Logistics of MRI scanning for ICU patients

Question 16 from the second paper of 2008 discussed the risks associated with MRI scanning for ICU patients. The college graciously omitted transport logistics from their question ("you do not have to outline risks associated  with transport to and from the scanner") these are still important considerations. , They are important because according to one risk/cost/benefit analysis, "transportation of patients from the ICU resulted in a large number of physiologic changes, each requiring changes in support". Of these physiologic changes, 68% were described as "serious" (eg. requiring more vasopressors or a higher FiO₂).

Now, to MRI issues. This article contains a chapter ("MRI Transport") which covers this topic in brief. A substantial detailed exploration can be found in David Olive's article for Australasian Anaesthesia(2005)

Risks from the magnet

• Ferromagnetic material movement
• Malfunction of pacemakers
• Projectile trauma from nearby objects
• Cardiac damage from PA catheters
• Pulse oximeters and ECG dots can overheat and cause burns. ECG cables are made of coiled copper, and will also heat up.

Risks from contrast

• Gadolinium is usually quite safe, but it may cause exacerbation of nephrogenic systemic fibrosis. Anaphylactic reactions are possible.

Risks from the isolated room

• Airway disconnection alarms might go unheard
• Long ventilator tubing creates excessive amounts of dead space
• Extra dead space makes is difficult to trigger.
• MRI-compatible anaesthetic machines are available, but they are expensive (~ $80,000) and frequently the ventilators on them are somewhat unsophisticated.
• Long infusion tubing results in a delay of medication administration
• Some drugs may require pumps, and cannot be given; pumps may require ridiculously long tubing and additional batteries to function
• The MRI chamber is usually cold, and hypothermia can develop
• Monitoring equipment is of poor quality

Risks from being critically ill

• Thermoregulation is impaired, and hypothermia is more likely to develop
• Judgement is impaired, and patient movement delays the process
• Resuscitation equipment cannot be taken into the room. Certainly, plastic disposable laryngoscopes do exist, but the batteries inside them are still affected.
• If cardiac arrest occurs, it can take some time to dismount the MRI couch