Successful use of a Fortec II vaporizer in the MRI suite: a case report with observations regarding magnetic field-induced vaporizer aberrancy

Anaesthesia of small rodents during magnetic resonance imaging

The use of experimental animals for magnetic resonance studies requires anaesthesia to provide immobility and acquire signals with minimal stress and maximal reproducibility. However, the conduct of anaesthesia within a magnetic resonance imaging (MRI) suite implicates many problems, because most of the anaesthetic and monitoring equipment contains ferromagnetic substances. To decrease disturbances during anaesthesia and make data interpretation more accurate, it is mandatory that investigators become familiar with methods and physiologic effects of anaesthesia under these special conditions. This article is intended to give an overview of anaesthetic medication, administration routes and practical instructions for anaesthesia in small rodents during MRI.

Newer diagnostic and surgical techniques and their impact on anesthesia

There are several newer diagnostic and surgical techniques available to veterinarians today. Careful anesthetic management is essential when using these modalities both to avoid accidents and to enable their use. For example, total intravenous anesthetic techniques can be used if the airway is occupied by an endoscope or laser surgery is being performed in the airway. The anesthesiologist must also be aware of the physiological changes that may occur during procedures such as laparoscopy and act to minimize their impact on patients.

[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.