Local anesthesia

LOCAL ANESTHESIA

LECTURE -3-

Adverse Effect of local Anesthesia

Local anesthetic solutions are quite safe when used by competent personal.
Various adverse reactions attests to the potential toxicity , particularly when they are used in a cavalier manner.

Adverse Effect of local Anesthesia

LocalComplications

1) Prolonged Anesthesia or Paresthesia

• Most paresthesias resolve within approximately 8 weeks to 2 months without treatment.

.

2) Facial Nerve palsy

• Reassure the patient
• Contact lenses should be removed until
muscular movement returns.
• An eye patch should be applied to the
affected eye until muscle tone returns


4) Trismus
• Prescribe heat therapy, warm saline rinses, analgesics (Aspirin )
• If necessary, muscle relaxants to manage the initial phase of muscle spasm - Diazepam (approximately 10 mg bid)
• Initiate physiotherapy
• Antibiotics should be added to the treatment regimen described and continued for 7 full days
• Patients report improvement within 48 to 72 hours

5) Soft tissues injury

• Analgesics, antibiotics,
• Cotton roll placed between lips and
teeth,minimizes risk of accidental mechanical trauma to anesthetized tissues.

6) Hematoma :

• Hematoma is not always preventable. Whenever a needle is inserted into tissue, the risk of inadvertent puncturing of a blood vessel is present.
• When swelling becomes evident during or immediately after a local anesthetic injection, direct pressure should be applied to the site of bleeding.
• For most injections, the blood vessel is located between the surface of the mucous membrane and the bone; localized pressure should be applied for not less than 2 minutes. This effectively stops the bleeding.
• Ice may be applied to the region immediately on
recognition of a developing hematoma

7) Pain on injection

• Use sharp needles.
• Use topical anesthetic properly before
injection.
• Use sterile local anesthetic solutions.
• Inject local anesthetics slowly.
• Make certain that the temperature of the
solution is correct
• Buffered local anesthetics, at a pH of
approximately 7.4, have been demonstrated to be more comfortable on administration

10) Edema

If edema occurs in any area where it compromises breathing, treatment consists of the following:
• P (position): if unconscious, the patient is placed supine.
• A-B-C (airway, breathing, circulation): basic life support is administered,as needed.
• D (definitive treatment): emergency medical services


Systemic Adverse Effect of local Anesthesia
Hypersensitivity (allergy)

Esters more likely because of p-aminobenzoic acid (allergen), amides can be used as alternatives in those patients.
Methylparaben preservative present in amides is also a known allergen

Clinical Manifestations of an Allergy

Adverse Effect of local Anesthesia
Hematologic effects


The administration of large doses (more than 10 mg/kg) of prilocain during L.A

accumulation of the metabolite o-toluidine

converting hemoglobin to methemoglobin

cause methemoglobinemia

hemoglobin

Pharmacokinetic Phases of Local Anesthetics

Site of Injection
Has a great impact on the blood levels of local anesthetics. The more vascular the tissue the greater the uptake and subsequent blood concentrations.

Site of Injection

From the greatest amount of uptake to the least:
IV> tracheal> intercostal> caudal> paracervical> epidural> brachial> sciatic> subcutaneous

DISTRIBUTION

 Once absorbed in the blood stream local anesthetics are distributed through out the body to all tissues.
 Highly perfused organs such as brain, head, liver, kidney, lungs have higher blood levels of anesthetic than do less higher perfused organs


Biotransformation and Excretion of Ester Local Anesthetics
Extensive hydrolysis in the plasma by pseudocholinesterase enzymes (plasma cholinesterase or butyrylcholinesterase).

Hydrolysis is rapid and results in water soluble metabolites that are excreted in the urine.
.

Biotransformation and Excretion of Ester Local Anesthetics

Patients with pseudocholinesterase deficiency are at risk for toxicity due to the slowed metabolism and risk of accumulation.
Procaine and benzocaine are metabolized to p-aminobenzoic acid (PABA) which is associated with allergic reactions.

Amide type LA

• Bound to alpha1 acid glycoprotein
• Hydrolyzed by liver microsomal enzymes (P450)
• Longer acting & more systemic toxicity than esters
• High first pass metabolism on oral ingestion

EXCREATION

Kidneys are the primary excretory organs for both the
local anesthetic and its metabolites
A percentage of given dose of local anesthetic drug is
excreted unchanged in the urine.
Esters appear in only very small concentration as the
parent compound in urine.


