This document discusses local anesthesia (LA), including its mechanism of action, factors influencing injection discomfort and techniques to reduce discomfort, testing the success of LA, causes and management of failed LA, complications of LA including local and systemic complications, and management of specific complications like needle breakage, pain/burning on injection, persistent anesthesia, and trismus. It provides anatomical and technical details related to achieving successful LA and avoiding complications.

1. LOCAL ANAESTHESIA
Lec .#7
Success and Complications of LA
Dr. Adel I. Abdelhady
BDS, MSC, (EG) Phd (EG,USA)
Oral and Maxillofacial Surgery Dept.
College of Dentistry, King Faisal University, KSA. .

2. Mechanism of Action




Ionized anesthetic binds to sodium
channel.
Sodium entry is blocked into these
channels.
Sodium channel blockade prevents
propagation of action potentials.
Lack of propagation blocks sensation, as
signal is not transmitted to brain.

3. The outline




Reducing discomfort during injection of LA
Testing the success of LA
Management of failure anaesthesia
Complications of LA
Local complications
 Systemic complications


LA and pregnancy

4. Factors influencing injection
discomfort?

The needle:
Sharp & small gauge

The syringe:
Aspirating to avoid local and systemic effects

The cartridge:
Smooth bung to avoid judder and allow steady injection

The solution:
Temperature: >15 – 37< is not detected by the patient.
pH: (LA with VC is acidic (3.2)…..Painful, LA without VC is
less acidic (6.8)……….Painless
Rate of injection: faster injection is painful.

5. Technique of reducing injection
discomfort?



Use the correct technique and equipments
Apply topical anaesthesia
Stretch the mucosa with finger

Distract the patient at the moment of the mucosa is pierced

Position the needle supraperiosteally
Direct the bevel toward the bone
Slow injection decrease pain and limit the LA to the
intended site
slow removal of the needle




6. Testing the success of LA

Testing for successful LA should be determined
before commencing any procedure by either:
 Subjective testing: by asking the patient to
describe areas of altered sensation, usually +ve
with nerve block and anterior maxillary and
mandibular injections.
 Objective testing: using probe, pulp testing or
percussion

7. Testing the success of LA




When you probe soft tissue, always consider
supplementary nerve supply
I A is usually +ve
The onset time for I A is 2-3 mn & for NB is 3-5 mn.
Pulpal LA has a longer onset time compared to soft
tissue anaesthesia

8. Causes of failure anaesthesia
•
•
Wrong technique
Anatomical variations:
•
•
•
•
•
•
•
•
Bifid or double nerve supply
Nerve anastomosis: central line
Secondary supply by a soft tissue nerve: LN, LBN & GPN
Inadequate dose
Sepsis
acidity
Injection in BV
Anxiety
reduced patient pain threshold
Patient immaturity

9. Management of failed local
anaesthesia
•
•
•
•
•
Check anatomical landmarks
Repeat injection
Consider alternate or additional technique
Consider whether anxiety may be contributory
Settle pain and inflammation and try again about
a week later

10. 
If local anaesthetic is deposited
too far medially away from the
inferior alveolar nerve, it is
blocked from travelling laterally
by the sphenomandibular
ligament and its associated
fascia. This ligament runs from
the sphenoid process to the
lingula, and attached to it is a
fascia that fans out in a sagittal
direction. Local anaesthetic
cannot cross this barrier, and it is
therefore crucial to inject lateral
to the ligament. Otherwise, the
patient will experience
incomplete anaesthesia or
maybe even no anaesthesia at
all.

11. 
Another anatomical factor to consider is the
vasculature. If the local anaesthetic is deposited into a
vessel, no anaesthesia is obtained. It is recommended to
use a wider-lumen (lower-gauge) needle to increase the
likelihood of success in obtaining a positive aspiration.
For example, a 25-gauge needle offers a much more
reliable indicator of positive aspiration than does a 30gauge needle, which offers a very poor indicator of
positive aspiration.

