Anesthesiology Ppt

7/28/2019 Anesthesiology Ppt

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ANESTHESIOLOGY(LOCAL ANESTHESIA)


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DEFINITION:

Anesthesia temporary loss ofsensation(including the loss of sensation totouch, pressure, proprioception, and loss ofmotor function) either with the patient consciousor unconscious. Analgesia temporary loss of painsensation Regonal(local) analgesia- temporaryloss of pain sensation over a portion of anatomywithout loss of consciousness.


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Pain and nerve conduction

Pain-an unplesant sensation

usually iniated by a noxiousstimulus and transmitted overa specialized neural networkwhere it is interpreted as pain.


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heories of pain conduction:

1.Specificity theory- descartes in1644.2.pattern/summation theory-goldscheider in1894.3.Gate control theory-melzack and wall in 1965a. Information about presence of pain from aninjury from peripheral nerves of the brain.b. These info either facilitated or inhibited by

larger peripheral nerves that also carry infoabout innocuous event (temp,pressure)c. ascending control system originating from thebrain modulated the excitability of cells that

transmit info about injury.


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Nerve conductionStep 1 resting potential- 70- -90 mv in the

inside of the cell because of the relativeimpermiability of the nerve membrane toNa+ ions and the action of the Na+

pump.Step 2 presence of stimulus (actionpotential)

a. Slow depolarizationb. Threshold potential or firing potential -

50- -60mv .

c. Rapid depolarization


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Step 3 repolarization- resting potential

Absolute refractory period- the return to

the resting (step 1 and 2) wherein thenerve cannot be stimulated.

Relative refractory period- when the

imbalance returns to the resting statewherein a greater stimulus is needed tostimulate the nerve.

All or non law of nerve conduction-thestimulus should be strong enough toreach the threshold potential to stimulate

the nerve.


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Methods of pain control:

1.removing the cause

2.Blocking the pathway of painful

impulses- local anesthesia3.Raising the pain threshold- sedation

anesthesia

4.Cortical depression- general anesthesia

5.Using psychosomatic methods-

hypnotism


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WHAT IS LOCAL ANESTHESIA?

is any technique to induce the absenceofsensation in part of the

body, generally for the aim ofinducing local analgesia, that is, localinsensitivity to pain, although other local

senses may be affected as well. It allowspatients to undergo surgicaland dental procedures with reduced pain

and distress.
http://en.wikipedia.org/wiki/Sensationhttp://en.wikipedia.org/wiki/Painhttp://en.wikipedia.org/wiki/Dentistryhttp://en.wikipedia.org/wiki/Dentistryhttp://en.wikipedia.org/wiki/Painhttp://en.wikipedia.org/wiki/Sensation


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*Local anesthesia, in a strict sense,is anesthesia of a small part of the body such asa tooth or an area of skin.

The following terms are often usedinterchangeably:

*Regional anesthesia is aimed atanesthetizing a larger part of the bodysuch as a leg or arm.

*Conduction anesthesia is acomprehensive term, which encompassesa great variety of local and regional

