Vinnitsya national pirogov memorial



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MINISTRY of PUBLIC HEALTH of UKRAINE

VINNITSYA NATIONAL PIROGOV MEMORIAL

MEDICAL UNIVERSITY
It is "confirmed"

on a methodical meeting of

department of pediatric dentistry

head-chair

doc.Filimonov Yu.V._____


" " in20


Methodical recommendation for 4d year students

of dental faculty

Educational discipline

Pediatric surgery

Module ¹

1

Rich in content module ¹

1

Topic

Local and general anaesthesia. Short anaesthesia in a dental chair. Equipment. Preoperative preparation and premedication.

Course

4

Faculty

Dental

Autor

Isakova N.M.

Vinnitsya 2012


Actuality of theme: Anaesthetizing in stomatological practice it is the very important stage in treatment. Not a single stomatological manipulation is not conducted practically without him. But it and one of more dangerous stages of treatment, because requires knowledge not only from the topography of certain area and methodology of realization, and it is necessary to have knowledge of ї from pharmacology, physiology of therapy, paediatrics and others like that. Realization of anaesthetizing has very many features of anatomic, physiology, age-old. It is also had much disadvantage. That study of anaesthetizing in stomatology is necessary to spare the special attention.

1. Concrete aims:

1.A student must familiarize with the problem of realization of anaesthetizing for children, among the different age-related groups.

2. A student must know the features of anatomic structure of maxillufacial area for the children of the different age-related groups and feature of physiology processes for children. A student must know classification of anaesthetizing, preparations which are used and methodologies of realization of the local anaesthetizing for children.Shows and against shows to the certain types of anaesthetizing.

3. A student must lay hands on methodologies of the local anaesthetizing for children.

4. A student must conduct differential diagnostics of the different urgent states and render the first medical aid.

3.Educator aims:

1. To develop professional internalss and feelings of responsibility during realization of anaesthetizing for children.



2. Able to carry out and psychological approach in-process with children

3 Base knowledges, abilities, habits which are necessary for study the topic.

Names of previous disciplines

Skills are got

  1. General anatomy

The structure of the maxillofacial region, the blood and nerve supply

  1. Gistology

Histological structure of the oral mucous cavity. The mechanism of development and phase of inflammation

  1. Therapy, pediatrics

Know the features of a child's body. Know the basic diseases of importance in conducting the diagnosis of major dental diseases




  1. Task for independent work during preparation to employment.




4.1. List of basic terms, parameters, descriptions which a student must master at preparation to employment :

Term

Determination

1. Anaestesia

Anesthesia, or anaesthesia (see spelling differences; "without"; "sensation"), traditionally meant the condition of having  sensation (including the feeling of  pain) blocked or temporarily taken away. It is a pharmacologically  induced and reversible state of amnesia,  analgesia, loss of responsiveness, loss of skeletal muscle reflexes or decreased stress response, or all simultaneously.

2. Topical anaestesia

The application of ointments or solutions containing local anaesthetic compounds to accessible structures, e.g. skin and mucous membrane is called topical anesthesia.

3. Infiltration anesthesia

Infiltration anesthesia is achieved when the terminal nerve ending supplying the operative area are flooded by the diffusion of the injected anaesthetic solution rendering them incapable of becoming stimulated.

4. Nerve block anaesthesia


The anaesthetic solution is deposited extraneurally or paraneurally in close proximity to the main nerve trunk supplying the operative area at an accesible point along its courseto the periphery of the region, and before it divides into its terminal branches, thus prevent afferent impulses from travelling centrally beyond that point.


4.2. Theoretical questions to employment:

1. Classification of anaesthetizing.

2. for the local and general anaesthetizing, that used for children.

3.Topographical anatomy of maxillufacial дідянки.

4. Local types of anaesthetizing, area of anaesthetizing.

5.Children have features of realization of the local anaesthetizing.

6.Complication during realization of anaesthetizing and urgent states.



4.3 Practical works (tasks)

To conduct the different types of the local anaesthetizing on phantoms.



5. A plan and organizational structure of lesson in discipline.



Stages of employment

Distribution of time

Types of control

Facilities of studies

1.

Preparatory stage

15 min

practical tasks, situatioonal tasks, verbal cross-examination at standart list of questions.

Text-books, methodical recommendations.

1.11.1

OThe organizational questions.




1.2

Forming of motivation.

1.3

Control of

initial level of preparation.



2.

Basic stage.


55 min

3.

Final stage

20 min

test tasks




3.1.

Control of eventual level of preparation.




3.2.

General estimation of studing activity of student.

3.3

Informing of students about the theme of next employment.


Maintenance of theme

Local Anaesthesia

Achieving good local anaesthesia is a prerequisite for virtually all dental surgery, and in oral surgery the confidence this gives is mandatory from both the patient's and the operator's point of view. The ability to administer a comfortable local anaesthetic to any patient is a fundamental skill that dental surgeons should strive to achieve. This will allow stress levels in both giver and receiver to be greatly reduced, and technique must be constantly reviewed and revised to this end.