12. 
A fourth factor, also anatomical, is the thickness
of the nerve. The inferior alveolar nerve, at the
level of the conventional mandibular nerve
block, is thinner than the core mandibular nerve,
which is approximated in the Gow-Gates block.
This thicker nerve requires a longer onset time
for complete infiltration; the conventional
mandibular nerve block takes 3 to 4 minutes to
complete anaesthesia, compared to the 10 to 12
minutes for the Gow-Gates block.

13. 
A fifth factor to consider is the actual volume of the
local anaesthetic. Some patients require more than one
cartridge of local anaesthetic to anaesthetize the
mandible. Accessory innervation (see below under
"Skeletal and neuroanatomic variations"), thicker nerves
and larger patients may necessitate more anaesthetic.
For such patients, a practitioner may decide to give two
cartridges of local anaesthesia in slightly different
locations - for example, one in the location of the
conventional block, and one in the area of the GowGates block. The extra dose maximizes the volume and
saturates the pterygomandibular space with anaesthetic.

14. 
Another crucial skeletal anatomical variant is the width of the
internal oblique ridge. It is on this ridge that the practitioner's
finger must rest for all mandibular block procedures, including
the conventional, the Vazirani-Akinosi and the Gow-Gates. If
the patient has an exceedingly wide internal oblique ridge and the
practitioner's finger is not resting on this ridge of bone, it is very
difficult to negotiate the needle past this bony ridge to approach
the inferior alveolar nerve. This nerve is located on the medial
aspect of the ramus behind the large ridge. Palpating a wide
inferior alveolar ridge is also cause to rotate the syringe more
posteriorly, toward the contralateral molars

15. 
A final skeletal anatomical factor is the position of the
mandibular foramen. The location of this foramen can
vary both in its anterior - posterior position and its
inferior - superior position. Blocks given more
superiorly, for example, the Gow-Gates block, may in
part be more successful due to the increased chance of
being superior to this foramen. Therefore, the local
anaesthetic is not being deposited inferior to where the
nerve enters the mandible (which would result in
incomplete anaesthesia).

16. Local anaesthetic or vasoconstrictor degradation
All local anaesthetic cartridges have an expiry date on their label. This date tells the
practitioner the product's shelf life from the time of manufacturing to the time when a
certain number of the anaesthetic or vasoconstrictor molecules have degraded to a
degree that the product may be less effective. Local anaesthetic molecules are relatively
stable and degrade very slowly. As a result, the shelf life of a local anaesthetic depends
mostly on the stability of the vasoconstrictor. For this reason, sodium metabisulphite
is used as a preservative or stabilizer for the vasoconstrictor molecule. A number of
factors can lead to the premature breakdown of an anaesthetic and the vasoconstrictor
within a cartridge, including extreme temperatures, excessive light and oxygen
exposure. To maximize the shelf life of the contents inside the cartridge, the local
anaesthetic molecule should be stored at room temperature away from sunlight and
room light. Dental offices are unlikely to experience temperature extremes, but
consideration should be given to how the local anaesthetic was delivered to the office.
Local anaesthetics can easily freeze or overheat if left in a delivery truck during
seasonal extremes. These temperature variations can lead to the premature degradation
of the molecules in the cartridge

17. Manarola,

18. Management of
failure maxillary
LA

19. Management of
failure mandibular
LA

20. Contraindications of LA
A. General Contraindications:
Un-cooperative patient
 Treatment factors:

Time consideration
 Access problem

Acute infection
 Allergy: ester > amide
 Medical conditions
 Poor blood supply


21. Contraindications of LA
B. Contraindications to specific techniques:



Bleeding diatheses: avoid N B
Susceptibility to endocarditis and incomplete root
formation : avoid intraligamentary
Trismus: precludes IANB, GPN, NPN, . use Akinosi
tech

Epilepsy, cardiac pacemakers, and cerebrovascular
disease: avoid Electronic LA

22. Complications of LA

Causes:
•
•
•
•
•
Doctor factor (wrong technique)
Vasoconstrictor
LA
Needle
Patient factor

23. LOCAL ANAESTHESIA
Complications of LA
Dr. Adel I. Abdelhady
BDS, MSC, (EG) Phd (EG,USA)
Oral and Maxillofacial Surgery Dept.
College of Dentistry, King Faisal University, KSA. .

