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Anesthesia

Use of airway nerve blocks

09/02/2008

Question:

I recently had surgery and found out I was difficult to intubate. I had to have 3 different types of nerve blocks to facilitate the procedure. Are there risks with these? Are other more topical methods attempted before going this route? Is this usually something that is discussed with patients prior to surgery if it is known that difficulty with intubation is probable? I had surgery the end of May and still have a constant need to clear my throat. Could that be related to the nerve blocks? I didn`t have that problem before surgery.

Answer:

Thanks for your questions.

It sounds as though you had what is known as an "awake fiberoptic intubation". This is a technique used in patients who are difficult to intubate by conventional means, in which the endotracheal tube (breathing tube) is placed using a fiberoptic bronchoscope. This is done while you are awake or sedated, rather than unconscious.

To assure the success of this technique and the comfort of the patient undergoing it, it is necessary to provide anesthesia to the throat (pharynx) and windpipe (trachea). This can be achieved using so-called "topical" anesthesia, which you have hinted at, or with nerve blocks. Both techniques are considered to be effective and safe, and so the choice would usually come down to the preference and proficiency of the anesthesiologist.

Topical anesthesia can be given by a variety of methods including spraying local anesthetic into the pharynx; administering a nebulised, inhaled solution of local anesthetic; gargling; or by placing swabs or pledgets soaked in local anesthetic near the tonsils. The trachea below the vocal cords can be anesthetised by injecting local anesthetic through the cricothyroid membrane (below the Adam's apple). This usually causes the patient to cough and thus distributes the local anesthetic widely. Some combination of the techniques described is usually adopted.

Topical anesthesia techniques are considered safe, with the only real drawbacks being possible allergy to the local anesthetic used (rare) or toxicity if very large amounts are used, because quite a bit of the drug tends to get absorbed into the bloodstream.

Nerve blocks used for airway anesthesia include superior laryngeal nerve blocks, administered on both sides of the neck, just above the laryngeal cartilages, and glossopharyngeal nerve blocks which are done inside the throat, again on both sides. The effectiveness of these blocks will depend on the proficiency of the individual performing them, and the suitability of the anatomy of the individual patient. Again, allergic reactions and toxicity from the local anesthetic can occur.

All nerve blocks may have complications. I am not familiar with how often a nerve injury might occur with the nerve blocks used to numb the airway, but this might be a rare possibility.

The topical anesthesia techniques described above are less dependant on the "operator", and much more dependent on the availability of time and the patience and cooperation of the individual. The local anesthetic drugs are not particularly pleasant to breathe or to swallow but the sedative drugs can help with this. In my own practice I find the topical anesthetic methods to be effective and I do not use the nerve blocks.

In both cases, the judicious use of intravenous sedation is very important and should convert a potentially unpleasant experience into something easy to tolerate, and quickly forgotten. Both sedation and airway anesthesia are necessary to achieve a safe intubation, without risk of airway or breathing problems, which is obviously the reason for all these maneuvers.

When difficult intubation is a known problem the normal practice would be to discuss the problem with the patient beforehand and get that patient to accept a plan of action to intubate safely. Awake fiberoptic intubation is one such plan, but not the only possible one.

If you are having persistent problems with swallowing it is less likely that these are due to a problem with the nerve blocks, and more likely to have something to with the intubation itself. It would be advisable to have an ear, nose and throat (ENT) doctor examine your airway. This can be done in the doctor's office with the aid of a small flexible fiberoptic scope passed through the nose, much smaller and easier to tolerate than the one that would have been used in the operating room.

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Response by:

Gareth S Kantor, MD Gareth S Kantor, MD
Assistant Professor of Anesthesiology
School of Medicine
Case Western Reserve University