Uses of local anaesthesia

Diagnostic use

Administration of local anaesthetic can be a useful way of finding the source of a patient's pain. An example of this is the pain of a pulpitis, which can be very difficult for both the patient and the dentist to isolate because of its tendency to be referred to other parts of the mouth or face. Particularly useful is the infiltration technique, which achieves a localized action and can discriminate between maxillary and mandibular sources, and even between individual upper teeth provided they are not immediately adjacent. Another example is the patient with myofascial pain who is convinced that an upper tooth is causing the problem. Local anaesthesia may help this patient and the surgeon in this situation to eliminate the tooth as the cause of pain and may thus avoid its unnecessary treatment.



Therapeutic use

Local anaesthetics can, in themselves, constitute part of a treatment regimen for painful surgical conditions. The ability of the dentist to abolish pain for a patient, albeit temporarily, is a therapeutic measure in its own right. The use of a block technique to eliminate the pain of dry socket (localized osteitis) can be immensely helpful to the management of this very painful condition, particularly in the first few days. Inferior dental blocks of long-acting local anaesthetics such as bupivacaine can give total comfort for several hours, allowing patients to catch up on lost sleep and perhaps reduce the use of systemic analgesics to avoid overuse. Moreover, the patient can return for further local anaesthesia if the pain once more becomes too demanding. Although it would be impossible to keep administering local anaestheticblocks, there is enough, albeit anecdotal, evidence to suggest that when the pain returns after the block wears off, it is not at the same level of intensity.



Perioperative use

The provision of pain-free operative surgery is by far the most common use of local anaesthetics, and provides an effective and safe method for almost all outpatient dentoalveolar oral surgical procedures. It can, in conjunction with sedation techniques, allow more difficult or protracted procedures to be carried out without the additional risks of general anaesthesia, and this may be particularly of value in patients with significant cardiovascular or airway disease.



Postoperative use

After surgery with either local or general anaesthesia, the continuing effect of the anaesthetic is a most beneficial way of reducing patient discomfort. It helps to reduce or even eliminate the need for stronger (often narcotic) systemic analgesics, which have their own drawbacks.



Local anaesthetic agents

Commonly used local anaesthetic agents

Lidocaine (lignocaine) hydrochloride 2%

Prilocaine hydrochloride 3%

Bupivacaine hydrochloride 0.5%

In oral surgery there is a distinct advantage in using a local anaesthetic with adrenaline (epinephrine), which, by its vasoconstrictive action, improves the visibility of the surgical site by reducing small-vessel bleeding.

Maximum safe dose

Local anaesthetics such as lidocaine (lignocaine) and prilocaine are extremely safe given their extensive use in both medicine and dentistry. The addition of adrenaline (epinephrine) to lidocaine (lignocaine) and of felypressinto prilocaine reduces the rate of uptake from the site of injection, thus reducing the possible toxic effects of the local anaesthetic agent and increasing, in theory, the volume that can therefore be used. Apart from the actual amounts used, three other considerations should be taken into account: (1) the avoidance of intravascular injection by use of an aspirating syringe; (2) the rate of administration of the local anaesthetic - a slow rate reduces the chance of overload and hence possible toxic effects; and (3) the status of the patient. Extremes of age, physical size and medical background should be determined for each individual patient, all of which may modify what could be considered a safe quantity.

The maximum safe dose can be expressed as 4.5-5.0 mg per kg body weight of lidocaine(lignocaine) with 1:80000 adrenaline (epinephrine) and 3 mg per kg body weight of prilocaine. When translated into millilitres of 2% lidocaine(lignocaine) with adrenaline (epinephrine) or 3% prilocaine with felypressin in a fit 70-kg adult patient this means that a maximum of six cartridges of lidocaine (lignocaine) (or four of prilocaine), each of 2.2 mL, is well within the safe limit. The preoccupation with volume is misleading as it tends to cause unthinking administration, and not consideration of each patient's individual situation allied to safe technique.

Local anaesthetictechnique

Infiltration

This can be used to achieve anaesthesia of upper teeth and lower anteriors. It is achieved by depositing the solution around the apex of a tooth on its buccal aspect in the sulcus. The porosity of the bone allows it to diffuse through the outer plate of bone to affect the apical nerve or nerves. It normally achieves anaesthesia within 1-2 min and has the added surgical advantage (where adrenaline is in the solution) of small-vessel vasoconstriction, which provides reduction in bleeding and increased visibility as a consequence.

Needle insertion

To achieve minimal discomfort, topical local anaestheticshould be applied 2-3 min before the injection. The index finger or thumb of the 'free' hand should pull the lip or cheek such that the sulcus tissues are taut, as this will minimize discomfort on introduction of the needle. The tip of the needle needs to be advanced only 3-4 mm into the tissue adjacent to the tooth to be anaesthetised.

