What EEG change is expected following the intra-carotid injection of sodium amytal?

The expected EEG change following the intra-carotid injection of sodium amytal is a decrease in high frequency waves on the ipsilateral side. Sodium amytal is a barbiturate that has a depressant effect on the central nervous system, particularly affecting neuronal firing rates and synaptic transmission. When administered to one side of the carotid artery, it predominantly affects the brain regions that are supplied by that artery.

Since sodium amytal depresses cortical activity, the ipsilateral hemisphere will show a noticeable decrease in high frequency activity, which typically includes beta waves. This effect is a reflection of the drug's influence on cortical function and neuronal excitability. The resulting EEG change demonstrates the inhibitory effects of the drug on the electrically active neurons within that hemisphere, highlighting how the drug can temporarily impair cortical function.

This understanding emphasizes the importance of monitoring EEG changes during intraoperative procedures, especially when local anesthetics or sedatives are being administered, as they can significantly impact brain activity and, consequently, intraoperative neurophysiological assessments.