Response of skin blood volume, velocity and flow to local warming in newborns, measured by laser Doppler flowmetry.

Background: In order to know the response of the skin microcirculation to local warming, we determined changes in the skin blood volume (Vol), velocity (Vel) and flow (F) by using a new laser Doppler device on newborns.
Methods: The study subjects were 39 infants whose gestational age was 34.1 +/- 2.8 weeks and birth weight was 2189 +/- 572 g. The study was performed from 8 h postnatally to 28 postnatal days. We measured skin blood volume, velocity and flow at 36 degrees C (Vol36, Vel36, F36), and each value at 5 min (Vol44-5, Vel44-5, F44-5) and 10 min (Vol44-10, Vel44-10, F44-10) after local warming was applied at 44 degrees C and the response curve of each parameter was obtained. Subsequently, serial changes in the response of skin microcirculation to local warming were investigated in nine very low birth weight (VLBW) infants (28.3 +/- 0.9 weeks, 1150 +/- 148 g) and 12 low birth weight (LBW) infants (32.8 +/- 1.3 weeks, 1971 +/- 292 g). The F36, the increment rate of blood volume (delta Vol) and the increment rate of blood velocity (delta Vel) were obtained within 24 h, from day 1 to day 7 and from day 8 to day 30 in both VLBW and LBW infants and from day 31 to day 60 and at more than 61 days in VLBW infants. The F36, delta Vol and delta Vel were compared during the study periods in VLBW and LBW infants. All results were expressed as mean +/- SD.
Results: The results showed that F36/F44-10 and F44-5/F44-10, Vol36/Vol44-10 and Vol44-5/Vol44-10, Vel36/Vel44-10 and Vel44-5/Vel44-10 were 0.25 +/- 0.09 and 0.74 +/- 0.17, 0.58 +/- 0.14 and 0.94 +/- 0.08, 0.42 +/- 0.12 and 0.79 +/- 0.15, respectively. Different modes of delivery did not have a significant effect on this response. The F36 in VLBW infants was high during the early neonatal period and gradually decreased with postnatal age. The delta Vol was low in VLBW infants during the neonatal period and gradually increased. The F36 in VLBW1-7 was significantly higher than in LBW1-7 (P < 0.01) and full-term controls (P < 0.001). The delta Vol in VLBW1-7 was 0.26 +/- 0.23, which is significantly lower than in LBW1-7 (0.57 +/- 0.17, P < 0.001) and full-term controls (0.77 +/- 0.21, P < 0.001). The delta Vel in VLBW1-7 and LBW1-7 was significantly higher than in controls (P < 0.05).
Conclusions: The skin blood flow increased continuously when local warming was applied at 44 degrees C. This high blood flow and limited potential of vasodilatation are the characteristics of the skin microcirculation in VLBW infants during the neonatal period.