24. Complications of LA
I. Localised
II. Systemic
I. Localised complications:



Pain: during and postinjection
Failure A
Equipment failure:


Broken needle
Cartridge failure.

Neurological problems:





Prolonged altered
sensation
Unilateral facial nerve
paralysis
Visual disturbances
Aural disturbances
Extensive paralysis:
reversed flow to the brain

25. Tasks
 Methemoglobinemia

Fainting/syncope

26. Complications of LA
 Causes:
•
•
•
•
•
Doctor factor (wrong technique)
Vasoconstrictor
LA
Needle
Patient factor

27. Factors influencing injection
discomfort?

The needle:
Sharp & small gauge

The syringe:
Aspirating to avoid local and systemic effects

The cartridge:
Smooth bung to avoid judder and allow steady injection

The solution:
Temperature: >15 – 37< is not detected by the patient.
pH: (LA with VC is acidic (3.2)…..Painful, LA without VC is
less acidic (6.8)……….Painless
Rate of injection: faster injection is painful.

28. Technique of reducing injection
discomfort?



Use the correct technique and equipments
Apply topical anaesthesia
Stretch the mucosa with finger

Distract the patient at the moment of the mucosa is pierced

Position the needle supraperiosteally
Direct the bevel toward the bone
Slow injection decrease pain and limit the LA to the
intended site
slow removal of the needle




29. Causes of failure anaesthesia
•
•
Wrong technique
Anatomical variations:
•
•
•
•
•
•
•
•
Bifid or double nerve supply
Nerve anastomosis: central line
Secondary supply by a soft tissue nerve: LN, LBN &
GPN
Inadequate dose
Sepsis
acidity
Injection in BV
Anxiety
reduced patient pain threshold
Patient immaturity

30. Management of failed local
anaesthesia
•
•
•
•
•
Check anatomical landmarks
Repeat injection
Consider alternate or additional technique
Consider whether anxiety may be
contributory
Settle pain and inflammation and try again
about a week later

31. 

Another anatomical factor to consider is
the vasculature. If the local anaesthetic is
deposited into a vessel, no anaesthesia is
obtained. It is recommended to use a
wider-lumen (lower-gauge) needle to
increase the likelihood of success in
obtaining a positive aspiration.
For example, a 25-gauge needle offers a
much more reliable indicator of positive
aspiration than does a 30-gauge needle,
which offers a very poor indicator of
positive aspiration.

32. Management of
failure maxillary
LA

33. Management of
failure mandibular
LA

34. Needle Breakage
Causes

Unexpected movement

Small needle size

Bent needles

Defective needles

35. Needle Breakage
Prevention

Use large needles

Use long needles for deep
injection,>18mm

Never insert to hub

Redirect only when adequately
withdrawn

36. Rush Hour, Venice

37. Needle Breakage
Management

Remain calm

Don't explore

Have the patient keep opening wide

If the needle is out remove it

Refer to an Oral Surgeon

39. Localised complications:

Vascular problems:







Intravascular injection
Haematoma
Sloughing of oral mucosa
Self-inflicted trauma
Trismus: due to bl. & LA
Infection
Interference with wound
healing: adrenaline & dry
socket

40. Pain on Injection
Causes

Dull needles

Rapid deposit of solution

Needles with barbs
 Careless technique

41. Pain on Injection
Prevention

Careful technique

Sharp needles

Topical anesthetic

Slow injections

Room temperature solutions

42. Burning on Injection
Causes

pH of solution

Rapid injection

Contamination

Warmed solutions

43. Burning on injection


A burning sensation on injection may
occur for two reasons. First, local
anaesthetics with a vasoconstrictor are
acidic because of the preservative
required for the vasoconstrictor.
This acidity can cause the anaesthetic to
burn when it is injected into tissues. As the
cartridge ages and approaches the expiry
date, the vasoconstrictor begins to break
down, resulting in even a lower pH and
therefore even more burning on injection.