Deposition of local anaesthetic solution

The solution should be deposited slowly because the lumen of a dental needle is very fine and undue force of the solution being injected can lead to unwanted pain and tissue damage. This therefore takes time and patience but is essential in reducing discomfort.



Block anaesthesia

Several block injections of nerve trunks can be used for oral surgical purposes. By far the most common is the inferior dental block, but others include the mental block, the posterior superior dental block and the infraorbitalblock. The hard palate can be anaesthetised by greater palatine and nasopalatine blocks if more extensive areas of palate require to be anaesthetised.



Inferior dental block

Several techniques have been suggested. The first being a standard block and the second a closed-mouth technique that can be very useful if restricted opening is a problem. The nerves affected are: (1) the inferior dental nerve, which provides sensation to the pulps and periodontal membranes of first incisor to third molar, the bone investing the teeth, thebuccal gingivae and the sulcus from premolars to incisors, lower lip and chin; and (2) the lingual nerve, which supplies the anterior two-thirds of the tongue, the floor of mouth and the lingual gingiva.



Technique

The precise technique will vary but the following willserve as a guideline for administering an inferior dental block injection. The patient should be seated with good head and neck support and with the neck slightly extended such that the lower occlusal plane will be approximately horizontal on fully opening the mouth. With the mouth widely opened, the finger or thumb of the 'free' hand should pass along the lower buccal sulcus until it rests posteriorly in the retromolar triangle, which lies between the (external) oblique line of the mandible and the continuation of the mylohyoid ridge or internal oblique line.The pterygomandibularraphe should then be identified as an almost vertically running soft tissue line. This takes its origin from the pterygoidhamulus and runs downwards to its insertion on the lingual aspect of the mandible in the third molar region. The raphe gives rise to muscle attachments running laterally (buccinator) and medially (superior constrictor).

The syringe should be introduced from the lower premolar teeth of the other side parallel to the lower occlusal plane such that the needle penetrates the tissues lateral to the pterygomandibular raphe and at a level halfway up the finger or thumb lying in the retromolar triangle. The 'long' dental needle (3.4 cm) should be advancedabout 2.5 cm until bone is touched lightly. The needleshould then be withdrawn a millimetre or two andaspiration performed. If blood in the form of a smoky redtrail is noted in the cartridge, the needle should be withdrawn a millimetre or so before reaspirating.

The local anaesthetic should then be deposited slowly, using most of the 2.2 mL cartridge and with the local anaesthetic being deposited on slow withdrawal to 'catch' the lingual nerve, which lies anteromedial to the inferior dental nerve.

This technique introduces a local anaesthetic solution to the inferior dental nerve as it enters the mandibular foramen on the medial aspect of the ramus. In patients who, for a variety of reasons, have trismus and cannot open sufficiently to allow this technique, a closed technique can sometimes be useful.

The patient should be seated such that the occlusalplane is approximately horizontal. The cheek should be retracted with the index finger or thumb of the 'free' hand and the needle advanced horizontally at about the level of the gingival margins of the upper molar teeth. The needle should penetrate to a depth of 1–1.5 cm before aspiration. Slow deposition of most of the 2.2 mL cartridge is normally required.

This technique leaves the local anaesthetic solution at a level higher than the standard technique, which means that it is deposited above the mandibular foramen but stillbelow the level of the mandibular notch.

Buccal injection

The sulcus region in the lower premolar and molar regions may have innervation from the buccal nerve and this must be covered by a separate injection. The buccal injection can be given more comfortably by waiting for the inferior dental block to become effective. Rather than a single block given in the cheek at the level of the crown of the third molar at the anterior border of the ramus, many operators simply infiltrate around the surgical site, for example, in the sulcus of the third molar region where an impacted third molar is being treated since this will have the added benefit of haemostasis of the flap.



Mental nerve block

This injection will anaesthetise the pulps and periodontal membranes of the lower incisors, canine, first premolar and variably the second premolar. For surgical procedures, it must be remembered that the lingual mucoperiosteumwill require separate infiltration as the mental block anaesthetises the teeth through the incisive branch of the inferior dental nerve and the peripheral distribution of the mental nerve.



Technique

In dentate patients, the mental foramen lies below and between the apices of the lower premolar teeth, approximately half way between the cervical margins of the teeth and the lower border of the mandible. The injection is similar in all respects to an infiltration injection, and the objective is to deposit the solution at or near the foramen. No attempt should be made to 'feel' the distally facing foramen because this is totally unnecessary and often causes haematoma formation through damage to the mental blood vessels.

In edentulous patients, the foramen may lie nearer the crest of the ridge as a result of alveolar resorption and due allowance for this should therefore be made before the injection is given.

Posterior superior alveolar (dental) block

This block is intended to anaesthetise the posterior superior dental nerve as it penetrates the posterolateralaspect of the maxillary tuberosity before it pierces bone. As such, a close relationship exists between the site of the injection and pterygoid venous plexus lying laterally and above and which can easily therefore be entered by the needle. This can cause an immediate and alarming haematoma visible both in the sulcus and externally in the face just below the zygomatic arch.



