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A’amer Khaled Local A – Sheet #89\11\2014

Lecture outline:

1- Basic injection technique : Chapter 11 (P.159)2- Anatomical Considerations : Chapter 12 (P.171)

PART ONE:

Basic injection technique

Local anesthetics should be administered in an atraumatic way and easily achieved.

The first and initial step is to prepare the syringe system and this can be achieved by using the appropriate syringe and the temperature of local anesthetic carpool

STEP 1: Use a sterilized and appropriate sharp needle:“Appropriate” means small diameter and larger gauge (25 to 30 gauge), so the smaller the gauge means wider diameter of needle and this will produce more pain because the exposed tissue will be more.

Note: Studies have demonstrated that patients cannot differentiate among 25-, 27-, and 30-gaugeNeedles inserted into mucous membranes, even without the benefit of topical anesthesia.3 Twenty-three-gauge and larger needles are associated with increased pain on initial insertion.

STEP 2: Check the flow of local anesthetic solution. : A few drops of local anesthetic should be expelled from the cartridge.

STEP 3: Determine whether or not to warm the anesthetic cartridge or syringe. : syringe system including the needle, metal part of the syringe, and carpool has not to be hot or even too cold in order not to disturb the patient during the initial contact with his skin, you can warm it up by holding it in your arm until reaching the room temp. Preferably without the use of any mechanical devices to achieve these temperatures. Holding the loaded metal syringe in the palm of one’s hand for half a minute before injection warms the metal. Plastic syringes do not pose this problem.

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STEP 4: Position the Patient. The ideal position of the patient before and during the administration of local anesthetic injection or even any stressful procedure should be the supine position.Supine position: head and heart parallel to the floor with the feet elevated slightly .(كل ما رفعتهم كل ما كان الوضع أفضل)

This position will make the blood returned to the heart easily and this is facilitated by the effect of gravity, so the heart can pump the blood to brain preventing patient fainting.

Rule: the blood pressure in cerebral arteries is decreased by 2 mmHg for each inch above the level of the heart. So the supine position is the ideal one.

Note: In the presence of anxiety, blood flow is increasingly, directed toward the skeletal muscles, the increased volume of blood in skeletal muscles remains there, decreasing venous return to the heart and decreasing the volume of blood available to be pumped by the heart to the brain. If this situation continues, cerebral blood flow declines still further and consciousness is lost.

Now we have to prepare the site of injection and this can be achieved by some optional steps: (step 5 to 7)

STEP 5: Dry the tissue: dry the tissue in and around the site of needle penetration and to remove any gross debris.

STEP 6: Apply topical antiseptic (optional): to decreases the risk of infection by using Betadine and Merthiolate or any solution that is not containing an irritant material like alcohol-containing antiseptics can cause burning of the soft tissue

STEP 7A: Apply topical anesthetic: If you want to apply it you have to use the cotton applicator stick and it should be applied only at the site of needle penetration. There is a high concentration of local anesthetic agents in topical. So, excessive amounts of topical anesthetic producing undesirably wide areas of anesthesia in addition to increasing the risk of toxicity. For this reason you have to apply it just on the cotton applicator stick and it has to be in definite contact with the mucosa for at least 1 min.

Note: Topical anesthetics produce anesthesia of the outermost 2 or 3 mm of mucous membrane

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STEP 7B: Communicate with the patient: During the preparation of injection site you have to explain the coming procedure and you have to use words that have positive connotation like saying “I want to introduce some local anesthetic to you to make the procedure more comfortable “instead of saying “I will stick you or inject you to make the procedure painless!! “So the patient hear onlyThe word pain or inject, ignoring the rest of the statement.

STEP 8: Establish a firm hand rest:

You have to hold your syringe in a way that will provide a good control over the syringe,So the highly recommended position is the palm up with finger support.

First picture: Palm up and better control over the syringe because it is supported by the wrist.Second picture Palm up and finger support so greatest stabilization. Third picture: Palm down and poor control over the syringe

Then you have so support your hand by using the patient’s chest ( with same gender) or chin, never place your the arm that holding the syringe directly on the patient’s arm or shoulder because this can lead needle-stick injury.

