Magnetic resonance imaging anesthesia: new challenges and techniques

Survey of centers performing cardiovascular magnetic resonance in pediatric and congenital heart disease: a report of the Society for Cardiovascular Magnetic Resonance

BACKGROUND

There are few data on practice patterns and trends for cardiovascular magnetic resonance (CMR) in pediatric and congenital heart disease. The Society for Cardiovascular Magnetic Resonance (SCMR) sought to address this deficiency by performing an international survey of CMR centers.

METHODS

Surveys consisting of 31 (2014) and 33 (2018) items were designed to collect data on the use of CMR for the evaluation of pediatric and congenital heart disease patients. They were sent to all SCMR members in 2014 and 2018. One response per center was collected.

RESULTS

There were 93 centers that responded in 2014 and 83 in 2018. The results that follow show data from 2014 and 2018 separated by a dash. The median annual number of pediatric/congenital CMR cases per center was 183-209. The median number of scanners for CMR was 2-2 (range, 1-8) with 58-63% using only 1.5T scanners and 4-4% using only 3T scanners. The mean number of attending/staff reading CMRs was 3.7-2.6; among them, 52-61% were pediatric or adult cardiologists and 47-38% were pediatric or adult radiologists. The median annual case volume per attending was 54-86. The median number of technologists per center doing CMRs was 4-5. The median scanner time allocated for a non-sedated examination was 75-75 min (range, 45-120). Among the 21 centers responding to both surveys, the mean annual case volume increased from 320 in 2014 to 445 in 2018; 17 (81%) of the centers had an increase in annual case volume. For this subgroup, the median attending/staff per center was 4 in both 2014 and 2018. The median scanner time allotted per study was unchanged at 90 min. The mean time for an attending/staff physician to perform a typical CMR examination including reporting was 143-141 min.

CONCLUSION

These survey data provide a novel comprehensive view of CMR practice in pediatric and congenital heart disease. This information is useful for internal benchmarking, resource allocation, addressing practice variation, quality improvement initiatives, and identifying unmet needs.

A Simulation Study of Propofol Effect-Site Concentration for Appropriate Sedation in Pediatric Patients Undergoing Brain MRI: Pharmacodynamic Analysis

PURPOSE

We aimed to establish the propofol effect-site concentration (Ce) for appropriate sedation by pharmacodynamic analysis and to determine the propofol Ce during occurrence of sedation-related side effects in pediatric patients undergoing brain magnetic resonance imaging (MRI).

MATERIALS AND METHODS

In 50 pediatric patients scheduled for brain MRI, sedation was induced with 2.0 mg/kg propofol; additional propofol doses were 0.5-1 mg/kg. Propofol Ce was simulated by inputting the propofol administration profiles of patients into a pediatric compartmental model (Choi model). The relationship between propofol Ce and probabilities of sedation and recovery were analyzed using a sigmoidal Emax model. The simulated propofol Ce for sedation-related side effects was investigated. Population model parameters were estimated using the Nonlinear Mixed-Effects Modelling software.

RESULTS

The mean values of propofol Ce₅₀ for sedation during the preparation, scanning, and recovery phases were 1.23, 0.43, and 0.39 μg/mL. The simulated propofol Ce values during oxygen desaturation (SpO₂ <90%) (3 patients; 6%), hypotension (16 patients; 32%), and bradycardia (12 patients; 24%) were 3.01±0.04, 2.05±0.63, and 2.41±0.89 μg/mL, respectively.

CONCLUSION

The required propofol Ce₅₀ for applying monitors during the preparation phase before the start of MRI was higher than the propofol Ce₅₀ required during the scanning phase. During low-intensity stimulation phases, such as scanning, propofol bolus dose should be strictly titrated not to exceed the propofol Ce that can lead to oxygen desaturation because of the relatively low propofol Ce (Ce₉₅, 1.43 μg/mL) required for sedation in most patients.

Guidelines and protocols for cardiovascular magnetic resonance in children and adults with congenital heart disease: SCMR expert consensus group on congenital heart disease

Cardiovascular magnetic resonance (CMR) has taken on an increasingly important role in the diagnostic evaluation and pre-procedural planning for patients with congenital heart disease. This article provides guidelines for the performance of CMR in children and adults with congenital heart disease. The first portion addresses preparation for the examination and safety issues, the second describes the primary techniques used in an examination, and the third provides disease-specific protocols. Variations in practice are highlighted and expert consensus recommendations are provided. Indications and appropriate use criteria for CMR examination are not specifically addressed.

