Anesthesia in Radiological suite

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anesthesia outside operating room, especially in radiology

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Anesthesia Outside the Operating Room :

Anesthesia Outside the Operating Room Dr. Habib Md.Reazaul Karim PGT, Anesthesia & ICU NEIGRIHMS,Shillong

Anesthesia Outside the OR [1]:

Anesthesia Outside the OR [1] Radiology- CT, MRI, Interventional Radiation Therapy Cardiology- Cardio version, PPM insertion, catheterization Psychiatry- Electroconvulsive therapy Gastroenterology- EGD, colonoscopy Urology- ESWL

Anesthesia Outside the OR :

Anesthesia Outside the OR Standards introduced by the Joint Commission on Accreditation of Healthcare Organizations The American Society of Anesthesiologists (ASA) has developed practice guidelines for sedation and analgesia by nonanesthesiologists The ASA has developed standards to apply to anesthesia in remote locations

Uniform Quality of Care Outside the OR? [2,3] :

Uniform Quality of Care Outside the OR? [2,3] Joint Commission on Accreditation of Healthcare Organizations (JCAHO) enacted several standards in 2001. These requirements include: -pre sedation assessment -continuous physiologic monitoring -credentialing of individuals providing different levels of sedation -post sedation recovery and discharge -maintenance of institution wide standards of care and quality assurance for all levels of care.

ASA Guidelines for Nonoperating Room Anesthetizing Locations [4]:

ASA Guidelines for Nonoperating Room Anesthetizing Locations [4] Approved by House of Delegates on October 19, 1994, and last amended on October 15, 2003. “Minimal guidelines which may be exceeded at any time based on the judgment of the involved anesthesia personnel”. “ASA Standards, Guidelines and Policies should be adhered to in all non-operating room settings except where they are not applicable to the individual patient or care setting”.

ASA Guidelines [4,5]:

ASA Guidelines [4,5] a reliable oxygen source with backup a suction source waste gas scavenging adequate monitoring equipment to meet the standards for basic anesthetic monitoring a self-inflating hand resuscitator bag sufficient safe electrical outlets adequate patient and anesthesia machine illumination with battery-powered backup sufficient space for the anesthesia care team emergency cart with a defibrillator emergency drugs, and other emergency equipment a means of reliable two-way communication to request assistance compliance of the facility with all applicable safety and building codes Adequately trained staff to support anesthesia team

JCAHO and ASA [7]:

JCAHO and ASA [7] Prospective study in a tertiary care center to determine the effects of the new guidelines on adverse events during sedation 14,386 patients received PSA between July 1, 2001, and June 30, 2004 7.6% of patients had an adverse event, with the most common being hypoxemia (39.7% of all adverse events). A trend toward a decrease in the incidence of adverse events was found during the study (Pearson product moment correlation, –0.68; P<.001). Led to a decrease in the incidence of adverse events during the study, implying that uniform standards of monitoring and care may lead to safer conditions for patients. Effect on Hospital-Wide Sedation Practices After Implementation of the 2001 JCAHO Procedural Sedation and Analgesia Guidelines. Raymond Pitetti, MD, MPH; Peter J. Davis, MD; Robert Redlinger, RN, MSN; Jean White, RN; Eugene Wiener, MD; Karen H. Calhoun, BSN, MBA. Arch Pediatr Adolesc Med . 2006;160:211-216.

Anesthesia Outside the OR :

Anesthesia Outside the OR It is vital to confirm the presence and proper functioning of all equipment an anaesthesiologist would expect to have in the operating room. The location of immediately available resuscitation equipment should be noted and protocols developed with the local staff for dealing with emergencies, including cardiopulmonary resuscitation and the management of anaphylaxis.

