Oxford Handbook of Anaesthesia (3 edn)
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Oral/maxillofacial surgery
General principles
Anaesthesia for intraoral/maxillofacial procedures requires management of a shared airway and potentially difficult intubation. Nasal intubation is frequently used to improve access to the mouth. At the preoperative visit check nostril patency and ask about epistaxis and the use of anticoagulants. Discuss choice of airway with surgeon.
Simple intraoral procedures are often possible using a reinforced laryngeal mask airway. However, access to the mouth is inevitably compromised. The LMA may be dislodged and vigilance is required. Similarly, for unilateral intraoral procedures an oral ETT placed on the opposite side of the mouth may be acceptable.
If the nasal route is chosen for intubation, use a local anaesthetic and/or vasoconstrictor mixture (cocaine 5–10%, lidocaine 5%/ phenylephrine 0.5%—Co-phenylcaine®) or xylometazoline (Otrivine®). There are many varieties of nasal tube—the ‘Polar Preformed North Nasal’ from Portex® is ideal. These ‘north-facing’ tubes are made of soft material and cause little nasal trauma. Sizes of 6.0, 6.5, and 7.0mm should be available. Place in warm water before use to soften the material even further.
Protect the eyes with tape and eye pads.
Position the patient with the head at the opposite end to the anaesthetic machine—a long breathing circuit is normally required.
Stabilise the head with a horseshoe or head ring. For operations on the roof of the mouth use a bolster under the shoulders to extend the neck further.
Throat packs are used to minimise contamination of the airway with blood and debris. Ribbon gauze or tampons may be used. A robust system should be in place to ensure that throat packs are not inadvertently left in situ. They should be included in the swab count (see p. 633).
Laryngoscopy should always be performed at the end of the procedure to clear any debris and ensure that packs have been removed.
Extubation
There is a risk of aspiration of blood, pus, and debris. Patients are therefore best extubated in the left lateral position with head- down tilt.
Some anaesthetists extubate the patient ‘deep,’ having used a spontaneous breathing technique, whereas others use opioid/relaxant and prefer to extubate awake. The use of a nasotracheal tube, which does not stimulate the gag reflex as much as an oral tube, facilitates the latter approach.
If a nasal tube has been used it is possible to convert it into a nasopharyngeal airway by withdrawing it until the tip lies in the oropharynx, cutting at the 15cm mark and inserting a safety pin at the proximal end (to prevent the tube slipping back into the nostril).
Cardiac arrhythmias
Cardiac arrhythmias may occur during dental extraction if a spontaneously breathing technique is chosen. Volatile agents (particularly halothane) sensitise the myocardium to catecholamines, but this is less common with isoflurane, sevoflurane, and desflurane. Contributory factors include hypercarbia, hypoxia, light anaesthesia, and injected sympathomimetic agents. Correction of the underlying problem and infiltration of local anaesthetic by the surgeon virtually abolishes arrhythmias.
Free-flap surgery
Many major maxillofacial reconstructions are performed using tissue/bone free flaps (particularly from the radial forearm).
These operations are lengthy, 6–18hr.
The same principles apply as for plastic surgery free flaps ( p. 524) with the added complication of a potentially difficult airway, both pre and post surgery.
Surgical tracheostomy may be indicated because of the potential for postoperative airway compromise.
HDU or ICU care is usually indicated postoperatively.
Extraction of impacted/buried teeth
Procedure | Removal of teeth |
Time | 3–45min |
Pain | + |
Position | Supine, head ring, bolster under shoulders if teeth to be extracted in roof of mouth |
Blood loss | Minimal |
Practical techniques | Nasal tube and IPPV—extubate awake Nasal tube and SV—extubate deep LMA and SV |
Procedure | Removal of teeth |
Time | 3–45min |
Pain | + |
Position | Supine, head ring, bolster under shoulders if teeth to be extracted in roof of mouth |
Blood loss | Minimal |
Practical techniques | Nasal tube and IPPV—extubate awake Nasal tube and SV—extubate deep LMA and SV |
Preoperative
Careful assessment of the airway. Check nostrils for patency.
If the patient has a dental abscess there may be marked swelling of the face and severe trismus. Awake fibreoptic intubation may be necessary (see p. 1000).
Perioperative
Consider LMA/oral tube for simple/unilateral extractions.
Intubate with a warmed, preformed nasal tube after applying vasoconstrictor to the nasal mucosa (see p. 668).
Protect the eyes with tape and pads.
