- Email: [email protected]
Intraoperative Monitoring Technician: A New Member of the Surgical Team
Intraoperative Monitoring Technician: A New Member of the Surgical Team MOLLY S. BROWN, BS; DEBRA S. BROWN, BSN, CNOR
ABSTRACT As surgery needs have increased, the traditional surgical team has expanded to include personnel from radiology and perfusion services. A new surgical team member, the intraoperative monitoring technician, is needed to perform intraoperative monitoring during procedures that carry a higher risk of central and peripheral nerve injury. Including the intraoperative monitoring technician on the surgical team can create challenges, including surgical delays and anesthesia care considerations. When the surgical team members, including the surgeon, anesthesia care provider, and circulating nurse, understand and facilitate this new staff member’s responsibilities, the technician is able to perform monitoring functions that promote the smooth flow of the surgical procedure and positive patient outcomes. AORN J 93 (February 2011) 242-248. © AORN, Inc, 2011. doi: 10.1016/j.aorn.2010.08.023 Key words: free-running electromyography, intraoperative monitoring technician, motor-evoked potentials, neurodiagnostic technician, neurophysiologic monitoring, pedicle screw monitoring, somatosensory-evoked potentials, spinal surgical procedures.
M
odern surgery bears little resemblance to the initial forays into the physical repair of the human body. The advent of anesthetics and sterilization revolutionized surgical capabilities, allowing surgeons to perform repairs and transplants on the human body. While rapidly evolving surgical technologies have modified and expanded the types of procedures that can be performed, the members of the in-room surgical team have not changed much, although the expertise, education, and professional levels of these team members have vastly improved over the years. The usual team consists of the surgeon, an assistant, an
anesthesia care provider, a sterile surgical scrub person, and a circulating nurse. There are also support personnel whose presence, absence, or level of expertise can affect how smoothly a day’s procedures run. A successful team mindset affects the success of the surgery and the patient’s outcome. The high-stress, highly technical, and extraordinary environment of an OR can be intimidating to those from other departments, so when the expertise of outside health care providers is necessary in the OR, there may be some disruption of the team function. Perioperative staff members, including visible team members (eg, surgeon, scrub doi: 10.1016/j.aorn.2010.08.023
242
AORN Journal ●
February 2011
Vol 93
No 2
© AORN, Inc, 2011
NEURODIAGNOSTIC TECHNICIAN person) and less visible members (eg, schedulers, supply technicians), have established roles and accepted responsibilities. As technology has advanced to require additional expertise, the surgical team has expanded to include other disciplines, but the process of changing to allow another member on the team can be jarring. As a result of the increasing role of fluoroscopy in the daily surgical schedule, the radiology technologist’s role in surgery has increased. In fact, it is common to have specific radiology staff members assigned to permanent duty in surgery because of their unique imaging responsibilities. Perfusion services, such as cell collection with reinfusion, also have expanded over the years, making the providers of perfusion services in the OR commonplace. A relatively new member to today’s surgical team is the intraoperative monitoring technician, sometimes referred to as a neurodiagnostic technician. The intraoperative monitoring technician’s job is to monitor the patient’s physiologic responses, both sensory and motor, during procedures that pose a higher risk of nerve damage. There are many factors that can affect spinal cord monitoring, including patient positioning, the use of anesthetic agents, and intraoperative retraction, all of which can affect the ability of the intraoperative monitoring technician to give the surgeon the information that he or she needs to provide safe patient care. Understanding what is being monitored and the technician’s role can help all perioperative team members to work together more smoothly, allowing each member to perform his or her specific functions. INTRAOPERATIVE MONITORING During procedures that pose a higher risk of nerve damage—which, at our facility, include open and minimally invasive discectomies, foraminotomies and laminectomies, open and minimally invasive spinal fusions, and anterior and posterior cervical procedures—multiple intraoperative monitoring modalities can be used. These modalities include brainstem auditory
www.aornjournal.org
evoked potentials and cortical mapping. For the purpose of this article, however, we will focus on the most common monitoring techniques that are performed during the previously mentioned surgical procedures. The four most common monitoring techniques that are used intraoperatively for tracking physiologic responses are somatosensory-evoked potentials (SSEP), motor-evoked potentials (MEP), free-running electromyography (EMG), and pedicle screw monitoring (Table 1).1 The type of intraoperative monitoring that is used depends on the procedure and surgeon preference. The type of monitoring determines lead placement, and the level of anticipated surgery will affect the number and location of electrodes that are placed. If multiple monitoring modalities are requested, the number of electrode placements increases. If the procedure involves multiple surgical levels, more electrodes must be placed. Should the surgeon need a baseline reading before the patient is positioned, the anesthesia care provider will need to know about this to be able to provide anesthesia for the patient without interfering with the monitoring process. The other perioperative team members also will need to know because the intraoperative monitoring technician will need to have all electrodes in place and connected to the monitoring equipment before the patient is positioned, which will slow down the progression of the procedure. A team-based approach involving all participants can address these problems and minimize obstacles that may occur during these complex surgeries. SSEPs Stimulating a sensory nervous pathway induces evoked potentials, which can be used to monitor the dorsal portion of the spinal cord.2 Electrical stimulation is applied to the skin of an underlying nerve of both the upper and lower extremities. The stimulus travels along the specific nerve pathway, inducing a potential (ie, response), which is recorded by electrodes placed over the sensory portion of the cortex of the brain. This AORN Journal
243
February 2011
Vol 93
BROWN—BROWN
No 2
TABLE 1. Intraoperative Monitoring Summary Somatosensoryevoked potentials
Motor-evoked potentials
Electromyography
Where stimulus is applied
Stimulus is applied near distal nerve.