44. Burning on injection

Second, if cartridges are immersed in
sterilizing solution and the solution
seeps into the cartridge, the sterilizing
solution can cause a burning
sensation upon injection.
The likelihood of a burning sensation
can be minimized by using fresh
anaesthetics with little or no
vasoconstrictor and by injecting
slowly.

45. Persistent Anesthesia
or Paresthesia
Causes




Trauma to nerve
Neurolytic agents (alcohol, phenol)
Intraneural injection
Hematoma

46. Persistent Anesthesia
or Paresthesia
Prevention

Careful injection technique

Unavoidable at times

47. Persistent Anesthesia
or Paresthesia
Management

Patient counseling and reassurance

Documentation

Follow-up

48. Trismus
A motor disturbance of
the trigeminal nerve
precipitating or
resulting in spasm of
the muscles of
mastication
Causes

Trauma to muscles
or blood vessels

Contaminated
anesthetic solutions

Hemorrhage

Infection

Excessive
anesthetic volume

49. 

Injection of local anaesthetic directly into muscle
may cause a mild myotoxic response, which can
lead to necrosis. The symptoms of trismus, often
associated with pain, arise anywhere from 1 to 6
days following an injection.
The duration of symptoms and their severity are
both variable. With management as described
below, improvement should be noted within 2 to
3 days. If there is no improvement within this
time, the dentist should consider other possible
causes (e.g., infection) and treat accordingly.

50. Trismus
Prevention

Sharp needles

Proper care and handling of cartridges

Aseptic technique and clean injection
site

Atraumatic insertion

Minimal injections and volume

51. Trismus
Management

Examination

Conservative therapy

passive ROM therapy

analgesics

heat

muscle relaxants

52. 



Prevention :Follow basic principles of
atraumatic injection technique.
Management: Apply hot moist towels to
the site for approximately 20 minutes
every hour.
Use analgesics as required.
Advise the patient to gradually open and
close the mouth as a means of
physiotherapy.

53. Hematoma
The effusion of blood into extravascular
spaces
 This localized mass of extravasated blood
may be seen after the inadvertent piercing of
a blood vessel during the injection or when
withdrawing the needle. Blood vessels are
often pierced during intraoral injections, but
only when there is sufficient blood
extravasation is there a hematoma.

54. Hematoma

A second relatively common localized
complication is a hematoma. The vessels
most commonly associated with a
hematoma are the pterygoid plexus of
veins, the posterior superior alveolar
vessels, the inferior alveolar vessels and
the mental vessels. The patient will notice
swelling and discolouration (bruising)
lasting 7 to 14 days.

55. Prevention

Follow basic principles of atraumatic injection technique.
Use a short needle for the posterior superior alveolar
nerve block.

Management

If hematoma is visible immediately following the
injection, apply direct pressure, if possible.
Once bleeding has stopped, discharge patient with
instructions to







Apply ice intermittently to the site for the first 6 hours.
Do not apply heat for at least 6 hours.
Use analgesics as required.
Expect discolouration.
If difficulty in opening occurs, treat as with trismus,
described above

56. Prolonged anaesthesia or paraesthesia


Prolonged anaesthesia or paraesthesia in the tongue or
lip is a known risk of surgical procedures such as
extractions but may also occur following non-surgical
dentistry if local anaesthetic has been administered.
These reactions are most often found after block
techniques and much less commonly after infiltrations.
The precise causes of paraesthesia are not certain, but
they may include needle trauma or the injection of
alcohol or sterilizing solutions. Articaine and prilocaine
are more likely than other anaesthetics to be associated
with paraesthesia and have most commonly affected the
lingual nerve.

57. 

Unfortunately, there is no method certain to
prevent paraesthesia or prolonged anaesthesia.
The inferior alveolar nerve block requires the
practitioner to advance the needle near the
inferior alveolar and lingual nerves. The needle
should come near these nerves without touching
them.
An accidental touch may be perceived as an
"electric shock" sensation by the patient but will
not necessarily result in paraesthesia. Direct
contact with these nerves is not an indication of
improper technique; it is simply a risk of intraoral
injection.

