Capillary Blood Cell Velocity in Full-Term Infants as Determined in Skin by Videophotometric Microscopy

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Abstract
In order to study the neonatal microcirculation, the capillary hemodynamics in skin was investigated in 43 full-term infants 2–7 days after birth. The nailfold capillaries of the thumb were visualized by means of television microscopy and the capillary blood cell velocity (CBV) was videophotometrically quantified in 107 microvessels. The skin temperature, mean arterial blood pressure, and heel puncture hematocrit were measured simultaneously to evaluate any relation with the CBV. The mean CBV in all infants was 0.38 ± 0.21 mm/s, with a range of 0.04 to 1.2 mm/s in individual capillaries. There was no correlation between CBV and skin temperature (27–33° C), mean arterial blood pressure (44–68 mm Hg), or postnatal age. However, a significant correlation was found between the log CBV and the skin prick hematocrit (r = −0.64, p < 0.001). It is concluded that the mean CBV during the 1st wk of life is not significantly different from the capillary velocity reported in adults. Normal variations in skin temperature and mean arterial blood pressure, as well as age differences 2–7 days after birth, do not significantly influence the neonatal skin capillary blood flow. However, the hematocrit is of major importance for skin capillary perfusion in the newborn infant.