Stimulus is applied above motor strip of cerebral cortex.
No stimulus is initiated by intraoperative monitoring staff.
Where stimulus is monitored
Cerebral cortex is monitored to record receipt of stimulus.
Muscle response is monitored to record receipt of stimulus.
Muscles are monitored to record irritation to muscles innervated at the surgical level.
Expected patient reaction
Can produce repetitive contractions of hands and feet.
Large muscle contractions may occur; bite blocks recommended.
Is muscle relaxant acceptable?
Yes—Because sensory is being tested, use of muscle relaxants is acceptable.
No—Because muscle motor response to intraoperative monitoring stimulus is being tested, use of muscle relaxants interferes with intraoperative monitoring.
If there is no irritation of the nerve roots, there will be no electrical activity. If a nerve were compressed, the irritation could be reflected in electrical activity of the muscle innervated by that nerve root. No—Because muscle motor response to surgical manipulation is being tested, use of muscle relaxants interferes with intraoperative monitoring.
electrophysiologic measurement of spinal cord sensory function can help in evaluating the integrity of both the peripheral and central pathways that are at risk during spinal manipulation.3 Somatosensory-evoked potentials are highly susceptible to anesthesia changes, including changes in blood pressure, anesthetic agents, and anesthetic gas levels in the patient, so careful monitoring of inhalation agents, blood pressure, body temperature, and other factors is necessary.4 For this modality, stimulating electrodes are typically applied in the distal portion of the extremities and recording electrodes are placed on the head. If signals cannot be elicited, the technician needs to 244
AORN Journal
Pedicle screw monitoring Stimulating probe is inserted into anticipated path of pedicle screw or to in-place screw. Resistance to the passage of the electrical stimulation at the anticipated screw site is measured. High resistance to the stimulus indicates the screw path is enclosed by the cortex of the pedicle. Low resistance may indicate the anticipated path breeches the pedicle.
No—Because muscle motor response to surgical manipulation is being tested, use of muscle relaxants interferes with intraoperative monitoring.
identify where disruption is occurring in the pathway. If cervical and cortical responses are present but more distal responses are not, improper positioning of the extremities may be causing impingement on the peripheral nerves. The team members may need to investigate the cause and possibly reposition the patient. Extra considerations for positioning-related sensory deficits are particularly important for procedures in which the patient may be prone for numerous hours. Extra padding and support may be required to alleviate any pressure that can be placed on the nerves. If cervical and cortical potentials are lost as well,
NEURODIAGNOSTIC TECHNICIAN this could be indicative of spinal cord compromise, and team members must work together to identify and correct the possible causes to restore those potentials before damage to the cord becomes permanent. Many institutions have outlined protocols for this adverse event, and these should be accessible and known to the surgical team. MEPs Also known as transcranial motor-evoked potentials, MEPs are electrophysiologic responses recorded in muscles after direct stimulation of the brain.2 When spinal procedures have the potential to cause injury to the anterior (ie, motor) portion of the spinal cord, monitoring of MEPs is highly recommended. Stimulating electrodes are placed over the motor portion of the cortex and are recorded in distal muscles of the extremities both above and below the surgical site.5 The main obstacle for this modality is the administration of muscle relaxants, which inhibits monitoring functions; therefore, communication with the anesthesia care provider before the administration of muscle relaxants is imperative.4 Stimulation can commonly cause a muscle contraction in various locations, so the technician needs to also communicate with the sterile staff members to inform them of possible movement that could compromise sterility or safety. If MEPs are lost, spinal cord function may be compromised. Intraoperative monitoring technicians need to communicate with the surgical team and anesthesia care provider to try to determine why the signals were lost and how to recover the signals before permanent damage is sustained. Protocols for this adverse event should be available and understood as well. EMG Spinal surgeries that involve working near spinal nerve roots can require the monitoring of muscles innervated by the roots at the surgical site level.2 Electrodes are placed in the subdermal layer over the muscles of the corresponding levels to record any nerve irritation that could be indicative of
www.aornjournal.org
compression, stretch, severing, or other irritant factors.6 Requirements for this modality are access to the muscles to be recorded and that no muscle paralytic be used. Communication between the intraoperative monitoring technician and the surgical and anesthesia team members before surgery can help ensure physical patient access and adherence to the agreed upon anesthesia care plans. Pedicle Screw Monitoring When spinal screws are being placed into the pedicles of the vertebrae, anticipated or actual screw testing can be performed. Stimulation of the screws or the drilled hole before screw placement can elicit a response in the EMG recording. The surgeon places the stimulation probe and notifies the technician to provide the electrical stimulus. The technician then relays to the surgeon the digital reading from the monitoring device. Potentials seen at low stimulation levels can be caused from a breach of the pedicle wall, misplacement of the screw or intended screw path, or bone weakness. If potentials are seen at low levels of stimulation, placement of the screw hole may need to be reevaluated and possibly be adjusted.7 Perioperative Implications For any given procedure, the number of electrodes, the time required for placement or insertion of electrodes, and the number of locations of insertion vary greatly. For example, for a onelevel lumbar discectomy, a few electrodes may be placed in only the lower extremities, and the technician may only need a few minutes with access to the legs. For multiple-level spinal procedures that include the thoracic region, however, all four mentioned modalities may be required during the procedure. Whereas SSEPs and EMGs are monitored continuously, MEPs and pedicle screw monitoring are tested as needed or as directed by the surgeon. In these surgeries, the intraoperative monitoring technician needs access to the patient’s entire body and more time to allow placing and securing as many as 50 electrodes, depending AORN Journal
245
February 2011
Vol 93
No 2
Portable intraoperative monitoring equipment. Image courtesy of Medtronic Spinal and Biologics, Minneapolis, MN.