Technique

The technique, which is in effect high infiltration, is seldom, if ever, really necessary as diffusion of anaesthetic from the conventional infiltration is almost always effective. If it is considered necessary, then the needle should be angled inwards towards the buccal plate as much as possible, given that the opening of the mouth will restrict this. The other angle to remember is the alignment of the needle at approximately 45° to the occlusal plane after entering the sulcus in the second molar region.



Infraorbital block

This injection, although given infrequently, can be a very valuable technique for achieving anaesthesia in the anterior part of the maxilla. The local anaesthetic solution is deposited around the infraorbital foramen, where it can diffuse back along the infraorbital canal to affect the anterior and, where present as a separate nerve, the middle superior dental nerve. Ideally, therefore, in addition to anaesthesia of the soft tissues of the upper lip, side of nose, cheek and lower eyelid, the upper incisors, canine and premolars will be affected together with the adjacent sulcus and gingivae.

For oral surgery purposes this injection can be given to avoid injecting into inflamed tissues in the incisor or canine region, but can also achieve a more dependable and profound anaesthesia for larger lesions such as cysts. Use of a long-acting agent such as bupivacaine to achieve control of trigeminal neuralgic pain breakthrough also makes knowledge of this technique valuable.

Technique

Although several techniques can be used, the most commonly employed, which uses the upper first and second premolar as the key landmark, is described.

The buccal sulcus is tensed with the finger or thumb of the 'free' hand in the premolar region. Some doctors suggest that a finger be placed over the infraorbitalforamen on the face to 'feel' the local anaesthetic as it is administered and ensure that it is in the correct location. In practice, however, this is often not a realistic measure. The needle is introduced such that it is parallel to the long axis of the premolars; it penetrates the lateral aspect of the sulcus about 1–1.5 cm from the buccal bone surface and it is advanced upwards approximately 1.5 cm into the tissues. After aspiration, the local anaestheticis slowly introduced to the tissues when 1.5–2.0 mL of the preferred solution is normally sufficient.

Alternative techniques include direct injection through the skin to the foramen. The lower orbital margin rim should be palpated carefully before injecting about 1 cm below this landmark, and at the midpoint of the infraorbitalbony margin. Administration of local anaestheticin this way can be alarming to a

patient, and carefulexplanation of what is being done is necessary. The eyeshould be protected by the fingers of the 'free' hand, withone finger carefully palpating the lower orbital bony margin.

Periodontal ligament injection

This technique introduces local anaesthetic directly into the periodontal space and, as the force required is quite substantial, specialised syringes are available to achieve this. In oral surgery, the intraligamentous injection is most frequently used if pain is being felt despite the normal techniques of infiltration or block anaesthesia. This can occur when a tooth is 'hot' through acute pulpitis or apical infection. It may also be of value if limitation of jaw mobility makes block injection difficult or impossible. One of its advantages is the small volume of local solution needed, but it is often uncomfortable to administer and will cause a bacteraemia which should be prophylactically covered with appropriate antibiotic in an endocarditis at-risk patient.



Intraosseous injection

This technique will achieve excellent anaesthesia limited, however, to the immediate locality of the injection. The local is administered through a trephined hole best prepared with a specially designed bur through the outer cortical plate of bone. Initial infiltration anaesthesia of the area is hence a prerequisite and, after the entry is cut, a short needle is introduced into the medullary space before injecting a small quantity of solution. The diameter of the trephined hole should ideally be matched to the needle to prevent leakage. Again, the advantages of the technique are the small quantity of local anaesthetic used and the ability to achieve a good depth of anaesthesiawhere access may be limited through trismus.



Intrapulpal injection

This injection is normally used where, despite apparently good anaesthesia by other conventional means, the tooth remains painful on manipulation. This again is a feature of some pulpal or apical infections. In oral surgery, the tooth is normally being extracted and either the pulp canal(s) are already accessible or can be accessed using a small round bur. The technique is imprecise and escape of the solution is almost invariable. It can, however, be remarkably successful if sufficient local can be introduced. Discomfort during its administration is often a reliable indication that it will prove of benefit.



General Anaesthesia

Anaesthesia means absence of all sensation; analgesia means absence of pain. General anaesthesia is a state where all sensation is lost and the patient is rendered unconscious by drugs. Some anaesthetic agents have little analgesic effect whereas some analgesics produce little sleep.

The surgeon and the anaesthetist have a shared responsibility for the patient's wellbeing, and so an understanding of general anaesthesia is important for all surgeons.

Assessment of risk

The patient should first be made as fit as possible for operation in the time available. Second, the anticipated benefits of surgery should outweigh the anaesthetic and surgical risks involved. The overall mortality rate attributable to anaesthesia itself is approximately 1 in 100 000, whereas a broad average of surgical mortality is more than 1 in 1000. Factors that have been shown to contribute to this mortality include poor preoperative assessment, inadequate supervision and monitoring in the intraoperative period and inadequate postoperative care.