anesthetic techniques.
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LOCAL ANESTHETICA local anesthetic is a drug that causes reversible localanesthesia and a loss of nociception. When it is usedon specific nerve pathways (nerve block), effects suchas analgesia (loss of painsensation) and paralysis (lossof muscle power) can be achieved. Clinical localanesthetics belong to one of two classes: aminoamideand aminoester local anesthetics. Synthetic localanesthetics are structurally related to cocaine. Theydiffer from cocaine mainly in that they have no abusepotential and do not act on the sympathoadrenergicsystem, i.e. they do not producehypertension orlocal vasoconstriction, with the exceptionof Ropivacaine and Mepivacaine that do produce weakvasoconstriction.
http://en.wikipedia.org/wiki/Medicationhttp://en.wikipedia.org/wiki/Nociceptionhttp://en.wikipedia.org/wiki/Nerve_blockhttp://en.wikipedia.org/wiki/Analgesiahttp://en.wikipedia.org/wiki/Painhttp://en.wikipedia.org/wiki/Paralysishttp://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Cocainehttp://en.wikipedia.org/w/index.php?title=Sympathoadrenergic_system&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Sympathoadrenergic_system&action=edit&redlink=1http://en.wikipedia.org/wiki/Hypertensionhttp://en.wikipedia.org/wiki/Vasoconstrictionhttp://en.wikipedia.org/wiki/Ropivacainehttp://en.wikipedia.org/wiki/Mepivacainehttp://en.wikipedia.org/wiki/Mepivacainehttp://en.wikipedia.org/wiki/Ropivacainehttp://en.wikipedia.org/wiki/Vasoconstrictionhttp://en.wikipedia.org/wiki/Hypertensionhttp://en.wikipedia.org/w/index.php?title=Sympathoadrenergic_system&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Sympathoadrenergic_system&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Sympathoadrenergic_system&action=edit&redlink=1http://en.wikipedia.org/wiki/Cocainehttp://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Paralysishttp://en.wikipedia.org/wiki/Painhttp://en.wikipedia.org/wiki/Analgesiahttp://en.wikipedia.org/wiki/Nerve_blockhttp://en.wikipedia.org/wiki/Nociceptionhttp://en.wikipedia.org/wiki/Medication


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ropert es o eaanesthetics1.Action must be reversible2.non-irritating to tissues3.Low degree of systemic toxicity4.Rapid onset and sufficient duration

5.Potency sufficient enough to producedcomplete analgesia without the use of harmfulconcentrated solution.6.Suffiecient penetrating properties7.Free for producing allergic reactions8.Stable in solution and undergobiotransformation readily.9.Sterile and capable of sterilization


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Groups of local anesthesia

I. ESTER GROUPA. Benzoic acid ester1.cocaine2.benzocaineB.PABA ESTERS1.procaine (novocaine)2. tetracaine (pontocaine)3.propoxycaine(ravocaine)II. AMIDE GROUP (anilide derivatives)1.bupivacaine(marcaine)

2.etidocaine (duranest)3.lidocaine (xylocaine)4.mepivacaine(carbocaine)5.prilocaine(citanest)


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Benzocaine (ester) Procaine (ester)

Mepivacaine (Polocaine/Carbocaine) Bupivacaine (Marcaine)


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MODE OF ACTION OF LALA drugs (weak base and not soluble in water)--- add

HCI (strong acid) --- create LA salts --- LA solution---

contain free base (RN) which are lipophilic and

cations (RHN+) which are hydrophilic

pKa- dissociation constant or measure of the affinity

of a substance to H+ ions

LA salt--- injected to tissues--- cation loses H+---

alkaloidal base--- penetrates nerve membrane

free bases attract H+ ions inside the nerve

membrane --- theories of regional anesthesia--- Na+

cannot enter the nerve--- nerve stabilize--- no

conduction


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VASOCONTRICTOR

The vasodilation activity of local anesthetics produce anincreased rate of absorption. This results in decreasedeffectiveness, short duration of anesthesia, and ahigher risk of toxicity.Bleeding in the area of injectionis increased. Vasoconstrictors are clinically useful in

counteracting these effects. Vasoconstrictors areadded to local anesthetics to decrease the absorptionof the drug and prolong the anesthetic effect thatproduces anesthesia that is more profound.Thevasoconstrictor also serves to reduce the risk oftoxicity because it is more slowly absorbed by thecirculatory system. The length of the procedure,desired level of hemostasis, and the medical health ofthe patient must all be considered when selecting anappropriate vasoconstrictor.


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*Epinephrine and levonordefrin (neo-cobefrin) are the most commonly used

vasoconstrictors in dentistry.

*Epinephrine is sensitive to heat and canbe inactivated if left too warm for too long.

*Epinephrine is available in concentrationsof 1:50,000 for better hemostasis.


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Epinephrine is contraindicated inpatients with

blood pressure over 200 torr systolic or 115 torrdiastolic,

uncontrolled hyperthyroidism,

severe cardiovascular disease including less than 6months after a myocardial infarction orcerebrovascular accident

daily episodes of angina pectoris or unstable angina cardiac dysrhythmias despite appropriate therapy

medicated with -blocker, monoamine oxidaseinhibitors, or tricyclic antidepressants; or generalanesthesia with a halogenated anesthetic likehalothane, methoxyflurane, or ethrane.


