الفهرس 
Pediatric Anatomy and PhysiologyOnly 14 pages are availabe for public view
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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 pharmacological
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 sedativehypnotic
actions. Excitatory effects should be minimal as should
be its respiratory and cardiovascular depressant effects.
SUMMARY
102
Drugs commonly used are chloral hydrate, propofol, ketamine,
short acting barbiturates, Benzodiazepines, short acting opioids.
Adjuvant agents as anticholinergic, antihistaminics, and antiemetics.
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.
SUMMARY
103
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 ferromagnetic
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
SUMMARY
104 care of the sedated children must therefore continue during
transportation to recovery areas, and throughout the postsedation
period until the patient awakened to their baseline mental and
ambulatory status and can be safely discharged to an unmonitored
setting. Discharge instructions should be reviewed with parents or
other responsible adults before the sedation and before discharge.
Recent sedation guidelines and standards of care stipulate that such
care be provided by qualified individuals throughout the sedation
episode until discharge criteria are met.
Magnetic resonance (MR) imaging is an imaging technology using nonionizing radiofrequency radiation inside a strong magnetic field to detect the location and local chemical environment of protons in water molecules. For this reason each
patient must be screened prior to scanning, for any implanted,
embedded, or attached devices or foreign objects is mandatory.
Screening should include taking a history for possible intraorbital
or intraocular metallic fragments, such as might become lodged
during machining. Patients are generally asked to remove jewelry
and clothing containing metallic components and change into agown.
Magnetizable materials and electronic devices represent potential hazards to the patient. A separate issue is that implanted devices and foreign bodies may induce image artifacts that impact the diagnostic quality of the examination.The American Society for
Testing and Material International developed the following terminology for labeling of implanted devices as MR safe, MR conditional and MR unsafe