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December 1, 2013 Volume 77, Number 12
Intraoperative Neurophysiological Monitoring and the Anesthesiologist Antoun Koht, M.D.
Committee on Neuroanesthesia

Tod B. Sloan, M.D., Ph.D., M.B.A.

Intraoperative neurophysiological monitoring (IOM) using evoked potentials and electromyography has become commonplace during many surgical procedures. It is used to identify and map areas of the central nervous system or monitor for neurological insults. It is believed to improve intraoperative decision-making and reduce neurological risk. A recent evidence-based review by the American Academy of Neurology and American Clinical Neurophysiology Society has reinforced its role during surgery on the spine.1 In particular, it can identify early neural dysfunction due to ischemia that could signal the need for improvement in blood flow and reduction of injury. Most anesthesiologists are now, with a varying degree, familiar with the need for a general anesthetic that is supportive of monitoring (e.g., reduced reliance on inhalational agents and neuromuscular blocking agents) with some of these monitoring techniques (especially motor evoked potentials). What anesthesiologists may not be familiar with is that the current monitoring process requires the active participation of the anesthesiologist beyond the choice and management of anesthetic agents.


The most common method for conducting monitoring involves the presence of two individuals: a qualified monitoring technical specialist in the O.R. and a second supervising individual who may not be in the O.R. A certification process for technologists present in the O.R. was developed by the American Board of Registration of Electroencephalographic and Evoked Potential Technologists and leads to certification for neurophysiological monitoring (CNIM). This person has primarily a technical role of conducting the various monitoring modalities to obtain the signals and identify significant changes. A second individual, the supervising neurophysiologist (M.D., Ph.D., Aud, etc.), oversees the process to ensure the quality of monitoring, provides an interpretation of the potential causes when responses change, and suggests possible methods that might mitigate potential injury. This interpretation takes into consideration the patient’s baseline pathology, the anatomy and physiology of the surgical techniques used, the specific risks of the surgical procedure being conducted, the current state of anesthesia and physiological parameters, and the various procedural factors that could be contributing to the deterioration of the responses. Typically this involves insights into the anesthetic, physiological, technical, positioning and surgical factors that may be occurring at the time.2 When the supervising neurophysiologist is in the O.R. (or nearby), it is possible to get these insights directly. However, there is an increasing trend for this individual to supervise by participating online using an Internet connection. This allows him or her to contemporaneously view the responses using a mirror image of the screen of the monitoring machine and communicate directly with the O.R. technologist. Because of the shortage of supervising individuals, the monitoring community has been increasing its reliance on this “remote” monitoring technique, with the supervising individuals often unable to personally participate in the O.R. (occasionally they are located in a distant city or state and simultaneously cover multiple cases). Since this person is not in the O.R., he or she must rely on communication through the intraoperative technologist to understand what is occurring during the procedure and the related anesthetic and physiological factors.


IOM monitoring


The current process with remote monitoring has substantially evolved from the early days of monitoring when the monitoring team was in the O.R. and had an intimate knowledge of the factors that could lead to response changes. In those early days, the anesthesiologist was an integral part of the monitoring team. Individuals such as Drs. Clyde Nash (orthopedic surgeon), Jerald Brodkey (neurosurgeon), Richard Brown (engineer) and Aage Moller (neurophysiologist) in the U.S. recognized the need for skilled anesthesiologists to make monitoring possible. Betty Grundy, M.D. brought anesthesia to this early group and pioneered these monitoring techniques into the overall care of the patient during the procedure. The anesthesiologist became a key part of the monitoring process because of his or her intimate knowledge of the patient’s comorbidities and neural pathology, in addition to the anesthesia, physiology, positioning and procedural issues involved in the patient care. The insights gained when the anesthesiologist directly participated in the monitoring, and the supervisory individuals were in the O.R., have laid the groundwork for much of our knowledge today.


