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Local Anesthesia problems andhints
Iyad M.Abou RabiiDDS. OMS. MSc. PhD
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Contents
Failure of Local Anesthesia
L A Local Hazards
LA General Hazards
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LA General Hazards
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LA Toxic effects
Adverse effects are usually caused by high plasma concentrations of a
local anesthetic drug that result from
inadvertent intravascular injection,
excessive dose or rate of injection,
delayed drug clearance,
or administration into vascular tissue.
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LA Toxic effects
Possible adverse effects include the following:
CNS: High plasma concentration initially produces CNS stimulation
(including seizures),
followed by CNS depression (including respiratory arrest). The CNS
stimulatory effect may be absent in some patients, particularly whenamides are administered.
Solutions that contain epinephrine may add to the CNS stimulatory effect.
Cardiovascular: High plasma levels typically depress the heart and may
result in bradycardia, arrhythmias, hypotension, cardiovascular collapse,
and cardiac arrest.
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Local Anesthesia Allergic shock
Esters are highly allergenic, their use should be avoided and restricted tospecial cases after allergy test.
There has never been a true, documented allergic reaction to an amine
anesthetic.
a patient may in fact be allergic only to the bisulfite preservative used tostabilize the vasoconstrictor.
If the allergic reaction was not too serious, it may be worth trying again
with eithermepivicaine or prilocaine without vasoconstrictor.
Anesthetic manufactures do not use preservatives in carpules that do not
also contain vasoconstrictor.
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Signs and symptoms of anesthetics allergic reaction
The signs and symptoms of allergic reaction include:
generalized body rash or skin redness
itching, urticaria (hives)
broncospasm (difficulty breathing)
swelling of the throat
asthma
abdominal cramping
irregular heartbeat
hypotension (low blood pressure) swelling of the face and lips (angioneurotic edema)
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Anaphylactic shock
Fortunately, the majority of allergic reactions to local anesthetics are fairlymild
In a very serious anaphylactic reaction, the patient may experience
serious difficulty breathing due to closing down of the bronchioles in the
lungs or swelling in the throat area due to urticaria as well as seriously
low blood pressure leading to anaphylactic shock. This set of events, leftuntreated can lead to death.
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Testing for anesthetic allergy using skin test
T.R.U.E. Test
This is a patch test that applies 23 allergens to the skin contained in 12
polyester patches. One of the patches contains a mixture of several
anesthetics and is used to test for allergy to local anesthetics in general.
The mixture used includes two ester based anesthetics and one amine
based anesthetic. This mixture of anesthetics is called the "Caine Mix"
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Management of anaphylactic shock : 1
Position the patient on his or her back with the feet elevated.
Maintain an airway
If the patient is not breathing on his own, use rescue breathing like you
learned in CPR class.
Check the carotid artery for heartbeat and use chest compressions ifnecessary.
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Management of anaphylactic shock : 2
The two drugs that you must have on hand to stabilize a patient inanaphylactic shock are as follows:
Epinephrine (adrenalin) 1:1000 subcutaneous injection. It opens the
bronchioles allowing free breathing, increases the blood pressure counteracting
shock and evens out and intensifies the heart beat. Its effects are drastic, but
short lived. The standard dose is 1 mg given in three doses five minutesapart.
Benedryl (diphenhydramine) 25-50 mgm injectable. This is an antihistamine
and can also be taken in pill form an hourbefore the procedure to help
prevent serious allergic reaction before it begins. Injectable diphenhydrimine
which can be administered either subcutaneously, or in the buccal fold if the
dentist is more comfortable with that route.
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Management of anaphylactic shock : 3
The following drugs are of little use to the dentist during the initial stagesof the emergency since they are generally used by EMS personnel
Aminophylline This drug opens blocked breathing passages.
Solu-cortef IV injection. This drug is a corticosteroid and reduces the
generalized allergic inflammatory reactions on a longer term basis. It will not
act rapidly enough to reverse anaphylaxis immediately, but is more of a longterm remedy.
Wyamine injection. This drug is used to counteract hypotension (low blood
pressure and shock) on a prolonged basis.
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LA Local Hazards
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Pain on injection
This is to a certain degree inevitable, but can be by patient relaxation;application of topical LA; stretching the mucosa; and slow, skilful,
accurate injection of slightly warmed solution in reasonable quantities.