58. 
The vast majority of paraesthesias are transient,
resolving within 2 months, but they can become
permanent. If the patient reports continuing
paraesthesia, the dentist should note the signs
and symptoms and maintain contact with the
patient. A change in the character of the
symptoms is encouraging in that it may indicate
healing of the nerve and resolution of
symptoms; with time, the patient may regain
normal sensation.

59. Prevention



If patient feels "electric shock", move the needle away
from the site before injecting.
Do not store cartridges of local anaesthetic in disinfecting
solutions.
Minimize the use of articaine and prilocaine for block
technique.

Management

Advise the patient that the paraesthesia or anaesthesia
is usually temporary, although, rarely, it can remain
indefinitely.
Note the signs and symptoms and follow up within 1
month.
If symptoms persist for more than 2 months, refer the
patient to an oral and maxillofacial surgeon who has
experience in this field.



60. Hematoma
Prevention

Care with needle placement

Minimize injections

Don't probe with needle

Modify technique
o
short needles
o
penetration depth

61. Infection
Causes

Needle contamination

Improper handling of armamentarium

Infection at injection site

Improper handling of tissue

62. Infection
Prevention

Disposable needles

Proper care of equipment

Aseptic technique

64. Infection
Management

Usual sign is trismus

Trismus persists (1-3 day resolution )

Antibiotics, if suspicious

65. Edema
Management

Address cause

Treat accordingly

hemorrhage

allergy

infection

66. Sloughing of Tissue
Causes

Topical anesthetic

Prolonged ischemia
Management

Observation

Documentation

67. Lip Chewing
Management

Analgesics

Antibiotics

Saline rinses

Lip lubricants

68. Facial Nerve Paralysis
Cause






Anesthesia of peripheral Facial nerve
branches
Temporal
Zygomatic
Buccal
Mandibular
Cervical

69. Facial Nerve Paralysis
Prevention

Bone contact when injecting

Avoid over penetration

Avoid arbitrary injection

70. Facial Nerve Paralysis
Management

Reassure patient

Cornea care

Documentation

Consider deferring dental care


71. Dolomite Mountains,

72. Complications of LA
Systemic adverse effects complications:





Toxicity (due to LA &  Methemoglobinemia:
VC)
(Haemoglobin contains iron in
 General NS toxicity
Ferric not Ferrous state
 Cardiovascular
leading to poor oxygenation
Toxicity
and cyanosis (Treated by IV
Drug interactions
1% methylene blue 1.5
Allergic effects
mg/kg. o-toluidine (oxidise
Iron) is a metabolic product
Fainting/syncope
of Prilocaine.
Idiosyncrasy
Articaine, Benzocaine?

73. LA Toxicity
LA Toxicity
Manifestations and management
Manifestations and management
Prevention

74. LA Toxicity


Local anaesthetic toxicity is due to systemic
absorption of an excessive amount of the drug.
Because local anaesthetics block conduction in
many tissues in addition to the peripheral nerve,
toxicity could result if sufficient amounts of the
anaesthetic reach these other tissues, such as
the heart or brain.
High blood levels of the drug may be secondary
to repeated injections or could be a result of a
single intravascular administration. This risk is
one reason why aspiration prior to every
injection is so important.

75. Calculations of Doses

Percent solutions represent grams per
100 mL Move the decimal place to the
right and this value = mg/mL (i.e. lidocaine
2% = 20 mg/mL)Most cartridges = 1.8 mL.
Therefore, one cartridge of 2% lidocaine
contains 1.8 mL x 20 mg/mL = 36 mg.

76. Manifestations and management of LA
toxicity a
Manifestations
•Mild
Management
toxicity:
• Stop administration of all local
Talkativeness, anxiety,
slurred speech, confusion anaesthetics
• Monitor vital signs
• Observe in office for 1 hr
Moderate toxicity:
• Stop administration of all local
Stuttering speech,
anaesthetics
nystagmus, tremors,
• Place in supine position
headache, dizziness,
blurred vision, drowsiness • Monitor vital signs
• Observe in office for 1 hr.