Following in Dr. Grundy’s footsteps, many anesthesiologists chose to specialize in monitoring and many remain active in the IOM field today. However, as the techniques have evolved, the number of monitoring cases expanded and other specialists entered into the field, anesthesiologists have generally become less directly involved in monitoring. Further, billing codes for monitoring excluded the anesthesiologist from billing when they were also the anesthesiologist of record for the same case. Hence a new profession of intraoperative monitoring developed with individuals participating from many specialties (audiology, neurology, neurosurgery, orthopedic surgery). A board (American Board of Neurophysiological Monitoring) was developed for individuals who did not have a certification process in their specialty (such as for Ph.D. specialists in neurophysiology and related fields). A society dedicated to the specialty was also developed (American Society of Neurophysiological Monitoring) and remains today as a focus for the multispecialty discipline of today’s IOM.


The field evolved further this past year through a new Medicare billing code (G0453). This reduced the reimbursement of the professional component of monitoring to 15-minute increments of remote monitoring. Although the number of simultaneously monitored cases is not restricted, the billing is restricted to the equivalent of one case per hour (i.e., only four 15-minute periods can be billed per hour). For private insurers, the new billing codes reimburse only for personalized service (where the supervisory individual is continually in attendance in the operating room – 95940) or in a remote capacity as described for Medicare individuals (95941). These reimbursement codes reduce the reimbursement for some cases, discouraging individuals from entering the field, which may lead to a shortage of supervisory personnel. Further, it encourages remote monitoring that places an increased emphasis on individuals who are present in the O.R.


With an increase in the number of cases monitored remotely, an increased emphasis on the role of the in-room anesthesiologist will be inevitable. One of the challenges of working remotely is the knowledge of the factors that could be contributing to neural compromise (e.g., changes in anesthesia, relative hypotension, unfavorable positioning) of which the anesthesiologist is aware. In addition, we may be able to actively participate in improving the neural environment (such as repositioning an arm or raising the blood pressure) when altered responses raise concern of possible reversible causes for neural injury.


As such, monitoring has truly become a team effort where each member of the team contributes his or her individual knowledge and skill to provide optimal care for the patient. If remote supervision continues to increase, the anesthesiologist’s knowledge of the surgical procedure, patient medical comorbidities, the physiological and pharmacological environment, and direct knowledge of the patient’s position make us poised to optimally contribute when the responses signal a possible condition that could lead to neural compromise. Further, our knowledge will position us well for direct participation to assist in reducing risks by improving the neural environment (such as raising the blood pressure with ischemia).


If there is a shortage of supervisory personnel, anesthesiologists may be faced by both a challenge and the opportunity to help the monitoring team when responses change and supervisory individuals are unavailable. The anesthesiologist’s experience of monitoring multiple systems and their intimate knowledge of surgical procedures in addition to their presence in the O.R. allow us to facilitate this important monitoring when the economics of billing preclude an adequate number of supervisory personnel.


Hence the anesthesiologist’s involvement with IOM is more important than ever, and we should be prepared to contribute our knowledge to make the monitoring most effective. As such, we need to be well versed in these monitoring techniques to provide management that is supportive of adequate monitoring signals and a physiological environment conducive to a reduced neurological risk. To acquire this knowledge, we need a concerted effort of individuals involved in these cases, as well as for ASA, the American Board of Anesthesiology, the Society for Neuroscience in Anesthesiology and Critical Care, and the Society for Education in Anesthesia to develop opportunities for learning catered to practicing anesthesiologists and residents and fellows in training. A curriculum for IOM could also be developed for anesthesiology training programs.


The time for action is now!

Antoun Koht, M.D. is Professor of Anesthesiology, Neurological Surgery and Neurology, Chief Neurosurgical Anesthesia and Fellowship Director, Northwestern University Feinberg School of Medicine, Chicago.


Tod B. Sloan, M.D., Ph.D., M.B.A. is Professor, University of Colorado, Aurora.


1. Nuwer MR, Emerson RG, Galloway G, et al.; Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology; American Clinical Neurophysiology Society. Evidence-based guideline update: intraoperative spinal monitoring with somatosensory and transcranial electrical motor evoked potentials. Neurology. 2012;78(8):585-589.

2. Koht A, Sloan TB, Toleikis JR. Monitoring the Nervous System for Anesthesiologists and Other Health Care Professionals. New York: Springer; 2012.


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