This document provides a historical overview of local anesthesia techniques from the 18th century introduction of chemical compounds to modern developments. It discusses key events and discoveries such as the first use of nitrous oxide and ether for dental procedures. The era of inhalation anesthesia gave way to injection techniques using hypodermic syringes and localized drugs like cocaine and procaine. Modern techniques for mandibular nerve blocks and vasoconstrictors that prolong anesthesia are also covered. The document concludes with sections on interactions, side effects, contraindications and toxicity of local anesthetic drugs and recommended maximum dosing.

1. LA Technique
Htay Htay Yi
UDM(Mdy)

2. Historical background
 18th
century – introduction of chemical compounds
 1844 – Horace Wells , a dentist , Nitrous Oxide in
dental practice
 demonstration at the carnival
 laughing gas was given to one of the audience
no pain when crashed into fences
 allowed himself for tooth removal
 did not appreciated nitrous was unsuitable for major
surgical procedure

3.  Dr WTG Morton ,
American(1819-68)
 Ether as a 1st
inhalation
anaesthesia
 discovery by applying to
the tooth for painful
procedures
 relayed to Dr Bott ,
English
 19.12.46 – molar
extraction of niece
 2 days later Dr Robert
Liston performed historic
operation , amputation
under ether
Era of inhalation anaesthesia

4. Era of injection anaesthesia
 1855 Alexander Wood
introduced hypodermic
syringe to inject drugs such
as morphine
 only inhalation ( nitrous ,
ether and chloroform )
before that
 short duration , stormy
procedure
 Supplemented with
trichlorethylene and
halothane – additional
hazards

5.  1884 Carl Koller discovered
cocaine , applied to mucous
memebrane
 American surgeon, William
Halsted used syringe to inject
cocaine
 Side effects – convulsion and
addition
 1905 Alfred Einhorn
synthesized safer Procaine
 1943 Nils Lofgren introduced
Lignocaine

18. Gow Gate’s mandibular nerve block
 Australian dentist named
Dr. George A.E. Gow-
Gates invented in the mid
1970's
 Injection is delivered at the
neck of the condyle just
under the insertion of the
lateral pterygoid muscle.

19. Injection is just below the mesiolingual
cusp of the maxillary second molar.

20. Vazirani-Akinosi Closed Mouth Mandibular block

24. Conventional IAN & Lingual

26. The point of needle insertion should always be lateral to the pterygomandibular raphe

29. Vasoconstrictors
 Adrenaline=epinephrine
 Noradrenaline = norepinephrine
 Levonordefrin = corbadine

31.  Increase depth of anaesthesia
 Increase duration of anaesthesia
 Reduce systemic toxicity
 Hemostasis

32. Interactions with vasoconstrictors
Non-selective beta-blockers eg. propranolol (Inderal),
 Normal compensatory v/d of sk m/s by Beta2 receptors is inhibited
 Uncompensated peripheral vasoconstriction
 Significant increase blood pressure.
 Reduced vasconstrictor use is warranted.
Tricyclic antidepressants
 Examples include imipramine (Tofranil), amitriptyline (Elavil), desipramine (Norpramin),
nortriptyline (Aventyl), doxepin (Sinequan) and protriptyline (Vivactil).
 This interaction may result in increased blood pressure.
 Levonordefrin is contraindicated.
 Reduced epinephrine use is warranted.
General anaesthetic: halothane (Fluothane)
 This interaction may result in a serious cardiac dysrhythmia.
 The anaesthetist should be advised of the need for epinephrine in local anaesthetic, and
epinephrine should be limited to 1 µg/kg if thiopental is used or 2 µg/kg otherwise.
Cocaine
 This interaction may result in increased blood pressure and cardiac dysrhythmia.
 Patient must be free of cocaine use for at least 24 hours prior to using epinephrine.
Digitalis glycoside (digoxin)
 This interaction may result in arrhythmia

33. Catecholamine;
 Hypertension – raise BP , CVA
 Coronary artery - Angina pectoris , CABG (1st
3
months ) > arrhythmia
 Heart attack ( myocardia infarct ) > rpt infarct within
6 months , arrhythmia , heart failure
 Arrhythmias
 Hyperthyroidism – thyroid storm
 Diabetes mellitus – hyperglycaemia due to
glycogenolysis in liver and skeletal muscle

34. Fellypressin
 non catecholamine vasoconstrictor
 is added to prilocaine
 0.003 i.u./ml.
 Ocitocin like effect – smooth muscle
constriction – uterine contraction , coronary vessel
constriction
 relatively safe in patient taking tricyclic ,
halogenated GA

35.  Continue to monitor as required.
 Maximum dose of epinephrine ; 0.2 mgm per appointment in healthy
0.04 mgm per appointment with severe systemic disease
 Maximum dose of norepinephrine ; 0.34 mgm per appointment in
healthy 0.14 mgm per appointment with severe systemic disease
 Never use epinephrine-impregnated retraction cord.

