Prerequisites
Before you perform a TOE, you should do the following (even be
obsessive, and have a checklist):
- Review the history, and examine the patient thoroughly. Often
a good history reveals clues to a diagnosis that might otherwise be
missed on echo! Don't trust the
history-taking skills of a very junior doctor - take a thorough
history yourself.
- Review the indications for TOE;
- List the information you want to acquire;
- Obtain informed consent. This must include an explanation of
what you are going to do, why you are doing it, the risks involved,
and alternative investigations that might give comparable clinically
relevant information, all in language that the patient understands!
- Again, explain to the patient what you are going to do.
Discuss reasons why sedation is not necessarily a good idea.
If the patient insists on sedation, they must not drive for
twenty-four hours after the procedure; if they are having an
out-patient TOE, someone must be available to drive them home.
- Starve the patient for at least four, and preferably six hours.
A note on probe care
The probe is expensive, and rather delicate. Only experienced individuals
should handle it. It should be stored unflexed in order to maximise
its lifespan. If a disposable sheath is used, then probe exposure to
'Cidex' can be limited to ten minutes, according to some authorities,
but always follow the manufacturer's instructions.
Proper use of a bite block will help protect the probe, but note
that you can even totally destroy a probe on sharp molars during
removal. Don't relax your guard at any time!
Preparation
Check the following:
A. In the environment
- At least one assistant should be present to help with monitoring, suction, and
sonographic contrast; two syringes and a three-way tap are
useful for preparing the 'contrast' (microbubble-filled saline);
- A fully-stocked resuscitation trolley ("crash cart");
- Cardioverter / defibrillator;
- Oxygen, suction, a pulse oximeter, an automated blood pressure
measuring device (or assistant with manual sphygmomanometer);
- Measures to give sedation (physician- or patient-controlled),
if required;
B. The patient
- Make sure the patient has no swallowing problem (suggesting
oesophageal disease), no coagulation disorder, and know
the drugs the patient is on;
- Confirm that the patient is starved, has given consent, and
has transport if they are to be sedated;
- An IV line is preferable, and required if contrast is to be
given;
- Confirm that the patient is not allergic to the local anaesthetic
being used (uncommon);
- Remove dentures.
- Glycopyrrolate 0.2mg IV as pre-medication (in a normal adult) will limit secretions,
but will often cause more problems than it solves, especially by
drying things out to the point where probe passage is more uncomfortable.
- Antibiotic prophylaxis is controversial, but the
risk of bacteraemia (and infective endocarditis) appears small.
In high risk cases, you might decide to give infective endocarditis
prophylaxis with, for example, amoxycillin, provided the patient
is not allergic to penicillin.
Topical Anaesthesia
There are as many ways of giving topical anaesthesia as there are
sonographers. Important points to remember are:
- Most of the commercial metered-dose (e.g. 10 mg) sprays contain
~ 30% alcohol, which is almost guaranteed to cause pharyngeal
irritation after the local has worn off;
- It is possible to overdose a patient, especially a small
patient, with over-enthusiastic "topicalisation". Know your toxic
doses, and the patient's weight!
- Inadequate local anaesthesia, or not waiting for it to work,
will result in an unpleasant experience for both patient and doctor.
- Ask the patient to swallow repeatedly while administering
topical local anaesthetic, or even consider using swallowed viscous
lignocaine solution, to maximise local analgesia.
A useful end-point for determining adequate topical anaesthesia is
suppression of the gag reflex.
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