Preoperative assessment and premedication

The anaesthetist must see and assess the patient preoperatively; failure to do so can be regarded as negligent. Many patients will be seen the night before surgery. Withincreasing economic pressures to admit patients on the day of operation, a screening process must be used to identify suitable patients.



Physical examination

A full physical examination is important to complement the history but the anaesthetist will also pay particular attention to the upper airway with a view to assessing the ease of tracheal intubation. This will involve assessment of the teeth and extent of mouth opening and flexibility of the neck.



Preoperative therapy

Patients with respiratory disease can be improved by physiotherapy or bronchodilator therapy. Prophylactic antibiotics are required in those at risk of subacutebacterial endocarditis. Hypertensive patients can sometimes require adjustment of their drug therapy to obtain optimal control, but it is usually reasonable to proceed with surgery if their diastolic pressure is below 110 mmHg.



Premedication

Whereas reassurance and explanation remain the mostimportant components of the preoperative visit, drugs can be used to obtain one or a combination of the effects.

Anxiolysis is most commonly achieved with the use of benzodiazepines such as diazapem or lorazepam, and these drugs also cause a degree of anterograde amnesia. Excessive secretions in the airway are less of a problem with modern anaesthetic agents but can be reduced with anticholinergic drugs either given before or at operation. Three drugs commonly used in this circumstance are the anticholinergic agents atropine, hyoscine and glycopyrronium. Vagal bradycardia, such as occurs with the oculocardiac reflex, can be severe and atropine is protective of all the above. Antiemetics such as metoclopramide, ondansetron or antihistamines are administered preoperatively from time to time; metoclopramide also enhances gastric emptying. If it is desired to reduce gastric acidity this can be achieved with sodium citrate, H2 blockers such as ranitidine or proton pump inhibitors. Alleviating the patient's anxiety is most important.

Induction of anaesthesia

Anaesthesia can be induced by inhalational agents or by drugs administered intravenously.



Inhalational induction

Inhalational induction is more commonly proposed for either young children or those with an obstruction somewhere in their airway (e.g. epiglottitis or a foreign body). Rapport and patient confidence are important to ensure the patient's cooperation, and a gentle and gradual approach should be used. An anaesthetic mask should be held gently on or very near the face and the patient should be talked to calmly and reassuringly while being encouraged to breathe normally. It is common for nitrous oxide 70% in oxygen to be used; anaesthesia is gradually deepened as the anaesthetist introduces a volatile anaesthetic agent by increments. Patient monitoring will have been attached before induction and the patient is observed carefully for skin colour; the pattern and rate of ventilation and the patient's pulse, blood pressure ECG and arterial oxygen saturation by pulse oximetry(SpO2) should all be observed. End tidal carbon dioxide concentration (ETCO2) can be monitored; this is mandatory in intubated patients. As consciousness is lost, the airway will require increasing support, which will usually involve pulling up the patient's chin. It can also require insertion of an artificial airway. This might be an oral or nasopharyngeal airway. A laryngeal mask airway (LMA) or an endotracheal tube can be inserted if required. For endotracheal intubation without muscle relaxants the patient must be at a much deeper level of anaesthesia. Airway obstruction is the most commonly encountered difficulty. Scavenging systems are usually employed to reduce environmental pollution from expired gases.



Intravenous induction

Induction of anaesthesia with an intravenous agent is used for most routine purposes and is the most appropriate technique for most patients undergoing emergency surgery. A cannula should be sited in a vein in the back of the hand or forearm to avoid the structures in the antecubital fossa or risk of intra-arterial injection of the brachial artery. Sterility should be maintained and local anaesthesia used if a large cannula is required for infusion of fluids. Prior to induction, the patient should breathe 100% oxygen with a tight-fitting mask for 3 min or, alternatively, be asked to take four deep breaths to vital capacity.



Maintenance of anaesthesia

Several options are available to maintain anaesthesia. Inhalational agents, intravenous anaesthetic agents or intravenous opioids can be used, either alone or in combination. Muscle relaxants are commonly used to facilitate tracheal intubation and subsequent ventilation of the lungs. Regional anaesthesia can be used to supplement any of these techniques.

Inhalational anaesthesia with spontaneous ventilation is appropriate for superficial operations where profound muscle relaxation is not required. The patient is allowed to breathe spontaneously and a volatile anaesthetic agent such as halothane, enflurane, isoflurane or sevoflurane is used with carrier gases nitrous oxide and oxygen. Most anaesthetic machines will not deliver less than 30% oxygen and have an interlocking device to ensure this. These volatile agents are delivered from vaporisers, which are specially calibrated containers that will deliver a constant percentage of agent irrespective of the gas flow through them, temperature or pressure. Analgesiaas determined by the patient's response might also be required.