Amides are present in the urine as a parent compound
in a greater percentage then are esters

Patient Alterations to Pharmacokinetics

Age: elderly and newborns. Newborns have an immature hepatic enzyme system whereas the elderly have decreased hepatic blood flow.
Disease: any disease process that impairs blood flow to the liver or the livers ability to produce enzymes.

Properties of local anesthesia

1) Not irritating to the tissue

2) No permanent alteration of nerve structure

3) Systemic toxicity should be low

4) Effective whether injected or applied topically

5) Time of onset of anesthesia should be as short as possible

6) Duration of action must be long enough to complete the procedure
but not so long as to require an extended recovery

7) Should be stable in solution and easily biotransformed


8) Should not cause allergic reactions

9) Should be sterile or capable of being sterilized by use of heat

DIFFERENCES

AMIDES
longer lasting analgesia.
Produce more intense analgesia.
Rarely cause hypersensitivity reactions-
Metabolized in liver

Very soluble in solution

ESTERS
Short duration of action
Less intense analgesia
Higher risk of hypersensitivity
metabolized by Plasma Cholinesterase.
• .
Not stable in solution
27

L.A agent(ester)

Cocaine The first local anesthetic was Cocaine which was isolated from coca leaves..
Vasoconstrictor use for nasal decongestion and ophthalmology)
It has euphoric properties (decrease dopamine inCNS)
It has sympathomimetic activity.
It is a powerful CNS stimulant.
It can induce psychic dependence with high rate of abuse.( not used as first choice)

‘
**tetracaine
-slow onset
-long duration(2-3hours)
-effective topically
-2% spray ,solution ,ointment
More potent(10times the potency and toxicity of procaine).
Not use in dentistry.


L.A agents(amide)

** lidocaine ( xylocaine , octocaine)

-1948
-rapid onset
-no cross allergy
-topical ,infiltration ,block ,spinal ,IV
-onset 2-3 min
-duration 1-1.5 hr (pulp)
3-4 hr (soft tissue)

Lidocaine

.used in dentistry
Used in the management of ventricular arrhythmias after an acute myocardial infarction.
Mepivacaine
Similar to lidocaine but less vasodilator.

Bupivicaine

Bupivicaine (Marcaine®
--Produce very long acting anesthetic effect to delay the post operative pain from the surgery for as long as possible
--0.5% solution with vasoconstrictor
--slow onset of action(high PKa).
-more potent.more cardiotoxic effect than lidocaine.


Articaine (Septocaine®)
Articaine (Septocaine®)
-- newest local anesthetic drug approved by FDA in 2000
--Same pKa and toxicity as lidocaine, but its half life is less than about ¼ of lidocaine(duration 1hour)
--Used with vasoconstrictor. -4% 1:100 000 epinephrine
--Rapid hydrolysis and reduce toxicity with slow absorption.
--The drug is widely used in most nations today in dentistry.

Eutectic = two solid substances mixed together in equal quantities by weight and form a eutectic mixture

the melting point of the mixture is lower than the melting points of the individual components
EMLA = lidocaine and prilocaine becomes an oily mixture

EMLA Eutectic mixture of local anesthetics

EMLA application

EMLA Uses of

lidocaine/prilocaine combination is indicated for dermal anaesthesia
Specifically it is applied to prevent pain associated with intravenous catheter insertion, blood sampling, superficial surgical procedures;


it can also be used to numb the skin before tattooing.

TAC: (LET)

• tetracaine 0.5%, adrenaline1 in 2000 and
cocaine 10%
• topical anesthetic mixture found to be effective for nonmucosal skin lacerations to the face and scalp
• applied directly to the wound using a cottontipped
applicator with firm pressure that is
maintained for 20 to 40 minutes
• maximum dose for children-0.05ml/Kg
• toxicity due to cocaine

DentiPatch (lidocaine transoral

delivery system) Preinjection – 10- 15 minutes exposure prior to injection - Root scaling/planing –
apply 5-10 minutes prior to
beginning procedure

DentiPatch (lidocaine transoral

delivery system) Preinjection – 10- 15 minutes exposure prior to injection - Root scaling/planing –
apply 5-10 minutes prior to
beginning procedure

Thanks

THAT’S IT!!