STEP 9: Make the tissue taut:Even in IM injection the tissue must be stretched before insertion of the needle to decrease the exposed tissue, the stretching should not affect the visibility of the injection site.

STEP 10: Keep the syringe out of the patient’s line of sight:The assistant should pass the syringe to the administrator behind the patient’s head or across and in front of the patient but below the patient’s line of sight.

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STEP 11A: Insert the needle into the mucosa:Rule: bevel of the needle should be oriented toward bone, insert the needle gently to the depth of the bevel.

STEP 11B: Watch and communicate with the patient: During insertion of the needle, the practitioner should communicate with the patient to distract him. You have to remember that the distraction of a child is different from distraction of adult and so on. Also, you have to watch the patient’s face during insertion.

STEP 12: Inject several drops of local anesthetic solution (it’s written in the book as an optional step!!).

You have to inject several drops during the insertion to make it painless. We are still at the level of superficial mucosa!!

STEP 13: Slowly advance the needle toward the target:During that, you have also to deposit just a small amount of LA before touching the periosteum, because touching the periosteum (richly Innervated) would be painful.

Note: aspiration always must be carried out before depositing any significant volume of solution, here we deposit just a small amount of anesthetic solution.

STEP 14: Aspirate:

When you reach the target area and before you inject the majority of the L. Anesthetic solution you have aspirate to avoid the risk of intravascular injection. When the risk of intravascular injection is high you have to use small diameter needle (large gauge). So when you use it, the needle will deflect (تسحل) when there is a vessel its way. In addition, you have to stabilize and support the needle in order to decrease the risk of intravascular injection.

So the thumb ring should be pulled back gently (1 or 2 mm is needed), then if the blood return, a positive aspiration has occurred so the needle tip should be repositioned. On the other hand, if there is no return at all or an air bubble this indicates a negative aspiration so you can proceed.

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The Dr. didn’t mention the next steps at all.

STEP 15: Slowly deposit the local anesthetic solution;

Slow injection: the deposition of 1 ml of local anesthetic solution in not less than 60 seconds.Therefore a full 1.8-ml cartridge requires approximately 2 minutes. But a more realistic time span in aClinical situation is 60 seconds for a full 1.8-ml cartridge

Slow injection is vital for two reasons: 1- utmost significance is the safety factor2- prevents the solution from tearing the tissue into which it is deposited

Rapid injection results in: immediate discomfort followed by a prolonged soreness.

Note: During this step you have to communicate with the patient.

STEP 16: Slowly withdraw the syringe.

STEP 17: Observe the patient:Patients should never be left unattended after administration of a local anesthetic. Most adverse drug reactions develop either during the injection or within 5 to 10 minutes of completion of the injection.

STEP 18: Record the injection on the patient’s chart: An entry must be made of the local anesthetic drug used, solution(s) used, the needle(s) used, the injection(s) given, and the patient’s reaction vasoconstrictor used (if any), dose (in milligrams) of the

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Part two:

Anatomical Considerations:

The trigeminal nerve is the largest cranial nerve and it is composed of a small motor root and large sensory root.

Note: sensory divisions of the trigeminal nerve: 1- The ophthalmic division2- The maxillary division3- The mandibular division

The small motor root travel from the posterior cranial fossa anteriorly along with the larger sensory root but entirely separated from each other until reaching the middle cranialFossa to exit from the skull through foramen ovale along with the third division of the sensory root (separately and median to it). After leaving the skull, the motor root intermingle with the 3rd division of sensory root (the mandibular division) in the infratemporal fossa to form a trunk (2 to 3 mm course).

The trunk gives off two branches:1- nervus spinosus or meningeal branch of the mandibular nerve or middle meningeal

nerve 2- medial pterygoid nerve to middle pterigoid muscle

Note: the maxillary division also gives off a small branch called the middle meningeal nerve!!

