Generan Anaesthesia for Dentistry

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General Anaesthesia for DentistryNaveen Malhotra

Summary

The first general anaesthetics administered were for dental extractions. General anaesthesia for dentistry is notwithout risk and should not be undertaken as a first-line means of anxiety control. Considerations should always begiven to the possibility of local anaesthetic techniques with or without conscious sedation. Patients requiring generalanaesthesia for dental work are frequently children or individuals with learning difficulties. The standards of generalanaesthesia for dentistry should be the same as those in any other setting.

General anaesthesia in dentistry covers three main types of surgical procedures: Dental chair anaesthesia, Daycare anaesthesia and In-patient anaesthesia. All standard equipments, gadgets, monitors and drugs for anaesthesiaand resuscitation should be available and checked before administering anaesthesia. Each individual must have hadappropriate experience of, and training in dental anaesthesia. Sevoflurane has largely replaced halothane as agent ofchoice for inhalation induction of anaesthesia and propofol is agent of choice for intravenous induction. The transpar-ent neonatal mask for nasal ventilation offers significant advantages. Laryngeal mask airway is being used for all butthe simplest extractions. The most commonly used operating position is semi-supine. In recovery, airway obstructionis common in patients undergoing dental procedures and they should be closely supervised by an experienced nurse.Routes of tracheal intubation in maxillo-facial surgical procedures are: oro-tracheal intubation, nasal intubation, retro-molar intubation and submento-tracheal intubation. A team of vigilant and experienced anaesthesiologist and dentalsurgeon is able to prevent and manage the complications associated with dental procedures under general anaesthe-sia.

Keywords Surgery: Dental; Anaesthesia: General.

Indian Journal of Anaesthesia 2008;52:Suppl (5):725-737

Associate Professor, Department of Anaesthesiology and Critical Care, Post Graduate Institute of Medical Sciences (PGIMS),Rohtak-124001 (Haryana) Correspondence to: Naveen Malhotra, 128/19, Naveen Niketan, Civil Hospital Road, Rohtak-124001(Haryana), E-mail: [email protected]

Introduction

There is a long historical association betweenAnaesthesia and Dentistry. Some of the initialanaesthetics given were for dental extractions.1, 2 Thefirst general anaesthetic administered for a dental ex-traction is credited to Horace Wells. Wells, on 11thDecember 1844, underwent extraction of one of hisown wisdom teeth by a colleague whilst under the in-fluence of nitrous oxide. In 1846, William Morton, apupil of Wells, successfully demonstrated the proper-ties of ether to facilitate dental extraction in Massachu-setts.3

Dentistry, in its surgical and restorative aspect, isin majority based on office practice. Limited dentists

work routinely in operation theatres.4 Majority of thedental procedures can be performed under local ana-esthesia which is inherently safe. Most dentists are skilledin techniques of local anaesthetics and nerve blocks.5General anaesthesia should not be used as a method ofanxiety control but for pain control, because more spe-cific methods (local anaesthesia with or without con-scious sedation and behaviour management techniques6)are available to manage anxiety. All general anaestheticsare associated with some risk and modern dentistry isbased on the principle that all potentially painful treat-ment should be performed under local anaesthesia, ifat all possible. General anaesthesia should be strictlylimited to those patients and clinical situations in whichlocal anaesthesia (with or without sedation) is not anoption. 7-13

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Indian Journal of Anaesthesia, October 2008(P.G.Issue)

In 1970s and 1980s there were numerous deaths,often in healthy children undergoing simple dental pro-cedures under general anaesthesia. The reasons weremultifactorial, including administration of anaesthesia inconditions with substandard monitoring, assistance andresuscitation equipments. Also, patients were poorlyprepared for anaesthesia and surgery.3 However, cur-rently there is a world wide trend that increasing num-ber of children are receiving dental treatment undergeneral anaesthesia.14-16.

General anaesthesia in dentistry covers three maintypes of surgical procedures: 3

1. Dental chair anaesthesia: It is outpatientanaesthesia, mainly for simple extraction of teeth espe-cially in children.

2. Day care anaesthesia: It is for minor oralsurgery.

3. In patient anaesthesia: It is for complicatedextractions, oral surgical procedures and maxillofacialsurgical procedures.