Anesthesia in Radiological suite:

Anesthesia in Radiological suite Dr. Habib Md.Reazaul Karim PGT, Anesthesia & ICU ,NEIGRIHMS, Shillong

MRI/CT/PET interventional radiology Radiotherapy/radiofrequency ablation:

MRI/CT/PET interventional radiology Radiotherapy/radiofrequency ablation

Patient Factors Requiring Sedation or General Anesthesia at Alternate Sites:

Patient Factors Requiring Sedation or General Anesthesia at Alternate Sites Anxiety and panic disorders Claustrophobia Developmental delay and learning difficulties Cerebral palsy Seizure disorders Movement disorders Severe pain Acute trauma with unstable cardiovascular, respiratory, or neurologic function Significant co-morbidity Child age

General Consideration:

General Consideration Limited patient access Absolute need to exclude ferromagnetic component Interference of monitoring equipment produced by the changing magnetic field and RF current Potential degradation of the imaging caused by the stray RF currents produced by the monitoring equipment and lead

Pre-anaesthetic assessment :

Pre-anaesthetic assessment History including any implant in body and allergy to contrast, shellfish, h/o pregnancy, co morbid conditions, sleep apnoea General physical/ systemic and Airway Examinations Relevant investigations

Check up:

Check up Review patient and PAC Sheet NPO Status Is patient dehydrated? Ferromagnetic elements/ implants

Anesthetic Considerations for MRI [12, 5]:

Anesthetic Considerations for MRI [12, 5] Physical Environment -pt positioning (area of interest must be close to MRI coil) -narrow aperture (Obese pt’s may not fit) -remote viewing necessary -limited access to pt/airway -noisy atmosphere (hearing protection)

Anesthetic Considerations for MRI [12, 5]:

Anesthetic Considerations for MRI [12, 5] Magnetic field/Radiofrequency signal - no ferromagnetic components (ETT, PPM, AICD, vascular clips, biologic pumps, shrapnel, ocular metal) - interference of monitors -necessity for immobilization of monitors to prevent degradations of magnetic field homogenity -physical harm to those in the room?

Monitoring Considerations:

Monitoring Considerations ECG -rapidly changing magnetic fields produce artifact, ST and T wave abnormalities, and may mimic arrhythmias -if ECG wires are in a loop, a the magnetic field may heat the wires and leads, thus leading to thermal injury (antenna coupling effect) Pulse oximetry -like ECG wires, the antenna effect may produce thermal injury Capnography -increased length of sampling line may have prolonged time delay Blood pressure - need for plastic components

ECG wave in MRI:

ECG wave in MRI Blood is a conductive medium—positive and negative charges exist and allow current flow. When moving blood is exposed to a magnetic field, charge separation occurs, inducing a time-varying electrical dipole signal that is a function of the magnitude and direction of flow within the field of the MR scanner. This dipole is detected as a time-varying electrical signal superimposed onto the ECG waveform. This second electrical signal precedes ventricular contraction and consequently is detected after the QRS complex of the ECG waveform. Ventricular re-polarization, as described by the ST segment, is detected at approximately the same time as the flow of blood through the aorta and, hence, is often superimposed onto the T wave of the ECG. This is most commonly known as “T-wave swelling” (or “T-wave elevation”) and can cause the T wave to be of even greater amplitude than the R wave. T-wave swelling often results in unreliable triggering and poor image quality. If ECG triggering is based on the peak voltage of the waveform, the scanner could trigger off the T wave or switch between the R-wave and T-wave peaks.

Thermal Injury:

Thermal Injury  Three mechanisms of heating copper wires in MRI -EM induction in conduction loop, induction in resonant loop, and EF coupling with a wire (antenna effect)  Temperature rises were 0.6, 0.61, and 0.63 C respectively.  Burns more likely to occur in the latter positioning of wires, thus wire positioning should be part of safety guidelines. Investigation of the factors responsible for burns during MRI. Journal of Magnetic Resonance Imaging. Mary F. Dempsey, BSc, MSc *, Barrie Condon, BSc, MSc, PhD, Donald M. Hadley, PhD, DMRD, FRCR. Volume 13 Issue 4, Pages 627 – 631. 21 Mar 2001