The surgeon should anaesthetise the appropriate terminal branches of the maxillary division (infraorbital, greater palatine, nasopalatine) and mandibular division (inferior alveolar, lingual, buccal, mental) of the trigeminal nerve with a long-acting local anaesthetic (bupivacaine 0.25% or 0.5% with adrenaline 1:200 000).
Give an intraoperative opioid and NSAID.
IV antibiotics are administered to minimise the risk of infection (usually benzylpenicillin 600mg).
Steroids (e.g. dexamethasone 8mg IV) are given to minimise swelling.
Extubate in the left lateral position with head-down tilt.
Postoperative
Balanced analgesia with regular paracetamol and NSAIDs. Prescribe rescue analgesia with PRN codeine phosphate/tramadol.
Special considerations
Talk to the surgeon to ascertain the likely length of surgery. Remember that some patients require general anaesthesia only because they are ‘dental phobic.’ The surgical extractions may be simple and operative time consequently very short. A short-acting muscle relaxant may be required.
Maxillary/mandibular osteotomy
Procedure | Surgical realignment of the facial skeleton |
Time | Lengthy, 4–6hr |
Pain | ++ |
Position | Supine, with head-up tilt, head ring |
Blood loss | Variable. Occasionally can be severe. G&S |
Practical techniques | Nasal tube and IPPV—extubate awake. Art line |
Procedure | Surgical realignment of the facial skeleton |
Time | Lengthy, 4–6hr |
Pain | ++ |
Position | Supine, with head-up tilt, head ring |
Blood loss | Variable. Occasionally can be severe. G&S |
Practical techniques | Nasal tube and IPPV—extubate awake. Art line |
Patients presenting for orthognathic surgery may have malformations isolated to one jaw or have multiple craniofacial deformities as part of a syndrome. They have often had prior dental extractions and preoperative orthodontic work. There are many surgical procedures performed to correct facial deformities. Patients are usually in their late teens or early twenties and are generally fit and healthy. When a mandibular osteotomy is performed, the bone is plated and often stabilised by wiring the maxilla and mandible together. If vomiting occurs postoperatively or intraoral bleeding occurs, fatal airway obstruction may occur unless the fixation can be instantly removed. This requires expert trained staff and adequate facilities postoperatively.
Preoperative
Assess the airway carefully. Check the nostrils for patency.
Check Hb and crossmatch blood as per surgical blood ordering schedule (2U).
Thromboembolic prophylaxis (TEDS, unfractionated or low-molecular-weight heparin). Consider the use of intermittent pneumatic compression boots in theatre.
Perioperative
Intubate nasally using a preformed nasal tube (see p. 668).
Good venous access. Consider invasive pressure monitoring due to length of surgery.
Put Lacri-Lube® into the eyes and protect them with pads and tape.
Position the patient carefully on the operating table. Place the head on a ring and tilt the table head up.
Use a balanced anaesthetic technique and aim for an awake, co-operative patient who can maintain their airway at completion of surgery. Induced hypotension is useful to help minimise blood loss. Remifentanil infusion (0.04–0.25µg/kg/min) as part of a balanced anaesthetic may help control blood pressure.
Give IV antibiotics and steroids (e.g. dexamethasone 8mg IV) to minimise swelling.
Keep the patient warm. Measure core temperature, warm IV fluids, and use a heating mattress and/or hot air blower.
Monitor blood loss carefully. The HemoCue® is an accurate way of tracking haemoglobin concentration in theatre.
The patient's jaws will frequently be wired together on completion of surgery. Ensure that throat packs are removed and that the oropharynx is cleared of blood and debris before this is done.
Administer prophylactic antiemetics (granisetron + cyclizine ± haloperidol) to minimise the risk of nausea and vomiting. Dexamethasone is also effective.
Extubate the patient once fully awake. Withdraw the nasal tube and cut (15cm mark at the nostril) to leave as a nasopharyngeal airway.
Prescribe small doses of IV opioid to be administered in recovery.
Ensure that you and the nursing staff are familiar with the position of the wires that hold the jaws together. Make sure wire cutters are with the patient at all times.
Postoperative
Some units send these patients to HDU. Others send them to the ward after a lengthy period in recovery.
Administer humidified oxygen.
Ensure all oral analgesics are prescribed in a soluble form. PRN IM or SC opioids should also be prescribed.
Continue prophylactic antibiotics and steroids postoperatively as per your unit's protocol.
Prescribe IV fluids. Encourage the patient to take fluid by the oral route as soon as possible.