77. Manifestations and management of LA toxicity b
Manifestations
Sever toxicity:
seizure, cardiac
dysrhythmia or
arrest.
Management
Place in supine position
• If seizure, protect from nearby objects and
suction oral cavity if vomiting occurs
• Have someone summon medical
assistance
• Monitor vital signs
• Administer oxygen
• Start IV
• Administer diazepam 5-10 mg slowly or
midazolam 2-5 mg slowly
• Institute BLS if necessary
• Transport to emergency care facility
•

78. Suggested maximum dosage of local
anaesthetics
Drug
Common
brand
Concentration
Percentage
Maximum
number
of 1.8 ml
cartridges
Lidocaine
Xylocaine
2%
10
Lidocaine +
Epin.
Xylocaine with
epinephrine
2% lidocaine
1:100000 epinephrine
10
Mepivacaine
Carbocaine
3%
6
Mepivacaine +
norad.
Carbocaine with
neo-cobfrin
2% mepivacaine
1:20000 levonordefrin
8
Prilocaine
Citanest
4%
6
Bupivacain +
Adren.
Marcaine with
epinephrine
0.5% bupivacaine
1: 200 000
10
Etidocaine
Duranest with
1.5% etidocaine
15

79. General Principles
No drug exerts a single action
 No drug is non-toxic
 Potential toxicity is user dependent


80. Adverse Drug Reactions
Direct extensions of usual effects

Side effects

Overdose

Local toxic effects

81. Adverse Drug Reactions
Altered recipient

Disease process

Emotional disturbances

Genetic aberrations

Idiosyncrasy

82. Adverse Drug Reactions
Allergic reaction

Immediate - anaphylaxis

Delayed - contact dermatitis

83. Overdose
Dose related
 Systemic distribution
 Extension of pharmalogic effects
 Selective CNS or CVS depression


84. Allergic Reactions
Not dose related
 May be systemic or localized
 Unrelated to pharmacological effects
 Exaggerated immune system response


85. Idiosyncrasy Reaction
Unexplained by any known mechanism of
the drug’s action
 Neither overdose nor allergic reaction
 Unpredictable; treat symptoms


86. Predisposition - Overdose
Patient factors

Age

Weight

Sex

Medications

87. Predisposition - Overdose
Drug factors

Rate of injection

Vascularity of site

Vasoconstrictors

Concentration

Dose

Route of administration

88. Cause of Overdose Levels
Total dose is too large
 Absorption is too rapid
 Intravascular injection
 Bio-transformed too slowly
 Eliminated too slowly


89. Biotransformation
Esters are hydrolyzed in the plasma and
liver by pseudo-cholinesterase into PABA
 Amides are bio-transformed by
microsomal enzymes in liver


90. Elimination
Both esters and amides are eliminated
through kidney, some in unchanged form
eg. (lidocaine - 10%)
 Prilocaine is eliminated by lungs


91. Rapid Absorption
Vasoconstrictors should be used unless
specifically contraindicated

92. Intravascular Injection
Toxicity
Occurrence varies with type of injection:
Nerve Block
% positive
aspirate
 Inf. alveolar
11.7
 Mental/Incisive
5.7
 Post. sup. alv.
3.1
 Ant. sup. alv./ Buccal
<1

93. Mild to Moderate
Symptoms:

Restless

Nervous
disturbances

Numbness
Visual disturbances
Auditory
Metallic taste

94. Mild to Moderate
Signs (cont.):

Elevated BP
Sweating

Elevated heart rate
Nausea/vomiting

Elevated resp. rate
Disorientation

Failure to follow commands / reason

Lack of response to painful stimuli

95. Mild to Moderate
Symptoms (cont.):

Light-headed and dizzy

Drowsy and disoriented

Losing consciousness

Sensation of twitching (before actual

twitching is observed)

