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Submitted by Dr. Yasser Mokhtar, MD. Dept. of internal
medicine. School of medicine, University of South Dakota.
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TEE improves diagnostic information in various cardiovascular diseases compared to conventional echo.
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Methodology
All
TEE devices have similar specifications including standard endoscope
without optics or suction, 5 MHz transducer, adult sized shaft with diameter
(8-11 mm), 100 cm shaft length, four way movable tip, pulsed, colored
and continuous wave Doppler capabilities and biplane transesophageal echocardiographic
capabilities (Seward et al., 1988).
Fisher et al. described the basic transesophageal instrument in 1991.
It consisted of a standard two-dimensional, Doppler color flow 5 MHz ultrasound
transducer attached to a conventional flexible endoscope. The endoscope
handle has an inner dial which allows anterior and posterior flexion and
an outer dial which provides left and right lateral movement converting
from short to long axis views
(Fisher
et al., 1991).
Monoplane horizontal array is limited to short axis and frontal views
of the heart. Biplanar and variable planar devices incorporate a longitudinal
plane that completes the three dimensional tomographic capabilities of
an esophageal imaging device. Two orthogonal planes permit a more nearly
complete examination of cardiac anatomy from the confines of the esophagus.
Newer variable planar devices allow the transducer to be rotated along
the long axis of the ultrasound beam
(Flachskampf
et al., 1991).
Preparation for
TEE examination
Medical history is taken specially
dysphagia,
hematemesis operations on GIT and cervical spine disease. The patient
must be fasting for at least 4-6 hours before the procedure. Blood pressure
and heart rate are measured. Dentures and oral prostheses should be removed.
Airway, oxygen delivery system, bite guard, suction, standard crash cart
should be immediately available. An intravenous access should be established.
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Premedication
Awake patients are premedicated for the following reasons:
-
Topical anesthesia: of oropharynx and
hard and soft palates diminishes gag reflex. It can be produced by an
aerosol local anesthetic lidocaine solution. Other agents used include
viscous lidocaine, dyclonine and tetracaine.
-
Sedation: is carried out intravenously
to decrease anxiety and discomfort, with administration of a sedative
belonging to the benzodiazepines group (e.g. diazepam or midazolam).
-
Drying agents: lessen salivary and gastrointestinal
secretions reducing the risk of aspiration. The anticholinergic agent
glycopyrrolate is used to control secretions effectively.
-
Antibiotics: help prevent infective endocarditis
in selected high-risk patients. The issue of endocarditis prophylaxis
during TEE remains controversial. Since the procedure is similar to
that of endoscopic examinations, there may be some merit to administering
bacterial endocarditis prophylaxis (Dajani
et al., 1990).
Technique of introduction
The pharynx is anesthetized with a topical anesthetic spray that should
be ideally applied with the patient in sitting position to reduce risk
of aspiration.
The patient is placed in the left lateral position and the neck slightly
flexed to allow for better oropharyngeal entry. Intubation can be performed
with the patient in the supine position and if necessary the upright sitting
position. A bite guard is essential to allow manipulation and protection
of the TEE probe. Distal portion of the transducer is coated with lubricating
jelly.
The examiner passes the probe tip through the bite guard and over the
tongue maintaining it in the midline. The tip is advanced until resistance
is encountered, then the patient is asked to swallow and with gentle forward
pressure the transducer is advanced until loss of resistance is felt then
the transducer is passed into position behind the heart.
When TEE procedure is over, the precautions that should be taken by
the patient include not to drink any hot liquid until oropharyngeal anesthesia
has worn off (1-2 hours), not to eat until gag reflex returns (1-4 hours)
and not to drive for 12 hours (if a sedative was given).
Care of the TEE
probe
The TEE probe should be inspected for defects with the transducer tip
in the neutral position and all flexed directions. These defects cause
trauma or expose the patient to infective, caustic or electrical complications.
After each procedure, flexible shaft of the TEE probe and the bite
guard should be cleaned and disinfected. They are first washed with an
enzymatic solution to remove saliva and secretions, then they are rinsed
thoroughly with tap water and placed in a gluteraldehyde disinfectant
solution such as cidex for twenty minutes - a period proved to be sufficient
to destroy any viral or bacterial contaminants. Then they are rinsed thoroughly
with tap water and allowed to dry for twenty minutes before use on another
patient to allow any residual adherent gluteraldehyde to evaporate (Mays
et al., 1991 and Mays et al., 1994).
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