Patient Positioning [12]:

Patient Positioning [12] Pt with spine disease had to undergo MRI with GA as they could not tolerate the supine position due to pain. Anesthetic course was unremarkable over the 2 hour study. Pt awakened with new-onset paraplegia, with an acute myelopathy at T12-L1. Pt underwent emergency decompressive laminectomy. Case Report Neurologic Deficits After General Anesthesia for MRI Margare Weglinski, MD; Keith H. Berge, MD; Dudley H. Davis, MD. New-Onset. Mayo Clin Proc. 2002;77:101-103 .

Safety Considerations [13,14]:

Safety Considerations [13,14] -ferrous oxygen tank brought to suite after piped in O2 to patient was not sufficient. -techs left to address pipeline 02 and left the machine unsupervised. -tank flew 20 feet/second resulting in blunt head trauma, s six year old pt died of massive hemorrhaging “Health Department Fines Westchester Medical Center $22,000 for its Failure to Ensure Patient Safety During MRI Procedures” AND… - a pt forgot about a hairpin in her hair, ended up traveling up her nose and lodging into her pharynx -In Rochester, the magnetic force pulled a gun out of a police officer’s holster and fired a round that lodged in the wall

Safety Considerations:

Safety Considerations

Remote Viewing [15]:

Remote Viewing [15] ASA Monitoring Standard I- -Qualified anesthesia personnel shall be present in the room throughout the conduct of all general anesthetics, regional anesthetics and monitored anesthesia care. Is this a violation of the ASA Monitoring Standards? “With the advent of MRI compatible instruments…anesthesia personnel should now remain in the room, as no biological hazard exists to normal human beings in the scanner room, especially at 10 feet from the magnet coil. However, individuals continue, by choice, to monitor from the SCR.”

Practice Guidelines for Sedation and Anesthesia by Non-Anesthesiologists [6]:

Practice Guidelines for Sedation and Anesthesia by Non-Anesthesiologists [6] Patient must be evaluated before the procedure by qualified personnel to ensure that patients are not compromised by coexisting medical conditions Appropriate NPO status. have given informed consent. During the procedure, the level of consciousness, ventilation, oxygenation, and hemodynamics are to be evaluated with standard monitors by a designated individual who should be trained to recognize complications of analgesia and sedation at least one individual trained in basic life support skills should be present continuously when moderate or deep sedation is used. Supplemental oxygen should be used for moderate and deep sedation, and emergency equipment, including pharmacologic antagonists, should be available. Adequate recovery care should be provided, with the patient observed in an adequately staffed and equipped recovery area; released only when acceptable discharge criteria have been met.

Types of Anesthesia:

Types of Anesthesia General anaesthesia Using ET Tube and IPPV Using LMA Conscious sedation TIVA “sleep-awake-sleep” anesthetic technique

General anesthesia:

General anesthesia No specific anesthetic technique is required Adequate length of lines / wire No looping of wire to prevent antenna effect and thermal injury Medication biased towards sedation, unless analgesia is required Induced in induction area adjacent to MRI room after standard monitoring are placed and airway secured by ETT/LMA MRI compatible instruments only inside Maintained with inhaled anesthetic/propofol Transfer back to induction area and awaken after the procedure Observation in recovery room by qualified person and discharge after criteria are fulfilled Hearing protection is mandatory for anaesthesiologist if they must remain in MRI room

sedation :

sedation Adequate sedation may result in apnea, hypoxia, hypercarbia Inadequate sedation may result in patient movement and a failed imaging study Controlled circumstances may be required in patients with more complex diseases to limit the time spent in the suite Efficacy of oral/rectally administered sedatives may not be predictable Patients with mental/emotional disorders may require deeper sedation

What Constitutes Sedation? [2]:

What Constitutes Sedation? [2] Minimal sedation (anxiolysis) Pt responds to commands, no change in ventilation/cardiovascular status, cognitive/motor function impaired Moderate Sedation/Analgesia - Pt responds purposely to commands alone or with light stimulation, maintains spontaneous ventilation, cardiovascular status maintained Deep Sedation/Analgesia Pt not easily arousable, responds to pain, may need assistance with airway and ventilation, cardiovascular status maintained General Anesthesia Unarousable even with painful stimulus, Intervention required for airway, spontaneous ventilation frequently inadequate, cardiovascular status may be impaired Levels defined by the ASA on October 13, 1999.

