This is the current release of the guideline.

Diseases or conditions requiring magnetic resonance imaging (MRI)

Education

1. Magnetic resonance imaging (MRI) magnet hazards
2. MRI monitoring limitations
3. MRI long-term health hazards

Screening

1. Mandatory screening of all personnel entering zone III or IV
2. Screening for patient-related risks for adverse outcomes related to MRI
3. Assessing equipment-related risks for adverse outcomes related to MRI

Management

1. Planning for the anesthetic care of the patient for the scan
2. Planning for rapidly summoning additional personnel in the event of an emergency
3. Monitoring the patient during MRI
4. Anesthetic care during MRI
5. Airway management during MRI
6. Managing medical and environmental emergencies
7. Postprocedure care consistent with that provided for other areas of the institution

For this Advisory, a systematic review and evaluation of the literature was conducted, and formal survey opinion data were obtained from experts and American Society of Anesthesiologists (ASA) members. Informal opinion-based information from other sources (e.g., open forums, Internet postings) was also used in the development of this document.

For the literature review, potentially relevant studies were identified via electronic and manual searches of the literature. The literature search covered a 36-year period from 1973 through 2008.

Opinion surveys were developed by the Task Force to address each clinical intervention identified in the document. Identical surveys were distributed to two groups of respondents: expert consultants and ASA members.

A total of 157 articles contained direct linkage-related evidence.

Scientific Evidence

Study findings from published scientific literature were aggregated and are reported in summary form by evidence category.

Category A: Supportive Literature: Randomized controlled trials report statistically significant (P<0.01) differences among clinical interventions for a specified clinical outcome.

Level 1: The literature contains multiple randomized controlled trials, and the aggregated findings are supported by meta-analysis.*

Level 2: The literature contains multiple randomized controlled trials, but there is an insufficient number of studies to conduct a viable meta-analysis for the purpose of this Advisory.

Level 3: The literature contains a single randomized controlled trial.

*All meta-analyses are conducted by the American Society of Anesthesiologists (ASA) methodology group. Meta-analyses from other sources are reviewed but not included.

Category B: Suggestive Literature: Information from observational studies permits inference of beneficial or harmful relations among clinical interventions and clinical outcomes.

Level 1: The literature contains observational comparisons (e.g., cohort, case-control research designs) of two or more clinical interventions or conditions and indicates statistically significant differences between clinical interventions for a specified clinical outcome.

Level 2: The literature contains noncomparative observational studies with associative (e.g., relative risk, correlation) or descriptive statistics.

Level 3: The literature contains case reports.

Category C: Equivocal Literature: The literature cannot determine whether there are beneficial or harmful relations among clinical interventions and clinical outcomes.

Level 1: Meta-analysis did not find significant differences among groups or conditions.

Level 2: There is an insufficient number of studies to conduct meta-analysis and (1) randomized controlled trials have not found significant differences among groups or conditions or (2) randomized controlled trials report inconsistent findings.

Level 3: Observational studies report inconsistent findings or do not permit inference of beneficial or harmful relations.

Category D: Insufficient Evidence from the Literature: The lack of scientific evidence in the literature is described by the following terms.

Silent: No identified studies address the specified relations among interventions and outcomes.

Inadequate: The available literature cannot be used to assess relations among clinical interventions and clinical outcomes. The literature either does not meet the criteria for content as defined in the "Focus" of the Advisory or it does not permit a clear interpretation of findings due to methodologic concerns (e.g., confounding in study design or implementation).

Opinion-based Evidence

Category A: Expert Opinion: Survey responses from Task Force–appointed expert consultants are reported in summary form in the text. A complete listing of consultant survey responses is reported in Table 2, Appendix 3 in the original guideline document.

Category B: Membership Opinion: Survey responses from a random sample of members of the ASA and, when appropriate, responses from members of other organizations with expertise in the selected topics of interest are reported in summary form in the text. A complete listing of ASA member survey responses is reported in Table 3, Appendix 3 in the original guideline document.

