Innovating Neuromonitoring: A Simulation-Driven Exercise

By Carla Todaro, MD, from the IARS, AUA and SOCCA 2019 Annual Meetings*

For the first time this year, the IARS 2019 Annual Meeting introduced innovative session formats to the program. The Anesthetic Management of Intraoperative Neurophysiologic Monitoring (IONM) Signal Changes: A Case-Based, Simulation-Driven Learning Experience, presented on Sunday, May 19, was one of these sessions.

The session, led by Colby G. Simmons, DO, MBA, and Leslie Jameson, MD, both from University of Colorado School of Medicine, was organized as an interactive, simulation-based learning experience. Presenters provided intraoperative neurophysiological monitoring (IONM) technical equipment, which included software for case-based simulation. Drs. Simmons and Jameson provided a basic overview of signal interpretation in IONM, and relevant anatomy, pharmacology, and physiology to set the scene for the simulation exercises.

They then loaded the simulation software and asked attendees to make assessments and recommendations based on case data.

Neuromonitoring has been utilized during spinal surgery to assess the function of the spinal cord for prevention of intraoperative injury. Damage to the spinal cord can occur during surgery  due to stretch of the cord/nerve, hypoxia, or direct damage.

The purpose of intraoperative neuromonitoring is to provide the surgeon with a continuous analysis of spinal cord function for early identification and possible correction of any risk of morbidity.

IOM is a diagnostic test and signal interpretation varies based on the anesthesiologist. Primarily, IOM is used to preserve the neurological tissue and improve overall outcomes, providing the best anesthetic.

Important considerations for interpretation of the diagnostic test include age, sex, frailty, and if the patient has a condition like diabetes. Age can influence the health of the motor or sensory nerves. Frailty may modify the muscle energy procedure (MEP) and somatosensory evoked potential (SSEP) waveforms.

There are opposing opinions on the effectiveness of using different combination of intravenous drugs, the presenters explained. Some studies ascertained that the use of dexmedetomidine in combination with propofol or lidocaine for response preservation or suppression could be a direct consequence of the combination of these drugs.

And if the signal changes, what can we do?

1. Remember to perfuse the cord and the brain:
2. Maintain MAP as high as 100 mmHg
3. Improve oxygen delivery capacity
4. Stop the bleeding
5. Adjust the anesthetic, see if the signal is still present and use a processed EEG to monitor the depth of anesthesia.
6. Wake up test? It may be an option.

*Coverage from the Innovative Session: Anesthetic Management of Intraoperative Neurophysiologic Monitoring (IONM) Signal Changes: A Case-Based, Simulation-Driven Learning Experience during the IARS 2019 Annual Meeting