on the monitoring modalities and the number of surgical levels being addressed. In any neurophysiologic monitored surgery, anesthetic limitations are present and must be discussed preoperatively by the intraoperative technician, anesthesia care provider, and surgeon so preparation can occur. Levels of inhalation agents and muscle paralytics can inhibit the intraoperative monitoring technician from performing a safe and effective study.8 The surgical team members need to help the anesthesia care provider work effectively with the intraoperative monitoring technician to achieve the anesthetic compromise that will allow the patient to receive the best care possible. Safety Concerns There are safety concerns with each type of neurophysiologic monitoring. The intraoperative monitoring technician observes the patient for these concerns. If monitoring is combined with other modalities that require lack of neuromuscular blockade, SSEP stimulation can cause a muscle contraction in distal extremities. Although stimulation levels are set below tissue-damaging levels, prolonged rapid muscle contraction can potentially cause 246
AORN Journal
BROWN—BROWN muscular injury.9 Modern monitoring techniques require technicians to use intermittent pulse trains at lower levels to prevent injury. Electrodes need to be placed and secured, usually with tape, to prevent accidental removal or loosening, which decreases conductivity. The lowest electrical stimulus level possible should be used to induce a response. High impedance levels or improper or loose electrode placement can generate heat to the level of burning in conjunction with use of electrosurgical units (ESUs). Typically, monopolar ESUs emit electrical current into the patient that, if functioning improperly, can exit at various points of the body or back to the ESU.9 If faulty equipment is being used, the patient is at risk for electrical burning of the tissue in contact with the electrodes. Safety concerns when the patient is being monitored via MEPs involve protecting the patient from stimulation responses, including muscle contractions and seizures. Although complications are rare, patients are at risk for bite injuries caused by the patient’s jaw having a large muscle contraction after stimulation. Routine placement of bite blocks or other devices should be used to protect the patient’s tongue and mouth. Typical intraoperative monitoring usage requires surface or subdermal electrodes to record neural irritation. In addition to the risk of infection, this presents a risk of intramuscular hematomas when deeper needles are used.9 Stimulation parameters for pedicle screw placement can require the slow increase of voltage until potentials are witnessed. If high stimulation is applied to a pedicle wall and it is breeched, nerve damage can occur even though the nerve root is not being directly stimulated. As with any invasive procedure, sterile technique must be observed to prevent any contamination and maintain the sterility of invasive intraoperative monitoring electrodes. Steps to ensure the safety of the technician as well as the patient include hand washing and using personal protective equipment.