Type of Anesthesia [16]:

Type of Anesthesia [16] Most of the patient will tolerate MRI with no/light sedation Deep sedation/analgesia not advisable, rather go for GA Contraindications to sedation -risk of aspiration -possible airway obstruction/anatomical abnormalities -raised ICP -desensitization to CO2 -altered drug metabolism Sedation versus general anesthesia in MRI

TIVA [18]:

TIVA [18] Utilization of propofol provided adequate levels of sedation at appropriate low doses 93% of children had no signs of airway obstruction with a shoulder roll. Mean infusion rate was 193 mcg/kg/min with patient movement at a mean of 175 mcg/kg/min. Mean time from end of MRI to discharge was 44 minutes Propofol total intravenous anesthesia for MRI in children. Andrew G. Usher MB ChB FANZCA, Ramona A. Kearney MD FRCPC and Ban C.H. Tsui MD FRCPC. Pediatric Anesthesia . Volume 15 Issue 1, Pages 23 – 28. Published Online: 20 Oct 2004.

Anesthetic Choices [19]:

Anesthetic Choices [19] Evaluate combination of midazolam/ketamine (study) versus GA (control) Rectal 0.5mg/kg Midazolam, 5mg/kg Ketamine given, after which spontaneous ventilation was maintained Induction/discharge times shorter in the study group (p <0.001) Recovery time showed no significant difference Rectal midazolam/ketamine is a safe alternative to GA. Anaesthesia with midazolam and S-(+)-ketamine in spontaneously breathing paediatric patients during magnetic resonance imaging. G. Haeseler, O. Zuzan, G. Köhn, S. Piepenbrock & M. Leuwer. Pediatric Anesthesia . Volume 10 Issue 5, Pages 513 – 519. Published Online: 25 Dec 2001 .

More Anesthetic Options:

More Anesthetic Options Comparison of the Sedative, Hemodynamic, and Respiratory Effects of Dexmedetomidine and Propofol in Children Undergoing Magnetic Resonance Imaging. Ahmet Koroglu, MD*, Huseyin Teksan, MD{dagger}, Ozlem Sagir, MD*, Aytaç Yucel, MD*, Huseyin I. Toprak, MD*, and Ozcan M. Ersoy, MD* Anesthesia and Analgesia. 2006;103:63-67.  The MAP and RR were significantly lower in Propofol group.

Specific Radiologic Procedures:

Specific Radiologic Procedures Cerebral and spinal angiography cause minimal discomfort and may be performed under local anesthesia with or without light sedation Neurologic disorders such as recent subarachnoid hemorrhage, stroke, and depressed level of consciousness or raised ICP may make it impossible for patients to tolerate these procedures unsedated Deep sedation or general anesthesia with airway protection is often required

Interventional Neuroradiology :

Interventional Neuroradiology General anesthesia and conscious sedation are both suitable techniques for interventional neuroadiology depending on the complexity of the procedure, the need for blood pressure manipulation, and the need for intraprocedural assessment of neurologic function Propofol infusions are widely used, as are combinations of a benzodiazepine (usually midazolam) and opioid (usually fentanyl). More recently, dexmedetomidine has been evaluated as a sedative agent that does not cause significant respiratory depression in patients requiring neurologic testing Anticoagulation with heparin is required during interventional neuroradiology During angioplasty or stenting of carotid artery stenosis, the anesthesia team should be prepared to treat severe bradycardias or transient asystole Two most catastrophic complications that can occur are intracranial hemorrhage or thromboembolic stroke Pulmonary embolic phenomena due to acrylic glues also occurs Controlled hypotension is often requested to facilitate embolization of AVMs. Esmolol, labetalol, metoprolol, and hydralazine are commonly used. Moderate hypertension may help reduce cerebral ischemia by maintaining cerebral perfusion; in this case. Phenylephedrine is the agent of choice

