Dear Rapid Response:
Are MRI-compatible laryngoscopes recommended or required in the MRI environment?
I am an anesthesiologist presently working in a community hospital and care for patients who receive anesthesia as part of their MRI exam. We have conventional laryngoscopes and blades available in MRI zone III and an MRI-compatible anesthesia machine in zone IV. If we need to intubate a patient, the expectation is that we can move the patient to zone III for intubation and return to zone IV to complete the study. I believe we should purchase MRI-conditional laryngoscopes and blades to be available in zone III, but am told it is not essential and many other institutions do not have MRI-compatible laryngoscopes.
Please let me know your thoughts on this patient safety question.
Dheeraj Nagpal, MD
Dr. Nagpal is an attending anesthesiologist at New York Presbyterian Queens, Flushing, NY.
Dr. Nagpal has no conflicts of interest.
This is an important question to address since modern anesthesia practice must meet the present and growing demand to provide anesthesia care to adults and children who require MRI.1 Further, the American Society of Anesthesiologists (ASA) closed claims project evaluated the risk and safety of anesthesia in remote locations and found that claims for death and specifically respiratory damaging events were more common in remote locations, most often during monitored anesthesia care. In addition, the majority of radiology claims were in MRI (7/10) and four of those claims were related to oversedation.2 Given the unique patient safety concerns in the MRI environment, we believe laryngoscopes that are safe to use in the MRI environment should be available whenever anesthesia care is being provided. Further, the process for airway rescue during emergencies in the MRI scanner needs to be clearly defined.
Providing safe care in the MRI arena requires a thorough understanding of the environment and potential hazards to patients and staff. The MRI environment is conceptually divided into four Zones designated I through IV. Zone III is typically reserved for MRI personnel and public access is restricted. The control room is in Zone III. Zone IV is the MRI scanner magnet room.3 The MRI magnetic field is invisible, always on, and can affect ferromagnetic equipment of any size in Zone IV, potentially converting it to a projectile that is drawn into the scanner with a strength and speed that can be deadly. Not only can patients be injured or killed, but damage to the scanner results in temporary closure and servicing or a costly and dangerous magnet quench. The unique safety concern of the magnetic field has significant impact on the care of patients presenting for anesthesia in MRI, and can become particularly challenging during an airway or medical emergency.
Very few airway devices have been specifically designed for safe use in MRI. Medical devices and equipment that might be used in the MR environments should be labelled as MR unsafe, MR conditional, or MR safe (Figure 1). Laryngeal mask airways and endotracheal tubes contain small amounts of ferromagnetic material in the pilot balloon, but are considered MR conditional as they will not cause patient harm but may affect image quality. These airway devices have been used safely along with plastic oropharyngeal airways and bag mask ventilation units. Classic metal laryngoscopes are considered unsafe as malfunction with sudden failure to operate can occur in Zone IV and nickel in the laryngoscope battery is ferromagnetic.4 Although expensive, single-use and reusable MRI-conditional devices are available.5 The quality of disposable laryngoscopes is variable but there are products available which are MRI-conditional and can be trialed to confirm that they are clinically acceptable. Whether single-use or reusable, MRI-conditional laryngoscopes can be brought into Zone IV safely.