Causes of pain include:
Touching the nerve when giving blocks, resulting in electric shock
sensation and followed by rapid analgesia (it is extremely rare for anypermanent damage to occur).
Injection of contaminated solutions (particularly by copper ions from a pre-
loaded cartridge). Avoid by loading the cartridge immediately prior to use.
Subperiosteal, and intraligamentary injections are painful andunnecessary, avoid.
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Pain on injection (Prevention and Management)
This is to a certain degree inevitable, but can be by
patient relaxation;
application of topical LA;
stretching the mucosa;
and slow, skilful, accurate injection of slightly warmed solution in reasonablequantities.
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Paresthesia
If the needle passes through a nerve in the area of injection, it may damagethe nerve and cause paresthesia. The injury is usually not long term or
permanent.
Make a note in the chart if the patient reports a shooting feeling during the
injection that would indicate needle contact with the nerve.
A local anesthetic that has been contaminated by alcohol or a sterilizing
solution may cause tissue irritation and edema, which will in turn constrict
the nerve and lead to paresthesia.
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Paresthesia (Prevention and Management)
Proper injection protocol and care of the dental cartridges will reduce theincidence of paresthesia, but it can still occur.
If the patient calls reporting paresthesia, explain to them that it is not an
uncommon result of an injection and make an appointment for
examination.
Make a note of the conversation in the patient's chart.
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Paresthesia (Prevention and Management)
The condition may resolve itself within 2 months without treatment.Examine the patient and schedule them for reexamination every 2 months
until sensation returns.
If the paresthesia continues after one year, refer the patient to a neurologist
or oral surgeon for a consultation.
If further dental treatment is required in the area, use an alternate local
anesthetic technique to avoid further trauma to the nerve.
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Hematoma
The needle can nick vessels as it passes through highly vascular tissues.A nicked artery will usually result in a rapid hematoma, while a nicked
vein may or may not result in a hematoma.
Hematomas most often occur during a posterior superior alveolar or
inferior alveolar nerve blocks.
Use a short needle for the PSA and be conscious of depth of penetration
for these injections.
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Hematoma (Prevention and Management)
Use a short needle for the PSA and be conscious of depth of penetrationfor these injections.
If the hematoma develops during an inferior alveolar nerve block, apply
pressure to the medial aspect of the mandibular ramus. The
manifestations will usually be intraoral.
If the hematoma develops during an infraorbital nerve block, apply
pressure to the skin directly over the infraorbital foramen. The
discoloration will be below the lower eyelid.
If the hematoma develops during a mental or incisive nerve block apply
pressure over the mental foramen. The skin will discolor over the mentalforamen and swelling will occur in the mucobuccal fold.
If the hematoma occurs during a posterior superior
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Hematoma (Prevention and Management)
If the hematoma occurs during a posterior superior alveolar nerve block,the blood will diffuse into the infratemporal fossa, and swelling will appear
on the side of the face just after the injection is completed. The swelling
occurs after a significant amount of blood has diffused, so direct pressure
is often useless. Apply external ice.
The hematoma will disperse within 7 to 14 days with or without treatment.Avoid dental therapy in the area until the tissue is healed.
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Trismus
Trismus is a motor disturbance of the trigeminal nerve and results in aspasm of the masticatory muscles causing difficulty in opening the mouth.
Trismus can be caused by
trauma to muscles
or blood vessels in the infratemporal fossa, injection of alcohol or sterilizing solution contaminated local anesthetic
hemorrhage,
large volumes of anesthetic solution deposited in one area,
or infection.
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Trismus (prevention)
Use of
disposable needles,
antiseptic cleansing of the injection site,
aseptic technique,
and atraumatic injection technique
will help prevent trismus.
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Trismus (Management)
Recommended treatment for trismus includes heat therapy with moist hottowels 20 minutes every hour, analgesics, and muscle relaxants if
necessary.
The patient should be instructed to exercise the area by opening, closing,
and lateral excursions of the mandible for 5 minutes every 3 to 4 hours.
The patient can chew sugarless gum to facilitate lateral movement of the
TMJ.
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Trismus (Management)
Continue therapy until the patient has no symptoms. If the pain continuesover 48 hours, an infection may be present.