1- The nervus spinosus: it reenters the cranium through the foramen spinosum to provide sensation to the posterior half dura mater of the middle cranial fossa and mastoid air cells. However, middle meningeal nerve of the maxillary division provide sensory innervation to the anterior half of dura mater.

2- Medial pterygoid nerve: It gives off two branches to the tensor veli palatine and tensor tympani.

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The main trunk divides into the anterior and posterior divisions.

Anterior division:The fibers is mainly motor except the buccal nerve. So it provides motor innervation to the muscles of mastication (except medial pterygoid) and sensory innervation to the mucous membrane of the cheek and buccal mucous membrane of the mandibular molars.

The buccal nerve also known as the buccinators nerve and the long buccal nerve. However, it does not supply the buccinators muscle ( it is supplied by the facial nerve) it just supply the skin , mucosa and buccal sheath around the buccinators muscle and then continue until it reach the angle of the mouth, so it does not supply the angle of the mouth and the lower lip.

When giving an ID block, if the patient have an anesthetized cheek but the lip and angle of the mouth was not anesthetized then the doctor anesthetize only the buccal nerve and the position of the needle was more superior. So you should give long buccal nerve block immediately after inferior alveolar nerve block.

???? 25:00

Posterior divisions:

It’s primarily sensory with a small motor component.

Branches of the posterior division:1- auriculotemporal nerve2- lingual nerve3- inferior alveolar nerve

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Auriculotemporal nerve: It gives a sensory innervation to the TMJ and it supply the parotid gland by sensory and secreto-motor fibers. When you eat stimulus from the inferior salivary nucleus and facial nerve will go the otic ganglion which in turn transport the stimulus to the post ganglionic fibers in the auriculotemporal nerve then stimulation of parotid gland happen.

Frey's syndrome:

In case of parotidectomy the auriculotemporal nerve fibers anastomosis to the sympathetic fibers that supply the sweat glands happen, so if the patient eat then sweating on the area of the cheek adjacent to the ear occur.

Inferior alveolar nerve:

It descends inferiorly and downward an before entering the mandibular canal it gives off the mylohyoid nerve branches, which travels on the medial surface of the ramus and along the body of the mandible to reach the mylohyoid muscle, so it provide the mylohyoid muscle and the anterior belly of the digastric muscle with motor fibers (posterior belly of digastric is innervated by the facial nerve). Also it contain some sensory fibers that supply the skin on the inferior and anterior surfaces of the mental protuberance. It also provides sensory innervation to the mandibular incisors or even to mesial root of the mandibular first molar.

So if you give an ID, lingual and long buccal block to the patient and he still feel pain, then you have to inject the mylohyoid nerve area. In this case there us an accessory innervation that come from the mylohyoid nerve branches. So the mylohyoid is a mixed nerve.

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Once the inferior alveolar nerve enters the mandibular canal, it travels anteriorly in the ramus and the body of the mandible. So it will innervate the alveolar bone, pulpal innervation through the dental plexus which innervate the mandibular posterior teeth, entering through their apices. Also the buccal periodontal tissues of the posterior teeth (molars and 2nd premolar) will be innervated by it.

Once reach the mental foramen, the inferior alveolar nerve divides into two terminal branches, the incisive nerve and the mental nerve. The incisive nerve remains within the mandibular canal and innervates the pulpal tissues of the mandibular 1st premolar and anterior teeth. Mental nerve exits the canal through them enter foramen and innervates the skin of the chin and the skin and mucous membrane of the lower lip.

Note : Inferior alveolar nerve innervates any bony structure once it enter the IA canal , buccal nerve supply the buccal soft tissue until the mental foramen then the mental nerve supply the remaining. The lingual nerve responsible for the innervation of lingual soft tissue.

Lingual nerve: Travels anterior and medial to the inferior alveolar nerve so the inferior alveolar nerve is posterior and lateral to it. So when you give an ID block the lingual nerve will be in your way to reach the inferior alveolar nerve (1cm between the two nerves). It provides sensory innervation to the anterior two thirds of the tongue (both general sensationAnd taste or gustation for that region) and it innervates mucous membranes of the floor of the mouth and the lingual gingiva of the mandible. It also gives off preganglionic parasympathetic secreto-motor fibers to the submandibular ganglion and secretomotor fibers to submandibular and sublingual glands, it provides the innervation to taste buds of the tongue (anterior 2/3) through the chorda tympani fibers.