36.  epinephrine, in concentrations
 1:50,000, 1:100,000 , 1:200,000
 1:100,000 – 1 Gm in 100,000 ml
- 0.01 mGm in 1 ml
- 0.018 mGm in 1.8 ml

37.  Adrenaline containing solutions should never be
used for infiltration around end-arteries i.e. penis,
ring block of fingers or other areas with a terminal
vascular supply as the intense vasoconstriction may
lead to severe ischaemia and necrosis

38. Local Anaesthesia
 Ester – (Amino ester)Procaine , Benzocaine ,
Tetracaine , Chloroprocaine , Propoxycaine
 Non-ester /Amide ( Amino amide)Lignocaine ,
Prilocaine , Mepivacaine , Bupiovacaine ,
Editocaine , Articaine


39.  Group I – short duration of action and low anaesthetic
potency , half life 5-10 minutes
 Procaine , Chloroprocaine
 Group II – intermediate duration of action and anaesthetic
potency, half life 30-90 minutes
 Lignocaine , Mepivacaine , Prilocaine , Articaine
 Group III – Long duration of action and high anaesthetic
potency , half life 90mins-3hrs
 Tetracaine , Bupivacaine , Etidocaine

40. Side effects of a L.A. – due to systemic actions ,
high concentration , readily cross the brain barrier
 On C.N.S. ; more resistant than C.V.S. , excitatory and / or
depression , nervousness , apprehension , agitation , nausea ,
nystagmus , logorrhoea , convulsion
 On Respiration ; respiratory depression , rsp. Arrest
 On C.V.S. ; (low - elevated B.P. , heart rate)
(high - peripheral vasodilatation , hypotension ,
conduction trouble , bradycardia ,fibrillation , arrest
 Drug interaction –beta blocker ,cimetidine – decrease the liver blood
flow
 Malignant hyperthermia – ( genetic variant ) , tacchycardia ,
tachypnea , unstable B.P. , cyanosis , fever , muscle rigidity , death

41. Contraindications to Amide type
 Allergy to amide
 Serious liver problems ; cirrhosis , elimination by the liver
cannot occur
 Malignant hyperthermia - crisis

42.  Lignocaine + Phenyltoin Na – sinoatrial arest
 Prilocaine – Methaemoglobinaemia d/t degradation products
 D toulidine or nitrosotoludine
 Articaine – Methaemoglobinaemia
 paroxysmal tachycardia , high frequency arrhythmia
 preservative sulphite – anaphylaxis , avoid in asthma
 deficit in cholinesterase
 narrow angle glaucoma
 cannot be used children under 4 yrs
 Epilepsy , Hyperthyroidism – can bring about crisis
 safe use in pregnancy has not been established
 excretion in human milk is unknown

43.  Most of the amide LA undergo biotransformation in the liver
 Prilocaine receives some metabolism in the lungs
 Articaine cannot cross the placenta barrier
 safe use in pregnancy has not been established

44. Adverse Reactions: Systemic

45. Fainting ( Vaso-vagal attack )
 spontaneous recovery is usual
 patient may complains of feeling dizzy , weak and nauseated ,
skin is pale , cold and clammy .
 head should be lowered , supine position with legs elevated ,
respiratory stimulant - smelling salt ( spirit ammonia )
 possible to complete the treatment in the same visit
 if not recover within 30-45 seconds , other causes rather than
vaso -vagal , airway maintained & Oxygen
 BLS - within 3 mins otherwise - irreversible brain damage

46.  3 months and above of pregnant mother - avoid supine position , gravid uterus
may press on the inferior venacava and aorta- supine hypotensive syndrome ,
should be laid on her side

47. Allergy
 allergy to an amide is rare
 the ester procaine is somewhat more allergenic
 the allergenic component is the breakdown product para-
aminobenzoic acid (PABA)
 an allergy to one ester rules out using another ester
 Conversely, an allergy to one amide does not rule out using
another amide
 Epinephrine has not been shown to have any allergenic
potential.

