Patient Safety Tip of the Week
February 19, 2008 MRI Safety
Joint Commission has just issued a new Sentinel Event Alert “Preventing accidents and injuries in the MRI suite”, with numerous excellent recommendations about MRI safety. Perhaps most surprising, however, is that Joint Commission has only five MRI-related cases in its Sentinel Event database. Also this February, the FDA updated a previous alert about avoiding burns from electrodes and cables during MRI exams. There are clearly many more MRI-related adverse events and near-misses from which valuable lessons can be learned. Now that HHS has announced its proposal to establish PSO’s (Patient Safety Organizations), we would hope that the confidential reporting to those organizations will result in dissemination of multiple other lessons learned from MRI-related events.
Given the astounding growth of MR imaging facilities over the past decade and the increasing indications for MR imaging, it is no surprise that more vulnerable patients are also having MR imaging studies. Critically-ill patients needing intensive monitoring and intensive care now often undergo MR imaging studies and are at risk for adverse events that may be directly related to the MR procedure or indirectly related. Our October 16, 2007 Patient Safety Tip of the Week “Radiology as a Site at High-Risk for Medication Errors” discussed multiple other types of adverse events that can occur when patients are in the radiology suite.
The American College of Radiology issued its updated guidance document for safe MR practices in the June 2007 issue of the American Journal of Radiology (Kanal et al 2007).
The Joint Commission Sentinel Event Alert and the ACR Guidance outline multiple safety issues related to MR imaging and provide recommendations.
Not even a month after the first published paper on projectile cylinder accidents in MRI units (Chaljub et al 2001), there was a fatality related to an MR-related projectile accident. A 6 y.o. boy developed respiratory distress while undergoing an MRI. There was a problem with the oxygen source in the MRI suite. Both MR technologists briefly left the MR suite to try to resolve the issue but in the interim a nurse responding to anesthesiologist’s calls for help found an oxygen cylinder in the control room and brought it into the MR room. Unfortunately, it was steel cylinder and the MR pulled the cylinder free, thrusting it into the bore of the MR machine and causing a fatal head injury to the boy. Root cause analysis of the latter event showed the typical cascade of events and errors that collectively led to the unfortunate outcome. Many of the same conditions and events occurred in the cases assembled by Chaljub et al. had reported on 5 projectile cylinder accidents at 2 academic medical centers. Cases involved ferromagnetic cylinders of oxygen or nitrous oxide inadvertently being introduced into the MR rooms and turned into projectiles by the magnetic forces of the MR machine, resulting in patient injury or damage to the MR unit or both. They also sent out questionnaires to multiple academic MR units and found slightly more than 50% of those who responded had experienced similar projectile incidents. Objects involved included vacuum cleaners, mop buckets, tools boxes, ventilators, defibrillators, wheelchairs, IV poles, etc. Failure to adhere to MR safety policies and human error were cited as the most common reasons for the accidents.
These and other events have been taken into account in the ACR Guidance, initially published in 2002 and updated in 2004 and 2007. They stress that each MRI facility needs to have safety policies and procedures, a medical director with overall responsibility for safety, adequate training of all individuals, and strict access restrictions. The MR suite needs to be divided into 4 “zones”, each with progressive access restriction based upon level of training. Zone 1 is really any area outside the MR suite where staff and the general public may be. Zone 2 is the area where patients begin to be accompanied by MR-trained personnel and screening begins. Zones 3 and 4 are where the magnetic fields come into play. It is important to understand that in most cases the magnetic forces are always “on” (many people erroneously think they are only present during actual scanning). Zone 3 is just outside the actual MR room and access here is strictly controlled. All individuals here must be escorted by designated MR personnel who ensure that safety policies and procedures are being followed. These areas should be physically restricted so that non-designated staff or the public cannot enter. Use of key locks or passkey locking systems or other reliable method should be used to prevent unauthorized access. (Even combination locks are discouraged because the combinations may be given out too easily). Zone 4 is the actual room where the magnet is housed. It should be clearly demarcated and marked as hazardous, with a red light and sign that the magnet is in operation (with appropriate power supply backup for these alerts). Individuals may enter Zone 4 only under supervision of level 2 MR-trained personnel (usually the MR technologist) and there should be visual control of all access paths to this zone by those personnel (direct line of sight or video camera).
Rescusciation of patients should not be carried out in Zone 4. In those patients in need of rescuscitation, appropriately trained and certified level-2 MR-personnel should perform CPR or other rescuscitative measures as the patient is immediately removed from Zone 4 to a predetermined safe area where full rescuscitative efforts may be continued.
Training is critical for MR personnel. The ACR guidance outlines training needs for level 1 and level 2 MR personnel. Strong consideration should also be given to providing some level of education/training to other individuals who might be called to the MR suite during emergencies (medical or nursing staff, respiratory therapy, outside firemen or police, etc.).
The MR screening process is critical. All non-MR personnel must pass the screening process before entering Zone 3. All individuals must be screened not only for ferromagnetic objects but also for other devices or conditions which may be adversely affected by magnetic forces. The screening must be performed by MR-trained personnel who are authorized to conduct the screening. The screening procedure is beyond the scope of this column and the reader is referred to the ACR Guidance for details. Note that use of conventional metal detectors is discouraged because of false positives and false negatives and other issues. The guidance talks about questions to be asked during screening, physical findings, screening techniques and procedures, who needs x-ray screening for potential ferromagnetic clips, implants, etc. It also discusses issues related to special circumstances such as pregnancy, patients needing sedation, patients needing accompaniment and other issues.
