What are the specific problems encountered with physiologic monitors and equipment in the MRI suite?
The use of a conventional electrocardiogram (ECG) monitor in the MRI suite can cause distortion of the image as a result of the wire leads acting as antennas. In addition, the ECG monitor may not be able to distinguish the ECG from the background static magnetic field and RF pulses. Voltage induced in the wire leads can cause electrical shock hazards and burns to the patient.
The magnetic fields produced by the MRI scanner can cause interference and possible inactivation of the conven-tional operating room pulse oximeter. Either a nonferrous or fiberoptically cabled pulse oximeter should be used. The pulse oximeter probe should be placed on a distal extrem-ity as far from the site to be scanned as possible, to prevent interference and possible scan artifact.
The oscillometric method is optimal for noninvasive blood pressure monitoring in the MRI suite because it is not affected by magnetic fields. Fiberoptic systems in conjunction with invasive blood pressure monitoring have been used successfully. In addition, central venous pressure can be monitored if necessary. There are several transduc-ers that lack ferrous components and can be used in the MRI suite.
The use of side-stream capnography with a long sampling line allows for monitoring of patient ventilation, anesthetic gas concentrations, and circuit disconnection during the MRI scan. However, the long sampling line may create a greater lag time between the actual event and the time of its detection.
There are several MRI-compatible anesthesia machines available commercially. Only oxygen, air, and nitrous oxide cylinders made of aluminum can be used in the MRI suite. Ferromagnetic compressed gas cylinders are pulled by the attractive force of the magnet, and have resulted in either injury or death to patients or personnel.
Infusion pumps should be checked for MRI compatibility as well.