Survey responses are recorded using a five-point scale and summarized based on median values.*

Strongly Agree: Median score of 5 (at least 50% of the responses are 5)

Agree: Median score of 4 (at least 50% of the responses are 4 or 4 and 5)

Equivocal: Median score of 3 (at least 50% of the responses are 3, or no other response category or combination of similar categories contains at least 50% of the responses)

Disagree: Median score of 2 (at least 50% of responses are 2 or 1 and 2)

Strongly Disagree: Median score of 1 (at least 50% of responses are 1)

Category C: Informal Opinion: Open-forum testimony, Internet-based comments, letters, and editorials are all informally evaluated and discussed during the development of the Advisory. When warranted, the Task Force may add educational information or cautionary notes based on this information.

*When an equal number of categorically distinct responses is obtained, the median value is determined by calculating the arithmetic mean of the two middle values. Ties are calculated by a predetermined formula.

For this Advisory, a systematic review and evaluation of the literature was conducted, and formal survey opinion data were obtained from experts and American Society of Anesthesiologists (ASA) members. Informal opinion-based information from other sources (e.g., open forums, Internet postings) was also used in the development of this document. Both the literature evaluation and the survey opinion data were based on evidence linkages, or statements regarding potential relations between patient care interventions and safety outcomes in the magnetic resonance imaging (MRI) suite.* The evidence linkage interventions are listed in Appendix 3 of the original guideline document.

State of the Literature

More than 1,200 citations were initially identified, yielding a total of 343 articles that addressed topics related to the evidence linkages and met the criteria for inclusion. After review of the articles, 186 studies did not provide direct evidence and were subsequently eliminated. A total of 157 articles contained direct linkage-related evidence (see Supplemental Digital Content 1 , which is a complete list of references used to develop this Advisory). No evidence linkage contained enough studies with well-defined experimental designs and statistical information to conduct a quantitative analysis (i.e., meta-analysis).

Interobserver agreement among Task Force members and two methodologists was established by interrater reliability testing. Agreement levels using a kappa (k) statistic for two-rater agreement pairs were as follows: (1) type of study design, k = 0.49–0.85; (2) type of analysis, k = 0.54–0.93; (3) evidence linkage assignment, k = 0.77–1.00; and (4) literature inclusion for database, k = 0.78–1.00. Three-rater chance-corrected agreement values were (1) study design, Sav = 0.65, Var (Sav) = 0.009; (2) type of analysis, Sav = 0.69, Var (Sav) = 0.010; (3) linkage assignment, Sav = 0.85, Var (Sav) = 0.004; and (4) literature database inclusion, Sav = 0.85, Var (Sav) = 0.013. These values represent moderate to high levels of agreement.

Consensus-based Evidence

Consensus was obtained from multiple sources, including (1) survey opinion from consultants who were selected based on their knowledge or expertise in MRI, (2) survey opinions solicited from active members of the ASA, (3) testimony from attendees of a publicly held open forum at two national anesthesia meetings, (4) Internet commentary, and (5) Task Force opinion and interpretation. The survey rate of return was 63% (n = 50 of 79) for the consultants, and 989 surveys were received from active ASA members. Results of the surveys are reported in Tables 2 and 3 in the original guideline document and are reported in summary form in the text of the Advisory.

The consultants were asked to indicate which, if any, of the evidence linkages would change their clinical practices if the Advisory was instituted. The rate of return was 29% (n = 23 of 79). The percent of responding consultants expecting a change in their practice associated with each linkage topic was as follows: (1) education, 30%; (2) screening of anesthesia care providers and ancillary support personnel, 13%; (3) patient screening, 26%; (4) preparation,13%; (5) patient management during MRI—monitoring, 4%; (6) patient management during MRI—anesthetic care, 0%; (7) patient management during MRI—airway, 0%; (8) patient management during MRI—emergencies, 13%; and (9) postprocedure care, 9%. Seventy-four percent indicated that their clinical practice would not need new equipment, supplies, or training to implement the Practice Advisory. Eighty-five percent indicated that the Advisory would not require ongoing changes in their practice that would affect costs. Ninety-five percent of the respondents indicated that the Advisory would have no effect on the amount of time spent on a typical case, and 5% indicated that there would be a 10-min increase in the amount spent on a typical case with the implementation of this Advisory.

