Anesthesia in MRI and remote locations
Stem
A 4-year-old boy, 17 kg, with autism spectrum disorder and suspected seizures, is scheduled for a 50-minute brain MRI under general anesthesia in a freestanding imaging suite one floor away from the main operating rooms. He has a ventriculoperitoneal shunt with a programmable valve, snores at night, and had an uneventful anesthetic for dental work last year.
Question
How will you set up and conduct anesthesia for this scan?
Ideal answer
HeadlineEvery person and object entering the magnet room screened first, then a secured airway, because I rescue him far from help.
- Screen him and myself for implants and ferromagnetic objects: his programmable shunt is a relative contraindication, so neurosurgery confirms the model, and the valve is checked and reprogrammed afterward.1
- Equipment labeled MR-safe or MR-conditional for this scanner: machine, monitors, pump and airway gear; I know where the resuscitation area outside zone IV is.2
- Mask induction outside the magnet room, then LMA or tube: sevoflurane, then IV; he snores and I will watch him through a window.
- Full ASA standard monitoring with capnography, because pulse oximetry does not monitor ventilation.2
- Straight, insulated, loop-free ECG leads, padding, ear protection, warming, for burns and noise, and because small children cool in the scanner.1
Watch for: capnogram and saturation, from the control room.
Breaking down the answer
- Screen people and devices first — the field is always on; the hazards are projectiles, torque, heating, artifact and device malfunction. Pacemakers that are not MR-conditional, cochlear implants, intraocular metal and ferromagnetic clips are contraindications unless cleared for this scanner.1 Judgment before pharmacology.
- Know the four zones — zone III is restricted to screened people, and zone IV, the magnet room, always sits inside zone III.2 Naming the zones shows organization.
- Secure the airway when access is poor — I cannot reach his head inside the bore; suite airway equipment must be MR-conditional, and the patient leaves zone IV as soon as feasible in any emergency.3 Changes if: a cooperative adult, short scan; sedation with capnography.
- Capnography is not optional — the ASA advisory says end-tidal CO2 monitoring should be considered for all deep sedation and oximetry is no substitute for monitoring ventilation; ST segments are unreliable in the field.2
- Prevent burns — resonant loops and the antenna effect of long leads heat tissue, so I remove loops and pad between skin and wires.1
- Remote location means a plan for help — oversedation figured in several MRI closed claims, so a skilled helper, suction, oxygen and a code cart are staged outside zone IV,3 with an exit plan agreed with the technologist.
Follow-up question
Thirty minutes into the scan, the capnogram goes flat, the saturation falls to 78% and then the pulse oximeter loses its signal. The technologist calls through the intercom.
What do you do?
Follow-up answer
HeadlineA possible disconnection or cardiopulmonary arrest, treated as arrest: I stop the scan and call a code to the resuscitation area outside zone IV.
One person guards the door so responders with ferromagnetic equipment do not run into the magnet room.3 I check the circuit as I go in, ventilate with 100% oxygen, and, if there is no pulse, start CPR while we immediately move him out to the designated resuscitation area with the defibrillator, monitors and code cart.2 I do not bring a defibrillator into the magnet room.1 Outside: pediatric ALS, the cause (hypoxemia, dislodged airway, anesthetic overdose), and whether the scan is finished another day.
Pitfalls that cost points
- Calling a quench for a cardiac arrest; it is reserved for life-threatening events such as a fire or a person pinned to the magnet.1
- Ignoring gadolinium in a patient with acute or severe renal insufficiency.
Rapid-fire
Q: What is a quench and what happens? A: Emergency shutdown of the magnet in which liquid helium is rapidly expelled and can displace room air; evacuate, and give oxygen to anyone who cannot leave.1
Q: What does "MR-conditional" mean? A: The device is safe only under the stated conditions, such as field strength, so I check the manufacturer's labeling for this scanner.1
Q: When does the ASA advise against gadolinium? A: In acute or severe renal insufficiency, because of nephrogenic systemic fibrosis.2
Q: Why does the scanner affect hearing? A: Noise above 90 dB can cause transient or permanent hearing loss, so patients and staff in the room wear protection.1
Q: Which patients does the advisory flag as high risk? A: Neonates and former premature infants, ICU patients, impaired respiratory function, hemodynamic instability, and comorbidities such as obesity.2
Numbers to know
| Item | Value |
|---|---|
| MRI zones | I (public) to IV (magnet room)2 |
| Scanner noise causing hearing loss | Above 90 dB1 |
| Recent tattoo, relative contraindication | Within 6 weeks1 |
| MRI share of radiology closed claims | 7 of 103 |
| Capnography | Consider for all deep sedation2 |
Links
- Procedural sedation and office-based anesthesia, Pulse oximetry: principles and limitations, Capnography: waveforms and sudden loss of ETCO2, Pacemakers and ICDs in the operating room, ACLS adapted to the operating room
- ASA Practice Advisory on Anesthetic Care for MRI (2015 update); ASA Statement on Nonoperating Room Anesthetizing Locations
Sources
- 1.Magnetic resonance imaging safety · OpenAnesthesia · openanesthesia.org
- 2.Practice Advisory on Anesthetic Care for Magnetic Resonance Imaging (updated report) · ASA, 2015 · asahq.orgAnesthesiology 2015;122:495-520; updates the 2009 advisory.
- 3.Airway Emergencies and Safety in Magnetic Resonance Imaging (MRI) Suite · APSF · apsf.org
Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.