Objective The skin as the child’s shock organ is easily accessible to evaluate the microcirculation non-invasively by sidestream dark field imaging (SDF) using the reflection of emitted light (530 nm) in the absorption spectra of hemoglobin.

Methods In 25 preterm infants (median (95% CI) gestational age: 28 (27 to 29) weeks, birth weight: 980 (849 to 1103) g) both the functional vessel density (FVD) and the vessel diameter were measured in the first 48 hours of life using SDF. The sequences were analyzed off-line by Microvision analysis software (MAS).

Results Post-natally, in the first 48 hours FVD increased significantly (from 212 (204 to 218) to 224 (219 to 232) cm/cm², p<0.018) with the greatest change between the 12th and 48th hours of life (from 211 (203 to 220) to 226 (219 to 232) cm/cm², p<0.001). The proportion of small capillaries (diameter <10 μm) increased from 31% (28 to 36) to 40% (36 to 42), (p<0.025). The proportion of the large vessels (diameter >20 μm) declined from 8% (7 to 15) to 6% (5 to 8), (p<0.001). The change of the medium capillaries (diameter 10–20 μm) did not reach statistical significance (from 56% (54 to 59) to 54% (52 to 57)). Blood pressure (syst., diastol. and MAP) and FVD did not correlate (MAP: r = −0.0245, p>0.85). Catecholamines/hydrocortison infusion increased FVD significantly (210 (198 to 221) versus 224 (212 to 232) cm/cm², (p<0.012), but not volume intervention (⩾10 ml/kg/BW 0.9% NaCl).

Conclusion There are significant changes in microcirculatory parameters postnatally but without direct correlation to blood pressure changes. Catecholamines/hydrocortison significantly improved both microcirculation and blood pressure.