48.  In the past, methylparabens were often found to be the source
of allergy
 Methylparabens are preservatives used for multi-dose vials
 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

49.  as metabisulfite is added as an antioxidant whenever a
vasoconstrictor is added
 a vasoconstrictor can be used with patients who have an
allergy to sulfa (the antibacterial agent sulfonamide), as there
is no cross-allergenicity with sulfites
 food additives; sulfites are present (soda, vine, deshydrated
food etc...)

50. Potential allergens:
 Esters
 Amide allergy very rare
 Metabisulfite (present with epinephrine or
levonordefrin)
 Methylparabens (now removed from all cartridges)

51.  Alternative to LA - GA

52. Toxicity
 Local anaesthetic toxicity is due to systemic absorption of an
excessive amount of the drug
 toxicity could result if sufficient amounts of the anaesthetic
reach these other tissues, such as the heart or brain
 secondary to repeated injections or could be a result of a
single intravascular administration
 aspiration prior to every injection is so important.

60. Recommended Maximum Doses of Local
Anaesthetic - doses are even more critical in the paediatric patient
 Articaine 4% with epinephrine
7 mg/kg in adults(up to 500 mg) 7 cartridge
5 mg/kg in children
 Bupivacaine
0.5% with epinephrine 2 mg/kg (up to 200 mg) 10
 Lidocaine 2% with epinephrine
7 mg/kg (up to 500 mg) 13
 Mepivacaine 2% with levonordefrin
6.6 mg/kg (up to 400 mg) 11
 Mepivacaine 3% plain
6.6 mg/kg (up to 400 mg) 7
 Prilocaine 4% plain or with epinephrine
8 mg/kg (up to 500 mg) 8

61. MSD for healthy 70kg
 Lignocaine – 4.4 mg/kg , with adrenaline 7mg/kg
 Mepivaciane – 4.4 mg/kg , with levonordefrin
6.6mg/kg
 Prilocaine – 6mg/kg
 Bupivacaine – 1.3 mg/kg , with adrenaline2mg/kg
 Etidocaine – with adrenaline 6mg/kg
 Articaine - with adrenaline 7mg/kg


62. MSD ; limit for 70kgm
2% - 2 Gm in 100 ml
20 mGm in 1 ml
36 mGm in 1.8 ml
 Lidocaine 2%
4.4 mg/kg (300mg) – 8 cartridges
 Lidocaine 2% with epinephrine
7 mg/kg (up to 500 mg) – 13 catridges

63. 10% - Spray
100 mGm in 1 ml

64.  May initially present as sedation, lightheadedness, slurred
speech, mood alteration, diplopia, sensory disturbances,
disorientation, muscle twitching
 Higher blood levels may result in tremors, respiratory
depression, tonic/clonic seizures
 If severe, may result in coma, respiratory arrest,
cardiovascular collapse

65. Methemoglobinemia
 most notably with prilocaine, but may also occur with articaine
or the topical anaesthetic benzocaine
 Methemoglobinemia is induced by an excess of metabolites of
these drugs
 presents as a cyanotic appearance
 does not respond to the administration of 100% oxygen
 cyanosis becomes apparent when methemoglobin levels are
low
 additional symptoms of nausea, sedation, seizures and even
coma may result when levels are very high
 prilocaine, articaine and benzocaine are best avoided in
patients with hereditary methemoglobinemia.

66. Malignant hyperthermia
 patients with this genetic disorder
 exposed to inhalation general anaesthetics or succinylcholine
 local anaesthetics are safe to use in patients who are
susceptible to malignant hyperthermia.

