introduction to la

8/20/2019 Introduction to LA

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LOCAL ANAESTHESIALOCAL ANAESTHESIA

ININ

DENTISTRYDENTISTRY

1

Dr Ahmed Osman

BDS 3 Semester 1- 2014


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Objectives of the course

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On completion of this course you should be able to demonstrate:

An a!areness of patients" attitudes to!ards# moti$ations for# and

apprehension of dental treatment%

&no!led'e of a ran'e of methods no! a$ailable for the control of

apprehension and pain durin' dental treatment%

An understandin' of ho! these methods can impro$e the (uality of dental

treatment

)he ability to e$aluate a patient"s 'eneral condition and select the appropriatepain control method to be used for their treatment%

*ompetence in dealin' !ith problems and emer'encies arisin' durin' dental

treatment +BDS4,%


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Definitions

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Anaesthesia: “reversible lack of awareness”.

It is the loss of sensation obtained by the(loal! ad"inist#ation of a e#tain he"ial

that te"$o#a#ily $#e%ents the ond&tion of$ain i"$&lses to the b#ain' itho&t the loss ofonsio&sness

Pain: is an &n$leasant sensation #eated by a

sti"&l&s and "ediated alon) s$ei* ne#%e$athays into the CNS he#e it is inte#$#etedas s&h.

Question: does it lead to complete lack of “awareness” ?


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History of Anaesthesia

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He#bal +,-- C / o$i&"' oaine' annabis. 0o#e than 1-- y#s a)o Ab& al23asi" and Ibn 4&h#

(A%en5oa#!' e#e *#st to &se inhalant anaesthesis and$e#fo#"ed h&nd#eds of s)e#ies ith the &se of na#oti2soa6ed s$on)es.

78th enty /79++ nit#o&s o:ide diso%e#ed by Ho#ae;ells. 79+a#l >olle# int#od&ed the to$ial and #e)ional

anaesthesia (oaine to eye s)e#y!. ?#oaine as the *#st in@etable "an2"ade loal anestheti

*#st synthesi5ed in 1898 by the e#"an he"ist “AlfredAlfredEinhornEinhorn””..

Sedish he"ist “Nils Löfgren”' de%elo$ed the Lidoaine Lidoaine 1943 de%elo$ed as a de#i%ati%e of :ylidine.

http://en.wikipedia.org/wiki/Abu_al-Qasimhttp://en.wikipedia.org/wiki/Ibn_Zuhrhttp://en.wikipedia.org/wiki/Lidocainehttp://en.wikipedia.org/wiki/Lidocainehttp://en.wikipedia.org/wiki/Lidocainehttp://en.wikipedia.org/wiki/Ibn_Zuhrhttp://en.wikipedia.org/wiki/Abu_al-Qasim


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Uses of LA


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Advantages of LA administration

.


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Aa6e Aslee$ Anyone Only healthy hea#tB l&n)s Day %isit hos$ital stay One doto# to doto#s Lo #is6 hi)h #is6 Eatin) fastin) Clini OT Alone Ao"$anied Chea$ E:$ensi%e

LA VS GA

/


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What causes pain at nerve endings?

?hysial Che"ial Ins&lts In@y tiss&eda"a)e #elease of Cyto6ines' ina""ato#y"ediato#s

(defense "ehanis"! Release of s&bstane2?. f#o" in@ed f#ee

ne#%e endin)s.

Question: What is hyperalgesia?

Can L cure or cause further damage?


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Chemistry of LAChemistry of LA

LA F Ati%e a)ent

?#ese#%ati%e/ Antibate#ial / 0ethyl$a#aben(ate#ioststi!

Antif&n)al / Thy"o#al

Gasoonst#ito#/ ad#enaline' no#2ad#enaline'fely$#essin.

Red&in) a)ent (GC $#ese#%ati%e!/ Sodi&" 0etabis&l*te.

Gehile/ Rin)e#s sol&tion/ Sodi&" hlo#ide -.1 )"'$otassi&" hlo#ide -.-,)". And distilled ate# 7-- .

