Bispectral index in a 3-year old undergoing deep hypothermia and circulatory arrest

We report a 3-year-old girl who presented with Scimitar syndrome and underwent hypothermic circulatory arrest for correction of anomalous pulmonary veins and an atrial septal defect. In this case the Bispectral Index (BIS) correlated significantly with the gradual onset of hypothermia and circulatory arrest. However, BIS remained low during the rewarming phase of cardiopulmonary bypass, in spite of adequate pump flows and stable haemodynamics. We postulate that this significant lag in BIS during the rewarming phase of deep hypothermic circulatory arrest may represent neuronal bewilderment or perhaps stunning, and differs from previous studies that show significant increase in BIS during rewarming from mild hypothermia.