Introduction
Amobarbital is a very short acting barbiturate which is injected in an internal carotid to perform Wada test for patients eligible for surgery treatment. Using Density spectral array (DSA) of Bispectral index (BIS) VISTATM Monitoring System (BVMS), we observed alpha oscillations in frontal areas, a characteristic event of general anaesthesia known as “anteriorization”1. Thus, we initiated a retrospective study analyzing the EEG recordings with 10-20 system, to confirm these findings. The aim of the study was to compare percentage of alpha power between occipital and frontal areas and differences between both hemispheres when amobarbital was injected. 
Method
Six patients underwent intracarotid amobarbital administration were included in the study.  The EEG was recorded during five stages:
A)	Epoch 1: baseline EEG, awake patient
B)	Epoch 2: left or right anaesthetized  hemisphere 
C)	Epoch 3: washout period
D)	Epoch 4: right or left anaesthetized  hemisphere
E)	Epoch 5: washout period
For patients 1, 2 and 6 Epoch 2 and Epoch 4 were left and right, respectively. For patients 3, 4 and 5 Epoch 2 and Epoch 4 were right and left, respectively.
For each EEG channel the mean alpha absolute power was calculated obtaining a single value for each Epoch. To assess significantly difference between alpha power for each study brain zone and each epoch the wilcoxon signed rank test is being used.
Results
After the administration of barbiturate, there was an increase of alpha oscillations more evident in occipital than anterior area and especially in healthy brain. Alpha power augmented more in the anesthetized brain. 
Discussion
This is a retrospective study where we injected an intraarterial barbiturate. DSA of BIS showed that the administration of intracarotid amobarbital in one hemisphere produced low frequency and alpha oscillations in the EEG of occipital and frontal hemispheres more evident in healthy brain, but patients did not loss the consciousness. The presence of this EEG pattern could be due to some cross-flow of the amobarbital and to an altered connectivity in the non-anaesthetized hemisphere produced by a transient functional disconnection from the injected hemisphere2.

Density spectral array of BIS VISTA monitoring system during Wada study