCs significantly increased (p=0.04) in neonates after delayed (42.1 +/- 7.8 mL/kg) versus immediate (36.8 +/- 6.3 mL/kg) cord clamping-a difference not detected indirectly by measuring Hct or estimating circulating RBC volume mathematically.
  
  
  CONCLUSIONS
  Because true hematologic effects of delayed versus immediate cord clamping may not be apparent or may be misinterpreted, when based on indirect measurements of Hct or calculations of circulating RBC volume, it is important to measure circulating RBC volume directly-as done with autologous, biotinylated RBCs-to document whether delayed cord clamping truly results in a transfer of significant quantities of RBCs from placenta to neonate. The clinical benefits and potential toxicities of increased RBC transfer to neonates require further studies.
authors.affiliation: Department of Pathology, University of Iowa Roy J. and Lucille A. Carver College of Medicine, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA. ronald-strauss@uiowa.edu
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Strauss
authors.forename: Donald M
authors.initials: DM
authors.lastname: Mock
authors.forename: Karen
authors.initials: K
authors.lastname: Johnson
authors.forename: Nell I
authors.initials: NI
authors.lastname: Mock
authors.forename: Gretchen
authors.initials: G
authors.lastname: Cress
authors.forename: Laura
authors.initials: L
authors.lastname: Knosp
authors.forename: Lori
authors.initials: L
authors.lastname: Lobas
authors.forename: Robert L
authors.initials: RL
authors.lastname: Schmidt
mesh_terms: D001710:Biotin / Q000494:pharmacology*; D003250:Constriction; D004911:Erythrocyte Volume; D004912:Erythrocytes / Q000187:drug effects*; D006400:Hematocrit; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D016037:Single-Blind Method; D013997:Time Factors; D014470:Umbilical Cord
chemical_list: D001710:Biotin