Minimal alveolar concentration (MAC) is the minimal alveolar concentration of an inhaled anaesthetic agent that prevents reflex movement in response to surgical incision in 50% of subjects. This value is commonly used as an index of relative potency and may be affected by the patient's age and concomitant use of other drugs.



Signs of anaesthesia

The signs and stages of anaesthesia were originally described by Guedel in patients premedicated with morphine and atropine and breathing ether and air. With newer agents the stages are less clearly differentiated but they remain a useful general guide.



Stage 1 - analgesia

This can be attained using nitrous oxide 50% in oxygen and provides 'relative analgesia'.



Stage 2 - excitement

This is seen with inhalational induction but with intravenous induction it is commonly bypassed. The eyelash reflex is often lost at this stage. Breathing is irregular and laryngeal and pharyngeal reflexes are still active. Patients might hold their breath and any instrumentation of the airway can produce laryngeal spasm.



Stage 3 - surgical anaesthesia

The patient develops rhythmic regular breathing and as they descend through the four plains from light to deep, respiratory reflexes are progressively abolished. Patients can no longer protect their own airway. The pupils become central and are classically large, although, with the newer agents, they are often much smaller than with the older agents.



Stage 4 - stage of impending respiratory and circulatory failure

In this stage, anaesthesia is too deep and brainstem reflexes are depressed by high anaesthetic concentrations. Anaesthetic agents should be withdrawn and oxygen administered.



Maintenance of the airway

Maintenance of the airway and of oxygenation is the cornerstone of safe anaesthesia. Inhalational agents can be administered with a face mask, a laryngeal mask airway (LMA) or an endotracheal tube.



Face mask

Face masks come in various shapes and sizes and should be chosen for the individual patient to provide an adequate seal. Nasal masks are used during dental anaesthesia. The mask is held against the patient's face and the mandible is held forwards because pressure on the submental soft tissues can exacerbate airway obstruction by pushing the tongue backwards. The reservoir bag on the anaesthetic circuit should be seen tobe moving in and out with the respiratory movement ofthe patient. There should be no indrawing of thesuprasternal and supraclavicular areas - this indicatesobstruction. Breathing should be quiet; noisy ventilation or stridor provides further evidence of obstruction. It should be always remembered that total obstruction is silent as there is no movement of air. An oropharyngealor Guedel airway can be used to assist in maintenance of the airway.



Laryngeal mask airway

Laryngeal mask airways (LMAs) can be considered a halfway house between a face mask and an endotracheal tube. They avoid the need for tracheal intubation during spontaneous ventilation while at the same time providing a clear airway without the need to hold on a mask. They can also occasionally be used to assist with difficult intubation.

They should not be used in patients who are at risk of regurgitation of gastric contents because an endotracheal tube is required to provide secure protection and there will be occasions when surgical access could be obstructed by the bulk of the cuff on the LMA.

Endotracheal intubation

An endotracheal tube provides the most secure airway short of tracheostomy. It is passed via the mouth or nose and between the vocal cords into the larynx. The cuff on the tube lies below the cords and when it is inflated with air protects the respiratory tract from blood, secretions or inhalation of gastric contents. Likewise, the cuff prevents leakage of air travelling upwards during controlled ventilation. The tube also allows access for suction of the respiratory tract. Cuffed tubes are used in adults, whereas uncuffed tubes provide an acceptable seal in children.

There are a multitude of designs for laryngoscopes. The McGill laryngoscope is favoured for children because their epiglottis is floppy. It has a straight blade and is designed to lift the epiglottis anteriorly, exposing the larynx. The Mclntosh laryngoscope, which has a curved blade, is designed so the tip lies anterior to the epiglottis in the vallecula and pulls the epiglottis anteriorly to expose the vocal cords.

Extubation

Patients can be extubated supine if there is no risk of regurgitation but it is often safer to remove the endotracheal tube with the patient in the lateral recovery position. Prior to extubation the patient is given 100% oxygen and suction is performed to remove secretions from the endotracheal tube and from the mouth. After extubation the patient's clear airway, ability to breath, cough and clear secretions are carefully assessed while oxygen is continued by face mask. Laryngeal spasm occurs if the vocal cords come together as a result of irritation. A 'crowing' sound is heard and the patient will show signs of airway obstruction. This is treated by clearing secretions and applying positive airway pressure with oxygen. Occasionally, reintubation might be required.



Anaesthetic gases

Nitrous oxide

Nitrous oxide delivered via a pipeline or from bluecylinders is used with oxygen as a carrier gas for thesepotent volatile agents. As the MAC value for nitrousoxide is over 100%, it cannot be used withoxygen as ananaesthetic agent without the addition of a potent volatileagent, but it has proved safe over a long period in use. Itis important that a high inspired oxygen concentration isgiven when nitrous oxide administration is discontinued.Nitrous oxide has also been incriminated in alteringvitamin B12 synthesis by inhibiting the enzyme methionine synthetase, and excessive occupational exposure canresult in myeloneuropathy. This condition is similar tosubacute combined degeneration of the spinal cord andhas been reported in individuals addicted to nitrousoxide.