Indications of general anaesthesia in den-tistry 3, 7, 8, 12

Decisions about general anaesthesia can only bemade on an individual patient basis, but its use in den-tistry should be limited to:

1. Acute infection: In such clinical situations itwould be impossible to achieve adequate local anaes-thesia and so complete treatment without pain, e.g.management of acute dento-alveolar abscess and se-vere pulpitis. In these conditions, drug therapy or drain-age procedures with other methods of pain relief areinappropriate or unsuccessful. The local anaesthetic maynot be effective in such conditions because of localchange in pH and there is a risk of spreading infectionalso.

2. Children: Majority of out-patient general ana-esthesia in dentistry is administered to small children

who may not tolerate dental surgery under local anaes-thesia or some may be failures of attempts using localanaesthesia. It is recommended that only specialist pae-diatric anaesthetists should administer general anaes-thesia to very young children.

3. Mentally challenged patients: Such patients,because of problems related to physical/mental disabil-ity, are unlikely to allow safe completion of treatmentunder local anaesthesia.

4. Dental phobia: Patients in whom long-termdental phobia will be induced or prolonged are admin-istered general anaesthesia in first sitting. The long termaim in such patients should be the graduated introduc-tion of treatment under local anaesthesia using, if nec-essary, conscious sedation and behaviour managementtechniques.

5. Allergy to local anaesthetics: It is rare andis due to amide group of local anaesthetics. The pre-servative methylparaben can also cause allergic reac-tions. However, allergic reaction should be differenti-ated from vasovagal attacks, palpitation and flushingoccurring as a result of absorption of adrenaline presentin local anaesthetic solution.

6. Extensive dentistry & facio-maxillary sur-gery: Local anaesthesia is unsuitable in an awake pa-tient when the dentistry is likely to be extensive.

General principles

Patient assessment

The initial screening of patients for general anaes-thesia should be performed as for any other anaesthetic.The anaesthesiologists should always be ready to dis-cuss with dental colleagues policies for general anaes-thesia, and their implications for an individual patient,to allow efficient patient management. 3, 12

The Clinical setting

Defining the setting in which a general anaesthetic

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is administered must take into account the worst casescenario because the uneventful anaesthetic is not theproblem. Complications of modern anaesthesia are rare,but skilled team work is required to prevent permanentharm to the patient. The further away from the supportof other clinical services that an anaesthetic is adminis-tered, the greater is the risk of death should a compli-cation occur. Ideally, all general anaesthetics for den-tistry should be administered within the administrativeaegis of the range of services typically provided by.The location of any such facility must allow easy ac-cess for emergency services.8

Equipments, monitors and drugs

All standard equipments, gadgets, monitors anddrugs for anaesthesia and resuscitation should be avail-able and checked before administering anaesthesia. Thisincludes (not exclusive) anaesthesia machine, vaporiz-ers, oxygen, nitrous oxide, breathing circuits (adult andpaediatric), nasal and facial masks, oral and nasal air-ways, different laryngoscopes with all sizes of blades,all range of nasal and oral tracheal tubes, independentsuction apparatus, etc. SAFE agents (Short acting fastemergence) have particular place in day care anaes-thesia.3, 7

Minimum monitoring standards during anaesthe-sia should be followed. Peripheral arterial oxygen satu-ration, ECG, non-invasive blood pressure andcapnography (when tracheal intubation is performed)should always be done. A precordial stethoscope canbe very helpful. The anaesthesiologist should be clini-cally vigilant and continuously monitor colour of lipsand mucosa, and movements of chest and reservoirbag. The alarms of monitors should never be switchedoff.10, 11

All resuscitation drugs and equipments, includingdefibrillator should be immediately available. Moreover,the whole staff should be adequately trained in resusci-tation (adult and paediatric). The dental chair shouldbe capable of head-down tilt and should be movable inthe event of power failure. The anaesthetist must check

all the equipment before use and there should be im-mediate access to spare apparatus in the event of fail-ure. Maintenance must be in accordance with themanufacturers instructions. Facilities for the supply andstorage of medical gases must meet the relevant regu-lations.8

Staffing standards

Each individual must have had appropriate expe-rience of, and training in, dental anaesthesia. Theanaesthesiologist must have a dedicated assistant (op-erating department assistant or practitioner, nurse ordental nurse) with recognised training in this role andno other contemporaneous responsibilities. Because thedentist also requires assistance, a minimum of fourpeople are required for any procedure under generalanaesthesia. Until consciousness returns, a patient re-covering from general anaesthesia must be appropri-ately protected and monitored continuously in adequaterecovery facilities. Such monitoring should be under-taken by the anaesthesiologist or a dedicated individualwho is appropriately trained, and directly responsibleto the anaesthesiologist. 8

