Background Neonates presenting with mild HIE within the first 6 h of life have not been included in therapeutic hypothermia trials. Consequently, aEEG, biochemical features and their temporal course are ill-defined. Our objective was to examine clinical and aEEG characteristics of neonates with perinatal HIE and mild initial encephalopathy.
Methods Prospective study including term neonates with HIE admitted in our centre January 2009–July 2011. Staging of encephalopathy was done before 6 h of age according to our validated scoring system. Clinical, aEEG and biochemical findings during the first 72 of infants with mild HIE were reviewed.
Results 55 patients were included, 12 of which were categorised as mild HIE: normal alertness but with altered tone or hyper excitability. All patients underwent aEEG monitoring during a mean time of 41.4 ± 25 h and starting at 2.5 ± 2.1 h. Temporal evolution of tracings (T) is described:
0: no recording; 1: continuous normal voltage with sleep-wake cycling (SWC); 2: continuous normal voltage without SWC.
Clinical or electrical seizures were not present during the first 72 h nor the staging of HIE increased during this period in any of the patients. Mean CSF NSE at 72 h was 26 ng/mL (+/-7.8).
Conclusions Clinical status of infants with mild HIE at 6 h of age does not worsen in the following 72 h. The aEEG traces are consistently normal and subclinical seizures are uncommon.