67. Serum hepatitis
 HBsAg

68. Adverse Reactions: Localized

69. Failure to obtain Anaesthesia
 After the expiration date , shelf - life of two years or more
 Variation between patients - duration of action may vary
 Individual reactions - resistance to the effects of certain drug
, insufficient dose , anxiety and fear - complain of pain ,
 Faulty technique - experience and competence of operator
,inadequate amount of L A in close proximity to the nerve
 Injection into muscle - deposition of solution a distance away
from nerve .e.g. IAN - medial pterygoid
 Intravenous injection - there will be no or little anaesthesia
effect
 always aspirate ( harphoon ended plunger , spiral claw )
 Anatomical variation - deviation in position of the nerve , thick
compact bone , accessory nerve supply

70.  Anastomoses - un-anaesthetized anastomosing nerve fibres
from the contralateral side , anterior region / midline -
supplementary L A injection of either infiltration or block
 Infection - L A agents are combination of weak base and
strong acid . They hydrolysed in the tissue ( pH 7.4 ) to
liberate alkaloid base which is taken up by nerve fibre . Free
base prevents the increase in sodium permeability of the
nerve membrane . In purulent - L A is not dissociated in an
active state resulting in lowering the anaesthetic potency .
Risk of spreading infection by infiltration - use block

71. Trismus
 limited jaw opening
 due to needle insertion into one of the muscles of mastication,
leading to bleeding, spasm or both
 most commonly involved is the medial pterygoid, which can be
penetrated during an inferior alveolar nerve block
 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
 duration of symptoms and their severity are both variable


72.  Prevention
Follow basic principles of atraumatic injection technique.
 Management
Use analgesics as required.
Advise the patient to gradually open and close the mouth as a
means of physiotherapy.

73. Hematoma
 localized mass of extravasated blood
 inadvertent nicking of a blood vessel during the injection or
when withdrawing the needle
 pterygoid plexus of veins, the posterior superior alveolar
vessels, the inferior alveolar vessels and the mental vessels
 patient will notice swelling and discolouration (bruising) lasting
7 to 14 days
 hematoma forms independently of aspiration results

75. Prevention
Follow basic principles of atraumatic injection technique.
Use a short needle for the posterior superior alveolar nerve
block.
Infiltration rather than post superior 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

76. Prolonged anaesthesia or paraesthesia
 after block techniques
 much less commonly after infiltrations
 Most commonly affected the lingual nerve , IAN
 the precise causes of paraesthesia are not certain
 needle trauma or the injection of alcohol or sterilizing solutions
 Articaine and prilocaine are more likely than other LA
 an accidental touch may be perceived as an "electric shock"
sensation by the patient
 majority of paraesthesias are transient
 resolving within 2 months, but they can become permanent

77. 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

78. Do not store cartridges of local anaesthetic in disinfecting
solutions

79. Pain on injection
 pain or a burning sensation
 needle goes into a sensitive structure such as muscle or
tendon , direct trauma from the bevel of the needle causes
laceration of periosteum which is richly vascularized and rich in
nerve supply
 administered too quickly and distends the tissue rapidly
especially to mucosa tightly adapted to periosteum – palate
 Too large injection volume
 LA solutions at extremes of temperature ( cold) may also cause
discomfort
 Solutions that are more acidic / nonisotonic (i.e., those
containing a vasoconstrictor)
 Cartridges stored in a disinfecting solution such as alcohol

80. Prevention
 Inject slowly: Try to take at least 1 minute to administer 1
cartridge.
 Use volume no more than absolutely necessary
 Bevel of the needle facing towards bone , supraperiosteal
deposition of the LA solution
 Store cartridge at room temperature.
 Do not store cartridges of local anaesthetic in disinfecting
solutions.
Management
 Pain or burning on injection is usually self-limiting

82. Needle breakage
 rare
 sudden unexpected movement of the patient
 prior to the introduction of disposable needle - hypodermic
needle in chemical disinfectant sol - corroded
 smaller-diameter needles (i.e., 30 gauge), are more likely to
break than the larger diameter (i.e., 25 gauge)
 usually occurs at the hub
 needles should never be inserted completely into tissue
 repeated bending weakens the connection at the hub

83. Prevention
 Do not insert a needle into tissues to its hub , always leave a
portion exposed.
 Use long needles if a depth of more than 18 mm is required.
 Use larger-diameter needles (25 gauge is ideal) for deeper
blocks
 Do not apply excessive force on the needle once it is inserted
in tissue.
 If redirecting a needle is required, withdraw it almost
completely before doing so.
 Do not bend a needle more than once.

84. Management
 Remain calm.
 Ask the patient to remain still; keep the mouth open by not
removing your hand.
 If a portion of the needle is visible, remove it with a hemostat
or similar instrument.
 If the needle is not visible,
 Inform the patient.
 Record the events in the patient's chart.
 Refer the patient to an oral and maxillofacial surgeon.
Surgical removal should only be attempted by someone
experienced with surgery of the involved region and after
radiographs have been taken to help localize the needle.