Acute Management of Neurologic Catastrophes :

Acute Management of Neurologic Catastrophes Initial resuscitation Communicate with radiologists Call for assistance Secure the airway and hyperventilate with 100% O 2 Determine if problem is hemorrhagic or occlusive Hemorrhagic: immediate heparin reversal (1 mg of protamine for each 100 units of heparin given) and low normal pressure Occlusive: deliberate hypertension, titrated to neurologic examination, angiography, or physiologic imaging studies (e.g., TCD, CBF) Further resuscitation Head up 15° in neutral position Titrate ventilation to a PaCO> 2 of 26–28 mm Hg 0.5 g/kg mannitol, rapid intravenous infusion Anticonvulsants: Dilantin (give slowly, 50 mg/min) and phenobarbital Titrate thiopental infusion to electroencephalogram burst suppression Allow body temperature to fall as quickly as possible to 33–34°C Consider dexamethasone, 10 mg

MRI:

MRI Most children younger than the age of 5 years and many as old as age 11 require sedation or general anesthesia to tolerate MRI Oral sedation techniques, if appropriately administered, have a success rate of 93% Oral chloral hydrate is a popular agent ( 25-50 mg/kg for infants younger than 4 months, 50 mg/kg for older children) Benzodiazepines such as midazolam administered either orally (0.25 to 0.75 mg/kg) or intravenously (0.05 to 0.15 mg/kg) are also commonly used for sedation Deep sedation with propofol infusion, oxygen administration via nasal cannula, and end-tidal carbon dioxide monitoring is a successful technique Children are initially sedated with incremental propofol boluses up to 3 mg/kg with or without midazolam, 0.2 to 0.5 mg/kg, and then maintained with an infusion rate of propofol, 1 to 3 mg/kg/hr, with supplemental boluses of 1 mg/kg for movement In the case of an emergency , the MRI technicians should be notified, the scan sequence stopped, and the patient rapidly removed. Resuscitation attempts should take place outside the scanner because equipment such as laryngoscopes, oxygen cylinders, and cardiac defibrillators cannot be taken close to the magnet

Risk and Quality [8]:

Risk and Quality [8] Complications of anesthesia outside the operating room are not well studied. A few closed claims are appearing in the literature suggesting there is a higher risk . Risk factors for these procedures are identified with emphasis on full oxygenation and end-tidal carbon dioxide monitoring. Non-operating room anesthesia requires skills, experience and organization. Quality can only be assured by ensuring all alternative locations adhere to operating room standards . Anesthesia and sedation outside the operating room : how to prevent risk and maintain good quality . Melloni, Claudio. Ambulatory anaesthesia: Current Opinion in Anaesthesiology. 20(6):513-519, December 2007.

Hazards of mri:

Hazards of mri Static magnetic fields Projectile Metal in body Gradient magnetic field Nerve stimulation Acoustic noise Radiofrequency electromagnetic fields Tissue heating Electrical burns

Failures of Anesthesia For MRI [22]:

Failures of Anesthesia For MRI [22] Agitation/delirium Airway obstruction Allergic reaction Apnea Aspiration Cardiac arrest Death Desaturation Laryngospasm Unexpected emergency airway management Stridor Prolonged recovery time Hypothermia Failed imaging study Inadequate sedation Hypoxemia

Reasons for Failure? [23] :