Anaesthesia for Paediatric Cardiac MRI

BACKGROUND

General anaesthesia (GA) for cardiac magnetic resonance imaging (MRI) in patients with congenital heart disease (CHD) is challenging for the anaesthesiologist.

METHODS

A retrospective review of anaesthesia for cardiac MRI between January 2002 and December 2005 was undertaken.

RESULT

28 children with cardiac disease were subjected to general anaesthesia for cardiac MRI, of which four patients were in ASA Grade I, five in Grade II, seventeen in Grade III and two in Grade IV. Two patients had undergone previous cardiac surgery. All the cases were managed as inpatients, of which 18 had cyanotic cardiac defects (SpO2 between 65 and 85%). On two occasions scans were interrupted because of low oxygen saturation or haemodynamic instability during GA. No patient was admitted to the hospital for complications related to general anaesthesia though all were kept under observation for two hours before being shifted to ward. Five patients had a brief episode of hypotension/desaturation during the MRI and responded quickly to interventions.

CONCLUSION

General anaesthesia for cardiac MRI can be administered safely in children with CHD.

Sedation medication received and adverse events related to sedation for brain MRI in children with and without developmental disabilities

BACKGROUND

There are few studies on sedation medication requirements and sedation related adverse events in developmentally disabled children.

OBJECTIVES

The objectives of our study were to compare sedation medication received and sedation related adverse events for brain magnetic resonance imaging (MRI) between children with and without developmental disabilities. We hypothesized that developmentally disabled children would require increased doses of sedative medications and will have increased frequency of adverse events when compared with normal children.

METHODS

We conducted a retrospective chart review on children 1-18 years, who required sedation for an elective brain MRI. Children were excluded if they required sedation for diagnostic imaging other than brain MRI, belonged to ASA category >3, or required general anesthesia. Data on developmental status, demographics and details of sedation medications received along with adverse events were collected.

RESULTS

About 53.5% (260/486) of the patients were classified as developmentally disabled. Pentobarbital and fentanyl were the two most common medications used for sedation in children with and without developmental disability. There was no difference in the mean dosages of pentobarbital (3.02 mg x kg(-1) vs 3.06 mg x kg(-1); P = 0.2) and fentanyl (1.01 mcg x kg(-1) vs 1.02 mcg x kg(-1); P = 0.81) in the two groups. There was a threefold increased incidence of hypoxia noted in children with developmental disability (11.9% vs 4.9%; P < 0.01). Presence of developmental disability alone was significantly associated with sedation related hypoxia (OR = 3.2, 95% CI: 1.8, 6.94; P < 0.01).

CONCLUSIONS

Children with developmental disabilities have similar requirements for sedation medications but are three times more likely to experience hypoxia when compared with normal children.

Anaesthesia considerations for cardiac MRI in infants and small children

BACKGROUND

General anaesthesia is frequently necessary in infants and small children undergoing cardiac magnetic resonance imaging (MRI), because of the imaging techniques, MRI environment and potential need for breath-holding to facilitate imaging. Anaesthetizing paediatric patients with congenital heart disease (CHD) for cardiac MRI poses many challenges for the anaesthetist and this report reviews our experience.

METHODS

We retrospectively reviewed the anaesthesia and MRI records of all patients who had undergone cardiac MRI between January 2000 and October 2002.

RESULTS

A total of 250 children with cardiac disease underwent general anaesthesia for cardiac MRI. ASA classification included class I, 2%; class II; 26%; class III, 60% and class IV, 12%. A total of 168 patients (67%) had undergone previous cardiac surgery, 182 patients (94%) were discharged the same day and 48 patients (19.2%) had cyanotic cardiac defects (SpO2 between 55 and 85%). No scans were interrupted because of low oxygen saturation during breath-hold or haemodynamic instability. No patient was admitted to the hospital from complications related to general anaesthesia, but one inhouse patient from the cardiology ward was admitted to the cardiac intensive care unit (CICU) after the MRI because of cyanosis and low cardiac output. Seven patients from the CICU were on inotropic infusions when they underwent the MRI procedure and two others needed inotropic support after induction of anaesthesia. Five patients had a brief episode of hypotension during the MRI and responded quickly to interventions.

CONCLUSION

Our experience demonstrates that general anaesthesia for cardiac MRI can be provided safely in infants and small children with CHD, despite the complexity and pathophysiology of many defects, the frequent breath-holding for image acquisitions and the MRI environment.