85. Soft-tissue injury
 a patient may bite into the lip , cheek or tongue when there is
the loss of sensation
 if traumatized, swelling and pain later result
 most common in children and in patients who are mentally
challenged

86. Prevention
 For the paediatric, mentally challenged or demented patient,
warn the parent, guardian or caregiver to watch the patient
carefully for the duration of soft-tissue anaesthesia.
Management
 Use analgesics as required.
 Use rinses or applications with lukewarm dilute solutions of
salt or baking soda.
 Consider applying petroleum jelly over the lip lesion.

87. Facial nerve paralysis
 if the needle penetrates the parotid gland capsule
 the seventh cranial nerve, is contained within the parotid gland
and provides motor function through its 5 branches
 the temporalis, zygomatic, buccal, mandibular and cervical
 Needle placement into the parotid may occur if there is over-
insertion ( too far back and behind the ascending ramus )
during an inferior alveolar nerve block
 cause a transient unilateral paralysis of the muscles of the
chin, lower lip, upper lip, cheek and eye
 loss of tone in the muscles of facial expression
 Bell's palsy was commonly used to refer to all paralyses of the
facial nerve
 lasts the expected duration of anaesthesia of soft tissue

91. Facial palsy
 unilateral facial dysfunction ,
expressionless on effected side
( weakness of ipsilateral ) and muscle
pulled towards the unaffected side
 motor function test
 Temporal - asking the patient to
wrinkle the forehead ( by asking
to look upward ) , raise eyebrow
 Zygomatic - close the eyes as
strong as possible/ against
resistance
 Buccal and mandibular - blow
out the cheeks against the closed
mouth , to purse the mouth and
to whistle
 Buccal – drooping of upper lip
when showing the teeth
 Mandibular – over-riding of lower
lip when showing the teeth

92. Prevention
 Follow basic principles of atraumatic injection technique.
 Avoid over-insertion of the needle.
 For the conventional inferior alveolar nerve block, do not inject
unless bone has been contacted at the appropriate depth.
Management
 Reassure the patient of the transient nature of the paralysis.
 Advise the patient to use an eyepatch until motor function
returns (protective reflex)..
 If contact lenses are worn, they should be removed.
 Record the details in the patient's chart.

93. Superfluous anaesthesia
 Unwanted anaesthesia of other nerves may also occur
 Ocular complications following temporary paralysis of cranial
nerves II, III, IV or VI due to intravenous transport of local
anaesthetic to the cavernous sinus
 the lesser palatine nerve is commonly anaesthetized when
performing a greater palatine injection , patient will notice a
transient loss of sensation on the affected side when
swallowing
 the auriculotemporal nerve is most often anaesthetized as
part of the Gow-Gates block , patient will notice loss of
sensation over the superior half of the ear and the temple.

94. Prevention
 As always, aspirate well.
 Superfluous anaesthesia is often unavoidable.
Management
 Reassure the patient of the transient nature of the superfluous
anaesthesia.
 If there is ocular involvement, monitor and manage
symptomatically.

95. Infection
 an extremely rare complication, since sterile disposable
needles are used universally
 Injection into the active site of infection ie abscess
 Not only would the low pH prevent onset of local anaesthetic
action, but the infection could spread
 manifest initially as pain and trismus one-day post-injection
 If the symptoms persist for 3 days and continue to worsen, the
possibility of infection should be considered
 other signs of infection, such as swelling, lymphadenopathy
and fever

96. Prevention
 Use sterile disposable needles , check seal.
 Do not contaminate the needle by contacting non-sterile
surfaces outside the mouth – aseptic technique
 Needles should not be inserted within the active site of
infection
 In severely immunocompromised patients, consider a topical
antiseptic prior to injection.
Management
 Prescribe antibiotics, such as penicillin, in an appropriate
dose and duration.
 Record the details in the patient's chart and follow up to
determine progress.

97. Blanching
 at injected site is due to tissue tension , vasoconstrictor
 remote from injected site - IV inj. , interference with
autonomic nerve supply of the blood vessels

98. Bleeding at the injection point
 stop spontaneously
 L A with low v/c , without v/c

99. Visual disturbances
 infiltrating the orbit to anaesthetize the motor muscles of the
eye
 squints or double vision
 vascular spasm or accidental intra- arterial injection -
transient blindness