NEURODIAGNOSTIC TECHNICIAN POTENTIAL INTERDEPARTMENTAL ISSUES The need for intraoperative monitoring by a staff member from a department outside surgery can introduce complications to the perioperative setting. Intraoperative monitoring is not used on all procedures by all surgeons, so the OR charge nurse should have knowledge of those procedures with the greatest likelihood of requiring intraoperative monitoring. When the schedule is juggled to accommodate scheduling changes, or when emergent spinal procedures are added, knowing to notify the intraoperative monitoring technician’s department of the need for services is invaluable. Ultimately, good communication is a must to facilitate this additional monitoring, especially for procedures that are not scheduled or are emergent. It is the surgeon’s responsibility to request intraoperative monitoring services when the procedure is scheduled so that the neurodiagnostic monitoring technician can accommodate these needs. The surgeon may fail to request intraoperative monitoring services or decide at the last minute that intraoperative monitoring is necessary for patient safety. Late requests can be difficult to fulfill, and the perioperative team members rely on the intraoperative monitoring technician to respond in a timely manner so that surgery can be accommodated without unnecessary delays. At our facility, the clinical coordinators and unit supervisors review the surgery schedule the day before and identify procedures that may require intraoperative monitoring. Preoperatively, it is important to keep the neurodiagnostic technician apprised of surgery times. Should there be a change in the OR time, surgery charge personnel are responsible for notifying the neurodiagnostic monitoring technician of these changes. This can be a problem if there is not a team mentality in the OR. Preoperative electrode placement is necessary, and the neurodiagnostic monitoring technician does not want to slow down the surgical team at the start of the procedure. Giving neurodiagnostic monitoring techni-
www.aornjournal.org
cians adequate notification of time changes enables them to plan their days most efficiently, so they can be available when they are needed in surgery. Many electrical devices are required throughout a surgical procedure. Electrical artifact emitted from these various devices can sometimes be seen in the intraoperative monitoring recording and can even prevent proper monitoring. Depending on the level of interference the electrical artifact has on monitoring, the electrical source may need to be found and turned off. The perioperative circulating nurse, anesthesia care provider, and intraoperative monitoring technician can work together to locate the source and remove or replace it if necessary. The most common sources for the electrical artifact are blood and fluid warmers, the surgical bed, and electrocautery. The procedures for notifying the surgeon of signal changes vary from surgeon to surgeon. Although it is necessary for the intraoperative monitoring technician to notify the surgeon when signals are decreasing or changing, overnotifying a surgeon of a signal decrease can be distracting. It is important for the technician to establish a rapport with surgeons to learn their preferences for how often they want to be notified of changing signals. The ability of the intraoperative monitoring technician to perform the job depends on his or her ability to sit comfortably for hours at a time, monitoring the computer screen to determine whether there is cause for alarm. The technician’s chair and computer height should be ergonomically comfortable, and the computer screen should be large enough for easy viewing of the screens involved in intraoperative monitoring. The OR temperature often feels cold to those who are not scrubbed in, so the intraoperative monitoring technician should wear appropriate clothing to provide warmth without violating the facility dress code. After surgery, the technician needs time to remove all placed electrodes and equipment. The amount of time will vary depending on how many AORN Journal
247
February 2011
Vol 93
BROWN—BROWN
No 2
electrodes were placed preoperatively. Ideally, electrode removal should occur after the surgical dressing is applied but before the patient emerges from anesthesia. This limited time can be stressful for all surgical team members as they conclude their tasks. The intraoperative monitoring technician needs to be sure that all electrodes are removed, especially any needles, for infection control and safety. At times, other OR staff members such as the circulating nurse may assist in electrode removal, although this may prevent the technician from knowing whether all of the electrodes have been removed safely. Nursing staff members can help best by providing time for the technician to complete his or her tasks without interruption or hindrance.
2.
3.
4.
5.
6.
7.
CONCLUSION As surgical procedures advance and change with time, the traditional surgical team must adapt to modifications, which includes cooperating with new surgical staff members, such as the intraoperative monitoring technician, in the OR. Identifying and addressing the issues that may arise when new processes are put into place can be challenging and put strain on staff members inside and outside perioperative services. New perioperative team members add a new dynamic to the OR and assist in promoting safety standards that are used during surgery. Working together to address scheduling, time-consuming access to patients to apply and remove monitoring electrodes safely and efficiently, and appropriate pharmaceutical administration is the goal of those involved in the surgical process. Teamwork is the cornerstone of any effective multidisciplinary environment, and the surgical suite is no exception. References 1.
248
Schwartz DM, Auerbach JD, Dormans JP, et al. Neurophysiological detection of impending spinal cord injury during scoliosis surgery. J Bone Joint Surg Am. 2007; 89(11):2440-2449.
AORN Journal
8.
9.
Glossary. Human spinal cord injury: new and emerging therapies. Icelandic Health Authorities and the World Health Organization. http://www.sci-therapies.info/ glossary.htm. Accessed September 14, 2010. Chung I, Glow JA, Dimopoulas V, et al. Upper-limb somatosensory evoked potential monitoring in lumbosacral spine surgery: a prognostic marker for positionrelated ulnar nerve injury. Spine J. 2009;9(4):287-295. Sloan TB, Jäntti V. Anesthetic effects on evoked potentials. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:94-126. Osburn LL. A guide to the performance of transcranial electrical motor evoked potentials. Part 1. Basic concepts, recording parameters, special considerations, and application. Am J Electroneurodiagnostic Technol. 2006; 46(2):98-158. Strommen JA, Crum BA. Intraoperative monitoring with free-running EMG. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:396-403. Balzer J, Crammond D, Habeych M, Sclabassi R. Intraoperative EMG during spinal pedicle screw instrumentation. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:404-422. Banoczi W. Update on anesthetic and metabolic effects during intraoperative neurophysiological monitoring (IONM). Am J Electroneurodiagnostic Technol. 2005; 45(4):225-239. MacDonald DB, Deletis V. Safety issues during surgical monitoring. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:882-898.
Molly S. Brown, BS, was a neurodiagnostic technician at Bronson Methodist Hospital, Kalamazoo, MI, at the time this article was written. Currently she is enrolled in an accelerated BSN program at Kent State University, Kent, OH. Ms Brown has no declared affiliation that could be perceived as posing a potential conflict of interest in the publication of this article. Debra S. Brown, BSN, CNOR, is a staff nurse, inpatient surgery, at Bronson Methodist Hospital, Kalamazoo, MI. Ms Brown has no declared affiliation that could be perceived as posing a potential conflict of interest in the publication of this article.
