Abstracts

Rationale: Electrocorticography (ECoG) is useful to identify the epileptic zone during epilepsy surgery and the Biespectral Index (BIS) evaluates depth of anesthesia. The correlation between the scores of BIS and ECoG patterns are unknown. Its knowledge would help optimize the quality and time of the ECoG recordings and decrease the risk of anesthesia. Analyze the correlation between the BIS scores and certain parameters of ECoG (duration of suppression in ECoG burst suppression [seg], background frequency (Hz) and type of ECoG patterns (1 [normal] to 5 [ECoG seizure, Bindra A et al., 2012] recordings obtained during epilepsy surgery under intravenous general anesthesia with propofol. Methods: Prospective descriptive study that included pharmacoresistant epilepsy patients who underwent epilepsy surgery guided by ECoG and BIS (September 2008 to October 2013) under intravenous general anesthesia with propofol. Results: We included 28 patients, 15/28 (53.5%) female, mean age 30.5 (13-56) years old, mean weight of 68.3 (42-100) kg, who underwent 22/28 (79%) temporal and 6/28 (21%) extra temporal epilepsy surgeries with propofol (mean plasmatic concentration 3.2 (0.75-4.4) µg/ml) and ECoG (mean duration 40 [5-178] min). We found a non-linear polynomial cubic relationship between the mentioned variables, for example, for a BIS range 40-60 (deep anesthesia) the following characteristics on ECoG were found: ECoG burst suppression (BS) periods <5 s, background brain frequency between 10-17Hz and type 2 ECoG patterns characterized by lack of brain waves >20 Hz on background frequencies. Figures 1-2. Conclusions: Our findings show for the first time that BIS is a non-linear multidimensional measure which possesses high variability when it is correlated with ECoG during epilepsy surgery. A nonsignificant trend exists between the increase in the duration of the burst suppression period regarding BIS values when compared to brain background frequency and ECoG patterns.