Oxygen

Although oxygen is life-giving, there are some dangers associated with its use. It is flammable, it can cause a rise in the partial pressure of CO2 (Paco2) in patients with chronic obstructive airways disease and, in high concentrations, it can lead to loss of pulmonary surfactant. On occasion, toxicity of the central nervous system can be seen. Hyperbaric pressures result in convulsions. Retrolental fibroplasia is retinal damage with new vessel formation seen in infants exposed to high concentrations.



Intravenous agents

Induction of anaesthesia with intravenous agents is usually more rapid and smoother than with inhalation agents. The ideal agent should have a rapid onset and recovery time with little hangover effect. It should be free of side-effects such as nausea, vomiting, cardiovascular and respiratory depression or toxicity to any major organs and it should also, if possible, be analgesic in low doses.

After intravenous administration, plasma concentrations rise rapidly and the drugs diffuse across the blood-brain barrier into the brain producing their effect. Reduced plasma concentrations and drug effects occur predominantly as they are distributed to other tissues. Metabolism occurs mostly in the liver but contributes relatively little to the recovery of consciousness.

Thiopentone sodium

Thiopentone sodium is one of a group of barbiturate agents and has proved safe in practice for over 50 years. It is important as a hypnotic but has an antianalgesiceffect that can result in a reduction of pain threshold and restlessness in the postoperative period. On induction, consciousness is rapidly lost and in the absence of other agents is not regained for 5 to 10 min. As it does not depress airway reflexes to the same extent as other agents, laryngeal spasm can be precipitated by stimulation of the airway. There is usually a moderate tachycardia and reduction in blood pressure. It is a relatively long-acting drug and a hangover effect is common. This length of action makes it unsuitable as a drug for use by infusion in total intravenous anaesthesia (TIVA). It is an anticonvulsant and can be used in the treatment of status epilepticus but must never be given to patients with porphyria, who might show severe cardiovascular collapse or neurological sequelae.



Propofol

Propofol has become a very popular agent. It has rapid recovery characteristics and gives rise to a lower instance of postoperative nausea and vomiting than most other agents. It is formulated as a white aqueous emulsion, which contains soya bean oil. Loss of consciousness is rapid but blood pressure tends to decrease to a greater degree than with other agents. Respiratory reflexes are suppressed quite markedly and there is a low incidence of coughing and laryngospasm. Many regard propofol as the agent of choice where a laryngeal mask airway is to be inserted. Recovery is rapid, with little hangover effect.The drug is redistributed rapidly and probably metabolized not in the liver but in extrahepatic sites. The eliminationremains constant, even after infusions lasting for severaldays, and it is thus the most suitable current agent for total intravenous anaesthesia (TIVA). It is also used by infusion for sedation in intensive care and is increasingly used as a form of relative analgesia and sedation during surgical procedures. Computer-operated infusion pumps are available, which aim to deliver a target plasma concentration based on patient's weight and age.



Ketamine hydrochloride

This differs from the other agents in producing a dissociative state rather than generalised depression of the central nervous system. Blood pressure might, in fact, increase with this agent and there is little respiratory depression. It is used in high-risk shocked patients and has, therefore, a place in anaesthesia and analgesia in times of war and at the scene of accidents. It can be given intramuscularly in low doses to produce analgesia. It has also been used in less developed countries, where equipment and staff are not readily available. Its use, however, is limited by the occurrence of restlessness, disorientation and often unpleasant nightmares or hallucinations, which can recur for up to 24 h.



Drugs used to supplement anaesthesia

Analgesics

Morphine

Morphine, produced from the poppy Papaversomniferum,and codeine are naturally occurring opium alkaloids. Morphine is the gold standard of analgesics affecting both the pain threshold and the psychological components of pain. Although it has little effect on the cardiovascular system, depression of ventilation is common; the cough reflex is also depressed. However, administration can be limited by distressing nausea and vomiting and it greatly reduces gut motility.



Pethidine

Pethidine is a synthetic opioid that, as it tends to relax the tone of smooth muscle, can be useful in renal colic; it can also be used to control postoperative shivering. Pethidine, however, should not be given to patients taking monoamine oxidase inhibitors (MAOI).



Buprenorphine

This can be useful on occasions as it can be administered sublingually. However, nausea and vomiting may be troublesome and subsequent use of other opioids, for example, morphine may be compromised as the drugs antagonise at opioid receptors.



Other opioids

Progressively shorter-acting synthetic agents are fentanyl, alfentanil and remifentanil. Remifentanil is sufficientlyshort acting to be useful administered by infusion.



Opioid antagonists

Naloxone is the drug of choice for reversing opioidinducedventilatory depression. It should be titrated slowly because convulsions can occur occasionally and it reverses not only respiratory depression but also theanalgesia.



