Effects of Two Different Sedation Regimes on Auditory Evoked Potentials and Electroencephalogram (EEG)

• BIS-Index [ Time Frame: awake and 3 sedation levels ] [ Designated as safety issue: No ]
• Entropy (State Entropy and Response Entropy) [ Time Frame: awake and 3 sedation levels ] [ Designated as safety issue: No ]

Sedation may be necessary in intensive care to facilitate diverse therapeutic interventions, but the use of sedative drugs may increase the risk of delirium and long-term cognitive impairment. Thus the implementation and monitoring of sedation remains difficult despite the use of sedation protocols and clinical sedation scores. Attempts to improve sedation monitoring through the use of the electroencephalogram(EEG) have been disappointing. Derived variables based on the unstimulated EEG fail to predict the response to external stimuli at the clinically most relevant light-to-moderate sedation levels, and the overlap between moderate and deep sedation levels is wide. We have demonstrated that long-latency auditory evoked potentials (ERPs)can be used to avoid deep levels of sedation in healthy volunteers during propofol sedation, independent of the concomitant administration of remifentanil. This approach has a potential clinical application for improved monitoring of sedation. Since the effects of different sedative drugs on the EEG may vary widely, the use of ERPs to monitor sedation needs to be evaluated with different sedative drugs. Therefore we will administer two widely used drug combinations (dexmedetomidine/remifentanil and midazolam/remifentanil) in healthy volunteers and record ERPS and processed EEG during clinical relevant sedation levels

Sedation may be necessary in intensive care to facilitate diverse therapeutic interventions, but the use of sedative drugs may increase the risk of delirium and long-term cognitive impairment. Thus the implementation and monitoring of sedation remains difficult despite the use of sedation protocols and clinical sedation scores. Attempts to improve sedation monitoring through the use of the electroencephalogram (EEG) have been disappointing. Derived variables based on the unstimulated EEG fail to predict the response to external stimuli at the clinically most relevant light-to-moderate sedation levels, and the overlap between moderate and deep sedation levels is wide. We have demonstrated that long-latency auditory evoked potentials (ERPs)can be used to avoid deep levels of sedation in healthy volunteers during propofol sedation, independent of the concomitant administration of remifentanil. This approach has a potential clinical application for improved monitoring of sedation. Since the effects of different sedative drugs on the EEG may vary widely, the use of ERPs to monitor sedation needs to be evaluated with different sedative drugs. The alpha-2 agonist dexmedetomidine (dex) has been approved for short-term sedation in surgical intensive care unit (ICU) patients. Preliminary data suggest that the risk of delirium may be substantially reduced when dexmedetomidine is used to produce sedation. Since dexmedetomidine acts via different receptors and brain areas than do benzodiazepines and propofol, its impact on the brain electrophysiology may also be different. The assessment of dexmedetomidine's effects on the EEG and ERPs at various sedation levels has been limited in humans. We hypothesized that the combinations DEXMEDETOMIDINE/REMIFANTANIL (dex/remi) and MIDAZOLAM/REMIFENTANIL (mida/remi) would induce the same changes in EEG and long-latency ERPs during light-to-moderate levels of sedation in healthy subjects, despite the different quality of sedation that they provide. The opioid remifentanil was added because virtually all patients in the ICU have some level of pain and receive an opioid analgesic in combination with a sedative. 10 healthy subjects were assessed with both drug combinations (dex/remi and mida/remi), at least 7 days apart. The sequence of the drug combinations were randomized.

• Conscious Sedation
• Deep Sedation
• Critical Care

• Drug: Dexmedetomidine
  Infusion of dexmedetomidine
• Drug: Midazolam
  Midazolam infusion
• Drug: Remifentanil
  Infusion of remifentanil

• Active Comparator: Dex/Remi followed by Mida/Remi
  Sedation with dexmedetomidine and remifentanil followed by sedation with midazolam and remifentanil separated by one week
  Interventions:

  • Drug: Dexmedetomidine
  • Drug: Midazolam
  • Drug: Remifentanil
• Active Comparator: Mida/Remi followed by Dexa/Remi
  Sedation with midazolam and remifentanil followed by sedation with dexmedetomidine and remifentanil separated by one week
  Interventions:

  • Drug: Dexmedetomidine
  • Drug: Midazolam
  • Drug: Remifentanil

• Haenggi M, Ypparila H, Hauser K, Caviezel C, Korhonen I, Takala J, Jakob SM. The effects of dexmedetomidine/remifentanil and midazolam/remifentanil on auditory-evoked potentials and electroencephalogram at light-to-moderate sedation levels in healthy subjects. Anesth Analg. 2006 Nov;103(5):1163-9.
• Haenggi M, Ypparila-Wolters H, Hauser K, Caviezel C, Takala J, Korhonen I, Jakob SM. Intra- and inter-individual variation of BIS-index and Entropy during controlled sedation with midazolam/remifentanil and dexmedetomidine/remifentanil in healthy volunteers: an interventional study. Crit Care. 2009;13(1):R20. Epub 2009 Feb 19.
• Haenggi M, Ypparila H, Takala J, Korhonen I, Luginbühl M, Petersen-Felix S, Jakob SM. Measuring depth of sedation with auditory evoked potentials during controlled infusion of propofol and remifentanil in healthy volunteers. Anesth Analg. 2004 Dec;99(6):1728-36, table of contents.

Inclusion Criteria:

• age 18 years and older
• healthy

Exclusion Criteria:

• History of problems during anesthesia
• Impairment of the auditory system