ABSTRACT As surgery needs have increased, the traditional surgical team has expanded to include personnel from radiology and perfusion services. A new surgical team member, the intraoperative monitoring technician, is needed to perform intraoperative monitoring during procedures that carry a higher risk of central and peripheral nerve injury. Including the intraoperative monitoring technician on the surgical team can create challenges, including surgical delays and anesthesia care considerations. When the surgical team members, including the surgeon, anesthesia care provider, and circulating nurse, understand and facilitate this new staff member’s responsibilities, the technician is able to perform monitoring functions that promote the smooth flow of the surgical procedure and positive patient outcomes. AORN J 93 (February 2011) 242-248. © AORN, Inc, 2011. doi: 10.1016/j.aorn.2010.08.023 Key words: free-running electromyography, intraoperative monitoring technician, motor-evoked potentials, neurodiagnostic technician, neurophysiologic monitoring, pedicle screw monitoring, somatosensory-evoked potentials, spinal surgical procedures.
M
odern surgery bears little resemblance to the initial forays into the physical repair of the human body. The advent of anesthetics and sterilization revolutionized surgical capabilities, allowing surgeons to perform repairs and transplants on the human body. While rapidly evolving surgical technologies have modified and expanded the types of procedures that can be performed, the members of the in-room surgical team have not changed much, although the expertise, education, and professional levels of these team members have vastly improved over the years. The usual team consists of the surgeon, an assistant, an
anesthesia care provider, a sterile surgical scrub person, and a circulating nurse. There are also support personnel whose presence, absence, or level of expertise can affect how smoothly a day’s procedures run. A successful team mindset affects the success of the surgery and the patient’s outcome. The high-stress, highly technical, and extraordinary environment of an OR can be intimidating to those from other departments, so when the expertise of outside health care providers is necessary in the OR, there may be some disruption of the team function. Perioperative staff members, including visible team members (eg, surgeon, scrub doi: 10.1016/j.aorn.2010.08.023
242
AORN Journal ●
February 2011
Vol 93
No 2
© AORN, Inc, 2011
NEURODIAGNOSTIC TECHNICIAN person) and less visible members (eg, schedulers, supply technicians), have established roles and accepted responsibilities. As technology has advanced to require additional expertise, the surgical team has expanded to include other disciplines, but the process of changing to allow another member on the team can be jarring. As a result of the increasing role of fluoroscopy in the daily surgical schedule, the radiology technologist’s role in surgery has increased. In fact, it is common to have specific radiology staff members assigned to permanent duty in surgery because of their unique imaging responsibilities. Perfusion services, such as cell collection with reinfusion, also have expanded over the years, making the providers of perfusion services in the OR commonplace. A relatively new member to today’s surgical team is the intraoperative monitoring technician, sometimes referred to as a neurodiagnostic technician. The intraoperative monitoring technician’s job is to monitor the patient’s physiologic responses, both sensory and motor, during procedures that pose a higher risk of nerve damage. There are many factors that can affect spinal cord monitoring, including patient positioning, the use of anesthetic agents, and intraoperative retraction, all of which can affect the ability of the intraoperative monitoring technician to give the surgeon the information that he or she needs to provide safe patient care. Understanding what is being monitored and the technician’s role can help all perioperative team members to work together more smoothly, allowing each member to perform his or her specific functions. INTRAOPERATIVE MONITORING During procedures that pose a higher risk of nerve damage—which, at our facility, include open and minimally invasive discectomies, foraminotomies and laminectomies, open and minimally invasive spinal fusions, and anterior and posterior cervical procedures—multiple intraoperative monitoring modalities can be used. These modalities include brainstem auditory
www.aornjournal.org
evoked potentials and cortical mapping. For the purpose of this article, however, we will focus on the most common monitoring techniques that are performed during the previously mentioned surgical procedures. The four most common monitoring techniques that are used intraoperatively for tracking physiologic responses are somatosensory-evoked potentials (SSEP), motor-evoked potentials (MEP), free-running electromyography (EMG), and pedicle screw monitoring (Table 1).1 The type of intraoperative monitoring that is used depends on the procedure and surgeon preference. The type of monitoring determines lead placement, and the level of anticipated surgery will affect the number and location of electrodes that are placed. If multiple monitoring modalities are requested, the number of electrode placements increases. If the procedure involves multiple surgical levels, more electrodes must be placed. Should the surgeon need a baseline reading before the patient is positioned, the anesthesia care provider will need to know about this to be able to provide anesthesia for the patient without interfering with the monitoring process. The other perioperative team members also will need to know because the intraoperative monitoring technician will need to have all electrodes in place and connected to the monitoring equipment before the patient is positioned, which will slow down the progression of the procedure. A team-based approach involving all participants can address these problems and minimize obstacles that may occur during these complex surgeries. SSEPs Stimulating a sensory nervous pathway induces evoked potentials, which can be used to monitor the dorsal portion of the spinal cord.2 Electrical stimulation is applied to the skin of an underlying nerve of both the upper and lower extremities. The stimulus travels along the specific nerve pathway, inducing a potential (ie, response), which is recorded by electrodes placed over the sensory portion of the cortex of the brain. This AORN Journal
243
February 2011
Vol 93
BROWN—BROWN
No 2
TABLE 1. Intraoperative Monitoring Summary Somatosensoryevoked potentials
Motor-evoked potentials
Electromyography
Where stimulus is applied
Stimulus is applied near distal nerve.