The most recent ASA Practice Advisory on anesthesia care in MRI provides useful guidance for preparing to manage airway emergencies in MRI.4 During an airway emergency, anesthesia professionals and other health care providers must be prepared to enter Zone IV quickly. Though not listing specific devices, the advisory states that “Alternative MRI safe/conditional airway devices should be immediately available in the MRI suite.” 4 Given the sense of urgency, personnel must recheck themselves for presence of ferromagnetic objects and equipment prior to entering the scanner. To avoid confusion and the risks of MR-unsafe devices inadvertently getting into Zone IV, airway equipment immediately available to the team in Zone III should be MR-conditional for all scanners in the location. If it is safe, the airway should be supported with bag mask ventilation while the patient is removed from Zone IV to a nearby location in Zone III or Zone II where a full complement of airway and resuscitation equipment can be used and emergency personnel summoned for help. If securing the airway is deemed emergent in the scanner (e.g., profound vomiting with risk of aspiration, inability to ventilate, etc.), it can be done only if MR-safe and -conditional equipment is available. If MR-safe and -conditional equipment is not available, the patient must be moved out of Zone IV risking the complications of hypoxia. In any situation, medical emergencies are difficult to manage in Zone IV, and the patient should be brought out of Zone IV as soon as feasible. Until the patient is safe or removed from Zone IV, at least one person should be designated to police the heightened traffic entering Zone IV during an emergency. On some newer MRI machines, the MRI table can be undocked from the magnet to move the patient from Zone IV and minimize the loss of precious time.
There is considerable variation in the physical layout, need for sedation, types of MRI procedures, and sedation services across the globe, and hence, there is no standard way to provide anesthesia or sedation care in MRI.
Airway emergency response in MRI may look somewhat different in each hospital. Key components of a comprehensive plan for safe emergency care in MRI involves partnering with the radiology department to determine the safety of equipment available for use in Zone IV, and a resuscitative area outside of, but not far from Zone IV. The Standard Operating Procedures and Hospital Policy for managing emergencies in MRI should be revisited as new guidelines emerge or demands for anesthesia services in MRI change. Simulations can help to insure the entire team can safely manage patient emergencies in Zone IV.
Routine availability of MR-safe-conditional laryngoscopes and other airway equipment in the MR environment will avoid inadvertent entry of MR-unsafe devices into Zone IV. This may involve purchasing additional equipment to maintain safety in the MRI environment. Injury to patients, staff, or MRI scanners is both unacceptable and expensive. As anesthesia care and complexity of patients continues to increase in the MRI suite, it is necessary to maintain vigilance for the distinct hazards present in the MR environment and create systems that protect our patients and staff from tragic but preventable accidents. MRIs cannot be easily shut down, and “quench” is an expensive and potentially dangerous operation. Consistent safety standards should be followed in all non-operating room locations, intraoperative MRI scanners or free-standing radiologic centers where anesthesia is provided. MRI safety is both an institutional and an individual responsibility.
Dr. McClung is an assistant professor in the Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
Dr. Subramanyam is an associate professor in the Department of Anesthesiology and Critical Care Medicine, Children’s Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
The authors have no conflicts of interest.
- United States Food and Drug Administration. Magnetic resonance imaging (MRI) safety and effectiveness. https://www.fda.gov/medical-devices/cdrh-research-programs/magnetic-resonance-imaging-mri-safety-and-effectiveness Accessed November 17, 2019.
- Metzner J, Posner KL, Domino KB. The risk and safety of anesthesia at remote locations: the US closed claims analysis. Curr Opin Anesth. 2009;22:502–508.
- Kanal E, Barkovich JA, Bell C, et al. Expert panel on MR safety: ACR guidance document on MR safe practices: 2013. J Magn Reson Imaging. 2013;37:501–530.
- The Joint Commission, Sentinel Event Alert: Preventing accidents and injuries in the MRI suite. Issue 38, Feb 14, 2008. https://www.jointcommission.org/assets/1/18/SEA_38.PDF. Accessed November 17, 2019.
- mrisafety.com. Accessed November 17, 2019.
- Practice advisory on anesthetic care for magnetic resonance imaging: an updated report by the American Society of Anesthesiologists task force on anesthetic care for magnetic resonance imaging. Anesthesiology. 2015;122:495–520.
The information provided is for safety-related educational purposes only, and does not constitute medical or legal advice. Individual or group responses are only commentary, provided for purposes of education or discussion, and are neither statements of advice nor the opinions of APSF. It is not the intention of APSF to provide specific medical or legal advice or to endorse any specific views or recommendations in response to the inquiries posted. In no event shall APSF be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with the reliance on any such information.