Anesthesia in the intraoperative MRI environment

Intraoperative MRI: A Review of Applications Across Neurosurgical Specialties

Intraoperative MRI (iMRI) made its debut to great fanfare in the mid-1990s. However, the enthusiasm for this technology with seemingly obvious benefits for neurosurgeons has waned. We review the benefits and utility of iMRI across the field of neurosurgery and present an overview of the evidence for iMRI for multiple neurosurgical disciplines: tumor, skull base, vascular, pediatric, functional, and spine. Publications on iMRI have steadily increased since 1996, plateauing with approximately 52 publications per year since 2011. Tumor surgery, especially glioma surgery, has the most evidence for the use of iMRI contributing more than 50% of all iMRI publications, with increased rates of gross total resection in both adults and children, providing a potential survival benefit. Across multiple neurosurgical disciplines, the ability to use a multitude of unique sequences (diffusion tract imaging, diffusion-weighted imaging, magnetic resonance angiography, blood oxygenation level-dependent) allows for specialization of imaging for various types of surgery. Generally, iMRI allows for consideration of anatomic changes and real-time feedback on surgical outcomes such as extent of resection and instrument (screw, lead, electrode) placement. However, implementation of iMRI is limited by cost and feasibility, including the need for installation, shielding, and compatible tools. Evidence for iMRI use varies greatly by specialty, with the most evidence for tumor, vascular, and pediatric neurosurgery. The benefits of real-time anatomic imaging, a lack of radiation, and evaluation of surgical outcomes are limited by the cost and difficulty of iMRI integration. Nonetheless, the ability to ensure patients are provided by a maximal yet safe treatment that specifically accounts for their own anatomy and highlights why iMRI is a valuable and underutilized tool across multiple neurosurgical subspecialties.

Body Interventional MRI for Diagnostic and Interventional Radiologists: Current Practice and Future Prospects

Clinical use of MRI for guidance during interventional procedures emerged shortly after the introduction of clinical diagnostic MRI in the late 1980s. However, early applications of interventional MRI (iMRI) were limited owing to the lack of dedicated iMRI magnets, pulse sequences, and equipment. During the 3 decades that followed, technologic advancements in iMRI magnets that balance bore access and field strength, combined with the development of rapid MRI pulse sequences, surface coils, and commercially available MR-conditional devices, led to the rapid expansion of clinical iMRI applications, particularly in the field of body iMRI. iMRI offers several advantages, including superior soft-tissue resolution, ease of multiplanar imaging, lack of ionizing radiation, and capability to re-image the same section. Disadvantages include longer examination times, lack of MR-conditional equipment, less operator familiarity, and increased cost. Nonetheless, MRI guidance is particularly advantageous when the disease is best visualized with MRI and/or when superior soft-tissue contrast is needed for treatment monitoring. Safety in the iMRI environment is paramount and requires close collaboration among interventional radiologists, MR physicists, and all other iMRI team members. The implementation of risk-limiting measures for personnel and equipment in MR zones III and IV is key. Various commercially available MR-conditional needles, wires, and biopsy and ablation devices are now available throughout the world, depending on the local regulatory status. As such, there has been tremendous growth in the clinical applications of body iMRI, including localization of difficult lesions, biopsy, sclerotherapy, and cryoablation and thermal ablation of malignant and nonmalignant soft-tissue neoplasms. Online supplemental material is available for this article. ^©RSNA, 2021.

Anesthetic challenges and outcomes for procedures in the intraoperative magnetic resonance imaging suite: A systematic review

BACKGROUND AND OBJECTIVE

Hybrid operating room suites with intraoperative magnetic resonance imaging enable image guided surgery in a fully functional operating room environment. While this environment creates challenges to anesthetic care, the effects on anesthetic adverse events and outcomes are largely unknown. This systematic scoping review aims to map the existing knowledge about anesthetic care in advanced imaging hybrid operating rooms.

METHODS

A broad-based literature search was performed using the PubMed (Medline), Embase, Cochrane Library, Web of Science, and Google Scholar databases. References published in English between January 1994 and August 2017 were included. Quality of evidence was assessed using the GRADE guidelines.

RESULTS

Forty-seven manuscripts were eligible for data collection. Adverse events were heterogeneously defined across 17 manuscripts and occurred in 0 to 100% (quality of evidence mostly very low). Monitoring difficulty was reported in 4 manuscripts of very low data quality. Interference between the magnet and the electrocardiogram was investigated in 2 manuscripts (quality of evidence low and very low, respectively). None of the reported events appeared to result in long-term patient harm. Author recommendations or a narrative review of the literature were provided in 40 manuscripts. Common safety concerns included lower equipment reliability, inaccessibility of the patient and airway, and the relative isolation of the suite (in relationship to other anesthesia care areas). Most authors also emphasized the importance of safety checklists, protocols, and provider training.

