Affiliations: [a]
Clinic of Neonatology, Department of Pediatrics, University of Heidelberg, Im Neuenheimer Feld, Heidelberg, Germany
| [b] Clinic of Pediatrics, SLK-Kliniken Heilbronn GmbH, Heilbronn, Germany
| [c]
Technical Expert’s Bureau for Rheology, Am Seeberg 14a, Bad Homburg vor der Höhe, Germany
Correspondence:
[*]
Corresponding author: Navina Kuss, Clinic of Neonatology, Department of Pediatrics, University of Heidelberg, Im Neuenheimer Feld 430, D-69120 Heidelberg, Germany. Tel.: +46 6221 5639337; E-mail: navina.kuss@med.uni-heidelberg.de.
Note: [1] Selected Presentation held at the 34th Conference of the German Society for Clinical Microcirculation and Hemorheology, Regensburg, Germany, 27-28 November, 2015.
Abstract: Determination of shear stresses at given shear rates allow approximation of flow curves by mathematical models and to calculate viscosities of non-Newtonian fluids. In term neonates, the mean arterial blood pressure (MAP) is markedly below that of adults, therefore rheological properties of blood play an important role in maintaining perfusion. Whole blood viscosity was measured in umbilical cord blood taken from 62 term neonates using the LS 300 viscometer. Individual parameters that influence the viscosity of whole blood were measured: red blood cell (RBC) aggregation, plasma viscosity, hematocrit, and RBC deformability. The flow curve of whole blood of neonates was approximated by the method of Ostwald with the highest quality whereas in adults the best approximation was found by the method of Casson. With hematocrits of 0.40, the viscosity of whole blood in newborns approximated by Ostwald (9.84 ± 5.12 mPa·s) was significantly lower than that of adults (15.34 ± 3.01 mPa·s). The aggregation index of the blood of newborns was markedly lower (2.98 ± 2.12) than in adults (14.63 ± 3.50) whereas RBC deformability was higher in neonates. The viscosity of plasma determined by Ostwald revealed a lower exponent (n) in neonates (0.94 ± 022) compared to adults (1.01 ± 0.12) and the viscosity determined by Newton was lower in neonates (1.04 ± 0.16 mPa·s) than in adults (1.19 ± 0.07 mPa·s). The flow curve of neonatal blood which is best approximated by the model of Ostwald emphasizes its important viscous properties necessary for conditions with physiologically low blood pressure.
