British Journal of Anaesthesia 1992; 69: 482-486
ANAESTHESIA FOR CRITICALLY ILL CHILDREN DURING MAGNETIC RESONANCE IMAGING J. R. TOBIN, E. A. SPURRIER AND R. C. WETZEL SUMMARY Magnetic resonance imaging (MRI) is becoming increasingly useful in children. Because of technical considerations and safety concerns, critically ill children have frequently been excluded from MRI. We have accomplished safely both transport and MRI in 21 patients from paediatric intensive care units (ICU). Three children were not considered appropriate for transport from the ICU to the MRI facility. All patients underwent assisted ventilation using a modified Map/eson D system. Monitoring of oxygenation, ventilation and haemodynamic state, including invasive arterial (n = 4) and intracranial pressures (n = 3) was continued successfully using routinely available equipment. All MRI studies were completed successfully with satisfactory image quality and all patients returned to the ICU in satisfactory condition. In contrast with previous reports which have excluded critically ill children, we have demonstrated that MRI may be undertaken safely and efficiently in critically ill children. (Br. J. Anaesth. 1992; 69: 482-486) KEY WORDS Anaesthesia: paediatric. Measurement techniques: nuclear magnetic resonance.
Magnetic resonance imaging (MRI) is used increasingly to improve accurate diagnoses [1-6], define plans for therapy [2] and provide new information on physiological changes [7-11] (table I). MRI examinations are of comparatively long duration, usually requiring 30-60 min of co-operation or immobility. The long cylindrical configuration of the MRI tunnel may be frightening to the conscious child and precludes visual assessment of the patient by personnel at the MRI control console. Monitoring equipment may malfunction in proximity to the magnet because of the high magnetic field strength and monitor wires may act as induction coils if looped, causing burns to the patient and poor scan quality [12]. In addition, ferrous objects brought into the scanning room may become dangerous missiles, potentially injuring the patient or attendants, or damaging the scanner [13, 14]. Ferrous and other metallic materials (praecordial stethoscope, subarachnoid bolts) in support and monitoring equipment, interfere with image generation of the MRI scanner [12]. These studies may also necessitate transportation to a site remote from the intensive care unit.
Patients who require airway control, assisted ventilation, supplementary oxygen, invasive monitoring, cardiovascular support, sedation or general anaesthesia for immobilization, pose challenging logistical problems. Critically ill patients must be monitored continuously and appropriately during MRI scanning, but there are some criteria for excluding patients (table II). We describe our experience with monitoring of critically ill children during MRI. PATIENTS AND METHODS
We studied 24 children, ages 3 days to 15 yr (2.5-60 kg), requiring paediatric intensive care, to assess if it was appropriate to obtain an MRI scan. Three patients were excluded because of severely labile intracranial hypertension, systemic hypotension and the presence of a cardiac pacemaker, respectively. The diagnoses of the 21 children deemed appropriate for study are detailed in table III. Of those 21, 18 required assisted ventilation (17 tracheal, one tracheotomy). In three patients the trachea was intubated to achieve airway control before transport and MRI. Therefore all MRI scans were obtained in patients with artificial airways. Three patients were receiving vasopressor agents. Invasive arterial (n = 4) and intracranial pressure (« = 3) monitoring were performed during transport and MRI. Informed consent for general anaesthesia and MRI was obtained from each patient's parent or guardian. All MRI scans were performed using a 1.5 Tesla MR scanner (GE Signa or Siemens). The patient and accompanying anaesthetist were screened for ferrous objects using a hand magnet. All children were monitored constantly by an anaesthetist at the patient's side throughout transport and MRI, and kept warm by wrapping with loose fitting blankets. A hat or plastic covering was used over the scalp in infants. The ECG was monitored (Hewlett-Packard HP78352A) continuously during transport and MRI. Heart and breath sounds were monitored by the
JOSEPH R. TOBIN, M.D.; RANDALL C. WETZEL, M.B., B.S., F.C.C.M.;
Departments of Anesthesiology/Critical Care Medicine and Pediatrics, The Johns Hopkins School of Medicine, 600 N. Wolfe Street - Blalock 1508, Baltimore, Maryland 21205, U.S.A. ELLEN A. SPURRIER, M.D., Departments of Anesthesiology and Pediatrics, The University of Maryland School of Medicine. Accepted for Publication: June 10, 1992. Correspondence to J.R.T.