*Outcomes for the listed interventions refer to the occurrence of safety-based outcomes.

The American Society of Anesthesiologists (ASA) appointed a Task Force of 13 members. These individuals included 10 anesthesiologists in private and academic practice from various geographic areas of the United States, 1 radiologist, and 2 consulting methodologists from the ASA Committee on Standards and Practice Parameters.

The Task Force developed the Advisory by means of a seven-step process. First, they reached consensus on the criteria for evidence. Second, a systematic review and evaluation was performed on original published research studies from peer-reviewed journals relevant to magnetic resonance imaging (MRI) safety. Third, a panel of expert consultants was asked to (1) participate in opinion surveys on the effectiveness of various MRI safety strategies and (2) review and comment on a draft of the Advisory developed by the Task Force. Fourth, opinions about the Advisory were solicited from a random sample of active members of the ASA. Fifth, the Task Force held an open forum at two major national meetings to solicit input on its draft recommendations. Sixth, the consultants were surveyed to assess their opinions on the feasibility of implementing this Advisory. Seventh, all available information was used to build consensus within the Task Force to create the final document, as summarized in Appendix 2 in the original guideline document.

Not applicable

A formal cost analysis was not performed and published cost analyses were not reviewed.

A panel of expert consultants was asked to review and comment on draft reports. Opinions about the Advisory were solicited from a random sample of active members of the American Society of Anesthesiologists (ASA). The Task Force held an open forum at two major national meetings to solicit input on its draft recommendations.

Zone definitions (III–IV) are provided at the end of the "Major Recommendations" field.

1. Education
   • All anesthesiologists should have general safety education on the unique physical environment of the magnetic resonance imaging (MRI) scanner, and specific education regarding the specific features of individual scanners within their institution.
     • Education should emphasize safety for entering zones III and IV, with special emphasis on hazards in this environment and effects on monitoring capabilities.
     • Education should address potential health hazards (e.g., high decibel levels and high-intensity magnetic fields).
     • Education should address necessary precautions to deal with the specific field strength and the safety of the MRI scanners within their institutions.
     • Education should include information regarding ferromagnetic items (e.g., stethoscopes, pens, wallets, watches, hair clips, name tags, pagers, cell phones, credit cards, batteries) and implantable devices (e.g., spinal cord stimulators, implanted objects) that should not be brought into zone III or IV of the MRI suite or should be brought in with caution.
   • Anesthesiologists should work in collaboration with radiologists, technologists, and physicists within their institutions to ensure that the above topics are included in their safety training programs.
   • Education should include how to safely respond to code blue situations in zones III and IV, and this information should be integrated into protocols for the designated code blue team.

2. Screening of Anesthesia Care Providers and Ancillary Support Personnel

   The anesthesiologist should work in collaboration with the MRI medical director or designee (e.g., safety officer) to ensure that all anesthesia team personnel entering zone III or IV have been screened for the presence of ferromagnetic materials, foreign bodies, and implanted devices.

