To Örebro University

Background: Data on cerebral pressure-flow autoregulation in the youngest children are scarce. We studied the correlation between mean arterial pressure and cerebral tissue oxygen saturation (rSO2 ) by near-infrared spectroscopy (NIRS) in patients undergoing nose, lip and palate (NLP) surgery.

Aim: We tested the hypothesis that cerebral pressure-flow autoregulation is impaired in children less than 1 year undergoing surgery and general anesthesia with sevoflurane under controlled mechanical ventilation.

Method: After approval from the Ethical board, 15 children aged <1 year were included. Before anesthesia induction, a NIRS sensor (INVOSTM , Medtronic, Minneapolis, USA) were placed over the cerebral frontal lobe. Frontal rSO2 , a surrogate for cerebral perfusion, mean arterial pressure, end-tidal CO2 - and sevoflurane concentration, and arterial oxygen saturation were sampled every minute after the induction. A repeated measures correlation analysis was performed to study correlation between mean arterial pressure and cerebral rSO2 and the repeated measures correlation coefficient (rrm ) was calculated.

Results: Fifteen patients, aged 7.7±1.9 months were studied. rSO2 showed a positive correlation with mean arterial pressure ([95% CI: 9.0-12.1], p<0.001) with a moderate to large effect size (rrm =0.462), indicating an impaired cerebral pressure-flow autoregulation. The slopes of the rSO2 -mean arterial pressure correlations were steeper in patients who were hypotensive (mean arterial pressure <50 mmHg) compared to patients having a mean arterial pressure ≥50 mmHg, indicating that at lower mean arterial pressure , the cerebral pressure-dependence of cerebral oxygenation is even more pronounced.

Conclusion: During sevoflurane anesthesia in the youngest pediatric patients, cerebral perfusion is pressure-dependent, suggesting that the efficiency of the cerebral blood flow autoregulation is limited.