96. Moderate to High
Generalized tonic-clonic seizure activity

followed by

Generalized CNS depression

Depressed BP, heart rate

Depressed respiratory rate


97. Pathophysiology
Local anesthetics cross blood-brain barrier,
producing CNS depression as level rises
eg. LIDOCAINE
 Blood Level
Action Produced
 < .5 ug/ml
- no adverse CNS
effects
 0.5-4 ug/ml
- anticonvulsant
 4.5-7.5 ug/ml
- agitation, irritability
 > 7.5 ug/ml
- tonic-clonic seizures

98. Pathophysiology
Local anesthetics exert a lesser effect on
the cardiovascular system
eg. LIDOCAINE
Blood Level
Action Produced
1.8-5 ug/ml
- treat PVCs, tachycardia
5-10 ug/ml
- cardiac depression
>10 ug/ml
- severe depression,
bradycardia, vasodilatation, arrest

99. Mild Reaction -slow onset
Reassure patient
 Administer O2
 Monitor vital signs
 Consider IV anticonvulsant
 Allow recovery or get medical help prn
 Get medical consultation, esp. if possibility
of metabolic or renal dysfunction


100. Severe Reaction - slow onset
Stop all treatment
 Establish airway, give O2 (BLS)
 Administer anticonvulsant
 Summon emergency medical help
 Consider vasopressors
 Get medical consultation, esp. if possibility
of metabolic or renal dysfunction


101. Psychogenic reactions



Anxiety-induced reactions are by far the most
common adverse event associated with local
anaesthetics in dentistry.
Fainting (syncope) is the most common
manifestation of fear of the injection.
Other common reactions include
hyperventilation, nausea, vomiting and changes
in heart rate or blood pressure. Because
psychogenic reactions can mimic allergic
reactions, such as urticaria (rash), edema
(swelling) and bronchospasm (wheezing), they
are often misdiagnosed.

102. Allergy



Reports of allergic reactions to local
anaesthetics are somewhat common, but
investigation finds most of these reactions to be
of psychogenic origin.
A confirmed allergy to an amide is rare; the ester
procaine is somewhat more allergenic.
An allergy to one ester rules out using another
ester, as the allergenic component is the
breakdown product para-aminobenzoic acid
(PABA), and all esters are metabolized to this
product. Conversely, an allergy to one amide
does not rule out using another amide.
Epinephrine has not been shown to have any
allergenic potential.

103. 

Allergies to the other contents in the cartridge
are possible. Methylparabens are preservatives
used for multi-dose vials. They were universally
used until the early 1980s, and certain products
continued to include them as late as 1994.
Today, they are no longer included in dental
cartridges, as these are all single-use items. In
the past, methylparabens were often found to be
the source of allergy; thus, a patient's history of
allergy "to dental anaesthetic" may originate
from a time when methylparabens were in use.

104. Allergy - signs/symptoms
Respiratory:

Laryngeal edema
 Bronchospasm, wheezing
 Use of accessory
muscles
 distress

dyspnea

anxiety
 cyanosis or flushing

tachycardia
Dermatologic:
 Urticaria - wheals,
pruritis
 Angioedema
 Minor rash

105. Adverse Drug Reactions
Allergic reaction

Immediate - anaphylaxis

Delayed - contact dermatitis

106. Allergic Reactions
Not dose related
 May be systemic or localized
 Unrelated to pharmacological effects
 Exaggerated immune system response


107. Allergens in Local
Esters - usually to the Para-amino-benzoicacid product
Na bisulfite or metabisulfite - found in
anesthetics as perservative for
vasoconstrictors
Methylparaben - no longer used as
perservative in dental cartridges

108. Management of Allergy Pts.

If the patient gives a history of allergy to
local anesthetics - Assume that an allergy
exists
Elective procedures

Postpone until work-up is completed


109. Anaphylaxis
Typical progression *
 Skin reactions
 Smooth muscle spasms (GI, GU,
respiratory)
 Respiratory distress
 Cardiovascular collapse
 *may occur rapidly, with considerable
overlap