3. Patient Screening
   • For every case, the anesthesiologist should communicate with the patient, referring physician, and radiologist to determine whether the patient:
     • Presents with a high-risk medical condition (e.g., neonatal status or prematurity; intensive or critical care status; impaired respiratory function; hemodynamic instability and vasoactive infusion requirements; comorbidities such as obesity and peripheral vascular disease)
     • Requires equipment (e.g., physiologic or invasive monitors; intubation, oxygenation, or ventilation equipment)
     • Has been screened for implanted devices (e.g., pacemakers, cardioverter–defibrillators, nerve stimulators)
     • Has been screened for implanted ferromagnetic items (e.g., surgical clips, prosthetic heart valves)
     • Has been screened for the presence of embedded foreign bodies (e.g., orbital iron filings, eyeliner tattoos)
   • The anesthesiologist should communicate with the technologist to ensure that the patient has been screened for the presence of foreign bodies on the patient (e.g., pierced jewelry, rings) before entering zone III.
   • If a patient presents with a high-risk medical condition, the anesthesiologist should collaborate with all participants, including the referring physician, radiologist, and technologist, to determine how the patient will be managed during the MRI procedure.
     • Anticipated changes in level of sedation, muscle relaxation, or ventilation may also place a patient in a high-risk situation.
   • For patients with acute or severe renal insufficiency, the anesthesiologist should not administer gadolinium because of the increased risk of nephrogenic systemic fibrosis.
   • Anesthesiologists should work with their institutions to properly identify and label anesthesia-related equipment according to convention (safe, unsafe, or conditional) for each MRI scanner.
   • For each MRI location, anesthesiologists should determine the safety and effectiveness of the equipment needed by the patient during the procedure.
     • Care should be taken to ensure that the patient's equipment does not interfere with image acquisition or quality.
   • Cardiac pacemakers and implantable cardioverter–defibrillators are generally contraindicated for MRI.
     • When MRI is considered essential by the referring physician and consulting radiologist, a plan for managing these patients during the scan should be developed in collaboration with the ordering physician, medical director or on-site radiologist, and other appropriate consultants (e.g., patient's pacemaker specialist or cardiologist, diagnostic radiologist, device manufacturer).
   • MRI may be performed on a limited basis for patients with certain implanted electronic devices (e.g., deep brain stimulators, vagal nerve stimulators, phrenic nerve stimulators, wire-containing thermodilution catheters, cochlear implants).
     • In consultation with the referring physician, the radiologist responsible for the procedure, and the neurosurgeon, the anesthesiologist should ensure that the presence of the device has been noted and determined to be MRI safe/conditional before imaging of these patients.

4. Preparation
   • For every case, the anesthesiologist should prepare, with support personnel, a plan for providing optimal anesthetic care within the special environment of the MRI suite.
     • In addition to addressing the medical needs of the patient, features of the plan should include (1) requirements of the scan and personnel needs, (2) positioning of equipment, (3) special requirements or unique issues of patient or imaging study, (4) positioning of the anesthesiologist and the patient, and (5) planning for emergencies.
   • The anesthesiologist should communicate with the radiology personnel to determine the requirements for the scan (e.g., duration of the scan, position of the patient or area of the body in the scanner, positioning of receiver coils, need for periods of paused respiration).
   • The anesthesiologist should communicate with other anesthesia team members regarding individual roles for anesthetic care.
   • The anesthesiologist should collaborate with the magnetic resonance (MR) technologist and/or facility biomedical engineer to determine and demarcate the optimal and safe location of movable equipment in relation to the gauss lines within the MRI suite.
   • The anesthesiologist should choose a location or position for optimal patient observation and vigilance during delivery of care, whether in zone III or IV.
     • Anesthesiologists should have (1) a clear line of sight of the patient and physiologic monitors, whether by direct observation or by video camera; (2) anesthetic delivery equipment located for optimal control of anesthetic depth and rapid intervention; and (3) access to hospital information systems integral to patient care.
     • In preparing for positioning, the anesthesiologist should take into account potential electromagnetic and auditory hazards.
   • Anesthesiologists should prepare a plan for rapidly summoning additional personnel in the event of an emergency.
     • The anesthesiologist should ensure that (1) emergency equipment and drugs are immediately accessible; (2) emergency communication (e.g., phone or code button) is immediately available; and (3) an evacuation plan is in place, including an appropriate location outside the scan room (zone IV) for resuscitation.
       • This location should be complete with physiologic monitors, oxygen, suction, and other appropriate resuscitation equipment.