Stimulus is applied above motor strip of cerebral cortex.
No stimulus is initiated by intraoperative monitoring staff.
Where stimulus is monitored
Cerebral cortex is monitored to record receipt of stimulus.
Muscle response is monitored to record receipt of stimulus.
Muscles are monitored to record irritation to muscles innervated at the surgical level.
Expected patient reaction
Can produce repetitive contractions of hands and feet.
Large muscle contractions may occur; bite blocks recommended.
Is muscle relaxant acceptable?
Yes—Because sensory is being tested, use of muscle relaxants is acceptable.
No—Because muscle motor response to intraoperative monitoring stimulus is being tested, use of muscle relaxants interferes with intraoperative monitoring.
If there is no irritation of the nerve roots, there will be no electrical activity. If a nerve were compressed, the irritation could be reflected in electrical activity of the muscle innervated by that nerve root. No—Because muscle motor response to surgical manipulation is being tested, use of muscle relaxants interferes with intraoperative monitoring.
electrophysiologic measurement of spinal cord sensory function can help in evaluating the integrity of both the peripheral and central pathways that are at risk during spinal manipulation.3 Somatosensory-evoked potentials are highly susceptible to anesthesia changes, including changes in blood pressure, anesthetic agents, and anesthetic gas levels in the patient, so careful monitoring of inhalation agents, blood pressure, body temperature, and other factors is necessary.4 For this modality, stimulating electrodes are typically applied in the distal portion of the extremities and recording electrodes are placed on the head. If signals cannot be elicited, the technician needs to 244
AORN Journal
Pedicle screw monitoring Stimulating probe is inserted into anticipated path of pedicle screw or to in-place screw. Resistance to the passage of the electrical stimulation at the anticipated screw site is measured. High resistance to the stimulus indicates the screw path is enclosed by the cortex of the pedicle. Low resistance may indicate the anticipated path breeches the pedicle.
No—Because muscle motor response to surgical manipulation is being tested, use of muscle relaxants interferes with intraoperative monitoring.
identify where disruption is occurring in the pathway. If cervical and cortical responses are present but more distal responses are not, improper positioning of the extremities may be causing impingement on the peripheral nerves. The team members may need to investigate the cause and possibly reposition the patient. Extra considerations for positioning-related sensory deficits are particularly important for procedures in which the patient may be prone for numerous hours. Extra padding and support may be required to alleviate any pressure that can be placed on the nerves. If cervical and cortical potentials are lost as well,
NEURODIAGNOSTIC TECHNICIAN this could be indicative of spinal cord compromise, and team members must work together to identify and correct the possible causes to restore those potentials before damage to the cord becomes permanent. Many institutions have outlined protocols for this adverse event, and these should be accessible and known to the surgical team. MEPs Also known as transcranial motor-evoked potentials, MEPs are electrophysiologic responses recorded in muscles after direct stimulation of the brain.2 When spinal procedures have the potential to cause injury to the anterior (ie, motor) portion of the spinal cord, monitoring of MEPs is highly recommended. Stimulating electrodes are placed over the motor portion of the cortex and are recorded in distal muscles of the extremities both above and below the surgical site.5 The main obstacle for this modality is the administration of muscle relaxants, which inhibits monitoring functions; therefore, communication with the anesthesia care provider before the administration of muscle relaxants is imperative.4 Stimulation can commonly cause a muscle contraction in various locations, so the technician needs to also communicate with the sterile staff members to inform them of possible movement that could compromise sterility or safety. If MEPs are lost, spinal cord function may be compromised. Intraoperative monitoring technicians need to communicate with the surgical team and anesthesia care provider to try to determine why the signals were lost and how to recover the signals before permanent damage is sustained. Protocols for this adverse event should be available and understood as well. EMG Spinal surgeries that involve working near spinal nerve roots can require the monitoring of muscles innervated by the roots at the surgical site level.2 Electrodes are placed in the subdermal layer over the muscles of the corresponding levels to record any nerve irritation that could be indicative of
www.aornjournal.org
compression, stretch, severing, or other irritant factors.6 Requirements for this modality are access to the muscles to be recorded and that no muscle paralytic be used. Communication between the intraoperative monitoring technician and the surgical and anesthesia team members before surgery can help ensure physical patient access and adherence to the agreed upon anesthesia care plans. Pedicle Screw Monitoring When spinal screws are being placed into the pedicles of the vertebrae, anticipated or actual screw testing can be performed. Stimulation of the screws or the drilled hole before screw placement can elicit a response in the EMG recording. The surgeon places the stimulation probe and notifies the technician to provide the electrical stimulus. The technician then relays to the surgeon the digital reading from the monitoring device. Potentials seen at low stimulation levels can be caused from a breach of the pedicle wall, misplacement of the screw or intended screw path, or bone weakness. If potentials are seen at low levels of stimulation, placement of the screw hole may need to be reevaluated and possibly be adjusted.7 Perioperative Implications For any given procedure, the number of electrodes, the time required for placement or insertion of electrodes, and the number of locations of insertion vary greatly. For example, for a onelevel lumbar discectomy, a few electrodes may be placed in only the lower extremities, and the technician may only need a few minutes with access to the legs. For multiple-level spinal procedures that include the thoracic region, however, all four mentioned modalities may be required during the procedure. Whereas SSEPs and EMGs are monitored continuously, MEPs and pedicle screw monitoring are tested as needed or as directed by the surgeon. In these surgeries, the intraoperative monitoring technician needs access to the patient’s entire body and more time to allow placing and securing as many as 50 electrodes, depending AORN Journal
245
February 2011
Vol 93
No 2
Portable intraoperative monitoring equipment. Image courtesy of Medtronic Spinal and Biologics, Minneapolis, MN.
