Effect of head-up body tilt position on autonomic function and cerebral oxygenation in preterm infants

Skin-to-skin care (kangaroo) of premature infants causes orthostatic stress. Therefore, the effect of head elevated body tilt position (HETP) of 30 degrees and supine repositioning on systemic and cerebral oxygenation, circulation and sympathetic-vagal balance was investigated in 36 pre-term infants (25-36 weeks), from day 2 to 12 of life. Continuous polygraphic recordings revealed initial maximal fluctuations of total cerebral hemoglobin content (tHb) up to 42% following HETP determined by near infrared spectroscopy. After stabilization within several minutes, prolonged tilting did not result in any further significant changes of tHb, heart rate, mean arterial pressure and oxygen saturation measured by pulseoxymetry. Respiratory frequency was reduced by 6-12%. Spectral analysis of heart rate variability revealed a greater increase in low frequency than high frequency activity following HETP reflecting a relative increase in sympathetic versus vagal activation. Only preterm infants < or =1,500 g showed a significant decrease of regional cerebral oxygen saturation (rSO(2)) of about 2-5% from day 2 to 8. As this mild decrease in rSO(2) is clinically insignificant, there were no severe side effects of prolonged tilting in stable preterm infants even during the first days of life. However, the initial decline of tHb might be critical in very immature infants and needs further investigations.