Xenon depresses aEEG background voltage activity whilst maintaining cardiovascular stability in sedated healthy newborn pigs

Background Changes in electroencephalography (EEG) voltage range are used to monitor the depth of anaesthesia, as well as predict outcome after hypoxia-ischaemia in neonates. Xenon is being investigated as a potential neuroprotectant after hypoxic-ischaemic brain injury, but the effect of Xenon on EEG parameters in children or neonates is not known. This study aimed to examine the effect of 50% inhaled Xenon on background amplitude-integrated EEG (aEEG) activity in sedated healthy newborn pigs. Methods Five healthy newborn pigs, receiving intravenous fentanyl sedation, were ventilated for 24 h with 50%Xenon, 30%O2 and 20%N2 at normothermia. The upper and lower voltage-range of the aEEG was continuously monitored together with cardiovascular parameters throughout a 1 h baseline period with fentanyl sedation only, followed by 24 h of Xenon administration. Results The median (IQR) upper and lower aEEG voltage during 1 h baseline was 48.0 μV (46.0–50.0) and 25.0 μV (23.0–26.0), respectively. The median (IQR) aEEG upper and lower voltage ranges were significantly depressed to 21.5 μV (20.0–26.5) and 12.0 μV (12.0–16.5) from 10 min after the onset of 50% Xenon administration (p = 0.002). After the initial Xenon induced depression in background aEEG voltage, no further aEEG changes were seen over the following 24 h of ventilation with 50% xenon under fentanyl sedation. Mean arterial blood pressure and heart rate remained stable. Conclusion Mean arterial blood pressure and heart rate were not significantly influenced by 24 h Xenon ventilation. 50% Xenon rapidly depresses background aEEG voltage to a steady ~ 50% lower level in sedated healthy newborn pigs. Therefore, care must be taken when interpreting the background voltage in neonates also receiving Xenon