Aftercare

The brief nature of most dental procedures meansthat the majority of patients may be managed on anambulatory basis. Modern anaesthetic drugs permitrapid recovery of consciousness and early discharge,but it should be recognised that it may take more than24 hours for all traces of the agents to be eliminated.Thus when, in the opinion of the anaesthesiologist, pa-tients are ready for discharge they must be accompa-nied by a responsible, legally competent adult who hasbeen given clear instructions regarding the implicationsof anaesthetic hangover effects. All patients must beassessed specifically for fitness for discharge by theanaesthesiologist. The administration of generalanaesthetics for longer periods of time demands a levelof recovery facility that can only be provided in a mod-ern day-surgery unit, and standard criteria for the du-

Naveen Malhotra. General anaesthesia for dentistry

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ration of day-stay procedures apply. 7-9

Types of dental surgery

Dental surgery comprises exodontia, which is re-moval of teeth, and conservation, which is filling them,crowning them and other restorative measures.

Exodontia : Removal of teeth, it is usually a shortprocedure.

Conservation: Conservation operations take longerand often involve using a drill, which squirts water, so apharyngeal pack is necessary to prevent aspiration evenwith a cuffed endotracheal tube.11

Consent

Written and informed consent by the patient orparent/ guardian if the patient is minor or mentally chal-lenged.

Dental chair anaesthesia

The common indications are:

1. Children: Majority of patients are children be-tween ages 4 and 10 years requiring extraction of tooth/teeth. Such patients frequently have upper respiratorytract infection.

2. Adult patients with acute infection.

3. Mentally challenged patients.

Only ASA physical status class I & II patientsshould be administered Dental Chair Anaesthesia orOffice-Based anaesthesia care. Patients with compro-mised airway requiring advanced airway managementdevices, haemodynamic instability requiring invasivemonitoring and those who require prolonged post-op-erative care should be operated in an in-patient setting.Congenital cardiac anomalies and syndromes (predis-posing to difficult airway, unstable spine, etc) shouldbe specifically looked for in paediatric patients. 3, 7, 11, 17,18

Pre-anaesthetic preparation

The patient is explained about the anaestheticand dental procedure and clear fluids are allowed upto 4 hours preoperatively. A proper consent should al-ways be taken. The patient must be accompanied be-fore and after the surgery and supervised by an adultfor 24 hours.

Premedication

This is not usual, but may be used in children withespecially challenging behaviour. Chloral hydrate (50-100mg.kg-1), trimeprazine (2mg.kg-1) or midazolam(0.50.75 mg.kg-1) may be given orally mixed with asmall quantity of juice to disguise the taste, or intrana-sally (midazolam 0.20.3 mg.kg-1). The patients are in-structed to empty their bladder and bowels before sur-gery.10, 11

Induction of anaesthesia

In small children, gaseous induction usingsevoflurane (with parental presence) is often easiest.Since its introduction, sevoflurane has largely replacedhalothane as agent of choice because inhalation is quickand smooth and there are limited cardiovascular andrespiratory effects.19 Sevoflurane supplementation of66% nitrous oxide in oxygen is used. Sevoflurane mayeither be introduced in 2% increments every 2 to 3breaths to a maximum of 8%, with maintenance of ana-esthesia at or around 4%, or it may be introduced atthe maximum concentration of 8%, with maintenanceat 4%. Induction using 8% sevoflurane does not ap-pear to cause any adverse effects.20 However, ifsevoflurane is not available halothane is preferred overisoflurane that is irritant and can lead on to coughingand laryngospasm.21 Desflurane offers the advantageof reduction in recovery time.22 A pulse oximeter andECG should be placed before the child goes to sleep.A cannula must be inserted once the child is asleep forall but the briefest general anaesthetic, for example ex-traction of one tooth that takes a couple of seconds.

