Chapter 13

Analgesia, anaesthesia, and sedation

Indications, contraindications, and common sense

When dealing with LA, GA, and sedative techniques, indications, and contraindications are often relative, and the following should be thought of as guidelines rather than immutable laws.

LA

The technique of choice for simple procedures or when a GA is C/I. LA is C/I in:

Adverse reaction to LA is a C/I, but in reality once allergy to preservatives in the solution is excluded, LA allergy probably does not exist.

Conscious sedation

This is an extension of LA technique using drugs and patient-management techniques. It is of benefit to anxious or mildly uncooperative patients and is a kind supplement to apicectomy or third-molar removal. C/I include:

GA

Indicated when LA or LA and sedation is ineffective or inappropriate (as above). C/I include:

The anaesthetist usually prefers hospital admission for patients with the following:

Ask about previous GA and any problems.

While all these conditions create problems with anaesthesia they may not preclude it absolutely within the hospital setting. They do, however, indicate the need for careful assessment and early prior consultation with the anaesthetist.

Local analgesia—tools of the trade

While any disposable needle and syringe system can be used to give LA, the vast number of LAs given in dental practice (>50 000/dentist/lifetime) has led to some very useful modifications.

LA cartridges

Two sizes, 1.8 and 2.2ml, come pre-sterilized. Commonest solution used is lidocaine 2% with adrenaline 1:80 000. A latex-free version is available for patients with latex allergy.¹

Cartridge syringes

Use with above, resterilizable. Used with ultra-fine disposable needles. Major advantage is the ability to perform controlled aspiration during LA injection (although the consistency with which this is achieved has been questioned).

Lidocaine/adrenaline

Most commonly used preparation (2% lidocaine 1:80 000 adrenaline), gives effective pulpal analgesia for 1.5h and altered soft-tissue sensation for up to 3h. Extremely safe; maximum dose (adult) 500mg (10 × 2.2ml cartridges). Also available in ampoules 1% + 2% lidocaine plain or 1:200 000 adrenaline. There are theoretical criticisms that the maximum dose is too high but these have not been borne out in practice.

Prilocaine/octapressin

Similar but slightly less duration and effect compared to lidocaine/adrenaline. May cause methaemoglobinaemia in excess. Maximum safe dose (adult) 600mg (8 × 2.2ml cartridges). In reality, there are few hard indications for the use of prilocaine over lidocaine.

Mepivacaine

Short-acting LA advocated for restorative work but has not really caught on. Maximum safe dose 400mg.

Bupivacaine

Long-acting LA (6h plain, 8h with adrenaline); useful as a post-op analgesic. Maximum safe dose 2mg/kg. Only available in ampoules. Levobupivacaine is a similar drug.

Articaine

At least as effective as lidocaine; said to diffuse through bone better. No hard evidence of superiority however not recommended for IDB due to cases of permanent altered sensation after its use.

Topical analgesics Lidocaine

is the only really useful topical analgesic among the above. It is available as a spray or a paste which is applied to mucosa several minutes prior to injecting. There is a high incidence of contact eczema in people frequently exposed to these preparations, so do not apply with bare fingers. Benzocaine in lozenge or paste form is used for mucosal analgesia. Amethocaine is a topical analgesic for use on mucous membranes. Cocaine 4% solution is used as a nasal mucosal analgesic and vasoconstrictor.

EMLA® cream, a eutectic mix of lidocaine and prilocaine, is an invaluable skin topical analgesic, used prior to venepuncture in children. Apply to puncture site and cover with ‘Opsite’ or equivalent dressing for at least 30min. Amethocaine (Ametop) is similar and has a quicker onset of action.

Handling equipment

One cartridge and needle per patient. Discard cartridge if a precipitant is seen in the solution or if air bubbles are present. Store in a cool dark place and use before expiry date. Warm cartridge to ↓ discomfort and load into the syringe immediately prior to use. Aspirate before injecting. The ↑ risk associated with needlestick injuries has spawned a number of devices to aid resheathing the needle. It is simpler to hold the cover in a pair of artery forceps.

Local analgesia—techniques

The inferior dental block and local infiltrations are the mainstay of LA technique; however, numerous others are available as alternatives, supplements, and fallbacks.

IDB

(inferior alveolar block) Technique of choice for mandibular molars; also effective for premolars, canines, and incisors (the latter if supplemented by infiltration). Aim is to deposit solution around the inferior alveolar nerve as it enters the mandibular foramen underneath the lingula. The patient’s mouth must be widely open. Palpate the landmarks of external and internal oblique ridges and note the line of the ptyerygomandibular raphe. With the palpating thumb lying in the retromolar fossa, the needle should be inserted at the midpoint of the tip of the thumb slightly above the occlusal plane lateral to the ptyerygomandibular raphe. The needle is inserted ~0.5cm and if a lingual nerve block is required 0.5ml of LA is injected at this point. The syringe is then moved horizontally ~40° across the dorsum of the tongue and advanced to make contact with the lingula. Once bony contact is made the needle is withdrawn slightly and the remainder of the LA injected. It should never be necessary to insert the needle up to the hub. Note that the mandibular foramen varies in position with age (children, see p. 78). In the edentulous, the foramen, and hence the point of needle insertion, is relatively higher than in the dentate.

Gow–Gates technique

Blocks sensation in Vc by depositing LA at head of condyle.¹ Akinosi approach: LA deposited above lingua.²

Long buccal block

The long buccal nerve is anaesthetized by injecting 0.5–1ml of LA posterior and buccal to the last molar tooth.

Mental nerve block

The mental nerve emerges from the mental foramen lying apical to and between the first and second mandibular premolars. LA injected in this region will diffuse in through the mental foramen and provide limited analgesia of premolars and canine, and to a lesser degree, incisors on that side. It will provide effective soft-tissue analgesia. Place the lip on tension and insert the needle parallel to the long axis of the premolars angling towards bone, and deposit the LA. Do not attempt to inject into the mental foramen as this may traumatize the nerve. LA can be encouraged in by massage.

Sublingual nerve block

An anterior extension of the lingual nerve can be blocked by placing the needle just submucosally lingual to the premolars, use 0.5ml of LA.

Posterior superior alveolar block

A rarely indicated technique. Needle is inserted distal to the upper second molar and advanced inwards, backwards, and upwards close to bone for ~2cm. LA is deposited high above the tuberosity after aspirating to avoid the ptyerygoid plexus.

Nasopalatine block

Profound anaesthesia can be achieved by passing the needle through the incisive papilla and injecting a small amount of solution. This is extremely painful (hints on how to overcome pain on palatal injections below).

Infra-orbital block

Rarely indicated. Palpate the inferior margin of the orbit as the infra-orbital foramen lies ~1cm below the deepest point of the orbital margin. Hold the index finger at this point while the upper lip is lifted with the thumb. Inject in the depth of the buccal sulcus towards your finger, avoid your finger, and deposit LA around the infra-orbital nerve.

Infiltrations

The aim is to deposit LA supraperiosteally in as close proximity as possible to the apex of the tooth to be anaesthetized. The LA will diffuse through periosteum and bone to bathe the nerves entering the apex. Reflect the lip or cheek to place mucosa on tension and insert the needle along the long axis of the tooth aiming towards bone. At approximate apex of tooth, withdraw slightly and deposit LA slowly. For palatal infiltrations, achieve buccal analgesia first and infiltrate interdental papillae; then penetrate palatal mucosa and deposit small amount of LA under force.