[Topographic electroencephalometry following anesthesia induction with ketamine-midazolam]

Area of Science:

• Neuroscience
• Anesthesiology
• Pharmacology

Background:

• Ketamine's neurophysiological effects and psychomimetic side effects are of growing interest.
• Combining ketamine with sedatives may mitigate side effects and hemodynamic changes.
• Previous studies often examine ketamine as a single anesthetic agent.

Purpose of the Study:

• To investigate the combined neurophysiological effects of ketamine and midazolam on cerebral activity.
• To analyze the topographical differences in the interaction of ketamine and midazolam across the cortex.
• To evaluate and compare cerebral and hemodynamic responses to anesthesiological stimuli like intubation and gastric tube insertion.

Main Methods:

• Topographical electroencephalometry (EEG) was used to record brain activity at 17 cortical points in 16 patients.
• Ketamine (3 mg/kg) and midazolam (0.15 mg/kg) were administered intravenously.
• Cerebral activity, heart rate, and arterial blood pressure were monitored during induction, intubation, and gastric tube placement.

Main Results:

• Ketamine-midazolam induction increased delta and beta 2 power while decreasing alpha 1, alpha 2, and beta 1 activity.
• Unlike ketamine alone, no significant increase in theta activity was observed.
• Intubation significantly increased power in temporal and parietal leads, but not frontally; gastric intubation had no effect.

Conclusions:

• The interaction between ketamine and midazolam on cerebral function is interactive, not merely additive.
• The combination suppressed typical ketamine-induced theta activity.
• Hemodynamic changes during intubation occurred despite anesthetic induction, suggesting incomplete cerebral suppression.