Office of Technology Transfer – University of Michigan

Symbolic Transfer Entropy to Assess Feedback Connectivity in the Brain

Technology #5147

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George A. Mashour
Managed By
Janani Ramaswamy
Licensing Specialist, Medical Deviceses 734-763-9081
Patent Protection
US Patent Pending

Patient Monitoring under Anesthesia

There are over 40 million patients a year receiving general anesthetics in North America. The ability to monitor a patient’s level of consciousness during surgery and ensure that the patient does not awake or feel pain during surgery is a skill that takes many years for an anesthesiologist to master. In some instances the patient may enter into a level of consciousness that is not fully awake but the ability to feel pain is regained. These instances are unrecognizable to an anesthesiologist and can lead to severe injury and even death. A supplemental monitoring device is needed for the detection of various brain states to ensure patient safety during the administration of general anesthesia.

Using EEG to Detect Various Levels of Brain Activity

Electroencephalography (EEG) sensors have been shown to noninvasively monitor brain activity in many areas of clinical and research needs. A unique method has been demonstrated to monitor the brain state of a human patient under general anesthesia. Published clinical data, of 18 patients undergoing elective surgery with general anesthesia, using this method shows a physician is able to detect in real-time levels of consciousness and unconsciousness during the administration of propofol and sevoflurane. The ability to ensure patient safety during surgery has been achieved with this new method using EEG sensors and statistical real-time analysis.

Applications and Advantages


  • Monitoring general anesthesia in humans
  • Monitoring coma or vegetative states
  • Monitoring sleep
  • Monitoring central pain states


  • Better control of patient level of consciousness during surgery
  • Neurodiagnostics for unconscious patients