The lingual nerve passes near the palatal cortex of the third molar, it is separated from it just by the periosteum if we make a gingival flap we are elevating the lingual nerve so we don’t make a lingual flap or lingual split technique for third molar extraction although some centers do (like Manchester) even there is a high risk of temporary paresthesia,, so we do a buccal flap to avoid lingual nerve damage.

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Maxillary nerve

It is purely sensory nerve, exit the cranium through the foramen rotundum and gives off branches in four regions:

1- cranium2- pterygopalatine fossa3- infraorbital canal4- Face.

In the cranium: before leaving the skull through foramen rotundum it gives off the middle meningeal nerve to provide sensory innervation to the dura mater (anterior half).

In the pterygopalatine fossa: gives off three branches (remember them!!):1- Zygomatic nerve: divides into the zygomaticotemporal and zygomaticofacial.2- pterygopalatine nerves3- Posteriorsuperior alveolar nerve.

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Posterior superior alveolar nerve:Provides sensory innervation to the alveoli, periodontal ligaments, and pulpal tissues of the maxillary third, second, and first molars except the mesiobuccal root of the first molar in 28% of patients.

Note:The middle superior alveolar nerve which is a branch of the maxillary nerve the infraorbital canal, present only in 28 % of the population. It provides sensory innervation to the two maxillary premolars and, and to the mesiobuccal root of the first molar (instead of PMSA!!) and the periodontal tissues, buccal soft tissue, and bone in the premolar region.

Pterygpalatine nerves:

Gives off four branches:1- The orbital branches: supply the periosteum of the orbit.2- The nasal branches 3- The palatine branches: greater palatine nerve and the lesser palatine nerve.4- The pharyngeal branch

Greater palatine nerve: come into hard palate through the greater palatine foramen supplying the palatal bone and soft tissues until the canine. However, greater palatine nerve does not supply the alveolar bone on the palatal side. Instead, the superior alveolar nerve (post, mid, ant) supply it.

Nasopalatine nerve:One of nasal branches, provide sensation to the palatal mucosa and bone in the region of the canines to central incisors.

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IMPORTANT NOTE: the Dr. stopped here and he said that we have to read about ophthalmic division, so the coming part of the sheet is copied from the last year sheet.

The Ophthalmic division of trigeminal Exits the skull through the superior orbital fissure then it divides into 3 terminal branches:

1- Lacrimal: small branch gives the lateral part of the upper eyelid and conjunctiva.2- Frontal: the largest branch which is divided into: supratrochlear closer to the mid line

supraorbital , innervates the frontal sinuses3- Nasociliary: gives off 5 branches:a) Short ciliary nerve b) Posterior ethmoidal nerve : gives innervation to the posterior ethmoidal cells and

sphenoid sinusesc) Long ciliary nerved) Infratrochlear nervee) Anterior ethmoidal nerve: gives innervations to the anterior and middle ethmoidal

cells.

If you want to do extraction for impacted 7 then you will extend the flap to the external oblique line or even you want to do BSSO (bisagittal split osteotomy) then you are very close to the buccal nerve, but to its terminal branches so if you cut these branches that will lead to localized anesthesia which is not significant by the patient. But if you do a good retraction to the mucosa this is better. like the nasopalatine nerve when it is cutted it will cause anesthesia that is not significant for the patient . but we have to try always to preserve these structures. If you insert the needle just inside the mandibular foramen the patient will feel electric shock pain followed by rapid and complete anesthesia, inconvenient for the patient but it is convenient for you so don’t worry and inject the anesthesia. Arteries and veins are surrounded by a sheath so even if you touch them by the needle it will slip but the touch itself will cause electric shock pain .

Done…

Note: I added some extra notes from the book especially in the part one.

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