Monitoring in MRI

Anesthesia during MRI procedure concerns mostly children, ranging from newborn to 15 year old. Some adults with impaired mental status also need anesthesia during MRI. The very nature of MRI examination makes it a unique situation in regard to anesthesia : the whole body must be introduced inside the MRI bore and no medical staff can stay near the patient. This makes it difficult to assess – from the distant control room – the well being of the anesthetized patient.

MRI bore

It is difficult to see the patient in the MRI bore, and even more to assess its well being during anesthesia. Medical staff can not stay near the patient, and have to leave the room, where the anesthetized patient stays alone. Monitoring has therefore to be very reliable.

The risks associated with anesthesia are mainly :
 arousal
 aspiration
 hypoxia
 allergic shock
 hemodynamic impairment

They call for continuous monitoring : from the beginning of anesthesia in the "induction room", during transportation to the MRI room, inside MRI bore during MRI examination and the during transportation back to "induction room", until arousal from anesthesia.

During MRI, the medical staff cannot stay continuously with the anesthetized patient. Monitoring systems have to send their data from the bedside monitor to the control room, which is usually adjacent to the MRI room. Distant monitoring is the only mean to make sure of the well being of the patient during anesthesia.

Many MRI compatible monitoring systems are not easily transportable. In many cases, the medical staff needs two to three different monitoring devices during the whole procedure : in the induction room, during transportation, and in MRI room. An easier and more efficient way would be to use a transportable – MRI compatible – monitoring device, that would be able to follow the patient from "induction room" to "MRI room" without being removed.

Children during anesthesia for MRI

Approximately 96% of MRI exams under anesthesia are currently performed on children (Source : Hopital Roger Salengro/CHRU Lille - 2004)

Anesthesia monitoring devices need to assess simple physiological functions such as heart rate, blood pressure, breathing and oxygenation. They also need to monitor delivered oxygen and volatile anaesthetics (when used). These parameters can be assessed by monitoring the following signals :
 ECG waveform (ECG) and heart rate (HR)
 Blood pressure (BP) with non invasive automatic cuff
 Plethysmographic waveform and SpO2 measure
 Temperature (T°) in case of a long procedure
 Inspired O2 (mandatory)
 Inspired and expired volatile anesthetic agents – (mandatory if used)
 CO2 waveform and Expired tidal CO2 (PetCO2) (mandatory if tracheal intubation)
 Tidal volume (Vt) and respiratory rate (mandatory if tracheal intubation)