Abstract

Background: Processed electroencephalographic (EEG) indices, such as the SedLine Patient State Index (PSI), are increasingly used to guide anesthetic depth in pediatric anesthesia. However, their reliability in neonates and ex-preterm infants remains uncertain because current algorithms are derived from adult EEG data, which differ significantly from immature neonatal patterns.
Case Presentation: We report a 3-month-old ex-preterm infant (former 29-week gestation) undergoing bilateral laser photocoagulation for retinopathy of prematurity under general anesthesia. Despite persistently low PSI values (3-10) with a high suppression ratio suggestive of deep anesthesia, the infant exhibited spontaneous limb movement and tachycardia during surgical stimulation, indicating inadequate anesthetic depth. Increasing the sevoflurane concentration and administering fentanyl eliminated movement, but PSI values remained unchanged. The remainder of the procedure was uneventful, and the infant recovered smoothly without postoperative complications.
Conclusion: This case highlights a physiologic-algorithmic mismatch between neonatal EEG patterns and processed EEG indices such as PSI. In neonates and ex-preterm infants, low PSI values may not accurately reflect anesthetic depth. Clinicians should interpret processed EEG indices cautiously in this population and rely on multimodal assessment and clinical judgment until neonatal-specific algorithms become available.

Key words: Neonatal anesthesia; Processed EEG monitoring; Patient State Index (PSI); Algorithm limitation; Premature infant.