Anesthesia for Magnetic Resonance Imaging

Anesthesia for magnetic resonance imaging

PURPOSE OF REVIEW

This review focuses on the technological principles, safety considerations, monitors and equipment, patient issues, and a general overview of the anesthetic management of both conventional and intraoperative magnetic resonance imaging based on the most recent literature.

RECENT FINDINGS

As a diagnostic imaging modality, magnetic resonance imaging remains unparalleled in its diagnostic and clinical value. The clinical applications for magnetic resonance imaging continue to evolve, and include its latest use in minimally invasive procedures as well as in the operating room. Intraoperative magnetic resonance imaging is steadily gaining acceptance for neurosurgical procedures. The safety considerations, monitor and equipment issues for intraoperative magnetic resonance imaging are similar to the conventional setting. However, they differ in their focus on anesthesia management. Most monitoring compatible with magnetic resonance imaging has been available for many years. In the USA, the newest available monitoring option during magnetic resonance imaging is for temperature. This option has been available in other countries for a number of years. A fiberoptic surface sensor provides a safe and accurate monitor of adult, pediatric, and neonatal body temperature.

SUMMARY

The magnetic resonance imaging suite is a challenging environment for the anesthesiologist, and carries inherent risks. Several factors account for this, including the remote location, the unique features of the magnetic resonance imaging scanner, and patient-related factors. Understanding the implications of the magnetic resonance imaging environment will facilitate ensuring the safety of the patient and personnel.

Anesthesia for magnetic resonance guided neurosurgery: initial experience with a new open magnetic resonance imaging system

The authors present their initial experience with a compact open magnetic resonance (MR) image-guided system, (PoleStar N-10, Odin Medical Technologies, Yokneam, Israel) used in a standard operating room, modified for radio frequency (RF) shielding. The low intensity of the magnetic field (0.12T), and the ability to lower the magnet from the operative field during surgery allows for an almost routine surgical procedure, in addition to the benefits of using intraoperative MR imaging. Although an MR compatible anesthesia machine and monitoring system are used, the system offers anesthesiologists access to the patient at all times during the procedure, and the ability to use conventional surgical equipment, syringe pumps, and warming devices. Propofol and remifentanil, used for maintaining anesthesia, allow early extubation and neurological evaluation at the end of surgery. Electrocorticographic monitoring can be used during surgery for epilepsy, and awake craniotomy can be performed. More experience with this new imaging system is required to assess its influence on clinical decision making and outcome.

A new frontier: magnetic resonance imaging-operating room

Developments in technology have led to the merger of two distinct environments, that of magnetic resonance imaging and that of the operating room. The major advantage of this merger for neurosurgical procedures is the ability to perform real-time imaging to help guide surgery. This review discusses the role of the anesthesiologist in the planning and administration of safe anesthesia in this new and challenging environment.

[Anesthesia for MRI examination]

Magnetic resonance imaging (MRI) requires the patients to stay for 30-45 min in a magnetic closed noisy space. Therefore most children and agitated adults require general anaesthesia or sedation in order to high quality images. Anaesthesia may be given by several routes (TIVA, inhalational or intrarectal administration) using common drugs. However, the magnetic field limits the selection of patients undergoing MRI and the spectrum of anaesthetic and monitoring equipment. The magnetic field may have deleterious effects on implanted ferromagnetic devices. It may attract objects towards the magnet centre at a dangerous speed. Moreover it may disturb the function of monitors and anaesthesia machines which should be tested for a specific magnetic field strength before introducing their use in a given MRI unit.