5. Patient Management During MRI

   Monitoring

   • MRI patients should be monitored in a manner consistent with the American Society of Anesthesiologists (ASA) Standards for Basic Anesthetic Monitoring.
   • The anesthesiologist should be familiar with the expected limitations of available monitoring equipment.
     • Information from electrocardiograms may be limited due to superimposed voltages from blood flow in the high magnetic field (e.g., ST-segment interpretation may be unreliable, even with highly filtered monitors).
   • The anesthesiologist should make sure that all monitors used in zone IV are safe/conditional for the scan.
   • A monitor should be available to view vital signs from zone III when the anesthesia care provider is not in zone IV.
   • Additional care should be taken in positioning electrocardiogram and other monitor leads to eliminate burns, even with nonferromagnetic leads.

   Anesthetic Care

   • Although lighter levels of anesthesia may be appropriate during an MRI scan, the anesthesiologist should be aware that these lighter levels may result in airway complications (e.g., laryngospasm, coughing, or other airway compromise), which may necessitate interruption of the scan for urgent treatment and alteration of anesthetic depth.
     • Institutional circumstances, patient characteristics, and anesthesiologist preference may warrant more aggressive airway management and deeper anesthetic levels.
   • Anesthesiologists should ensure that patients who receive moderate or deep sedation are monitored in a manner consistent with their institution's protocol for monitoring similarly sedated patients elsewhere in the facility.
   • Monitoring of exhaled carbon dioxide should be considered for all patients receiving deep sedation and for patients whose ventilation cannot be directly observed during moderate sedation.
   • Monitoring oxygenation by pulse oximetry is not a substitute for monitoring ventilatory function.
   • Equipment and drugs for anesthetic care in the MRI suite should mirror what is available in other anesthetizing locations, including (1) an integrated anesthesia machine, medical gases, and waste anesthesia gas disposal or gas scavenging, when inhalational anesthesia is administered; (2) suction; (3) adequate electrical outlets and lighting; and (4) storage areas for equipment and drugs.
   • Equipment used in the MRI suite should be appropriate for the age and size of the patient.
   • MRI-safe/conditional anesthesia machines are always preferred for use in an MRI facility.
     • When an MRI-safe/conditional anesthesia machine is not available, inhalational anesthetics can be administered from an anesthesia machine inside zone III via an elongated circuit through a wave guide.
     • If total intravenous anesthesia is used, it should be administered by using (1) MRI-safe/conditional pumps in zone IV, (2) traditional (i.e., MRI unsafe) pumps in zone III with intravenous tubing passed through a wave guide, or (3) periodic bolus injections in zone III or IV.
   • Although an anesthesia machine may not be required for the administration of total intravenous anesthesia, there must be equipment immediately available for the administration of positive pressure ventilation with oxygen.

   Airway Management

   • The anesthesiologist should have an advance plan in place to deal with instrumentation of the airway and common airway problems (e.g., obstruction, secretions, laryngospasm, apnea and hypoventilation) when patients are in an MRI environment.
   • If the patient is at risk for airway compromise, more aggressive airway management (e.g., use of an endotracheal tube or laryngeal mask airway), should be instituted because the patient's airway may be less accessible when the patient is in the scanner.
   • Complex airway management (e.g., fiberoptic intubation) should be performed in a controlled environment outside of zone IV.
   • Alternative airway devices should be immediately available in the MRI suite.
   • Suction equipment should be immediately accessible to the patient's airway at all times.

