Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Experiment Videos

Auditory evoked responses and learning and awareness during general anesthesia.

M M Ghoneim1, R I Block, V J Dhanaraj

  • 1Department of Anesthesia, University of Iowa, Iowa City 52242, USA.

Acta Anaesthesiologica Scandinavica
|March 1, 2000
PubMed
Summary

This study examined whether patients can form memories while under general anesthesia and if brain wave patterns, known as auditory evoked responses, can predict this awareness. Researchers found that while explicit recall was rare, some patients showed signs of implicit memory, and specific brain wave changes correlated with these states.

Related Concept Videos

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

DTI of the Olfactory Bulb in COVID-19-Related Anosmia: A Pilot Study.

AJNR. American journal of neuroradiology·2023
Same author

Assessment of COVID-19 outbreaks in long-term care facilities.

The Journal of hospital infection·2023
Same author

Realigning the conventional routes of transmission: an improved model for occupational exposure assessment and infection prevention.

The Journal of hospital infection·2020
Same author

Predictors of difficult videolaryngoscopy with GlideScope® or C-MAC® with D-blade: secondary analysis from a large comparative videolaryngoscopy trial.

British journal of anaesthesia·2016
Same author

Sugammadex and residual neuromuscular block: what is acceptable normal practice?

British journal of anaesthesia·2016
Same author

Polymer complexes. LX. Supramolecular coordination and structures of N(4-(acrylamido)-2-hydroxybenzoic acid) polymer complexes.

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy·2015

Area of Science:

  • Clinical anesthesiology research within auditory evoked responses science
  • Cognitive neuroscience and perioperative medicine

Background:

No prior work had resolved the precise relationship between brain electrical activity and memory formation during surgical sedation. It was already known that distinguishing between conscious and unconscious learning remains a significant clinical challenge. That uncertainty drove researchers to investigate how specific anesthetic regimens influence patient awareness levels. Prior research has shown that monitoring brain responses to sound might offer a window into hypnotic depth. This gap motivated a detailed look at how different drug combinations affect memory retention. Scientists previously struggled to link objective physiological markers with subjective patient experiences during procedures. Establishing reliable indicators for unconscious processing during surgery remains a persistent goal for medical teams. This study addresses these issues by correlating auditory signals with postoperative memory performance in a large cohort.

Purpose Of The Study:

The aim of this study was to investigate the presence of explicit and implicit memories in patients following general anesthesia. Researchers sought to determine if specific brain electrical signals could serve as reliable indicators for the adequacy of the hypnotic state. The team addressed the major distinction between conscious and unconscious learning during surgical procedures. They aimed to clarify how different anesthetic drug combinations influence the risk of patient awareness. This motivation stemmed from the need to improve monitoring techniques for patients undergoing elective surgeries. The study specifically examined the relationship between auditory evoked responses and postoperative memory performance. By analyzing these connections, the authors intended to provide insights into the efficacy of current anesthetic protocols. The investigation was driven by the goal of reducing the incidence of unintended awareness during medical interventions.

Keywords:
perioperative awarenessimplicit memoryhypnotic stateanesthetic depth

Frequently Asked Questions

The researchers propose that awareness and memory formation correlate with specific brain wave patterns. Explicit recall was linked to higher Nb amplitudes, while implicit priming was associated with shorter wave latencies during the surgical procedure.

The study utilized a structured interview process to assess implicit memory through story-related free associations. Patients were exposed to audio recordings of stories, and their subsequent word associations were compared against control stories to detect priming effects.

Recording these responses is necessary because they provide objective physiological markers of the hypnotic state. Unlike subjective reports, these electrical signals offer a potential real-time method to predict awareness and memory formation during surgical interventions.

Related Experiment Videos

Main Methods:

The review approach involved a prospective analysis of one hundred eighty patients undergoing elective surgical procedures. Investigators administered four distinct anesthetic regimens to compare their effects on memory and brain activity. The team recorded electrical responses to sound before induction, shortly after incision, and at regular intervals throughout the surgery. Researchers played continuous audio recordings of stories to test for both explicit and implicit memory retention. Postoperative assessments included structured interviews to evaluate recall, recognition, and free associations related to the audio content. The study utilized McNemar's test to determine the statistical significance of priming effects observed in the patient groups. This methodology allowed for a direct comparison between physiological data and subjective memory reports. The design ensured that various drug combinations were systematically evaluated against consistent auditory stimuli.

Main Results:

The strongest finding indicates that priming occurred significantly in the opioid bolus group, with a 26% association rate for presented stories. This value was double the 13% frequency observed for control stories, reaching statistical significance at P=0.02. Six patients reported explicit recall of events during their surgery, and all of these individuals received the opioid bolus regimen. About 7% of the total patient population reported dreaming during the procedure. The ability of patients to identify the correct story presented during anesthesia averaged 49%, which is near chance levels. The researchers identified significant associations between awareness and higher Nb amplitudes during the surgical period. Furthermore, implicit memory was linked to shorter wave latencies in the recorded brain responses. The incidence of awareness in patients receiving nitrous oxide and bolus supplementation reached 6%.

Conclusions:

The authors propose that monitoring brain electrical signals during surgery may help predict potential awareness and implicit memory. Their findings suggest that specific anesthetic techniques do not necessarily lower the risk of patient consciousness compared to simpler methods. The researchers observed that explicit recall occurred exclusively in patients receiving a specific opioid bolus regimen. Furthermore, the data indicate that implicit memory formation is possible even when patients are under nitrous oxide and bolus supplementation. The team notes that dream recall remains a confounding variable that could complicate future investigations. They emphasize that awareness, priming, and physiological wave patterns show significant statistical associations. The study highlights the limitations of current anesthetic protocols in preventing all forms of memory formation. These results provide a foundation for refining how clinicians assess the adequacy of hypnotic states during operations.

The researchers used story-related free associations as a primary data type to measure implicit memory. This approach allowed the team to quantify priming effects by comparing associations to presented stories versus control stories, revealing significant differences in the opioid bolus group.

The researchers measured the frequency of story-related free associations to target words. They found that priming occurred only in the opioid bolus group, where the association frequency for presented stories was 26%, significantly higher than the 13% observed for control stories.

The authors propose that monitoring these brain responses could help predict awareness and implicit memory. They caution that current anesthetic techniques, particularly opioid bolus regimens, may not effectively reduce the risk of awareness compared to other methods.