Other analgesics

Non-steroidal anti-inflammatory drugs such as diclofenac, ketorolac and indomethacin can be used as analgesia in a balanced anaesthetic technique. The new alpha2 adrenergic agonist dexmedetomidine is currently proving promising because it results in profound analgesia with less sedation.



Benzodiazepines

Benzodiazepines such as diazepam and midazolam can also be used as anaesthetic agents, but they have a longer duration of action than other agents. These drugs can be reversed with flumazenil, which is a competitive antagonist and again should be given in small titrated increments.



Neuromuscular blockade

Muscle relaxation is the third of the triad of anaesthesiathat includes narcosis and analgesia. Neuromuscular blocking agents are classified into depolarising (or noncompetitive) and non-depolarising (or competitive) agents.



Depolarising agents

The only depolarisingagent now available in clinical practice is suxamethonium. After administration it results in an initial depolarisation of muscle cells. Muscular contractions can be seen and are known as fasciculation. Repolarisation does not occur and the muscle becomes flaccid. It produces a profound neuromuscular block within a minute and is useful to achieve rapid tracheal intubation in a patient who may have a full stomach. Recovery usually begins to occur within 3 min. It is metabolised by the enzyme cholinesterase and recovery can be delayed if this enzyme is either structurally abnormal or reduced in quantity. This is usually genetically determined and might require the patient to be ventilated until muscle function returns. Suxamethoniumcan give rise to muscle pains after operation. A rise in the plasma potassium can occur, which can be dangerous particularly in patients with burns or in those with neuromuscular disease.



Non-depolarising neuromuscular blocking agents

These compete with the neurotransmitter acetylcholine at the postsynaptic junction to prevent the threshold for an action potential being reached, and so the muscle does not contract. Tubocurarine(curare) was used for centuries by native South Americans as an arrow poison and was the first agent to be used in humans. It has, however, been superseded. Atracurium degrades spontaneously in plasma and is therefore very safe for patients with liver or renal dysfunction. Such drugs have a longer duration of action of around 30 min. Vercuronium is also used and, because it releases less histamine, many consider it to be the drug of choice in asthmatics. Pancuronium, and more recently rocuronium, are aminosteroids. The advantage of rocuronium is its very rapid onset, which provides good intubating conditions within 90 s. Neuromuscular blockade can be monitored with a nerve stimulator intraoperatively and at the end of operation this block can be reversed by the administration of the anticholinesterase neostigmine in combination with either atropine or glycopyrronium. The addition of atropine or glycopurronium reduces respiratory secretions and prevents bradycardia.



Postoperative care

The patient must be supervised and monitored closely at all times and should not be discharged from the recovery ward to the surgical ward until they are fully awake and maintaining their own airway, ventilation is adequate, the cardiovascular system is stable and they are not bleeding excessively.



Central nervous system - conscious level

The patient's airway must be carefully maintained until they are awake. If the patient is not awake in a reasonable time then other factors should be considered. Hypo- or hyperlgycaemia may occur particularly in diabetics and intracranial pathology may occur. The following, most particularly, should be excluded: hypoxaemia, hypercapnoea, hypotension and hypothermia.

Confusion and agitation may occur at this time particularly in the elderly. This may be associated with anticholinergic drugs such as atropine or hyoscine but pain may also be a contributory factor. Bladder distension may be covert. If neuromuscular blockade has not been adequately reversed the patient may appear agitated and distressed with uncoordinated movements.

Oxygen

Particular care should be given to the patient's requirements for oxygen which should be monitored by oximetry. All patients should be given oxygen postoperatively.



Intravenous fluids

They may also require fluids as a result of either intraoperative blood loss or preoperative fluid depletion.



Analgesia

Good pain control starting in the intraoperative period should be established in the recovery ward before return to the ward. This may be achieved with opioids which if the patient is sufficiently awake can be administered by a patient-controlled infusion device. Non-steroidal anti-inflammatory drugs and local and regional techniques may also be very valuable.

The recovery ward should have the staff, equipment and monitoring to deal with the full range of complications. Problems are as liable to arise there as in the anaesthetic room or operating theatre.

Patients should be closely watched for a number ofsurgical complications which may include haemorrhageand blockage of drains or catheters. This high intensity environment should allow the patient to return to the appropriate level of ongoing care in the optimum condition.



Literature.

Basic:

1.Lectures which are read on the department of pediatric dentistry.

2. Pinkham J.R. Pediatric dentistry. – 2nded.- W.B. Sounders Company. – 1994.- 647 p.

3. Pediatric dentistry /Ed. R.R.Welbury.- Oxford, 1997 – 584p.



Additional:

  1. Колесов А.А “ Стоматологія дитячого віку “ , 1978 ,ст. 44-63.

  2. Дунаевський В.А. “Хірургічна стоматологія “ , 1979 ,ст. 111-118.

  3. Бернадский Ю.И. «Основы хирургической стоматологии», К., 1998

  4. Евдокимова А.И. «Руководство по стом. детского возраста», 1976


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