   Management of Emergencies

   • When a patient has a medical emergency (e.g., cardiopulmonary arrest) in the MRI scanner, the following should occur: (1) Immediately remove the patient from zone IV while initiating cardiopulmonary resuscitation, if indicated; (2) call for help; and (3) transport the patient to a previously designated safe area for resuscitation that is not in zone IV.
     • This location should be as close to zone IV as possible so as not to delay resuscitation efforts, and should contain the following resuscitation equipment: a defibrillator, vital signs monitors, and a code cart that includes resuscitation drugs, airway equipment, oxygen, and suction.
   • When a fire occurs in the MRI suite, team members should perform their preassigned fire management task as quickly as possible, in accordance with the ASA Practice Advisory for the Prevention and Management of Operating Room Fires.
     • If a team member cannot rapidly perform his or her task in the predetermined order, other team members should perform their tasks without waiting.
     • When a team member has completed a preassigned task, he or she should help other members perform tasks that are not yet complete.
   • In the case of projectile emergencies, team members should perform their institution's protocol in reaction to this occurrence.
     • If possible, immediately remove the patient from zone IV and discontinue the scan.
     • If the patient is injured, proceed with medical emergency management as indicated above.
     • A controlled quench may be necessary to remove the patient from the bore.
   • When a quench occurs, team members should perform their institution's protocol in reaction to this occurrence. If possible, (1) immediately remove the patient from zone IV and (2) immediately administer oxygen to the patient.
     • Powerful static magnetic fields may persist after a quench, and therefore the usual precautions apply when entering zone IV.
   • Emergency response personnel should be restricted from entering zone IV during any environmental emergency because of the persistent magnetic field.

6. Postprocedure Care
   • The anesthesiologist should collaborate with the radiologist and other staff in the postprocedure care of the patient.
   • Patients receiving sedation or anesthesia within the MRI suite should have access to postanesthetic care consistent with that provided in other areas of the institution, including transport to other recovery rooms, dedicated intensive care, or recovery areas within the MRI suite.
   • In all situations, intensive care and recovery areas should include access to vital sign monitors, oxygen, suction, resuscitation equipment, and trained personnel.
   • Patients should be given oral and written discharge instructions.

Zone Definitions

Zone III

This area is the region in which free access by unscreened non-MR personnel or ferromagnetic objects or equipment can result in serious injury or death as a result of interactions between the individuals or equipment and the MR scanner's particular environment. These interactions include, but are not limited to, those with the MR scanner's static and time-varying magnetic fields. All access to zone III is to be strictly restricted, with access to regions within it (including zone IV; see below) controlled by, and entirely under the supervision of, MR personnel.

Zone IV

This area is the MR scanner magnet room. By definition, zone IV will always be located within zone III because it is the MR magnet and its associated magnetic field, which generates the existence of zone III.

None provided

Evidence was obtained from two principal sources: scientific evidence and opinion-based evidence.

The Task Force believes that cardiac pacemakers and implantable cardioverter–defibrillators are generally contraindicated for magnetic resonance imaging (MRI). These devices pose an extreme hazard in this environment and may be life-threatening within the 5 gauss line.

An implementation strategy was not provided.

Not applicable: The guideline was not adapted from another source.

American Society of Anesthesiologists

Task Force on Anesthetic Care for Magnetic Resonance Imaging

Task Force Members: Jan Ehrenwerth, M.D. (Co-Chair), Madison, Connecticut; Mark A. Singleton, M.D., San Jose, California (Co-Chair); Charlotte Bell, M.D., Milford, Connecticut, Jeffrey A. Brown, D.O., Cleveland, Ohio; Randall M. Clark, M.D., Denver, Colorado; Richard T. Connis, Ph.D., Woodinville, Washington; Robert Herfkens, M.D., Stanford, California; Lawrence Litt, M.D., Ph.D., San Francisco, California; Keira P. Mason, M.D., Wellesley Hills, Massachusetts; Craig D. McClain, M.D., Brookline, Massachusetts; David G. Nickinovich, Ph.D., Bellevue, Washington; Susan M. Ryan, M.D., Ph.D., San Francisco, California; and Warren S. Sandberg, M.D., Ph.D., Boston, Massachusetts

Not stated

This is the current release of the guideline.

Electronic copies: Available from the Anesthesiology Journal Web site .

Print copies: Available from the American Society for Anesthesiologists, 520 North Northwest Highway, Park Ridge, IL 60068-2573.

A continuing medical education (CME) activity is available from the Anesthesiology Journal Web site .

None available

This NGC summary was completed by ECRI Institute on May 11, 2010. The information was verified by the guideline developer on June 24, 2010.

This NGC summary is based on the original guideline that is copyrighted by the American Society of Anesthesiologists.