The Influence of Injection Rate on EEG Propofol Peak Effect as Measured by Bispectral Index

• maximum hypnotic effect as indicated by the minimum BIS value.
  

• time to loss of consciousness
  
• time to loss of eye lash reflex
  
• time to BISmin
  
• BIS at LOC
  
• BIS at LOL
  
• BIS 30 seconds after LOC
  

The clinical daily routine indicates that slowing the rate of administration of propofol can lead to a reduction of up to 50% in the dose of propofol required to achieve the onset of a clinical endpoint of anesthesia (i.e. loss of consciousness) when titrating to effect. Therefore, it has been concluded that a slow injection requires a smaller dose of propofol as the graded effect is weakened by fast injection. This conclusion contradicts pharmacologic considerations, that a fast injection would lead to a higher peak concentration and in consequence, to a higher peak effect at the effect side, the brain.

The present study was designed to measure the Electroencephalogram (EEG) peak effect of a propofol bolus (2 mg/kg) injected with different infusion rates.

Although it is known that propofol has cardiovascular effects, the influence of injection rate on these cardiovascular changes is less clear. Others found that faster injection rates of propofol caused greater reductions in blood pressure. Other similar studies have shown no difference in blood pressure for different injection rates. An additional aim of this study was therefore to investigate the influence of different injection rates on hemodynamic parameters.