&e#/ Sodi&" hyd#o:ide)he addition of $asoconstrictor and sodium metabisulfite lo!ers local anesthetic solution p#

resultin' in a slo!er onset of action and an increased burnin' sensation durin' in5ection

+necessitatin' the addition of buffers,


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Structure of LA

An or'anic compound that is basically a tertiary AmineAmine ha$in' 1#2 or the 3

hydro'en atoms ha$e been replaced by or'anic radicals%


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Structure of LA

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7. A Li$o$hili #o&$/ an a#o"ati $o#tion that $#o%ides li$idsol&bility

,. A Hyd#o$hili #o&$/ a te#"inal a"ide that $#o%ide ate#sol&bility

J. An Inte#"ediate hain ith eithe# Ester or Amide lin6a)e


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The a#o"ati end is li$o$hili (sol&ble inli$ids!. ea&se ne#%e ell is "ade of li$idbilaye# it is $ossible fo# anestheti

"ole&le to $enet#ate th#o&)h the ne#%e"e"b#ane.

The a"ine end is hyd#o$hili (sol&ble in

ate#!' anestheti "ole&le dissol%e inate# in hih it is deli%e#ed f#o" thedentists sy#in)e into the $atients tiss&e.

Structure of LA


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LA Action

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Action relies on:

Diffusion of 6A base throu'h tissue and ner$esheath

Bindin' at receptor site of ner$e


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Types of anasethetic agents:

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The inte#"ediate hain an be of/

Este# ty$e 2COO2 / Readily hyd#olysed in $las"ath#o&)h $se&doholineste#ases and not stable in

sol&tion

e). ?#oaine ' Coaine. A"ide ty$e FNH2 / 0etaboli5ed in li%e#K and' to a

lesse# e:tent' in othe# tiss&es' and is %e#y stablein sol&tion ("o#e #esistant to hyd#olysis!

e). Lidoaine' 0e$i%aaine' ?#iloaine.

! "y microsomal #$%&' en(ymes in the liver )*$dealkylation and hydro+ylation,


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1


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1.

Types of anasethetic agents:


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1/

)hiophene 7in'


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1

All commonly used local anaesthetics in dentistry ha$e

some $asodilator acti$ity that leads to the follo!in':

8ncreased rate of absorption into the blood streamdecreased duration of action and effecti$eness

8ncreased bleedin' at the site of in5ection#

And possible o$erdose reactions due to hi'h blood

le$els%


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Effect of LA agent on BVs

1


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1. Adrenaline1. Adrenaline 0ost o""only &sed %asoonst#ito#

Conent#ation in LA #an)e f#o" 7/1-'--- B7/9-'--- B7/7--'--- 7/,--'---

Ats on al$ha and beta ad#ene#)i #ee$to#sK

! lpha stimulation leads to: contraction of smooth muscle cells )-C of skin.salivary glands and gut,

"eta stimulation causes: increased /t rate. bronchodilatation and -0 ofcardiac and skeletal muscle arteries and with depressed 123 motility andgluconeogenesis4

Chemistry of LA:Chemistry of LA:(( Vasoconstrictors): Vasoconstrictors):


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2.Noradrenaline2.Noradrenaline Si"ila# to ad#enaline

Ats on al$ha "o#e than beta ad#ene#)i#ee$to#s and onst#its al"ost all blood

%essels(s"all and la#)e!K th&s a#e "&st beta6en hen )i%en to a hy$e#tensi%e $t.

! 5pinephrine is preferred than norepinephrine and levonordefrin as these e+ert ane+cessive alpha 6 stimulation causing more peripheral -C 77"#4 While epinephrinee+erts both alpha and beta e8ects where the beta 9 stimulation vasodilates the skeletalmuscles which decreases the diastollic "# compensating somehow to the alpha e8ects4



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3. Fel!ressin "o#ta!ressin$3. Fel!ressin "o#ta!ressin$

Co""only &sed %asoonst#ito#

A syntheti analo)&e of the ADH %aso$#essin

Has O:ytoi eet' th&s sti"&lates &te#ines"ooth "&sle ont#ation. The#efo#e not &sein $#e)nany $atients.



