New Trends In Pediatric Sedation For Magnetic Resonance Imaging

Abstract

An MRI study usually consists of multiple image sequences, each taking up to 10 min to acquire, and any movement during this time will produce profound distortion of the final images. The number and duration of scans is variable, with some complex studies lasting up to 2 h. The MRI is a noisy and claustrophobic environment with restricted access to the patient. The aims of sedation are therefore to provide immobility to obtain the best possible images, while maintaining patient safety and comfort throughout which require meticulous organization, education, and training of all staff involved.

This essay reviewed the anatomical, physiological and pharma- cological differences related to pediatric. The clear understanding of these differences and the good preparations of the patients who are in need of this procedure, including psychological preparation, medical evaluation and preparation, physical examination, laboratory tests and premedication are the key stone of provision of safe anesthesia in pediatrics. A wide variety of drugs are used to provide sedation and analgesia and a clear understanding of the pharmacokinetic and pharmacodynamic effects of the individual agent is vital when choosing the most appropriate drug for a particular patient/ scenario. The ideal drug should have a rapid onset of action with a predictable dose-effect relationship with respect to its sedative-hypnotic actions. Excitatory effects should be minimal as should be its respiratory and cardiovascular depressant effects. Drugs commonly used are chloral hydrate, propofol, ketamine, short acting barbiturates, Benzodiazepines, short acting opioids. Adjuvant agents as anticholinergic, antihistaminics, and anti-emetics. A wide variety of routes of administration can be used (e.g. oral, nasal, parenteral or rectal) as well as techniques (e.g. Intermittent boluses or continuous infusion)

There are four levels of sedation as defined by ASA:minimal sedation (anxiolysis), moderate sedation/analgesia, deep sedation/ analgesia and general anesthesia.It is important to understand that sedation and analgesia represent a continuum of depth of sedation and that patients can rapidly pass into a level of sedation deeper than intended. Therefore, assessment of pain degree and sedation depth must be to achieve safety and the target of the sedation process.

Pre-sedation evaluation should identify children who may experience serious adverse events with sedation in accordance with the American Society of Anesthesiologists (ASA) classification system and those with a potential difficult airway. Healthy patients or those with mild systemic disease (ASA class I or II) and no evidence of a difficult airway are suitable candidates for procedural sedation outside of the operating room. Patients with severe or poorly controlled systemic disease (ASA class III, IV, or V) or a strong potential for a difficult airway warrant the involvement of a pediatric anesthesiologist or clinician with similar pediatric sedation expertise.

Pediatric sedation can only be accomplished safely if the physiologic effects of the sedative agents are continuously evaluated by a trained individual who is assisted by data provided by devices, that monitor the cardiopulmonary system. Since sedation is on a continuum from the awake and alert state to general anesthesia, the monitors employed during sedation should be similar to those used during the provision of anesthesia. the American Society of Anesthesiologists (ASA) published standards for monitoring during anesthesia . These guidelines have been extended into the post-anesthesia care unit, and have more recently been applied to sedation . It is important that the safety standards for monitoring be maintained regardless of the individuals providing sedation or the specific environment.

Because of the high electromagnetic field of MRI causes severe monitor artifact, Monitoring requires modified monitors so that they are compatible with the MRI environment. These modifications include nonferromagnetic electrocardiographic electrodes, graphite and copper cables, extensive filtering and gating of signals, extra-long blood pressure cuff tubing, and use of fiberoptic technologies. Anesthesia machines with no ferro- magnetic components (eg, aluminum gas cylinders) have been fitted with MRI-compatible ventilators and long circle systems or Mapleson D breathing circuits . Patients who receive sedation or analgesia for diagnostic and medical procedures remain at significant risk for associated adverse events until the pharmacologic effects of the sedative or analgesic agent(s) subside. Vigilant physiologic monitoring and