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Older children may be offered a choice of gas-eous or intravenous induction, and letting them decideis a good way of enlisting cooperation because the childfeels less threatened. Propofol is agent of choice forintravenous induction and it ensures clear headed re-covery and good anti-emesis, however thiopentone canalso be used. Ketamine has delayed recovery charac-teristics and induces dysphoria. Application of localanaesthetic cream (EMLA) to the skin will ensure thatinsertion of the cannula is painless. However, it has tobe applied one hour prior to procedure which can bedifficult in out-patient setting.3, 11

Airway for exodontia

The type of airway chosen depends on the sur-gery, and it is vital to liaise with the surgeon. Extractionof a few easy baby teeth is done using a transparentneonatal mask over the nares. The surgeon inserts agauze pack from one buccal sulcus to the other in or-der to prevent too much mouth breathing and aspira-tion of tooth fragments. A gag or bite-block is posi-tioned on the side opposite the extractions to open themouth. However, the nasal mask is still used by somedental anaesthetists (Fig. 1). The transparent neonatalmask has significant advantages: the external nares canbe seen with a transparent mask so that it is possible tocheck that they are not obstructed, and misting of the

mask may indicate breathing. Still, constant vigilance isneeded as the bag on the breathing circuit may not moveeven with adequate ventilation, and no CO2 trace willbe obtained.3, 11 Adenotonsillar hypertrophy can com-promise the nasal airway and nasopharyngeal airwayshave been shown to significantly improve airway pa-tency and reduce episodes of airway obstruction.23

Laryngeal mask airway (LMA) is being used forall but the simplest extractions. It provides some bar-rier to aspiration when compared to mask. Thearmoured variety is more suitable as its tube is nar-rower and takes up less room in the mouth and its flex-ibility makes it easier to keep out of the dentists way.It is important to hold the LMA firmly in place duringthe surgery because it has a tendency to move. Down-ward pressure on the jaw during extractions may ob-struct it.24-25

The airway is shared by the anaesthesiologist anddentist. Too large mouth gag should not be used be-cause it can make airway maintenance difficult. The oralpack should not be placed too far posteriorly in themouth, otherwise it can compromise nasal airway. Theanaesthetist must hold the patients head both to pre-vent excessive movement of the neck, which can causepain postoperatively, and to provide support to the jawand counter pressure to the dentists pushing and pull-ing.

Operating position

The operating position is controversial. Tradition-ally, patients sat upright in the dental chair but it cancause postural hypotension. The sitting position hasgradually become less common for dental surgery un-der general anaesthetic. In the supine position, the inci-dence of airway obstruction is high due to falling backof tongue and there is greater risk of pharyngeal soilingdue to blood. Overall, maintaining airway with nasalmask is difficult in supine position. The most commonlyused position is semi-supine. In this position, erect headand neck helps in maintenance of airway, besides car-diovascular and respiratory advantages of semi-reclin-Fig.1 Mask for nasal ventilation


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ing position and elevated legs.3, 7, 11

Airway for conservation

Operations for dental conservation and periodon-tal procedures tend to take longer and to involve quan-tities of water being squirted into the mouth. They shouldtherefore be performed with an endotracheal tube andpharyngeal pack in place to prevent aspiration, whichcan otherwise occur even with a cuffed tube. It is usualto intubate nasally. An LMA makes the surgery difficultbecause it leaves little space for the dental drill and suc-tion.11

Maintenance

For short operations it is often easier to use a tech-nique involving spontaneous respiration of inhalationalagent, nitrous oxide and oxygen, which gives flexibilityand rapid recovery. Using 50% inspired oxygen con-centration is beneficial and has been shown to decreasethe incidence and severity of hypoxaemic episodes.Incremental doses/continuous/ target controlled infu-sion of propofol can be used for maintenance of ana-esthesia. For extensive and complicated restorations,it is better to paralyse and ventilate the patient.

Recovery

The tooth sockets continue to bleed after dentalextraction, especially in the presence of infection. Ini-tially, patients are best nursed in left lateral position witha degree of head-down tilt to encourage drainage ofany blood and secretions away from the larynx andadministered 100% oxygen. Thorough but gentle oro-pharyngeal suctioning is done. The LMA or endotra-cheal tube should not be removed until the cough reflexhas returned. Removal of the LMA while the child isstill deeply anaesthetized has been associated with loweroxygen saturations in dental patients.26 A study of deathsrelated to dental anaesthesia found that more than halfoccurred in recovery.27 Significant desaturation is com-mon after brief dental anaesthesia and the principalcause is airway obstruction, these patients should be

supervised by an experienced nurse. Oxygen supple-mentation ameliorates the severity of desaturation butdoes not prevent it. 28 The patients are monitored in therecovery area for at least 30 minutes before returningto dental clinic. No oral fluids are given for 2-3 hoursto avoid vomiting and aspiration.