MRI IN CRITICALLY ILL CHILDREN
483
TABLE I. Indications for MRI in critically ill children CNS imaging
Spinal cord imaging
Posterior fossa pathology Tumours, vascular, cerebellum Encephalopathies Encephalitis Cerebritis Myelitis Acute ischaemia Strokes Brain abscess
Injury Myelopathies Tumours Invasive, primary
TABLE II. Criteria for exclusion from MRI scanning Unstable vital signs including severely labile intracranial hypertension Permanent cardiac pacemaker Temporary cardiac pacemaker Automated internal cardiac defibrillator Intravascular wire or transthoracic pacing wires Neuroaneurysmal or vascular surgical clips (ferrous) Intraocular metallic foreign body Ferrous endoprostheses Dependence on technology incompatible with MRI: Extracorporeal membrane oxygenator, intra-aortic balloon pump, ventricular assist device
Body imaging Airway malformations Cardiac Tumours, congenital malformations Vascular anomalies and occlusions Systemic and pulmonary Liver vascularity Prepperanve vascular evaluation
anaesthetist throughout the scanning process, with a plastic oesophageal stethoscope connected to a plastic earpiece. The patients' posterior tibial or dorsalis pedis pulses were palpated intermittently. The ECG and base unit of the end-tidal carbon dioxide (PE'CO,) monitor were located outside the MRI room with the video screens positioned at the radiofrequency (RF) screen window, easily visible to the anaesthetist in the MRI room. All the remaining monitors were located in the magnet room, beyond the 50-gauss line. Pulse oximetry was used continuously throughout MRI scanning. The Nonin series 8604D (Nonin Medical, Plymouth, MN) oximeter was compatible with both the General Electric 1.5 Tesla and the
TABLE III. Patients evaluated and subsequently supported for MRI scan. All patients were monitored with ECG, pulse oximetry, non-invasive arterial pressure (Dinamap) and a plastic praecordial or oesophageal stethoscope. Additional monitors used in selected patients: ICP •= intracranial pressure; IA = invasive arterial; V = vasopressor support; CVP = central venous pressure. Other abbreviations: SVC = superior vena cava; CNS = central nervous system Diagnosis
Age
6 months 16 months 5yr 4yr
Pulmonary hypoplasia Arnold-Chiari malformation, basilar artery compression Encephalopathy Congenital heart disease and SVC syndrome
13 months
Apnoea, cervical cord compression
5yr 15 yr
Closed head trauma Chemotherapy-induced spinal cord myelopathyj and encephalopathy Posterior fossa tumour
2yr 14 yr 7 months 3yr
Subarachnoid haemorrhage Hydrocephalus Supratentorial aitrocytoma
2 months
Encephalopathy/encephalitis
6 yr 3yr
Moyamoya arteritis and cerebral ischaemic accident Brain abscess
4 weeks
Vocal cord paralysis, Arnold-Chiari malformation, hydrocephalus Metastatic tumour to CNS, sepsis
15 yr 5yr
Supratentorial tumour, subdural hygromas
9yr
Cerebellitis Intracerebral cyst
3days 13yr 10 yr
Extradural and parenchymal haematoma, closed head trauma Brain abscess
Comments Diagnostic information, therapeutic intervention Diagnostic information, surgical intervention Intubated for MRI, diagnostic information Intubated for MRI, diagnostic information, therapeutic intervention Diagnostic information, surgical intervention Diagnostic information ICP, IA, V. Diagnostic information, therapeutic intervention Diagnostic information, surgical intervention CVP, IA, ICP, V. Diagnostic information Surgical intervention Diagnostic information, surgical intervention Diagnostic information, therapeutic intervention Diagnostic information Diagnostic information, surgical intervention Diagnostic information, surgical ' intervention IA, V. Diagnostic information, therapeutic intervention ICP, IA. Diagnostic information, surgical intervention Diagnostic information Intubated for MRI. Diagnostic information, surgical intervention Diagnostic information, therapeutic and surgical intervention Diagnostic information, surgical intervention
484
Siemens 1.5 Tesla MRI scanner. The oximeter did not cause degradation of the scan quality. PE' COJ was measured by side-stream sampling to an Argon laser spectroscopy unit (Raman Spectroscopy, RASCAL, Albion, Salt Lake City, UT) with an easily visible digital and graphic display. For small infants (
ANAESTHESIA FOR CRITICALLY ILL CHILDREN DURING MAGNETIC RESONANCE IMAGING J. R. TOBIN, E. A. SPURRIER AND R. C. WETZEL SUMMARY Magnetic resonance imaging (MRI) is becoming increasingly useful in children. Because of technical considerations and safety concerns, critically ill children have frequently been excluded from MRI. We have accomplished safely both transport and MRI in 21 patients from paediatric intensive care units (ICU). Three children were not considered appropriate for transport from the ICU to the MRI facility. All patients underwent assisted ventilation using a modified Map/eson D system. Monitoring of oxygenation, ventilation and haemodynamic state, including invasive arterial (n = 4) and intracranial pressures (n = 3) was continued successfully using routinely available equipment. All MRI studies were completed successfully with satisfactory image quality and all patients returned to the ICU in satisfactory condition. In contrast with previous reports which have excluded critically ill children, we have demonstrated that MRI may be undertaken safely and efficiently in critically ill children. (Br. J. Anaesth. 1992; 69: 482-486) KEY WORDS Anaesthesia: paediatric. Measurement techniques: nuclear magnetic resonance.