Fractures of the zygomatic complex
Procedure | Elevation of fractured zygomatic complex ± fixation |
Time | 10–180min |
Pain | +/++ |
Position | Supine |
Blood loss | Minor (significant with internal fixation) |
Practical techniques | Oral RAE tube and IPPV LMA/SV for simple elevation |
Procedure | Elevation of fractured zygomatic complex ± fixation |
Time | 10–180min |
Pain | +/++ |
Position | Supine |
Blood loss | Minor (significant with internal fixation) |
Practical techniques | Oral RAE tube and IPPV LMA/SV for simple elevation |
These fractures may occur in isolation or may be associated with damage to other parts of the facial skeleton. There may be limitation of mouth opening due to interference with movement of the coronoid process of the mandible by the depressed zygomatic complex. Following elevation, the fracture may be stable or unstable and require internal fixation. Most surgery is carried out via a temporal approach or a percutaneous route through the cheek. Intraoral and transantral routes have also been described but are rarely used. Unstable fractures require plating or wiring via skin or intraoral incisions.
Preoperative
Assess the patient carefully for associated injuries. Treatment of these fractures does not have high clinical priority. The operation is often easier if a period of time elapses (5–7d) to allow the associated facial swelling to disperse.
Make a careful airway assessment.
Perioperative
Intubate the patient with an oral RAE tube. For simple fracture elevations a flexible LMA may be used, but discuss with surgeon whether open fixation of the fracture is planned.
Lubricate and protect the eyes.
Give antibiotics and steroids as requested.
Extubate in the lateral position with the fractured side uppermost.
Postoperative
IV opioids may be required in recovery.
Consider balanced oral analgesia for the ward.
Mandibular fractures
Procedure | Reduction and fixation of a fractured mandible |
Time | 2–3hr |
Pain | + |
Position | Supine, with head-up tilt, head ring |
Blood loss | Variable. Consider G&S |
Practical techniques | Nasal tube and IPPV Fibreoptic intubation may be required |
Procedure | Reduction and fixation of a fractured mandible |
Time | 2–3hr |
Pain | + |
Position | Supine, with head-up tilt, head ring |
Blood loss | Variable. Consider G&S |
Practical techniques | Nasal tube and IPPV Fibreoptic intubation may be required |
Mandibular fractures can be treated by either closed reduction and indirect skeletal fixation (using interdental wires, arch bars, or splints) or open reduction and direct skeletal fixation using bone plates. When indirect skeletal fixation is used the patient's jaws are wired together at the completion of surgery. When direct skeletal fixation is used this is not usually the case.
Preoperative
Ensure careful assessment for associated injuries.
Make a meticulous assessment of the airway. There may be severe trismus and marked soft tissue swelling.
Assess nostril patency. Check for evidence of basal skull fracture and CSF leak as these contraindicate nasal intubation.
Perioperative
Trismus makes intubation look potentially difficult preoperatively as mouth opening may be markedly limited, but this tends to relax following induction.
Bilateral mandibular fractures also allow increased anterior jaw displacement after induction, but airway maintenance by facemask may not always be easy due to increased jaw movement/swelling. A rapid sequence induction with suxamethonium is usually appropriate.
Marked swelling may make intubation more difficult and an awake fibreoptic intubation may occasionally be required.
Gas induction is often difficult due to pain when applying the facemask.
Postoperative
As for patients having maxillary/mandibular osteotomies.
Anaesthesia for dentistry
General considerations
General anaesthesia for dental procedures should be reserved for patients unable to tolerate local anaesthesia (i.e. young children and adults with mental disability) and undertaken in a hospital setting.
Facilities should be the same as for any other day surgery procedure.
Selection criteria. Patients with significant intercurrent disease should be referred for in-patient treatment, as for any other day-case procedure. Mentally disabled patients may have difficulty understanding the procedure and are often anxious. A short-acting anxiolytic agent, such as oral midazolam, and topical anaesthetic cream may be helpful. Mental disability may be part of a more complex medical disorder, such as Down's syndrome or other congenital abnormality. It is important to exclude any significant cardiac pathology and consider endocarditis prophylaxis depending on local guidelines. Patients requiring extensive extractions or restoration work can be admitted to a day-case unit for treatment, but may require overnight stay if medically compromised.
Positioning. There is no longer a place for ‘chair dental anaesthesia.’ Postural hypotension can be easily overlooked and it is now standard practice to keep patients supine.
