Background. Leukocyte counts may influence peripheral (micro) circulation due to changes in rheology. The aim of this study was to investigate a possible association between leukocyte counts and peripheral tissue oxygenation/perfusion measured with near infrared spectroscopy (NIRS) in term and preterm neonates.
Methods. In this observational study we included term and preterm neonates within the first 2 months of life, in whom peripheral tissue NIRS measurements were performed and blood samples (leukocytes and C reactive protein (CRP)) taken to investigate clinical signs of infection. Tissue-oxygenation index (TOI), fractional oxygen extraction (FTEO), oxygen delivery (DO2), oxygen consumption (VO2) and vascular resistance (VR) were measured by NIRS and venous occlusion method. TOI, FTOE, DO2, VO2 and VR were correlated to leukocyte counts on the same day and maximal CRP levels within 24 hours (CRP max).
Results. In 180 infants, with a mean gestational age of 35.5±3.3 weeks, leukocyte counts were 16546± 8830/µl (median 14830; range 1790 to 67840) and CRP max was 8.0± 19.0 mg/l (median 0.0; range 0.0 to 110.0mg/l).
TOI was 71.1±5.5%, FTOE 28.5±6.1%, DO2 46.7±19.7, VO2 12.5±4.4 and VR 11.7±6.4.
Leukocyte counts correlated negatively (r= -0.21; p= 0.005) with TOI and positively (r=0.17; p=0.029) with VR. Correlations with CRP max did not reach significance.
Conclusion. We demonstrated that peripheral tissue oxygen consumption decreases and vascular resistance increases with increasing leukocyte counts.
Key words: near-infrared spectroscopy, neonate, microcirculation, leukocytes.