TOE - Preparing the patient  

Prerequisites

Before you perform a TOE, you should do the following (even be obsessive, and have a checklist):
  1. 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.
  2. Review the indications for TOE;
  3. List the information you want to acquire;
  4. 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!
  5. 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.
  6. 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

  1. 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);
  2. A fully-stocked resuscitation trolley ("crash cart");
  3. Cardioverter / defibrillator;
  4. Oxygen, suction, a pulse oximeter, an automated blood pressure measuring device (or assistant with manual sphygmomanometer);
  5. Measures to give sedation (physician- or patient-controlled), if required;

B. The patient

  1. Make sure the patient has no swallowing problem (suggesting oesophageal disease), no coagulation disorder, and know the drugs the patient is on;
  2. Confirm that the patient is starved, has given consent, and has transport if they are to be sedated;
  3. An IV line is preferable, and required if contrast is to be given;
  4. Confirm that the patient is not allergic to the local anaesthetic being used (uncommon);
  5. Remove dentures.
  6. 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.

  7. 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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