Postoperative analgesia

Extraction of baby teeth is not especially painful.The main problem is the psychological trauma of wak-ing up uncomfortable in a strange place. It is importantthat the parents are present, and the administration ofparacetamol 10-15 mg.kg-1 is usually all that is needed.Analgesia may be given rectally (paracetamol ordiclofenac suppositories) during the operation, but forshort operations this is of no major advantage.Ibuprofen or paracetamol may be given orally in liquidform in recovery.

The extraction of adult teeth is undoubtedly pain-ful. Non-steroidal analgesics are effective, and it hasbeen shown that oral diclofenac given on admission isas effective as rectal diclofenac given peroperatively.11

Fitness for discharge

Patients should be clinically observed to be alert,oriented, able to stand and walk unassisted, andhaemodynamically stable. There should be no obvioussurgical complications. Simple scoring systems, likeAldrete post anaesthetic recovery score (uses colour,respiration, circulation, consciousness and activity ascriteria) can be applied.7

Day care anaesthesia

In day care facility, patient undergoes formal ad-mission to the hospital but is discharged home later inthe day. The procedures which are usually done areminor oral surgical procedures including laser treatmentand limited extractions. The surgical procedure usuallylasts not longer than one hour and there are no antici-pated post operative complications. The patients are

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usually adults belonging to ASA physical status class Ior II. They are accompanied by a responsible adultand home circumstances should be suitable for con-tinuing post-operative care.

Patients are assessed formally by theanaesthesiologist and investigated. Usually for patientsbelow 40 years complete blood examination and urinecomplete examination is done. For patients aged 40years or more an ECG is done. Adequate preopera-tive fasting is necessary, usually six hours for adults andfour hours for children. If patient is anxious, premedi-cation is advised in form of oral alprazolam ormidazolam, but it can delay recovery. A proper con-sent is taken. Intravenous induction with propofol isdone in adults and older children. Neuromuscular block-ade is achieved with atracurium or vecuronium. Theuse of depolarizing neuromuscular blocking agent suc-cinylcholine is best avoided in such predominantly am-bulatory patients because of muscle pains. Naso-tra-cheal intubation is commonly done but oro-tracheal in-tubation can be done if only one side of the mouth is tobe operated. Pharynx is properly packed. Anaesthesiais maintained with administration of halothane /sevoflurane and nitrous oxide in oxygen. Diclofenac anddexamethasone are administered to reduce pain andswelling. Local anaesthetic may be infiltrated into thesockets by the surgeon, or a block is performed if sur-gery is limited to one or two quadrants. For more ex-tensive procedures, short acting opioid like fentanyl isadministered. Long acting opioid, like morphine isavoided in day care surgery.3, 11

In- patient anaesthesia

It is for complicated extractions, oral surgical pro-cedures and maxillofacial surgical procedures (fixationof maxillary, mandibular and nasal fractures, mandibu-lar set back, maxillary advancement, osteotomies andremoval of tumours.

Pre-anaesthetic evaluation

It is same as for any other major operation. How-

ever, it is pertinent to note that these patients can haveswelling of face, missing or loose teeth, pain and tris-mus limiting the mouth opening or a maxillo-mandibu-lar fixation may be in situ. Thorough airway evaluationshould be done and necessary radiographs evaluated,especially the antero-posterior and lateral views of neck.The nasal patency should be done to facilitate nasalintubation. Such patients may have polytrauma andcomplete evaluation is necessary, including completehaemogram. Neurological evaluation is necessary inpatients with co-existing head injury. The electrolytestatus must be assessed because such patients have alimited oral intake (usually liquids). 3, 7

Principles of airway management7, 29

1. Patients with complex maxillo-facial injuries arepotential difficult airway patients. Difficult airway trol-ley should be checked and immediately available.