on the monitoring modalities and the number of surgical levels being addressed. In any neurophysiologic monitored surgery, anesthetic limitations are present and must be discussed preoperatively by the intraoperative technician, anesthesia care provider, and surgeon so preparation can occur. Levels of inhalation agents and muscle paralytics can inhibit the intraoperative monitoring technician from performing a safe and effective study.8 The surgical team members need to help the anesthesia care provider work effectively with the intraoperative monitoring technician to achieve the anesthetic compromise that will allow the patient to receive the best care possible. Safety Concerns There are safety concerns with each type of neurophysiologic monitoring. The intraoperative monitoring technician observes the patient for these concerns. If monitoring is combined with other modalities that require lack of neuromuscular blockade, SSEP stimulation can cause a muscle contraction in distal extremities. Although stimulation levels are set below tissue-damaging levels, prolonged rapid muscle contraction can potentially cause 246
AORN Journal
BROWN—BROWN muscular injury.9 Modern monitoring techniques require technicians to use intermittent pulse trains at lower levels to prevent injury. Electrodes need to be placed and secured, usually with tape, to prevent accidental removal or loosening, which decreases conductivity. The lowest electrical stimulus level possible should be used to induce a response. High impedance levels or improper or loose electrode placement can generate heat to the level of burning in conjunction with use of electrosurgical units (ESUs). Typically, monopolar ESUs emit electrical current into the patient that, if functioning improperly, can exit at various points of the body or back to the ESU.9 If faulty equipment is being used, the patient is at risk for electrical burning of the tissue in contact with the electrodes. Safety concerns when the patient is being monitored via MEPs involve protecting the patient from stimulation responses, including muscle contractions and seizures. Although complications are rare, patients are at risk for bite injuries caused by the patient’s jaw having a large muscle contraction after stimulation. Routine placement of bite blocks or other devices should be used to protect the patient’s tongue and mouth. Typical intraoperative monitoring usage requires surface or subdermal electrodes to record neural irritation. In addition to the risk of infection, this presents a risk of intramuscular hematomas when deeper needles are used.9 Stimulation parameters for pedicle screw placement can require the slow increase of voltage until potentials are witnessed. If high stimulation is applied to a pedicle wall and it is breeched, nerve damage can occur even though the nerve root is not being directly stimulated. As with any invasive procedure, sterile technique must be observed to prevent any contamination and maintain the sterility of invasive intraoperative monitoring electrodes. Steps to ensure the safety of the technician as well as the patient include hand washing and using personal protective equipment.
NEURODIAGNOSTIC TECHNICIAN POTENTIAL INTERDEPARTMENTAL ISSUES The need for intraoperative monitoring by a staff member from a department outside surgery can introduce complications to the perioperative setting. Intraoperative monitoring is not used on all procedures by all surgeons, so the OR charge nurse should have knowledge of those procedures with the greatest likelihood of requiring intraoperative monitoring. When the schedule is juggled to accommodate scheduling changes, or when emergent spinal procedures are added, knowing to notify the intraoperative monitoring technician’s department of the need for services is invaluable. Ultimately, good communication is a must to facilitate this additional monitoring, especially for procedures that are not scheduled or are emergent. It is the surgeon’s responsibility to request intraoperative monitoring services when the procedure is scheduled so that the neurodiagnostic monitoring technician can accommodate these needs. The surgeon may fail to request intraoperative monitoring services or decide at the last minute that intraoperative monitoring is necessary for patient safety. Late requests can be difficult to fulfill, and the perioperative team members rely on the intraoperative monitoring technician to respond in a timely manner so that surgery can be accommodated without unnecessary delays. At our facility, the clinical coordinators and unit supervisors review the surgery schedule the day before and identify procedures that may require intraoperative monitoring. Preoperatively, it is important to keep the neurodiagnostic technician apprised of surgery times. Should there be a change in the OR time, surgery charge personnel are responsible for notifying the neurodiagnostic monitoring technician of these changes. This can be a problem if there is not a team mentality in the OR. Preoperative electrode placement is necessary, and the neurodiagnostic monitoring technician does not want to slow down the surgical team at the start of the procedure. Giving neurodiagnostic monitoring techni-
www.aornjournal.org