DISCUSSION

While intraoperative magnetic resonance imaging hybrid operating rooms are increasingly utilized, the existing literature does not allow estimating adverse event rates in this location. Prospective studies quantifying the effect of the environment on anesthesia outcomes are lacking. Despite this, there is a broad consensus regarding the anesthetic and safety concerns. More research is needed to inform practice standards and training requirements for this challenging environment.

The Role of Intraoperative MRI in Awake Neurosurgical Procedures: A Systematic Review

Background: Awake craniotomy for brain tumors remains an important tool in the arsenal of the treating neurosurgeon working in eloquent areas of the brain. Furthermore, with the implementation of intraoperative magnetic resonance imaging (I-MRI), one can afford the luxury of imaging to assess surgical resection of the underlying gross imaging defined neuropathology and the surrounding eloquent areas. Ideally, the combination of I-MRI and awake craniotomy could provide the maximal lesion resection with the least morbidity and mortality. However, more resection with the aid of real time imaging and awake craniotomy techniques might give opposite outcome results. The goal of this systematic review.is to identify the available literature on combined I-MRI and awake craniotomy techniques, to better understand the potential morbidity and mortality associated.

Methods: MEDLINE, EMBASE, and CENTRAL were searched from inception up to December 2016. A total of 10 articles met inclusion in to the review, with a total of 324 adult patients.

Results: All studies showed transient neurological deficits between 2.9 to 76.4%. In regards to persistent morbidity, the mean was ~10% (ranges from zero to 35.3%) with a follow up period between 5 days and 6 months.

Conclusion: The preliminary results of this review also suggest this combined technique may impose acceptable post-operative complication profiles and morbidity. However, this is based on low quality evidence, and is therefore questionable. Further, well-designed future trials with the long-term follow-up are needed to provide various aspects of feasibility and outcome data for this approach.

Anesthetic management and human factors in the intraoperative MRI environment

PURPOSE OF REVIEW

The use of intraoperative MRI technology during neurosurgery has become increasingly more common over the past several years. These surgical procedures require a specialized operating room designed to accommodate an MRI machine, as well as MRI-compatible anesthesia equipment and monitors. The MRI environment also poses unique risks and challenges to both patients and medical staff.

RECENT FINDINGS

General anesthesia in the MRI operating room suite poses several challenges not routinely experienced in a conventional operating room suite, and anesthesia providers delivering care in these suites must complete specialized training and screening. The presence of a magnetic field, as well as reduced access to the patient during the MRI scan, require high levels of vigilance.

SUMMARY

The use of checklists and teamwork training can maximize both patient and provider safety in the intraoperative MRI environment.

"Low-field" intraoperative MRI: a new scenario, a new adaptation

AIM

To describe the adaptation of Cruces University Hospital to the use of intraoperative magnetic resonance imaging (ioMRI), and how the acquisition and use of this technology would impact the day-to-day running of the neurosurgical suite.

MATERIALS AND METHODS

With the approval of the ethics committee, an observational, prospective study was performed from June 2012 to April 2014, which included 109 neurosurgical procedures with the assistance of ioMRI. These were performed using the Polestar N-30 system (PSN30; Medtronic Navigation, Louisville, CO), which was integrated into the operating room.

RESULTS

A total of 159 procedures were included: 109 cranial surgeries assisted with ioMRI and 50 control cases (no ioMRI use). There were no statistical significant differences when anaesthetic time (p=0.587) and surgical time (p=0.792) were compared; however, an important difference was shown in duration of patient positioning (p<0.0009) and total duration of the procedure (p<0.0009) between both groups.

CONCLUSIONS

The introduction of ioMRI is necessary for most neurosurgical suites; however, a few things need to be taken into consideration when adapting to it. Increase procedure time, the use of specific MRI-safe devices, as well as a checklist for each patient to minimise risks, should be taken into consideration.

Intraoperative MRI in pediatric brain tumors

Intraoperative magnetic resonance imaging (iMRI) has emerged as an important tool in guiding the surgical management of children with brain tumors. Recent advances have allowed utilization of high field strength systems, including 3-tesla MRI, resulting in diagnostic-quality scans that can be performed while the child is on the operating table. By providing information about the possible presence of residual tumor, it allows the neurosurgeon to both identify and resect any remaining tumor that is thought to be safely accessible. By fusing the newly obtained images with the surgical guidance software, the images have the added value of aiding in navigation to any residual tumor. This is important because parenchyma often shifts during surgery. It also gives the neurosurgeon insight into whether any immediate postoperative complications have occurred. If any complications have occurred, the child is already in the operating room and precious minutes lost in transport and communications are saved. In this article we review the three main approaches to an iMRI system design. We discuss the possible roles for iMRI during intraoperative planning and provide guidance to help radiologists and neurosurgeons alike in the collaborative management of these children.

