326 Permissive Hypercapnia Results in a Decreased Functional Vessel Density in the Skin of Extremely Low Birth Weight Infants

Background: Due to the increasing number of extremely low birth weight infants (ELBI) long term ventilation and its aftermath has become an important issue. One of the newer concepts for gentle ventilation is permissive hypercapnia. We were interested in the effects of the higher pCO 2 - levels on the microcirculation of ELBIs. Methods: Data were collected from 12 infants, who were randomized either to treatment with permissive hypercapnia or normocapnia. Inclusion criteria were a birth weight between 400g and 1000g, a gestational age from 23 rd to 28 th+6 weeks, intubation during the first 24 hours of life and no malformations. The pCO 2 target range was increased stepwise and was 15mmHg higher in the intervention group. Skin microvascular parameters were assessed noninvasively with SDF on the right arm every 24h during the first week of life and on the 14 th day. Result: pCO 2 (AUC: 639 ± 62 vs 744 ± 62) differed significantly between the two groups (p=0,04). Functional vessel density (FVD) was significantly lower in the intervention group on the 14 th day of life (395 ± 43 vs 281 ± 67 cm/cm 2 ; p=0.04) The proportion of small vessels increased in the control group whereas they decreased slightly in the intervention group, but did not reach stat sig. Increasing target pCO 2 lead to a temporary hyperdynamic flow in both groups. Conclusions: pCO 2 -levels influence significantly the microcirculation in preterm infants. Elevation of pCO 2 -levels leads to a decrease in FVD, presumably due to shunting and vasoconstriction and might cause temporarily hyperdynamic flow.