2. Do not administer neuromuscular blockingagent until it is possible to do mask ventilation.

3. Maxillo-Mandibular Fixation:

It is important to understand that in patients withpanfacial trauma, surgical reconstruction often involvesintraoperative maxillo-mandibular fixation to restoredental occlusion and it is the important aspect of surgi-cal procedure. The fixation is done with high tensilestrength elastic bands (common) or classical wires.Discuss with the surgeon, the possibility of removingmaxillo-mandibular fixation just before induction of ana-esthesia. Removal of bands/wires can make airwaymanagement quite easier. It can be redone intra-op-eratively after securing the airway. If possible, subse-quent removal at the end of surgery makes trachealextubation and recovery simple. The maxillo-mandibularfixation can be finally put in situ in the ward once pa-tient is fully conscious and airway oedema subsided.

4. Throat pack is put to prevent ingestion of bloodinto the stomach or its settling above the cuff of tra-cheal tube.


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5. A reinforced or flexo-metallic tube is most com-monly used for tracheal intubation.

6. Such patients commonly receive steroidsperioperatively to reduce airway oedema.

7. A tongue suture is applied if there is gross air-way oedema and mouth is open.

8. Displacement of tracheal tube can occur be-cause the tracheal tube is quite close to the surgicalfield. Proper fixation of tracheal tube should be doneand anaesthesiologist should be vigilant to promptlydetect it.

9. Routes of tracheal intubation

A) Oral tracheal intubation:It can be done under direct laryngoscopic view,

fiberoptic bronchoscope guided, by using lighted stylet,through LMA (guided by fiberoptic bronchoscope) orintubating LMA. Oro-tracheal intubation is not feasibleif intraoperative maxillo-mandibular fixation is to bedone.30

B)Nasal intubation:It is the most common route of tracheal intuba-

tion. It can be laryngoscope guided, fiberoptic bron-choscope guided or blind. Depending upon the clinicalcircumstances the patient may be anaesthetized andbreathing spontaneously or paralyzed, or may beawake. Nasal passage is well prepared with a vaso-constrictor and a topical anaesthetic.

However, nasotracheal intubation is not possiblein some patients (10-15%) due to associated skull basefractures, cerebrospinal fluid rhinorrhoea (any attempttowards nasotracheal intubation may lead to passageof tracheal tube into cranium, meningitis, sepsis andepistaxis), fractures of nasal skeleton and anatomicalobstruction of nasal airway (deviated nasal septum,nasal spur, and hypertrophied nasal turbinates). Theseconditions cause physical obstruction to the passage of

nasotracheal tube. Further, the presence of nasotrachealtube can interfere with the surgical reconstruction ofnaso-orbital - ethmoid (NOE) complex.31-33

C) Retromolar intubation 34, 35

When orotracheal intubation is not feasible andnasotracheal intubation contraindicated, retromolar in-tubation is indicated to secure the airway perioperatively.In this technique, oral endotracheal intubation is donewith a flexometallic tracheal tube which is then placedin the retromolar region. The retromolar space is thespace behind the last erupted upper and lower molarteeth. The retromolar tube is stabilized in position byfixation to first or second molar tooth in figure of eightfashion. (Fig. 2) It allows intraoperative maxillo-man-dibular fixation, thus restoring dental occlusion, whichis the important step for successful facio-maxillary sur-gery.

Fig 2 Retromolar Intubation

The adequacy of retromolar space can be deter-mined by introducing the index finger in the patientsmouth and asking him or her to close the mouth. If thereis no compression on finger, the retromolar space isadequate. Success of retromolar intubation can alsobe increased by selecting one size smaller tracheal tubewhich has a corresponding smaller outer diameter.

Advantage: This technique avoids the need ofany surgical technique i.e. tracheostomy and submento-tracheal intubation for securing airway perioperatively.

Disadvantages: These are minor and avoidable-

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1. The tracheal tube can interfere with the mainsurgical field and positioning and application of dentalfixation devices.

2. Too jealous fixation of flexometallic trachealtube with wire ligature should not be done because itcan deform the tube.

D) Submento-tracheal intubation 29, 36-39

Submento- tracheal intubation is an alternatetechnique of airway management in patients with cranio- faciomaxillary trauma when retromolar intubation isnot possible. It is an alternative to short-term tracheo-stomy.

