1. Local Anesthesia problems and
hints
Iyad M.Abou Rabii
DDS. OMS. MSc. PhD

2. Contents
LA General Hazards
L A Local Hazards
Failure of Local Anesthesia
Page  2

3. LA General Hazards

4. 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.
Page  4

5. 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 when
amides 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.
Page  5

6. Local Anesthesia Allergic shock
 Esters are highly allergenic, their use should be avoided and restricted to
special 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 to
stabilize the vasoconstrictor.
 If the allergic reaction was not too serious, it may be worth trying again
with either mepivicaine or prilocaine without
vasoconstrictor. Anesthetic manufactures do not use preservatives in
carpules that do not also contain vasoconstrictor.
Page  6

7. 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)
Page  7

8. Anaphylactic shock
 Fortunately, the majority of allergic reactions to local anesthetics are fairly
mild
 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, left
untreated can lead to death.
Page  8

9. 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"
Page  9

10. 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. Thanks for Dr. Yasser
 Check the carotid artery for heartbeat and use chest compressions if
necessary.
Page  10

11. Management of anaphylactic shock : 2
 The two drugs that you must have on hand to stabilize a patient in
anaphylactic 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 minutes
apart.
– Benedryl (diphenhydramine) 25-50 mgm injectable. This is an antihistamine
and can also be taken in pill form an hour before 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.
Page  11

12. Management of anaphylactic shock : 3
 The following drugs are of little use to the dentist during the initial stages
of 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 long
term remedy.
– Wyamine injection. This drug is used to counteract hypotension (low blood
pressure and shock) on a prolonged basis.
Page  12

13. LA Local Hazards

14. 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 any
permanent 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 and
unnecessary, avoid.
Page  14

15. 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 reasonable
quantities.
Page  15

16. Paresthesia
If the needle passes through a nerve in the area of injection, it may damage
the 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.
Page  16

17. Paresthesia (Prevention and Management)
Proper injection protocol and care of the dental cartridges will reduce the
incidence 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.
Page  17

18. 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.
Page  18

19. 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.
Page  19

20. Hematoma (Prevention and Management)
 Use a short needle for the PSA and be conscious of depth of penetration
for 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 mental
foramen and swelling will occur in the mucobuccal fold.
 If the hematoma occurs during a posterior superior
Page  20

21. 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.
Page  21

22. Trismus
 Trismus is a motor disturbance of the trigeminal nerve and results in a
spasm 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.
Page  22

23. Trismus (prevention)
Use of
– disposable needles,
– antiseptic cleansing of the injection site,
– aseptic technique,
– and atraumatic injection technique
will help prevent trismus.
Page  23

24. Trismus (Management)
 Recommended treatment for trismus includes heat therapy with moist hot
towels 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.
Page  24

25. Trismus (Management)
 Continue therapy until the patient has no symptoms. If the pain continues
over 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.
Page  25

26. Infection (Prevention)
 Infection from a dental injection has become rare due to the use of sterile
disposable 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 eliminate
infection at the injection site.
Page  26

27. Infection (Management)
 The patient reports post injection pain and dysfunction one or more days
following 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.
Page  27

28. Broken Needles
 The most common cause of needle breakage is sudden unexpected
movement 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 weakened
in this area.
Page  28

29. Broken Needles (Prevention)
 The best way to avoid needle breakage is to routinely use a 25-gauge
needle 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.
Page  29

30. 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 patient
what 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.
Page  30

31. Other problems with LA administration
 Lacerated artery May be followed by an area of ischaemia in the region
supplied, 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.
Page  31

32. Failure of Local Anesthesia

33. Failure of Anesthesia
Psychological causes
Pathological causes
Anatomical causes
Operator dependent
Page  33

34. Failure of anesthesia
 Psychological causes of failure
 Pathological causes of failure of anesthesia
– Factors precluding access
– Inflammation
Page  34

35. 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.
Page  35

36. Accessory nerve supplies
Page  36

37. 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.
Page  37

38. Management of failure of Anesthesia
 A technique suggested for patients who have experienced local anesthetic
failure in the mandible is
Conventional inferior alveolar and lingual block with lignocaine and adrenaline
(1.5ml), followed by long buccal nerve block with remainder of cartridge.
Repeat inferior alveolar and lingual block injection using 3% prilocaine with
0.03IU/ml felypressin
Buccal and lingual infiltrations adjacent to the tooth of interest using around 1.0
ml of lignocaine and adrenaline
Intraligamentary injection of 0.2ml lignocaine with adrenaline per root.
Page  38

39. Failure Management : Mandible
Page  39

40. Management of failure of Anesthesia
 A technique suggested for patients who have experienced local anesthetic
failure in the maxilla is
Buccal infiltration
Buccal and palatal infiltration
Nerve bloc : posterior superior, infraorbital
Intraligamentary injection of 0.2ml lignocaine with
adrenaline per root.
Page  40

41. Failure management : Maxilla
Page  41

42. Important general points
 Thick nerve trunks require more time for penetration of solution and more
volume 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.
Page  42

43. Page  43

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