Antibiotic therapy for 7 full days is indicated. If there is no improvement
after 2 to 3 days without antibiotics or 7 to 10 days with antibiotics, refer
the patient to an oral surgeon for evaluation.
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Infection (Prevention)
Infection from a dental injection has become rare due to the use of steriledisposable needles and one-patient use cartridges.
The needle will always be contaminated when it comes in contact with the
patient's mucosa.
Proper tissue preparation and sterile technique will virtually eliminateinfection at the injection site.
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Infection (Management)
The patient reports post injection pain and dysfunction one or more daysfollowing treatment,
manage as with trismus. If the symptoms do not resolve within three days,
prescribe a seven day course of antibiotic therapy. (Usually 500 mg.
penicillin V immediately then 250 mg. four times a day or erythromycin if
the patient is allergic to penicillin.)
Record the incident and treatment in the patient's chart.
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Broken Needles
The most common cause of needle breakage is sudden unexpectedmovement of the patient.
Smaller gauge needles (size 30) are more likely to break than larger ones
(size 25).
Some practitioners habitually bend the needle and the metal is weakenedin this area.
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Broken Needles (Prevention)
The best way to avoid needle breakage is to routinely use a 25-gaugeneedle for any injection where there is a significant penetration of tissue.
The hub is the weakest part of a needle, so unless the injection technique
specifically requires it, the needle should not be inserted all the way to the
hub. A longer needle should be used.
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Broken Needles (Management)
When a needle breaks, remain calm.
Instruct the patient to keep their mouth open, and if at all possible, place a
biteblock. If an end of the needle is visible, retrieve it with a hemostat or
cotton pliers.
If it is not visible, do not try to retrieve it at this time. Explain to the patientwhat has happened.
Make a note in the patient's chart about the incident.
Send the patient to an oral surgeon for consultation.
They may surgically remove the fragment or if the procedure will cause
too much damage they may leave it where it is.
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Other problems with LA administration
Lacerated artery May be followed by an area of ischaemia in the regionsupplied, or painful haematoma. Rare.
Lacerated vein Followed by a haematoma which resolves fairly quickly.
Facial palsy Can be caused by incorrect distal placement of the needle
tip, allowing LA to permeate the parotid gland. The palsy lasts for the
duration of the LA.
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Failure of Local Anesthesia
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Failure of Anesthesia
Pathological causes
Psychological causes
Anatomical causes
Operator dependent
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Failure of anesthesia
Psychological causes of failure
Pathological causes of failure of anesthesia
Factors precluding access
Inflammation
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Failure of anesthesia
Anatomical causes of failure of anesthesia
Soft-tissue analgesia is more easily obtained, needing a lower degree of
penetration of solution into nerve bundles, than does analgesia from pulpal
stimulation.
A numb lip does not indicate pulpal anaesthesia.
Accessory nerve supply
Barriers to anaesthetic diffusion
Dense compact bone can prevent a properly given infiltration from working.
Counter by using intraligamentary or regional LA.
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Accessory nerve supplies
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Failure of anesthesia
Operator dependent causes of failure of Anesthesia Choice of LA
Poor technique
inadequate volume of LA.
Injection into a muscle (will result in trismus which resolves spontaneously). Injection into an infected area (which should not be done anyway as this risks
spreading the infection).
Intravascular injection; clearly of no analgesic benefit. Small amounts of
intravascular LA cause few problems.
M f f il f A h i
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Management of failure of Anesthesia
A technique suggested for patients who have experienced localanesthetic failure in the mandible is
F il M t M dibl
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Failure Management : Mandible
M t f f il f A th i
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Management of failure of Anesthesia
A technique suggested for patients who have experienced localanesthetic failure in the maxilla is
F il t M ill
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Failure management : Maxilla
I t t l i t
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Important general points
Thick nerve trunks require more time for penetration of solution and morevolume of LA.
In nerve trunks autonomic functions are blocked first, then sensitivity to
temperature, followed by pain, touch, pressure, and motor function.
Soft tissue anesthesia is reached before the levels needed for pulpal
anesthesia, which takes several minutes and will wear off first (usually
within an hour of a standard lidocaine/adrenaline LA).
Disinfection of mucosa prior to LA is not required in reality; however,
sterile disposable needles are absolutely mandatory due to risks of cross-
infection.
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