Technique

Orotracheal intubation with reinforced(flexometallic) endotracheal tube is done using stan-dard general anaesthesia technique. At the start of pro-cedure, nitrous oxide in switched off and patient is ad-ministered 100% oxygen. A 1.5-2 cm incision is madein the submental region parallel and medial to the infe-rior border of the mandible. The incision is lateral tothe anterior belly of digastric muscle. When ever pos-sible, the right side is preferred because it allows bettervisualization of the intraoral position of tracheal tubewith direct laryngoscopy. The incision is extendedintraorally by blunt dissection with artery forceps throughthe subcutaneous layers, mylohyoid muscle, submucosaand mucosa. The intraoral opening is lateral to the sub-mandibular and sublingual ducts. Thus, a submentaltunnel is created.

The tracheal tube is briefly disconnected fromthe breathing circuit and the tube connector is removedfrom the tube. The pilot balloon followed by the tra-cheal tube is gently pulled out through the submentaltunnel. During this step, the endotracheal tube is stabi-lized intraorally manually or by Maggils forceps. Thetube connector is reattached and endotracheal tube isconnected to the anaesthesia breathing circuit. Bilat-eral air entry is checked. The distance marking on the

endotracheal tube at the submental skin exit point isnoted. It is usually 2 cm more than the oral fixation.This helps in checking the tube position intraoperatively.The tube is fixed in position with suture (as chest tubedrain). (Fig. 3)

Fig 3 Submento-Tracheal Intubation

Intraorally, the tracheal tube lies in the sublin-gual sulcus between the tongue and mandible. It is awayfrom the surgical field and allows intraoperative maxillo-mandibular fixation. The total procedure is usually com-pleted within 5-10 minutes and the blood loss is mini-mal (

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done through the submentally placed tube. The avail-ability of reinforced tracheal tubes made of polyvinylchloride has the advantage of a low pressure, high vol-ume tracheal tube cuff. However, when submental en-dotracheal tube is not removed, it is mandatory thatimmediate access to oral airway is ensured at all times.Maxillo-mandibular fixation should be deferred till ex-tubation and confirmation of secure airway. If maxillo-mandibular fixation is necessary then cutter should beimmediately available. If reinforced tube is removedoutside the operating room, then after extubation clo-sure of submental incision is done under local anaes-thesia.

Damaged submento tracheal tube (leaking cuff,loose universal connector) can be replaced success-fully with the use of tracheal tube exchanger, while thetracheal tube is placed submentally. The apparent steepangle of insertion in the submental approach can benegotiated successfully.

Advantages

This technique provides a secure airway, un-obstructed intraoral surgical field, allows intraopera-tive maxillo-mandibular fixation and avoids complica-tions of tracheostomy. It is a simple, safe and usefultechnique with very low morbidity.

Disadvantages

It can cause trauma to submandibular duct,sublingual gland or duct and facial nerve or lingual nerve.Superficial infection of the submental wound can occurwhich if not treated properly can result in oro-cutane-ous fistula. Incidence of hypertrophic scarring is low.

E) Retrograde intubation and tracheostomy: veryrarely required.

Airway management in patients with cranio-facio-maxillary trauma is a challenge for bothanaesthesiologists and surgeons. It requires close in-teraction between them. Retromolar intubation is a

simple, easy and non invasive technique of tracheal in-tubation when oral intubation is not feasible andnasotracheal intubation is contraindicated. When ret-romolar intubation is not possible, submento-oral intu-bation is a relatively harmless alternative to tracheo-stomy for securing the airway perioperatively.

Complications of dental anaesthesia

1. Hypoxaemia:

During dental chair anaesthesia, there is high po-tential for airway obstruction resulting in hypoxaemia.This can result from inhalation of teeth, crowns, por-tions of filling, etc. A sudden decrease in arterial oxy-gen saturation by up to 10% can occur under generalanaesthesia due to upper airway obstruction at the timeof insertion of the dental prop and pack and duringextractions. This obstruction is accentuated by coex-isting rhinitis and hypertrophied adenoids and tonsils inyoung children. Further, in such patients airway clo-sure occurs at lung volumes well above functional re-sidual capacity (FRC), producing a large intrapulmo-nary shunt. During general anaesthesia, there is furtherreduction in FRC and intrapulmonary shunt is exacer-bated and together with propensity for upper airwayobstruction, there is greater tendency to hypoxia.28, 40,41