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Why is Epinephrine a perfect

vasoconstrictor?

Epinephrine, also known as adrenaline is a naturallyoccurring hormone and a neurotransmitter.Epinephrine is a perfect vasoconstrictor because it isproduced naturally by the body as adrenaline,occasionally called the "fight or flight hormone". If itenters the normal circulation, it can causean increased heart rate and stronger heart beatwith afeeling of anxiety, besides causing a constrictionofblood supply. So, it increases heart rate,

constrictsblood vessels, dilates air passages andparticipates in the acute stress response of thesympathetic nervous system, one of the three parts ofthe autonomic nervous system. These side

effects describe for the "rush" that some people feelafter ettin an anesthetic shot.
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What is the concentration of

vasoconstrictor in Anesthesia?

The concentration ofvasoconstrictor in any given carpule of anesthesiais represented by a ratio of vasoconstrictor per mL of solution. Forinstance, a solution may be labeled as 1:100,000. This concentration

represents 1000mg/100,000mL or 0.01mg/mL, or 1 gram per 100Liters. A 1:1000 solution translates to 1 mg vaoconstrictor per mL ofsolution, or 1 gram per Liter. Most anesthetic solutions contain theminimum amount of anesthesia required to constrict local blood vesselsand extend the action of the anesthetic. A few, however, contain ahigher concentration ofvasoconstrictor for use in controlling bleedingfor specific purposes, such as periodontal surgery. For instance, generalpurpose lidocaine contains epinephrine in the amount of 1/100,000 forproducing deep, extended anesthesia. On the otherhand, lidocaine also comes with epinephrine at twice the normalconcentration (1/50,000) used mostly by periodontists who need to

control gingival bleeding during surgery.

h h d f h
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What is the advantage of anesthetics

that don't have a vasoconstrictor?

The majority of anesthetic solutions have added vasoconstrictor. Onlytwo, mepivicaine and prilocaine are sold with or withoutvasoconstrictor. Mepivicaine and prilocaine have the advantage ofproducing only minor vasodilation and, though both are short actingwithout their vasoconstrictor added. However, they still produce

sufficient anesthesia for short procedures. The most importantadvantage of using an anesthetic without a vasoconstrictor is thatthere are virtually no interactions with other drugs the patient may betaking.

Also, carpules that do not contain vasoconstrictor do not containpreservatives either. This is a vital point, because it is most often thepreservatives, and not the anesthetics themselves which play a role inallergic reactions. There has never been a recognized caseofallergy to the modern amine based anesthetics themselves;nevertheless, many people are allergic to the preservatives linked withthe vasoconstrictor.

What is the disadvantage of
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What is the disadvantage of

anesthetics that don't have a

vasoconstrictor? The use ofvasoconstrictor has a disadvantage. These

naturally occurring hormones are not very stable, andmust be stabilized by the addition of an acidic

preservative. The presence of the preservative canlower the PH of the anesthetic solution to the range of3.8 to 5.0, thus reducing the amount of the neutralbasic radical (RN) and slowing the beginning of actionof the anesthetic. This effect is, however not

particularly major, and anesthesiawith vasoconstrictoris a very popular choice among practitioners whenother medical considerations authorize its use.
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Are vasoconstrictors safe?

The use ofvasoconstrictor in dentistry has been proven to be

very safe for approximately all patients. Actually, the use of

vasoconstrictor is highly recommended due to the increase in

effectiveness and prolonged existence of dental anesthesia.

There are no absolute contraindications to the useofvasoconstrictors in dental local anesthetics, as epinephrine

is an endogenously produced neurotransmitter. According to

the American HeartAssociation and the American Dental

Association, the characteristic concentrationsofvasoconstrictors present in local anesthetics are not

contraindicated with cardiovascular disease so long as

preliminary objective is accomplished, the agent is injected

gradually, and the smallest effective dose is offered.
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Anesthesiology Ppt

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