Arrhythmias. Dental anaesthesia is associated with a high incidence of arrhythmias, usually related to hypoxia, hypercarbia, inadequate anaesthesia, and volatile anaesthetic agents. Arrhythmias are mainly ventricular and may progress (rarely) to ventricular fibrillation. Halothane is associated with an arrhythmia frequency of up to 75% in dental anaesthesia and is rarely used now. The incidence of hypoxia-induced arrhythmias can be reduced by using 100% oxygen for maintenance. End-tidal CO2 may be difficult to measure when using a nasal mask but can be controlled when using an LMA.
Local anaesthetic infiltration should be used whenever possible—ensure caution in very young children, where it may lead to accidental biting/laceration.
Dental labelling. Deciduous teeth are assigned letters A–E in each quadrant and adult teeth are numbered 1–8.
Simple extractions are very quick procedures lasting only a few minutes. A nasal mask can be used, but laryngeal mask airways (plain or flexible) are preferable for multiple extractions. A prop/gag and a mouth pack are inserted by the dentist to prevent soiling of the lower airway—ensure that it does not obstruct the airway. When extractions are complete, a pack is positioned over the dental sockets to absorb any oozing blood. During extractions, patency of the airway must be maintained and may require support of the jaw.
Restoration work can take over an hour and often requires intubation and ventilation.
Simple dental extractions
Procedure | Dental extractions |
Time | 2–10min |
Pain | +/++ |
Position | Supine |
Blood loss | Nil |
Practical techniques | Nasal mask/LMA |
Procedure | Dental extractions |
Time | 2–10min |
Pain | +/++ |
Position | Supine |
Blood loss | Nil |
Practical techniques | Nasal mask/LMA |
Preoperative
Usually children 3–12yr.
Beware of undiagnosed pathology, e.g. heart murmurs.
Obtain consent for analgesic suppositories if required.
Perioperative
Give pre-emptive oral analgesia if possible, e.g. paracetamol (20mg/kg), and NSAID.
Apply topical anaesthetic for cannulation if IV induction planned.
Give propofol for induction, sevoflurane for gas induction.
Tape the eyes.
Maintenance with volatile agent or IV agent.
Use local anaesthetic infiltration (by dentist); avoid opioids except in longer cases or in-patients.
Stabilise the head and neck manually during the procedure.
Place in lateral position, slightly head down at the end.
Postoperative
Regular paracetamol (15mg/kg) for 12–48hr.
Diclofenac (1mg/kg) or ibuprofen (5–10mg/kg) as indicated.
Special considerations
The dentist may apply considerable pressure during extraction and the anaesthetist should apply counter-pressure to support and stabilise the head and jaw.
Beware of potential hypoxia. Give 100% oxygen for maintenance if necessary.
When using a nasal mask, mouth breathing can occur around the dental pack, resulting in decreased uptake of the anaesthetic agent and the patient becoming light. This can be a problem when using short-acting agents such as sevoflurane—use isoflurane for maintenance or give small increments of propofol.
Children with blocked noses can be safely anaesthetised using an LMA (provided there is no upper respiratory tract infection).
Sedation for dentistry
Patients who are unable to tolerate dental treatment under LA can often be managed by a combination technique using sedation. These procedures are usually performed by the dentist in the dental clinic. Oral or IV sedation can be provided by short-acting benzodiazepines such as midazolam, but the effects can be unpredictable, especially in children. Inhalational sedation can be provided by subanaesthetic concentrations of nitrous oxide (up to 50%) in oxygen using a nasal mask—termed ‘relative analgesia.’ Whichever route of administration is used, it is important to ensure that the patient remains conscious throughout.
General considerations
Ideally patients should be ASA1 or 2.
Patients will require an escort for the procedure and to care for them afterwards.
Written instructions should be provided regarding limitations on driving (as for GA) and operating machinery postoperatively. The patient should also be told to avoid a heavy meal/alcohol prior to treatment.
Inhalational sedation cannot be used in patients with nasal obstruction or those unable to co-operate with breathing through a nasal mask.
LA is used in all patients after sedation has been established.
The patient should be able to communicate throughout the procedure.
Suitable regimes
For adults, midazolam 2mg IV, wait 90s, then give 1mg every 30s until sedated.
Low-dose propofol infusion (only with suitable training).
100% oxygen via nasal mask, add 10% nitrous oxide for 1min, then 20% for 1min. Continue increments of 5% until sedated (up to 50%).
Special considerations
Do not use mouth props as the ability to keep the mouth open is an important indicator of consciousness.
Have flumazenil available for reversal of midazolam.
Allow at least 1hr for recovery following IV sedation.
Following nitrous oxide sedation, 100% oxygen must be administered to prevent diffusion hypoxia.
The patient can be discharged once they are able to stand and walk unaided.
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