Reasons for Failure? [23] Adverse events of hypoxemia and/or failed sedation occurred more often in older children, those with benzodiazepines as the sole medication, and those with ASA Class IV or higher. Preselection of GA was utilized for those patients with a history of failed sedation or high potential for failure. Sedation and general anaesthesia in children undergoing MRI and CT: adverse events and outcomes. S. Malviya, T. Voepel-Lewis, O. P. Eldevik, D. T. Rockwell, J. H. Wong and A. R. Tait. British Journal of Anaesthesia , 2000, Vol. 84, No. 6 743-748

Prevention of Anesthetic/MRI Failure [25]:

Prevention of Anesthetic/MRI Failure [25] Organized sedation/anesthetic protocols outside of the OR Adherence to ASA monitoring standards Adequate training for sedation by non-anesthetists Utilization of proper monitors and MRI compatible equipment Adhere to American College of Radiology recommendations

Contrast nephropathy:

Contrast nephropathy CN is the third leading cause of hospital-acquired acute renal failure, accounting for 12% of cases. Patients with chronic renal disease, diabetes, and hypovolemia are most at risk for CN Patients taking metformin are at risk of developing lactic acidosis Adequate hydration, monitoring of urine output, and the use of low-osmolarity and nonionic contrast media help reduce the risk. CN may be prevented by the use of adequate hydration and sodium bicarbonate infusions 1 hour before the procedure. Antioxidants such as N-acetylcysteine, ascorbic acid may be useful in preventing CN

Other Solutions?:

Other Solutions? Open MRI for obese patients and those with claustrophobia Music/images within MRI Low intensity MR machines Stress reduction techniques during imaging study Temperament assessment

Other Solutions?:

Other Solutions?

Radiation Therapy :

Radiation Therapy External beam radiation treatments, usually for children with malignancies, and intraoperative radiation to tumor masses that cannot be completely resected Direct observation of the patient is not possible General anesthesia or deep-sedation techniques with propofol are preferable to prevent patient movement and to allow children to tolerate what can be fairly length procedures The goals of anesthesia for pediatric radiotherapy Assurance of immobility Rapid onset Brief duration of action Not painful to administer Prompt recovery Minimal interference with eating or drinking and playing Avoidance of tolerance to the anesthetic agents Maintenance of a patent airway in a variety of body positions

References:

References 1 - Stoelting , Robert K. and Miller, Ronald, et al. Basics of Anesthesia. 5 th ed. Churchill, Livingstone, Elsevier. Philadelphia. 2007. pp. 551 2- Barash , Paul G., Cullen, Bruce F., Stoelting , Robert K. Handbook of Clinical Anesthesia. 5 th ed. Lippincott Williams & Wilkens . Philadelphia. 2006. pp. 828-852. 3- Leak, Jessie A. Hospital-Based Anesthesia Outside of the Operating Room. ASA Newsletter October 2003, Volume 67, Number 10. 4- Guidelines for Nonoperating Room Anesthetizing Locations. American Society of Anesthesiologists. http://www.asahq.org/Washington/oba.htm 5- Miller, Ronald D. Miller’s Anesthesia. 6 th ed. Churchhill Livingstone. Philadelphia. 2004. 6- American Society of Anesthesiologists, Inc. Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists An Updated Report by the American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiologists . Anesthesiology 2002; 96:1004 7- Effect on Hospital-Wide Sedation Practices After Implementation of the 2001 JCAHO Procedural Sedation and Analgesia Guidelines. Raymond Pitetti , MD, MPH; Peter J. Davis, MD; Robert Redlinger , RN, MSN; Jean White, RN; Eugene Wiener, MD; Karen H. Calhoun, BSN, MBA. Arch Pediatr Adolesc Med . 2006;160:211-216. 8- Anesthesia and sedation outside the operating room: how to prevent risk and maintain good quality. Melloni , Claudio. Ambulatory anaesthesia : Current Opinion in Anaesthesiology . 20(6):513-519, December 2007. 9- Adult claustrophobia, anxiety and sedation in MRI. Murphy KJ, Brunberg JA. Magnetic Resonance Imaging. 1997;15(1):51-4. 10- http://health.ucsd.edu/specialties/mri/ptinfo/how.htm. UCSD Radiology Department 11- http://spnl.stanford.edu/participating/mriwork_detailed.htm. http://spnl.stanford.edu/images/top_bar.jpg 12- Margare Weglinski , MD; Keith H. Berge, MD; Dudley H. Davis, MD. New-Onset Neurologic Deficits After General Anesthesia for MRI. Mayo Clin Proc. 2002;77:101-103. Case Report..

