title: Actual vs optimal fetal hematocrit measured with punctures of cord blood in utero: Relationship with umbilical artery resistance.
abstract: Physiological studies on fetal blood in narrow glass tubes have suggested that fetal optimal hematocrit (hct) might be as high as 60%. A theoretical 'ideal' hct can also be predicted with a theoretical curve of hematocrit/viscosity (h/η) ratio vs hct constructed with Quemada's model. We used the database of one of our previous papers on fetal hemorheology to reinterpret its results with this concept. A series of 28 intrauterine cord punctures (between 19 and 33 weeks gestation) with doppler measurements of resistance in umbilical arteries was studied. The theoretical 'optimal hematocrit' was well correlated to actual (r = 0.857, p < 0.01) but systematically lower (Bland-Altman plot +12.1[8.52-15.7]) than the actual one. Umbilical artery resistance index is correlated with actual hematocrit (r = 0.407, p < 0.05), the discrepancy between ideal and actual (r = - 0.542, p < 0.05) but not predicted ideal hematocrit, suggesting that the discrepancy between ideal and actual may reflect an adaptative decrease aiming at reducing vascular resistance. These findings indicate that prediction of ideal hematocrit with Quemada's equation makes sense in fetal blood, and suggest that a 'viscoregulatory mechanism' maintains hematocrit below this theoretical value in order to avoid excess vascular resistance.
authors: UMRCNRS 9214-InsermU1046, «Physiopathologie & Médecine Expérimentale du Cœur et desMuscles - PHYMEDEXP», Unité d'Explorations Métaboliques (CERAMM), Université de Montpellier, Département de Physiologie Clinique, Hópital Lapeyronie CHU Montpellier, France.
authors: Jean-Frédéric
authors: JF
authors: Brun
authors: Service de Gynécologie Obstétrique, Hópital Arnaud de Villeneuve, CHU Montpellier, France.
authors: Pierre
authors: P
authors: Boulot
authors: Service de Gynécologie Obstétrique, Hópital Arnaud de Villeneuve, CHU Montpellier, France.|Institut des Biomolécules Max Mousseron (IBMM) UMR CNRS 5247, Université de Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier, France.
authors: Emmanuelle
authors: E
authors: Varlet-Marie
mesh_terms: D001809:Blood Viscosity; D004907:Erythrocyte Deformability; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D006400:Hematocrit / Q000379:methods*; D018056:Hemorheology; D006801:Humans; D011247:Pregnancy; D014469:Umbilical Arteries / Q000166:cytology / Q000378:metabolism*; D014655:Vascular Resistance
keywords: Blood viscosity; erythrocyte deformability; exercise; fetus; hematocrit