Effect of dexmedetomidine and ketamine on bispectral index during induction with propofol: A randomised double blinded controlled study

Bispectral index (BIS) is a widely used electroencephalography (EEG) based quantitative parameter utilised for monitoring the depth of anaesthesia.

BIS combines the information from 3 analyses : the spectrogram, the bispectrum, time domain assessment of burst suppression. It is recorded from a 4 lead frontal montage.The value of BIS ranges from 0-100 and indicates the patient’s anaesthetic state. Recommended BIS values during general anaesthesia range between 40-60.

Hypnotic drugs used in anaesthesia produce sleep by different mechanisms and hence produce variable effects on the EEG. The effect of several hypnotic drugs such as ketamine on the BIS values and EEG is still not clear.This becomes a limitation of the BIS monitor. The degree of effect of individual drugs and agents such as dexmedetomidine , propofol , isoflurane and sevoflurane on the BIS value and its correlation with the degree of sedation has also been food for several researchers.

Ketamine is an intravenous dissociative anaesthetic with analgesic properties in subanaesthetic doses. It is a non-competitive antagonist of N-methyl-D-aspartic acid (NMDA) receptor that participants in excitatory neuro transmission in the central nervous system. Some studies have shown that ketamine increases the BIS value,whereas others have shown that ketamine does not increase the BIS values.

Dexmedetomidine is an alpha-2 receptor agonist ,widely used in anaesthesia for its sympatholytic , sedative and analgesic effects . It acts on the locus coeruleus , produces physiological sleep like phenomena in the EEG and characteristic arousable sedation,which is markedly different from that of other sedatives such as gamma aminobutyric acid agonists (eg-propofol). Studies have shown that dexmedetomidine increases the BIS values produced by induction doses of propofol and BIS has been used as a monitoring parameter to assess and compare the level of sedation and hypnosis in several studies wherein these drugs have been administered.The relationship between BIS and dexmedetomidine administration/ ketamine administration has been studied individually by researchers.

However, there is scarce literature available on the combined effect of dexmedetomidine-propofol and ketamine-propofol on the BIS value. These drug combinations are nowadays commonly employed in anaesthetic practice. Hence, this study is planned to study the effect of these drug combinations on bispectral index values.

Aim of the study

To study the combined effect of dexmedetomidine-propofol and ketamine-propofol on the BIS value.

Objectives -

Primary Aim :

To compare BIS values with propofol, propofol-dexmedetomidine, propofol -ketamine and to find out how addition of dexmedetomidine /ketamine to propofol can affect BIS.

Secondary Aim:

To assess hemodynamic and EtCO2 level changes with dexemedetomidine /ketamine addition to propofol.

Materials and methods- Prospective randomised double blinded controlled trial.

Sample size- 28 patients in each group