Think about all the reports you hear about things missed during airport security screening. No one could possibly remember everything that must be considered during the MR screening process. Ferromagnetic materials may be present in things like tattoos, makeup, drug patches, unretrieved device fragments, and other places you’d never suspect. Hence, good use of checklists is a must.
Projectile accidents are not the only kind of adverse event that may be encountered in the MR suite. Burns and thermal injury are other potentially significant consequences. The magnetic forces may induce voltage and currents in electrically conductive materials, resulting in significant heat generation. All unnecessary electrically conductive materials should be removed during the screening process. When they cannot be removed, care should be taken during positioning to avoid large diameter conducting loops, which are particularly vulnerable to heat generation (see the ACR Guidance for details). The FDA updated alert on burns from MRI discusses patients wearing ECG electrodes and cables suffering burns during MRI. It, and the nursing journal article that served as a source (Lange 2006), discuss proper techniques for managing patients with such electrodes or cables who must undergo MRI. Note that thermal injury may also occur internally, related to implants or wires.
Fires have been reported during MRI as well. Frankly, we’re surprised they haven’t occurred more often given that MRI may result in heat generation and many patients have an oxygen source during the MRI (see our December 4, 2007 Patient Safety Tip of the Week on Surgical Fires). Fire extinguishers need to be MR-safe or MR-compatible.
Maintenance issues become important (see our August 7, 2007 Patient Safety Tip of the Week on the Role of Maintenance in Incidents). Many hospitals and facilities use outside vendors for maintenance of equipment and supplies such as oxygen cylinders and fire extinguishers. It is crucial that such vendors understand the issues related to MR and use appropriate labeling to minimize the chance of inadvertently storing ferromagnetic versions in or near the MR area.
Stronger magnets, such as 3-tesla units, are being used more and more often. One would expect projectile accidents to be more serious with stronger magnets. While there is some evidence that thermal injury may be more likely with stronger magents, the ACR guidance cautions that one can’t assume safety when a patient has safely undergone a previous MRI. There have been cases where thermal injury occurred during exam with a weaker magnet after prior exam with a stronger magnet, and vice versa.
Issues related to use of gadolinium and contrast agents are discussed in the ACR Guidance, as are issues related to acoustic trauma, pacemaker or other device malfunction, cryogen injury, and other special considerations.
Your quality improvement program obviously needs to review all incidents and near misses related to MR imaging (directly or indirectly). But you should also perform some sort of audits of adherence to the screening and other safety procedures. Results need to be incorporated into feedback to staff and lessons learned need to be readily shared.
Looking for a topic for FMEA (Failure Mode and Effects Analysis) to meet your Joint Commission requirements (or better yet just because you are proactive in your patient safety culture!)? What better place to look than your MR unit? You can ask what you’d do if there was a problem with oxygen source or a problem related to a hi-alert drug like a sedating agent or neuromuscular blocking agent used in the MR unit. You could simulate a cardiac or respiratory arrest or a fire in the MR unit. In any event, you should have periodic drills for some of the potential disasters, such as fires. The appendix in the ACR Guidance has a good section on Emergency Preparedness.
An MRI suite safety calculator is available online and is a good place to start when you are looking at your MR safety program.
Update: See also our May 13, 2008 “Medication Reconciliation: Topical and Compounded Medications” where we noted that drug patches may become patient safety issues in patients undergoing MRI. and the FDA alert in our March 2009 What’s New in the Patient Safety World column “Risk of Burns during MRI Scans from Transdermal Drug Patches”. Also see our October 2008 What’s New in the Patient Safety World “Preventing Infection in MRI” and our March 17, 2009 Patient Safety Tip of the Week “More on MRI Safety”.
References:
Kanal E et al. ACR Guidance Document for Safe MR Practices: 2007. AJR 2007; 188: 1-27 http://www.acr.org/SecondaryMainMenuCategories/quality_safety/MRSafety/safe_mr07.aspx
Chaljub G, Kramer LA, Johnson RF, Johnson RF, Singh H, Crow WN. Projectile Cylinder Accidents Resulting from the Presence of Ferromagnetic Nitrous Oxide or Oxygen Tanks in the MR Suite. Am. J. Roentgenol., Jul 2001; 177: 27 – 30
Lange S, Nguyen QN. Cables and electrodes can burn patients during MRI. Nursing 2006; 36: 18
http://www.fda.gov/cdrh/psn/show-60-electrodes.html
Updates: See also May 13, 2008 Patient Safety Tip of the Week “Medication Reconciliation: Topical and Compounded Medications”
Also, many of the patients at highest risk for transmission of nosocomial pathogens are also the likeliest to get high tech imaging studies in the radiology suite, such as CT or MRI scanning. Dr. Peter A. Rothschild has been running an excellent series on “Preventing infection in MRI: Best practices for infection control in and around MRI suites” on the radiology website AuntMinnie.com.
Rothschild PA. Preventing infection in MRI: Best practices for infection control in and around MRI suites. Auntminnie.com 2008
Part I
http://www.auntminnie.com/index.asp?sec=sup&sub=mri&pag=dis&itemid=81530
Part II
http://www.auntminnie.com/index.asp?Sec=sup&Sub=imc&Pag=dis&ItemId=81616
Part III
http://www.auntminnie.com/index.asp?Sec=sup&Sub=imc&Pag=dis&ItemId=81666
Further
Update: See
October 2008 What’s New in the Patient Safety World “Preventing
Infection in MRI”
http://www.patientsafetysolutions.com
Patient Safety Tip of the Week Archive
What’s New in the Patient Safety World Archive