Increasing fractional inspired oxygen concentra-tion to 0.3 reduces the incidence and severity ofperoperative desaturation. However, increasing theFiO2 further to 0.5 has not been shown to result inmore improvement in oxygen saturation.42, 43 Applica-tion of 5cm H2O continuous positive airway pressure(CPAP) can result in significant reduction in incidenceand severity of peroperative arterial desaturation byincreasing FRC and overcoming partial airway obstruc-tion.44

2. Arrhythmias:

There is high incidence of cardiac arrhythmias,especially with the use of halothane. They are usually

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attributed to light anaesthesia, elevated levels of cat-echolamines and trigeminal nerve stimulation. They areincreased in the presence of hypercarbia or hypoxia.The arrhythmias usually occur during extraction of teethbut are transient, seldom require treatment and respondto cessation of pull on the tooth.45

3. Subcutaneous emphysema:

Subcutaneous emphysema of face and cervicalareas, although rare but can occur due to the use of airdriven, ultra-high speed dental instruments. The air en-ters along the mandibular periosteum at the operativesite. Nitrous oxide is discontinued on detection of em-physema and respiratory parameters closely moni-tored.46

4. Dislocation of temporo-mandibular joint: Itoccurs not infrequently in children if mouth is openedwidely. It can predispose to airway obstruction due toalteration in position of tongue. It can be easily reducedat the end of surgery.

5. Operating room pollution: Dental surgeriesare areas of high contamination with anaesthetic gases.Efficient ventilation (12-15 room changes of air per hour)and scavenging are required.

6. Hyperthermia: Tissue destruction, environ-mental temperature during surgery, administration ofcertain drugs, dehydration and bacteraemia have allbeen implicated in temperature rise after anaesthesia.Procedures provoking bacteraemia (extractions) canbe managed by routine administration of antibiotics.6, 47

7. Non-compliance of post-operative instruc-tions: Patients undergoing day surgical procedures aregiven instructions not to drink alcohol, drive vehicles ormake important decisions for 24 hours. Some patientsdo not comply with these instructions. Compliance canbe improved by physician reinforcement of instructionsand patient education.48

Conscious sedation

Definition: It is a minimally depressed level ofconsciousness that retains the patients ability to inde-pendently and continuously maintain an airway and re-spond appropriately to physical stimulation and verbalcommand. It is produced by a pharmacological or non-pharmacological method or a combination thereof. Indentistry, it is used to reinforce positive suggestion andreassurance in a way which allows dental treatment tobe performed with minimal physiological and psycho-logical stress, and enhanced physical comfort. The tech-nique must carry a margin of safety wide enough torender loss of consciousness highly unlikely.13

Conscious sedation may be induced by any oneof the following modalities:

1. Oral administration of a single sedative drug(midazolam, diazepam, alprazolam, lorazepam,zolpidem, promethazine, chloral hydrate).

2. Nitrous oxide and oxygen

3. Combination of oral sedative drugs or nitrousoxide and oxygen with an oral sedative drug

4. Parenteral administration of sedative drugs (in-travenous- midazolam, propofol; intramuscular; sub-cutaneous; submucosal or intranasal-midazolam).

Relative analgesia

It is an inhalation sedation technique consisting ofthree elements: First, administration of low to moder-ate concentration of nitrous oxide in oxygen (0-70%);Second, as nitrous oxide begins to exert its pharmaco-logical effects, the patient is subjected to reassuring andsemi-hypnotic suggestions; and thirdly the use of fail-safe equipment with a range of safety features, espe-cially preventing accidental administration of 100% ni-trous oxide.50 Sevoflurane 0.1-0.3% and 40% nitrousoxide in oxygen has been used for inhalational con-scious sedation in children undergoing dental treat-ment.51

To conclude, provision of treatment under gen-


736


eral anaesthesia in selected children is justified and suchservices should be provided safely, effectively and effi-ciently in the appropriate environment. Dental treatmentunder general anaesthesia can be carried out in a daycare facility with a high level of patient and parent sat-isfaction. Anaesthetic management by a qualified andexperienced person and dental treatment by a qualifiedoperator allow the procedure to be carried out withminimal morbidity.

If the otherwise well-trained anaesthesiologist failsto meet the challenge of office dentistry, the field is leftby default to either the poorly trained physician, or thedentist who may be tempted to essay surgery and ana-esthesia simultaneously. In either case, the patient ispoorly served, and anaesthesia slips backward, notforward.49

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Generan Anaesthesia for Dentistry