3: Control of pain and anxiety: selection of and preparation for sedation or anaesthesia

3 Control of pain and anxiety: selection of and preparation for sedation or anaesthesia


What pain is

Pain is a defence reaction that tends to be associated with actual or perceived injury. A key feature of pain is that it conditions avoidance. It must be unpleasant to be effective. Not all pain, however, is the same. The distinction between the sharp pain of a needle prick and the ache of overworked muscles is all too obvious and the separation of these two examples into fast, type 1, or acute pain and slow, type 2 or more chronic pain is fairly easy. It is also of considerable therapeutic advantage because the latter responds well to analgesics, but the former does not. However, there are almost as many types or descriptions of pain as there are conditions that cause it. Colicky abdominal pain, the throbbing pain of an abscess and the dull ache of myofascial pain are remarkably different in nature.

Pain may result from a range of stimuli: penetrating injury, pressure, heat, electrical stimulation, inflammation, muscular fatigue, etc. Almost any tissue (excluding dental enamel) may be the source.

This chapter is concerned with pain associated fairly closely with surgery. This includes the pain that would be associated with the surgery if no measures (such as local anaesthesia) were taken to prevent it and the pain so often experienced after surgery, which is more associated with inflammation.

Although we have said that pain is a defence reaction, there is little evidence that it is in any other way beneficial and for that reason we should do all that we can to prevent it during and after any surgery.

It is important to remember that only one individual is in a position to define pain: the patient. Therefore when a patient says that they have pain, they have—it is of no practical benefit to debate with them whether their experience is pressure, movement or whatever! It is wise to remember also that pain requires consciousness to be experienced, and that it is influenced by emotional state, tiredness and anticipation. Local sensitization of the peripheral nerves by inflammatory mediators considerably increases pain experience and can cause difficulty in controlling the pain of patients who have been in pain for several days. This is probably one of the commonest reasons for failure of local anaesthesia in such patients.



Reducing pain on administration

The application of lidocaine or benzocaine in the form of a paste, gel or spray to the oral mucosa can result in loss of sensibility to a depth of a few millimetres in a few minutes. This can abolish the pain of needle penetration and, for superficial injections, dramatically reduce the discomfort on injection. This can also have a major impact on the anticipation of pain in those particularly frightened by injections.

The use of topical local anaesthetics does have disadvantages, however. By spreading widely around the mouth they can induce numbness in a much wider area than would otherwise be necessary. Also, they cannot penetrate to the depth at which the inferior alveolar nerve block or greater palatine nerve block injections are given.

For procedures involving the skin topical lidocaine is of no value. However, EMLA cream does penetrate deeply enough to be effective. It should be left on the skin for at least one hour before the procedure. Amethocaine gel can also be effective on skin, and possibly over a time period shorter than that of EMLA, but is more likely to cause skin irritation.

Pain of injection can also be reduced by injecting slowly, distracting the patient and perhaps by stimulating nearby tissues (such as by compressing the cheek between finger and thumb) to activate the central neurological ‘gate mechanism’. Rapid penetration of the mucosa by the needle results in far less discomfort than that experienced on slow pressure. This is made easier in lax tissues by tensing the mucosa before needle penetration.

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Jan 14, 2015 | Posted by in Oral and Maxillofacial Surgery | Comments Off on 3: Control of pain and anxiety: selection of and preparation for sedation or anaesthesia

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