Submitted by Dr. Yasser Mokhtar, MD. Dept. of internal medicine. School of medicine, University of South Dakota.
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.
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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