To the Editor:

We read with interest the article by Roh et al.  concerning exposure to low-frequency electromagnetic fields (EMFs) and wish to comment on another great source of exposure to EMF that anesthesiologists face in the hospital. Although the risk factors of magnetic fields are well known for patients, exposure limits to EMFs are unknown in healthcare providers who are continuously exposed to the magnetic resonance imaging (MRI) environment.1,2*The MRI environment exposes anesthesiologists to static and gradient magnetic fields, with the exposure limits dependant not only on the strength of the MRI scanner (1.5 T vs.  3.0 T) and length of the scanning sequences but also on which anesthetic technique is chosen and whether the intravenous pumps, monitors, and anesthesia machines used are MRI compatible.

The lack of MRI safe or compatible monitors and machines forces the anesthesiologist to choose a technique that requires being in the magnet room closer to the magnet bore, and thus potential exposure to higher levels of EMF. Not only the exposure is potentially greater but also the tracking of individual anesthesiologist's exposure time during monitoring is lacking.

Because of the lack of studies of healthcare personnel to the long-term risks of EMF, certain groups are beginning to examine issues such as risk of mortality or cancer rates in personnel working in the MRI environment. Numerous groups, including the World Health Organization, National Health Service (United Kingdom), and the Health Protection Agency, are becoming involved in the design and epidemiologic studies about long-term exposure to EMF in healthcare personnel working in MRI are implemented. The European Union is also proposing a directive that will limit the exposure of healthcare workers to the EMF of MRI magnet rooms. Implementation of these directives will ban anesthesiologists from staying in the magnet room during MRI scans. We have not found any studies of MRI-induced injury to healthcare personnel from long-term exposure to EMFs or any studies correlating exposure levels to disease. Anesthesia personnel who provide limited or occasional care in the MRI environment run a risk of exposure to EMFs.3,4Anesthesia providers should carefully consider their anesthetic technique to minimize the time spent in the MRI magnet room. In the future, exposure limits to EMFs should be recorded by anesthesia personnel to facilitate future epidemiologic studies to determine EMF exposure rates. More research is required in developing anesthetic techniques to minimize the EMF exposure limits.

†Wake Forest University School of Medicine, Winston-Salem, North Carolina.


Roh JH, Kim DW, Lee SJ, Kim JY, Na SW, Choi SH, Kim KJ: Intensity of extremely low-frequency electromagnetic fields produced in operating rooms during surgery at the standing position of anesthesiologists. Anesthesiology 2009; 111:275–8
Riches SF, Collins DJ, Charles-Edwards GD, Shafford JC, Cole J, Keevil SF, Leach MO: Measurements of occupational exposure to switched gradient and spatially-varying magnetic fields in areas adjacent to 1.5 T clinical MRI systems. J Magn Reson Imaging 2007; 26:1346–52
Henderson M. EU directive doesn't scan; junk medicine MRI scans. The Times  (London) December 20, 2008: 53
Smith R. MRI scanners to be examined for cancer risk. The Daily Telegraph  (London) May 22, 2008: 8