Magnetic resonance imaging (MRI) is used increasingly to improve accurate diagnoses [1-6], define plans for therapy [2] and provide new information on physiological changes [7-11] (table I). MRI examinations are of comparatively long duration, usually requiring 30-60 min of co-operation or immobility. The long cylindrical configuration of the MRI tunnel may be frightening to the conscious child and precludes visual assessment of the patient by personnel at the MRI control console. Monitoring equipment may malfunction in proximity to the magnet because of the high magnetic field strength and monitor wires may act as induction coils if looped, causing burns to the patient and poor scan quality [12]. In addition, ferrous objects brought into the scanning room may become dangerous missiles, potentially injuring the patient or attendants, or damaging the scanner [13, 14]. Ferrous and other metallic materials (praecordial stethoscope, subarachnoid bolts) in support and monitoring equipment, interfere with image generation of the MRI scanner [12]. These studies may also necessitate transportation to a site remote from the intensive care unit.
Patients who require airway control, assisted ventilation, supplementary oxygen, invasive monitoring, cardiovascular support, sedation or general anaesthesia for immobilization, pose challenging logistical problems. Critically ill patients must be monitored continuously and appropriately during MRI scanning, but there are some criteria for excluding patients (table II). We describe our experience with monitoring of critically ill children during MRI. PATIENTS AND METHODS
We studied 24 children, ages 3 days to 15 yr (2.5-60 kg), requiring paediatric intensive care, to assess if it was appropriate to obtain an MRI scan. Three patients were excluded because of severely labile intracranial hypertension, systemic hypotension and the presence of a cardiac pacemaker, respectively. The diagnoses of the 21 children deemed appropriate for study are detailed in table III. Of those 21, 18 required assisted ventilation (17 tracheal, one tracheotomy). In three patients the trachea was intubated to achieve airway control before transport and MRI. Therefore all MRI scans were obtained in patients with artificial airways. Three patients were receiving vasopressor agents. Invasive arterial (n = 4) and intracranial pressure (« = 3) monitoring were performed during transport and MRI. Informed consent for general anaesthesia and MRI was obtained from each patient's parent or guardian. All MRI scans were performed using a 1.5 Tesla MR scanner (GE Signa or Siemens). The patient and accompanying anaesthetist were screened for ferrous objects using a hand magnet. All children were monitored constantly by an anaesthetist at the patient's side throughout transport and MRI, and kept warm by wrapping with loose fitting blankets. A hat or plastic covering was used over the scalp in infants. The ECG was monitored (Hewlett-Packard HP78352A) continuously during transport and MRI. Heart and breath sounds were monitored by the
JOSEPH R. TOBIN, M.D.; RANDALL C. WETZEL, M.B., B.S., F.C.C.M.;
Departments of Anesthesiology/Critical Care Medicine and Pediatrics, The Johns Hopkins School of Medicine, 600 N. Wolfe Street - Blalock 1508, Baltimore, Maryland 21205, U.S.A. ELLEN A. SPURRIER, M.D., Departments of Anesthesiology and Pediatrics, The University of Maryland School of Medicine. Accepted for Publication: June 10, 1992. Correspondence to J.R.T.
