Outline
Properties
of LA
Components
of LA & Types of LA
Methods
of administration
Complication
of administration
Contraindication
of LA
Side
effects & treatment
Properties
of LA :
1)Potency & Reliabiability
2) Reversibility of action
3)Safety “should not be toxic”
4)Lack of irritation
5)Rapidity of onset
6)Duration of effect
7)Adequate shelf life
8)Penetration of mucous membrane
Components
of LA
1)Local Anesthetic Agent (Main
component)
-Ester : benzocaine, cocaine (topical
only)
-Amide : Lidocaine, mepivacaine ,
Bupivacaine
-short acting :procaine,
chloroProcaine , lidocaine
-long acting : Bupivacaine, etidocaine
* Bupivacaine “in toxicity , cause cardiovascular collapse and ventricular tachycardia.
* Bupivacaine “in toxicity , cause cardiovascular collapse and ventricular tachycardia.
2)
Vasoconstrictor : ( Adrenaline , felypressin ,
noradrenaline )
- In some preparations, vasoconstrictors are not added and the anesthetic drug is used as plain solution.
* when plain anesthetic solution is used the will be a quick absorption and short duration of action. Chance of overdosage should be kept in mind.
- In some preparations, vasoconstrictors are not added and the anesthetic drug is used as plain solution.
* when plain anesthetic solution is used the will be a quick absorption and short duration of action. Chance of overdosage should be kept in mind.
Concentration of adrenaline
:
* 1:50,000
* 1:80,000
* 1:100,000
* 1:50,000
* 1:80,000
* 1:100,000
Advantages Of Vasoconstrictors:
1) Reduce the toxic effect by retarding the absorption of the constitution
2) Increase the depth & duration of Anesthesia
3) Produce bloodless field of operation for surgical procedures
1) Reduce the toxic effect by retarding the absorption of the constitution
2) Increase the depth & duration of Anesthesia
3) Produce bloodless field of operation for surgical procedures
3) Reducing agent : sodium metabisulphite
-
Vasoconstrictors used in anesthetic solution are unstable. They might get
oxidized and discoloration of the solution occurs. To prevent this, small
quantity of sodium metabisulphite is added to anesthetic solution. Sodium metabisulphite has great affinity to oxygen compared to
the vasoconstrictors and thus prevent its oxidation.
* Sulphites may result in allergic reactions
* some Anesthetic preparations Capryl hydro-cuprinotoxin is add as a preservative as this doesn’t cause any allergic reacthions.
4)
Preservative : methyl or propyl paraben * Sulphites may result in allergic reactions
* some Anesthetic preparations Capryl hydro-cuprinotoxin is add as a preservative as this doesn’t cause any allergic reacthions.
- maintain sterility of the solution
- increase it’s shelf life
* Parabens are known to cause allergic reactions
* Parabens are known to cause allergic reactions
5)
antifungal agents : Thymol
- Prevent any fungal growth
- Prevent any fungal growth
6)
Vehicle : Ringer’s solution
is used to dissolve all the above constituents and render the anesthetic solution compatible with tissue fluids .
is used to dissolve all the above constituents and render the anesthetic solution compatible with tissue fluids .
Methods
of administration
1)Infiltration
2)Topical anesthesia
3)Nerve block
Local
Complications
§Post injection Pain
§Paresthesia : most common with
lingual nerve block
§Trismus : due to truma to muscles in the infratemporal fossa (medial Pterygoid muscle).
§Truma to
nerve sheath : sensation of electric shock through out the distribution of the
nerve
§Syncope : most common dental
complication, in form of neurologic shock , also known as vasovagal attack or
fainting fit. (management?)
§Prolonged anesthesia : Due to
hemorrhage in neural sheath
§ Hematoma : common with posterior superior alveolar
block & infraorbital nerve block – rare with palatal inj. Due
to dense hard palatal tissue
§Facial paralysis : due to inj. Of
LA in or near parotid gland capsule
(high inferior alveolar NB or more posterior PSA NB)
§Post injection
infection : mostly due to infected Local Anesthetic solution or needle!
§Idiosyncracy : due
to underlying genetic cause
§Sterile abscess : in palatal tissue only
§Over dose
: mostly with amide LA. , Allergy mostly with ester LA.
* Oxygen is given with overdose to prevent acidosis.
* Oxygen is given with overdose to prevent acidosis.
Contraindication
of LA
-Cocaine C/I in Kidney disease
-Articaine C/I
in patients allergic to Sulphur containing compounds.
-Etidocaine,
bupivacaine not given to children due to long duration
-Amide LA : C/I in patient with malignant
hyperthermia
-Ester type LA : C/I in patient with
cholinesterase deficiency
-Adrenaline : C/I in hyperthyroidism
-Vasoconstrictors : absolute C/I is
thyrotoxicosis & in present of MAO-I drugs
-Fellypresin : C/I in pregnant patients
& not recommended for hemostasis
Side effects
1)
Allergy : To Ester is common due to “PABA” but rest with amide type.
If
allergy to both ester & amide then Diphenhydramine can be used as
anesthetic “1.5 – 2.0 ml or 15 – 20 mg to give 30 min. of action”
2)
Malignant Hyperthermia
3)
Toxicity if inject IV & IA local anesthetic
4)
Effect on CNS is biphasic “stimulation followed by depression”.
* CNS depression can be the first s/s rather than CNS excitement with lidocaine.
5) Effect on CVS : only depression
* CNS depression can be the first s/s rather than CNS excitement with lidocaine.
5) Effect on CVS : only depression
Treatment in case of toxicity
airway
is maintained and oxygen administered by facemask, using artificial ventilation
if apnoea
occurs.
Convulsions
should be treated with anticonvulsant drugs such as thiopentone
(150-250mg I.V.) or diazepam (10-20 mg I.V.) repeated as necessary.
Profound
hypotension and brady
-arrhythmias should be treated with intravenous atropine (0.5-1.5mg) and
colloid or crystalloid infusions as plasma expanders may be necessary.
Occasionally
adrenaline may be required for severe
hypotension or bradycardia
In
patients with ventricular fibrillation due to bupivacaine toxicity,
cardiopulmonary resuscitation should be continued for at least 60mins. Bretyllium may
facilitate cardioversion.
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