Feasibility of anaesthetic provision for paediatric patients undergoing off-site intraoperative MRI-guided neurosurgery: the Singapore experience from 2009 to 2012

The benefits of using intraoperative magnetic resonance imaging (iMRI) for neurosurgery have been recognised. However, iMRI facilities are not available in all hospitals. For example, in Singapore iMRI is currently available only at the Singapore General Hospital, an adult hospital without facilities for intensive care management of patients less than 12 years of age. KK Women's and Children's Hospital is a dedicated children's hospital situated 6.3 km away from this facility. In order to obtain iMRI services for our paediatric patients, transport to Singapore General Hospital is required, with return to our hospital for postoperative management. Since July 2009 we have managed nine paediatric patients in this manner: three children with arteriovenous malformations and six children with brain tumours. There was no morbidity or mortality that could be attributed to the transport of patients either to or from Singapore General Hospital. Our experience suggests that with adequate planning and preparation, providing anaesthetic care and transporting children for off-site iMRI-guided neurosurgery is feasible and safe for selected children.

Anesthetic concerns for pediatric patients in an intraoperative MRI suite

PURPOSE OF REVIEW

Intraoperative magnetic resonance imaging (iMRI) is an evolving technology used to provide precise intraoperative navigation during a variety of neurosurgical and other types of surgical procedures. Anesthesiologists need to be aware of the unique challenges created by this environment. Failure to recognize the differences between the diagnostic MRI environment and the iMRI environment can compromise the safety of the patient and operating room staff and present logistical problems.

RECENT FINDINGS

Recent surgical reports herald the uses and benefits of iMRI. However, there are a few in the anesthesia literature addressing the significant benefits and the anesthesia-specific issues this technology creates. We will review recent reports describing anesthetic care of patients in this environment as well as examine the recent surgical and radiologic literature as they relate to issues faced by anesthesiologists.

SUMMARY

We describe the design of different iMRI suites as well as provide a breakdown of both patient and equipment issues encountered by anesthesiologists practicing in this environment. Finally, we offer our ongoing experience in this environment and provide suggestions to optimize patient outcomes.

Anesthesia can be safely provided for children in a high-field intraoperative magnetic resonance imaging environment

OBJECTIVES

To describe the challenges associated with providing safe anesthesia and perioperative care for children in a remote intraoperative magnetic resonance (iMR) operating room (OR) and to identify perioperative anesthesia outcomes, including adverse events related to the iMR environment.

BACKGROUND

Increasingly, children undergo neurosurgical procedures in a high-field iMR OR. We describe a 10-year experience of providing anesthesia for children in this environment with a mobile 1.5-Tesla magnet.

METHODS

A 10-year retrospective analysis was conducted of children who underwent neurosurgical procedures in a high-field mobile iMR OR. Primary outcomes related to perioperative adverse events and recovery profiles. Results were expressed as mean ± sd or median (range), as appropriate.

RESULTS

One hundred and five procedures were performed on 98 children, aged 4 months-18 years, weighing 6-112 kg. The commonest two diagnostic categories were tumor (n = 52) and seizures (n = 27). Median anesthetic time was 439 (185-710) mins. There were no significant adverse events related to the iMR environment. The mean postanesthetic care unit admission temperature was 37 ± 0.9°C and the mean modified Aldrete Score at 30 mins was 7.2 ± 0.9. Two patients experienced seizures in the immediate postoperative period, readily controlled with propofol. There was one breach of MR safety protocol, and no adverse events related to patient transport.

CONCLUSIONS

Anesthesia and perioperative care of children in an iMR setting were associated with a very low incidence of complications, despite the duration of the procedures involved. Such success depends upon a cohesive team-based approach.

Safety in magnetic resonance units: an update

The number of anaesthetists who are involved in magnetic resonance (MR) units is increasing. Magnetic resonance systems are becoming more powerful and interventional procedures are now possible. This paper updates information relating to safety terminology, occupational exposure, reactions to gadolinium-based contrast agents and the risk of nephrogenic systemic fibrosis. Magnetic resonance examinations of patients with pacemakers are still generally contra-indicated but have been carried out in specialist centres under strictly controlled conditions. As availability of MR increases, so the education of anaesthetists, who are occasionally required to provide a service, must be considered.

Anaesthesia in MR units was first described in the 1980s. Guidelines on the provision of anaesthetic services in MR units were published by the Association of Anaesthetists of Great Britain and Ireland (AAGBI) in 2002 [1]. Since then, the number of hospitals with MR units, and hence the number of patients requiring anaesthesia for MR, has increased. While the issues relating to setting up anaesthetic services in MR have not changed, there have been a number of developments that warrant this update:

Safety terminology and guidelines have changed.

MR systems utilise higher magnetic-field strengths and more open designs are available.

Interventional and intra-operative MR are now routine in some centres.

Mobile MR scanners are increasingly used to reduce waiting lists.

Although still generally contra-indicated, some patients with pacemakers have been scanned under strictly controlled conditions in specialist centres.

‘MR safe’ medical implants are now being produced.

New equipment is now available for use in MR.

Out-of-hours availability of MR investigations has increased.

Reports of allergic reactions to MR contrast media have increased.

Gadolinium based contrast agents (Gd-CAs) are associated with a varying degree of risk of nephrogenic systemic fibrosis in patients with impaired renal function.