References:

References 13- “ Health Department Fines Westchester Medical Center $22,000 for its Failure to Ensure Patient Safety During MRI Procedures”. http://www.health.state.ny.us/press/releases/2001/wmcmri.htm 14- “ Boy, 6, Dies of Skull Injury During MRI,” David W. Chen. New York Times . July 31, 2001 15- Paul M Kempen, MD, PhD. Editorial- http://www.apsf.org/resource_center/newsletter/2005/summer/05mri.htm 16- Sedation versus general anesthesia in MRI . M.P. Boidin MD, PhD, G.R. Wolff MD, C. Doelman MD Afdeling Anesthesiologie Amphia Ziekenhuis Breda. Breda, The Netherlands. ClinicalWindow.net, Issue 10 August 2002. 18- Propofol total intravenous anesthesia for MRI in children. Andrew G. Usher MB ChB FANZCA, Ramona A. Kearney MD FRCPC and Ban C.H. Tsui MD FRCPC. Pediatric Anesthesia . Volume 15 Issue 1, Pages 23 – 28. Published Online: 20 Oct 2004. 19- Anaesthesia with midazolam and S-(+)-ketamine in spontaneously breathing paediatric patients during magnetic resonance imaging. G. Haeseler, O. Zuzan, G. Köhn, S. Piepenbrock & M. Leuwer. Pediatric Anesthesia . Volume 10 Issue 5, Pages 513 – 519. Published Online: 25 Dec 2001.

References:

References 20- Sedation and Anesthesia Protocols Used for Magnetic Resonance Imaging Studies in Infants: Provider and Pharmacologic Considerations. Priti G. Dalal, MD, FRCA, David Murray, MD, Thomas Cox, MD, John McAllister, MD, and Rebecca Snider, RN. Anesthesia and Analgesia 2006;103:863-868. 21- Comparison of the Sedative, Hemodynamic, and Respiratory Effects of Dexmedetomidine and Propofol in Children Undergoing Magnetic Resonance Imaging. Ahmet Koroglu, MD*, Huseyin Teksan, MD{dagger}, Ozlem Sagir, MD*, Aytaç Yucel, MD*, Huseyin I. Toprak, MD*, and Ozcan M. Ersoy, MD* Anesthesia and Analgesia. 2006;103:63-67. 22- Incidence and Nature of Adverse Events During Pediatric Sedation/Anesthesia for Procedures Outside the Operating Room: Report From the Pediatric Sedation Research Consortium. Joseph P. Cravero, MDa,b, George T. Blike, MDa, Michael Beach, MDa, Susan M. Gallagher, BSc, James H. Hertzog, MDd, Jeana E. Havidich, MDe, Barry Gelman, MDf and the Pediatric Sedation Research Consortium. Pediatrics. Vol. 118 No. 3 September 2006, pp. 1087-1096 23- Sedation and general anaesthesia in children undergoing MRI and CT: adverse events and outcomes. S. Malviya, T. Voepel-Lewis, O. P. Eldevik, D. T. Rockwell, J. H. Wong and A. R. Tait. British Journal of Anaesthesia , 2000, Vol. 84, No. 6 743-748 25- Magnetic resonance imaging anesthesia: new challenges and techniques. Osborn IP. Curr Opin Anaesthesiol . 2002 Aug;15(4):443-8.

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