MRI IN CRITICALLY ILL CHILDREN
483
TABLE I. Indications for MRI in critically ill children CNS imaging
Spinal cord imaging
Posterior fossa pathology Tumours, vascular, cerebellum Encephalopathies Encephalitis Cerebritis Myelitis Acute ischaemia Strokes Brain abscess
Injury Myelopathies Tumours Invasive, primary
TABLE II. Criteria for exclusion from MRI scanning Unstable vital signs including severely labile intracranial hypertension Permanent cardiac pacemaker Temporary cardiac pacemaker Automated internal cardiac defibrillator Intravascular wire or transthoracic pacing wires Neuroaneurysmal or vascular surgical clips (ferrous) Intraocular metallic foreign body Ferrous endoprostheses Dependence on technology incompatible with MRI: Extracorporeal membrane oxygenator, intra-aortic balloon pump, ventricular assist device
Body imaging Airway malformations Cardiac Tumours, congenital malformations Vascular anomalies and occlusions Systemic and pulmonary Liver vascularity Prepperanve vascular evaluation
anaesthetist throughout the scanning process, with a plastic oesophageal stethoscope connected to a plastic earpiece. The patients' posterior tibial or dorsalis pedis pulses were palpated intermittently. The ECG and base unit of the end-tidal carbon dioxide (PE'CO,) monitor were located outside the MRI room with the video screens positioned at the radiofrequency (RF) screen window, easily visible to the anaesthetist in the MRI room. All the remaining monitors were located in the magnet room, beyond the 50-gauss line. Pulse oximetry was used continuously throughout MRI scanning. The Nonin series 8604D (Nonin Medical, Plymouth, MN) oximeter was compatible with both the General Electric 1.5 Tesla and the
TABLE III. Patients evaluated and subsequently supported for MRI scan. All patients were monitored with ECG, pulse oximetry, non-invasive arterial pressure (Dinamap) and a plastic praecordial or oesophageal stethoscope. Additional monitors used in selected patients: ICP •= intracranial pressure; IA = invasive arterial; V = vasopressor support; CVP = central venous pressure. Other abbreviations: SVC = superior vena cava; CNS = central nervous system Diagnosis
Age
6 months 16 months 5yr 4yr
Pulmonary hypoplasia Arnold-Chiari malformation, basilar artery compression Encephalopathy Congenital heart disease and SVC syndrome
13 months
Apnoea, cervical cord compression
5yr 15 yr
Closed head trauma Chemotherapy-induced spinal cord myelopathyj and encephalopathy Posterior fossa tumour
2yr 14 yr 7 months 3yr
Subarachnoid haemorrhage Hydrocephalus Supratentorial aitrocytoma
2 months
Encephalopathy/encephalitis
6 yr 3yr
Moyamoya arteritis and cerebral ischaemic accident Brain abscess
4 weeks
Vocal cord paralysis, Arnold-Chiari malformation, hydrocephalus Metastatic tumour to CNS, sepsis
15 yr 5yr
Supratentorial tumour, subdural hygromas
9yr
Cerebellitis Intracerebral cyst
3days 13yr 10 yr
Extradural and parenchymal haematoma, closed head trauma Brain abscess
Comments Diagnostic information, therapeutic intervention Diagnostic information, surgical intervention Intubated for MRI, diagnostic information Intubated for MRI, diagnostic information, therapeutic intervention Diagnostic information, surgical intervention Diagnostic information ICP, IA, V. Diagnostic information, therapeutic intervention Diagnostic information, surgical intervention CVP, IA, ICP, V. Diagnostic information Surgical intervention Diagnostic information, surgical intervention Diagnostic information, therapeutic intervention Diagnostic information Diagnostic information, surgical intervention Diagnostic information, surgical ' intervention IA, V. Diagnostic information, therapeutic intervention ICP, IA. Diagnostic information, surgical intervention Diagnostic information Intubated for MRI. Diagnostic information, surgical intervention Diagnostic information, therapeutic and surgical intervention Diagnostic information, surgical intervention
484
Siemens 1.5 Tesla MRI scanner. The oximeter did not cause degradation of the scan quality. PE' COJ was measured by side-stream sampling to an Argon laser spectroscopy unit (Raman Spectroscopy, RASCAL, Albion, Salt Lake City, UT) with an easily visible digital and graphic display. For small infants (
