Phenobarbital and neonatal seizures affect cerebral oxygen metabolism: a near-infrared spectroscopy study

BACKGROUND: Near-infrared spectroscopy (NIRS) measures oxygen metabolism and is increasingly used for monitoring critically-ill neonates. The implications of NIRS-recorded data in this population are poorly understood. We evaluated NIRS monitoring for neonates with seizures. METHODS: In neonates monitored with video-EEG, NIRS-measured cerebral regional oxygen saturation (rSO(2)) and systemic O(2) saturation were recorded every 5 seconds. Mean rSO(2) was extracted for 1-hour blocks before, during, and after phenobarbital doses. For each electrographic seizure, mean rSO(2) was extracted for a period of 3-times the duration of the seizure before and after the ictal pattern, and during the seizure. Linear mixed models were developed to assess the impact of phenobarbital administration and of seizures on rSO(2) and fractional tissue oxygen extraction (FTOE). RESULTS: For 20 neonates (EGA 39.6±1.5 weeks), 61 phenobarbital doses and 40 seizures were analyzed. Cerebral rSO(2) rose (p=0.005), and FTOE declined (p=0.018) with increasing phenobarbital doses. rSO(2) declined during seizures, compared with baseline and post-ictal phases (baseline 81.2 vs. ictal 77.7 vs. post-ictal 79.4; p=0.004). FTOE was highest during seizures (p=0.002). CONCLUSIONS: Cerebral oxygen metabolism decreases after phenobarbital administration and increases during seizures. These small, but clear, changes in cerebral oxygen metabolism merit assessment for potential clinical impact.