cians adequate notification of time changes enables them to plan their days most efficiently, so they can be available when they are needed in surgery. Many electrical devices are required throughout a surgical procedure. Electrical artifact emitted from these various devices can sometimes be seen in the intraoperative monitoring recording and can even prevent proper monitoring. Depending on the level of interference the electrical artifact has on monitoring, the electrical source may need to be found and turned off. The perioperative circulating nurse, anesthesia care provider, and intraoperative monitoring technician can work together to locate the source and remove or replace it if necessary. The most common sources for the electrical artifact are blood and fluid warmers, the surgical bed, and electrocautery. The procedures for notifying the surgeon of signal changes vary from surgeon to surgeon. Although it is necessary for the intraoperative monitoring technician to notify the surgeon when signals are decreasing or changing, overnotifying a surgeon of a signal decrease can be distracting. It is important for the technician to establish a rapport with surgeons to learn their preferences for how often they want to be notified of changing signals. The ability of the intraoperative monitoring technician to perform the job depends on his or her ability to sit comfortably for hours at a time, monitoring the computer screen to determine whether there is cause for alarm. The technician’s chair and computer height should be ergonomically comfortable, and the computer screen should be large enough for easy viewing of the screens involved in intraoperative monitoring. The OR temperature often feels cold to those who are not scrubbed in, so the intraoperative monitoring technician should wear appropriate clothing to provide warmth without violating the facility dress code. After surgery, the technician needs time to remove all placed electrodes and equipment. The amount of time will vary depending on how many AORN Journal
247
February 2011
Vol 93
BROWN—BROWN
No 2
electrodes were placed preoperatively. Ideally, electrode removal should occur after the surgical dressing is applied but before the patient emerges from anesthesia. This limited time can be stressful for all surgical team members as they conclude their tasks. The intraoperative monitoring technician needs to be sure that all electrodes are removed, especially any needles, for infection control and safety. At times, other OR staff members such as the circulating nurse may assist in electrode removal, although this may prevent the technician from knowing whether all of the electrodes have been removed safely. Nursing staff members can help best by providing time for the technician to complete his or her tasks without interruption or hindrance.
2.
3.
4.
5.
6.
7.
CONCLUSION As surgical procedures advance and change with time, the traditional surgical team must adapt to modifications, which includes cooperating with new surgical staff members, such as the intraoperative monitoring technician, in the OR. Identifying and addressing the issues that may arise when new processes are put into place can be challenging and put strain on staff members inside and outside perioperative services. New perioperative team members add a new dynamic to the OR and assist in promoting safety standards that are used during surgery. Working together to address scheduling, time-consuming access to patients to apply and remove monitoring electrodes safely and efficiently, and appropriate pharmaceutical administration is the goal of those involved in the surgical process. Teamwork is the cornerstone of any effective multidisciplinary environment, and the surgical suite is no exception. References 1.
248
Schwartz DM, Auerbach JD, Dormans JP, et al. Neurophysiological detection of impending spinal cord injury during scoliosis surgery. J Bone Joint Surg Am. 2007; 89(11):2440-2449.
AORN Journal
8.
9.
Glossary. Human spinal cord injury: new and emerging therapies. Icelandic Health Authorities and the World Health Organization. http://www.sci-therapies.info/ glossary.htm. Accessed September 14, 2010. Chung I, Glow JA, Dimopoulas V, et al. Upper-limb somatosensory evoked potential monitoring in lumbosacral spine surgery: a prognostic marker for positionrelated ulnar nerve injury. Spine J. 2009;9(4):287-295. Sloan TB, Jäntti V. Anesthetic effects on evoked potentials. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:94-126. Osburn LL. A guide to the performance of transcranial electrical motor evoked potentials. Part 1. Basic concepts, recording parameters, special considerations, and application. Am J Electroneurodiagnostic Technol. 2006; 46(2):98-158. Strommen JA, Crum BA. Intraoperative monitoring with free-running EMG. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:396-403. Balzer J, Crammond D, Habeych M, Sclabassi R. Intraoperative EMG during spinal pedicle screw instrumentation. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:404-422. Banoczi W. Update on anesthetic and metabolic effects during intraoperative neurophysiological monitoring (IONM). Am J Electroneurodiagnostic Technol. 2005; 45(4):225-239. MacDonald DB, Deletis V. Safety issues during surgical monitoring. In: Nuwer M, ed. Intraoperative Monitoring of Neural Function: Handbook of Clinical Neurophysiology. 8th ed. Philadelphia, PA: Elsevier Ltd; 2008:882-898.
Molly S. Brown, BS, was a neurodiagnostic technician at Bronson Methodist Hospital, Kalamazoo, MI, at the time this article was written. Currently she is enrolled in an accelerated BSN program at Kent State University, Kent, OH. Ms Brown has no declared affiliation that could be perceived as posing a potential conflict of interest in the publication of this article. Debra S. Brown, BSN, CNOR, is a staff nurse, inpatient surgery, at Bronson Methodist Hospital, Kalamazoo, MI. Ms Brown has no declared affiliation that could be perceived as posing a potential conflict of interest in the publication of this article.