The Role of Electrodiagnostic Technologists
in the Operating Room

POSITION STATEMENT

Physicians and electrodiagnostic technologists are frequently requested to come to the operating room in order to perform various electrodiagnostic techniques, including sensory evoked potentials, auditory evoked potentials, facial nerve monitoring, somatosensory evoked potentials, visual evoked potentials, and intraoperative monitoring during spinal cord surgery.  The American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM [formerly AAEM]) developed The Role of Electrodiagnostic Technologists in the Operating Room to address this recent direction in electrodiagnostic medicine.  The document was derived from a number of sources, including directives generated by the American Electroencephalographic Society (now the American Clinical Neurophysiology Society) in 19941.

Monitoring Systems

1. Any evoked potential system assembled “in-house” must be inspected and deemed to be safe before being utilized in the operating room.  Evoked potential systems should comply with recent standards: a 100 µA limit on total chassis leakage and a 10 µA limit for isolated patient connections.

2. Both commercial and custom-made evoked potential systems must be inspected biannually.

Monitoring Techniques

1. Before any new electrophysiologic monitoring technique is offered to the surgical staff, it is advisable that monitoring be applied to patients undergoing general anesthesia for procedures not affecting the central or peripheral nervous systems.  Recording should be repeated several times until the evoked potential team becomes confident in the techniques’ ability to reliably record electrophysiologic waveforms continuously and its ability to interpret electrophysiologic changes induced by systemic factors.

2. In many cases, it is advisable to measure evoked potentials in a contralateral organ system (e.g., brainstem auditory evoked potential, opposite arm or leg, or opposite facial nerve) in order to determine whether a change from baseline reflects a focal or generalized process.

Monitoring Team

1. Appropriate intraoperative monitoring is best conducted using a team approach.  The team should be composed of surgeons, monitoring team, and anesthesiologists.  The surgeon should have a fundamental background in the neurophysiology of evoked potentials monitoring, as s/he may be called upon to participate in solving some of the problems that may arise from artifacts introduced by stimulating or recording electrodes.

2. The monitoring team must have a thorough background in intraoperative recording and electrodiagnostic technique so that immediate feedback can be given to the surgical team and anesthesiologist should any unusual changes occur in the recorded waveforms.

3. Monitoring should commence before any surgical manipulation of the central or peripheral nervous system begins and should continue until the surgical procedure is terminated.

4. The electrodiagnostic technologist should complete a logbook on each patient.  The logbook should include the following entries:

1. The timing of various procedures.

2. The sequence of surgical manipulation of the central or peripheral nervous system.

3. The use and timing of anesthetics and drugs.

Electrodiagnostic Technologists

1. The electrodiagnostic technologist should be under the direct supervision of a trained clinical neurophysiologist (MD, PhD, or DO) who has extensive background training in electrophysiologic monitoring and the fundamentals of clinical neurophysiology.

2. The electrodiagnostic technologist must have a minimum of 3 to 5 years of training and experience in routine electroneurodiagnostic testing and a minimum of 1 year of experience monitoring evoked potential procedures in the operating room under the qualified supervision of a physician or neurophysiologist.  This training should include the performance of at least 100 studies in the operating room.

3. The electrodiagnostic technologist must have a solid background in electrical safety and its relevance to patients in the operating room.

4. The electrodiagnostic technologist must have a sufficient knowledge base in the pharmacologic, physiologic, and pathophysiologic influences that may change or distort electrodiagnostic waveforms.

5. The electrodiagnostic technologist must have a solid background in the influence of filter settings on the amplitude, duration, and latency of electrophysiologic potentials.

6. The electrodiagnostic technologist must understand basic neuroanatomy and neurophysiology, the location of evoked potential generators and the pathways between generators, medical terminology, evoked potential correlates of specific neurologic, neurosurgical, orthopedic, audiologic and visual disorders, and must have a grasp of the pathologic and nonpathologic factors affecting evoked potentials, electrical hazards, and normative data for evoked potentials.

7. The electrodiagnostic technologist should have a thorough background in electronics and its application to neurophysiology.  The electrodiagnostic technologist should understand and be able to interpret artifact rejection and signal to noise ratio, identify whether a waveform is physiologic or nonphysiologic, identify the source of an artifact, estimate the frequency in hertz of rhythmic artifacts, have a thorough understanding of proper patient grounding, and understand the concept of enhancement of the signal to noise ratio by increasing the number of averaged potentials.

8. The electrodiagnostic technologist should have sufficient educational background in any intraoperative monitoring procedures in which the technologist participates.  These procedures may include:

1. Sensory evoked potentials.

2. Auditory evoked potentials.

3. Facial nerve stimulation and responses.

4. Somatosensory evoked potentials.

5. Spinal cord monitoring.

6. Visual evoked potentials.

9. The electrodiagnostic technologist should maintain and improve interpretive skills by reviewing evoked potential records with the clinical neurophysiologist on a regular basis.

References

1. American Electroencephalographic Society.  Guideline Eleven: Guidelines for intraoperative monitoring of sensory evoked potentials.  J Clin Neurophysiol 1994; 11:77-87.

Approved by the American Association of Neuromuscular & Electrodiagnostic Medicine (formerly AAEM) Board of Directors: April 6, 2000.

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