local anesthesia

what is anesthesia?

a controlled, medically induced state of temporary insensibility or loss of awareness. achieved using medications called anesthetics, it prevents pain and can cause partial numbness, muscle relaxation, or full unconsciousness during surgical and medical procedures

what are the types of anesthesia?

1. general anesthesia

2. regional anesthesia

3. local anesthesia

4. topical (surface) anesthesia

general anesthesia

affects the entire body, including the brain. administered via IV or through inhalation. there is a loss of consciousness

regional anesthesia

involves larger region of the body, it can either be peripheral nerve block or spinal anesthesia, such as epidurals

local anesthesia

types used in minor surgeries where a small part of the body, as those used in dentistry

topical (surface) anesthesia

for the skin or cornea

which form of anesthesia is used the most in dentistry?

local anesthesia

when are topical anesthetics used in dentistry?

as a pre-injection prep before local anesthetics to temporarily numb the surface of the gums and oral mucosa. used commonly in pedodontics

what are local anesthetics?

an agent that interrupts pain impulses in a specific region of the body without a loss of patient consciousness, and it is normally completely reversible. used primarily for pain control

the deposition of local anesthetics is where?

near the nerve, never directly in the nerve, as that causes complications. deposition in blood vessels should also be avoided

what is the composition of most local anesthetics?

basic, so to be stable in storage and increase their solubility, they are mixed with acids such as hydrochloric acid to form stable salts like hydrochloride salts

what is the most commonly used local anesthetic agent in dentistry?

Lidocaine

why is Lidocaine the most commonly used local anesthetic agent?

• good duration

• no strong or adverse side effects

• can tell working time

• know when side effects such as facial paralysis will end

what will occur if during administration of an inferior alveolar nerve block, the needle goes more posteriorly and hits or grazes the parotid gland?

it will temporarily anesthetize CN V (7), or the facial nerve, causing temporary facial paralysis (facial palsy).

in Lidocaine and Epinephrine, which is the local anesthetic agent?

Lidocaine. epinephrine simply boosts its effects.

what is the classification of local anesthetic agents based on their intermediate chain?

1. ester type (COOR₁)

2. amide type (NHCO)

intermediate chain is what changes the family type of local anesthesia, true or false?

true

what are some characteristics of ester types?

• shorter duration (15-20 minutes)

• metabolism is in blood (plasma), which causes shorter duration and makes it less stable

• less stable in solution and cannot be stored for long

• unstable in heat and are prone to hydrolysis, meaning they cannot be autoclaved

when esters are metabolized, what metabolite is produced?

para-aminobenzoate, or (PABA), which is associated with allergic reaction. for every 10,000 patients, 1,000 will have a reaction, making hypersensitivity to it common

what are some characteristics of amides?

1. longer duration (2-4 hours)

2. metabolism is in the liver, making it more stable

3. more stable and can be stored for long

4. does not trigger allergic reaction in patients and is rare

5. heat stable and can be autoclaved

which LA agent type is preferred between ester and amides in dentistry?

amides as they are more stable, have a longer duration and do not have a higher risk for allergy

what are ester type LA agents used for in dentistry?

topical (surface) anesthesia prior to needle injection

when are ester LA agents preferred over amide LA agents in dentistry?

for patients with severe hepatic impairment or liver disease

what are some examples of ester type LA agents?

1. cocaine

2. procaine

3. chloroprocaine

4. tetracaine

what are some examples of amide type LA agents?

1. bupivacaine

2. lidocaine

3. mepivacaine

4. prilocaine

5. ropivacaine

what is an example of a local anesthetic agent that has both amide and ester aspects?

articaine (4%), which is strong and has good potency

all local anesthetic agents cross BBB and placenta, true or false?

true, however, LA are not teratogenic, meaning they can be given to pregnant women with precaution. the best time to get dental work done when pregnant would be second trimester

lidocaine is an ester group, true or false?

false

cocaine is metabolized in the liver, true or false?

false

tetracaine is an amide group, true or false?

false

lidocaine is metabolized in the plasma, true or false?

false

what are some uses of lidocaine?