110. Management of Reactions







Delayed skin reaction
Benadryl - 50 mg stat & Q6H X 3-4 days
Immediate skin reaction
Epinephrine 0.3 mg IM or SC
Benadryl - 50 mg IM
Observation, medical consultation
Benadryl - 50 mg Q6H X 3-4 days

111. Management of Reactions
Bronchial constriction
 Semi-erect position, O2 - 6 L/min
 Inhaler or Epinephrine 0.3 mg IM or SC
 Benadryl - 50 mg IM
 Observation, medical consultation
 Benadryl - 50 mg Q6H X 3-4 days


112. Management of Reactions
Laryngeal edema

Place supine, O2 - 6 L/min

Epinephrine 0.3 mg IM or SC

Maintain airway

Benadryl - 50 mg IV or IM

Hydrocortisone - 100 mg IV or IM

Perform Cricothyrotomy

113. Management of Reactions
Anaphylaxis

Place supine, on flat surface

ABCs of CPR, call for medical help

Epinephrine 0.3 mg IV or IM (Q 5 mins)

O2 - 6 L/min, monitor vital signs

After clinical improvement,

Benadryl and Hydrocortisone

114. Differential Diagnosis
Pyschogenic reaction (Syncope)
 Overdose reaction
 Hypoglycemia
 Stroke (CVA)
 Acute adrenal insufficiency
 Cardiac arrest


115. LA and pregnancy

LA pass passively through the placenta, yet, rate
and degree are dependent on the LA protein
binding.

LA of choice is Lignocaine with Adrenaline
Others cause cardiovascular collapse as:
Bupivacaine and Oxytocin effect as felypressin
(VC).

116. Leaning Tower of Pisa

117. Prevention and management of medical
emergencies


Prevention
Preparation




Personal continuing education in emergency
recognition and management
Auxiliary staff education in emergency
recognition and management
Establishment and periodic testing of readily
access medical assistance.
Equipping office with supplies necessary for
emergency care.

118. Medical emergencies commonly
provoked by anxiety in dental unit
•
•
•
•
•
•
•
•
•
•
Fainting/ syncope
Angina pectoris
Myocardial infarction
Asthmatic bronchospasm
Adrenal insufficiency
(acute)
Severe hypertension
Thyroid storm
Insulin shock
Hyperventilation
Epilepsy

119. References
1.
2.
SF Malamed: Pain and anxiety control for
the conscious dental patient, 1997.
Meechan, et al., Hand book of local
anaesthesia, 1998.

123. Church of Selva Di Cadore, Colle Santa Lucia

125. Child -Toxic dose of LA

126. 






Examples of calculations of maximum local
anaesthetic doses for a 20-kg (44-lb) child
(assuming that each cartridge holds 1.8 mL)
Articaine
5 mg/kg x 20 kg = 100 mg
4% articaine = 40 mg/mL
100 mg / (40 mg/mL) = 2.5 mL
Each cartridge = 1.8 mL, therefore maximum
dose = 2.5 mL / 1.8 mL
Therefore maximum dose = 1.4 cartridges

127. 
Lidocaine

7 mg/kg x 20 kg = 140 mg
2% lidocaine = 20 mg/mL
140 mg / (20 mg/mL) = 7.0 mL
Each cartridge = 1.8 mL, therefore
maximum dose = 7.0 mL / 1.8 mL
Therefore maximum dose = 3.9 cartridges





128. Mepivacaine





6.6 mg/kg x 20 kg = 132 mg
3% mepivacaine = 30 mg/mL
132 mg / (30 mg/mL) = 4.4 mL
Each cartridge = 1.8 mL, therefore maximum
dose = 4.4 mL / 1.8 mL
Therefore maximum dose = 2.4 cartridges
Prilocaine





8 mg/kg x 20 kg = 160 mg
4% prilocaine = 40 mg/mL
160 mg / (40 mg/mL) = 4 mL
Each cartridge = 1.8 mL, therefore maximum
dose = 4 mL / 1.8 mL
Therefore maximum dose = 2.2 cartridges