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Duration of action:Duration of action:


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Mode of action of LAMode of action of LA(Theories)(Theories)

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0ECHANICAL (the f#ee base a&ses te"$o#a#yoa)&lation of li$oid ontent of ne#%e!

0ETAOLIC ( the base inte#fe#es ith o:y)en

inta6e a&sin) disto#ted int#aell&la# o:idationof )l&ose a&sin) $a#alysis!

?HAR0ACOLOIC/ to:iity of the sol&tion is“seleti%e” to ne#%e tiss&e a&sin) essation

of f&ntion. ELE%&'(%: "de!olari)ation theor$


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Conduction of nerve impulses

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esting potential across membrane $;' to $


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2.

Variation in neural response to LA


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Effectiveness of LA depend onEffectiveness of LA depend on

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Prior e*!erien#e of !ain &!e of LA %on#entration

+ol,me gi-en +as#,larit of site +aso#onstri#tor !/ of tiss,e at site of in0e#tion %orre#t &e#hni,e


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Absorption, biotransformation and elimination

The li%e# is the "a@o# o#)an fo# the biot#ansfo#"ation of LA d#&)sM

b&t this also ta6es $lae in the "&osa of the )&t' the l&n)s'blood $las"a and 6idneys.

One it is abso#bed by loal i#&lation it ente#s the bloodst#ea"to be t#ans$o#ted to li%e#' he#e a $#o$o#tion of it beo"es

bo&nd to $las"a $#oteins hile the f#ee (&nbo&nd! anaestheti

a)ent beo"es (#e!dist#ib&ted to tiss&es th#o&)ho&t the body(es$. in hi)hly %as&la# tiss&es s&h as s6eletal "&sle!.

The#e a#e to "a@o# ste$s in d#&) "etabolis"M

Phase ( in hih the d#&) "ole&le beo"es ati%ated in theblood st#ea" and loal tiss&es by eithe# o:idation' #ed&tion o#hyd#olysis.

Phase (( ta6es $lae afte# ati%ation and os &s&ally in the li%e#'in the fo#" of on@&)ation of the d#&) ith so"e othe# he"ialsto #ende# it "o#e ate# sol&ble in #eadiness fo# e:#etion.

2


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Estert!e/ a#e hyd#olysed #a$idly in the $las"a by holineste#ase

en5y"es and is dissoiated into ?a#aa"inoen5oi aid (?AA! andalohol .i.e. o:idation and hyd#olysis ta6es $lae "ostly in tiss&es 'and in blood (he#e they a#e bo&nd to $las"a $#oteins b&t , a#e&nbo&nd Ff#ee! and to a lesse# e:tent in li%e#! . And then it isfthe# b#o6en don in the li%e# befo#e e:#etion.

Amidet!e: is "o#e o"$le: and ta6es lon)e# than the

b#ea6don of este#s. ?hases I and II both o in the li%e# fo# the"a@o#ity of a"ide anaesthetis. i.e. they a#e not b#o6en don in bloodst#ea" b&t #athe# in the $#esene of atalysts in the li%e# (microsomal #$%&' en(ymes, then products are further o+idi(ed and some areconugated with glucuronic acid4

Eli"ination/

oth the este# and a"ide loal anaesthetis and thei# "etabolites(conugated and unconugated products, a#e e:#eted by the6idneys. In healthy indi%id&als only a s"all $e#enta)e of the

anaestheti a)ent is e:#eted &nhan)ed as the $#i"a#yo"$o&nd.

2

Absorption, biotransformation and elimination


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Clinical hint:

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All ne#%e *be#s a#e sensiti%e to loalanesthetis' b&t )ene#ally' those ith as"alle# dia"ete# tend to be "o#e sensiti%e

than la#)e# *be#s. Loal anesthetis blo6ond&tion in the folloin) o#de#/ s"all"yelinated a:ons (e.). those a##yin)noie$ti%e i"$&lses!' non2"yelinated a:ons'then la#)e "yelinated a:ons.

Th&s' a die#ential blo6 an be ahie%ed (i.e.$ain sensation is blo6ed "o#e #eadily thanothe# senso#y "odalities!.


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References

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Best wishes

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introduction to la

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