• widely used local anesthetic

• also used via IV for ventricular arrhythmia

what is one of the most common trade names of lidocaine?

xylocaine

what is the mechanism of action of local anesthetic agents?

they produce reversible loss of sensation by blocking voltage-gated sodium channels, preventing depolarization, action potential generation and propagation, and ultimately preventing pain impulses from reaching the CNS.

what are some ways local anesthetics are given?

1. infiltration anesthesia: Injection near small nerve endings (commonly used for individual teeth).

2. nerve block anesthesia: Injection near a major nerve trunk to anesthetize a larger area. (inferior nerve block)

3. regional anesthesia: Anesthetizing a specific region supplied by a nerve. (maxillary nerve block)

what is the effect of local anesthetics on blood vessels?

it is a vasodilator, so a vasoconstrictor such as adrenaline should be added to reduce local blood flow and systemic absorption to decrease systemic toxicity and increase duration of action

what are some complications of local anesthetics?

1. trismus

2. facial nerve palsy

3. edema

4. failure of LA

5. complication arising from drugs or chemicals

6. tech or needle stick injury or breakage

7. hematoma

8. paresthesia

how is trismus due to LA managed?

1. analgesic

2. heat therapy

3. heister / jaw stretcher

4. rinse warm saline

5. muscle relaxant

6. brisement F U/LA

how is facial nerve palsy due to LA managed?

• reassurance to patient

• eye dressing

• contact lens removal if present

how is edema due to LA managed?

1. antihistamine

2. if breathing is compromised, CPR is done

3. epinephrine and corticosteroids

4. refer to oral surgeon if severe

how is failed local anesthesia managed?

• repeat dose

• if infection is present, increase dose

how is complications due to drug or chemicals managed?

• analgesic

• antibiotics if infection develops

• topical anesthesia

how are technical complications such as needle stick breakage managed?

• inform appropriate authority

• catch (try to retrieve) needle if possible

• refer to oral surgeon if necessary

how is hematoma due to LA managed?

• ice pack 2-3 minutes

• reassure the patient

• antibiotic for infection

• analgesic

how is paresthesia due to LA managed?

• follow up for up to two months

• usually subsides by 2 weeks

• prescribe vitamin B 1, 6, and 12

what is a common adverse effect of local anesthesia?

psychogenic, which is fainting or a vasovagal attack. it is the most common cause of loss of conscious in dental clinics and occurs due to anxiety, fear and pain

what are some adverse effects of local anesthetics?

they generally occur due to overdose when injection of LA agent into the vascular system occurs. it causes:

• dizziness and tremor (CNS)

• bradycardia develops as a result of blocked sodium channels in cardiac pacemaker

• severe hypotension can develop as a result of vasodilation and cardiac depression

what occurs if local anesthesia is deposited in the blood vessels?

toxicity

is the one of the most dangerous adverse side effect of local anesthesia allergy?

yes, due to possible anaphylactic shock. to avoid it, good medical history must be taken, and possibly, an intradermal test. allergic reactions usually happen in the second exposure of a drug

what is the inferior nerve block?

a local anesthetic used to numb the mandibular teeth on one side. it is injected near the inferior alveolar nerve before it enters the mandibular foramen

what are the areas anesthetized when inferior nerve block is administered?

1. all lower teeth on the same side

2. lower lip and chin (mental nerve)

3. buccal gingival anterior to the mental foramen

4. part of the tongue and floor of the mouth (lingual nerve)

what are signs of successful anesthesia by IANB?

1. numbness of lower lip

2. numbness of chin

3. tongue numbness, if lingual nerve is affected

what are common complications of IANB?

1. failure of anesthesia

2. temporary facial paralysis

what are the uses of IANB?

1. tooth extraction

2. root canal treatment

3. deep restorations