local anaesthetics local anaesthetics anton kohút anton kohút

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Local Local anaesthetics anaesthetics Anton Anton Kohút Kohút

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Page 1: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

Local anaestheticsLocal anaesthetics

Anton KohútAnton Kohút

Page 2: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút
Page 3: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

Local annaesthetics (LA) are Local annaesthetics (LA) are drugs emploed to produce drugs emploed to produce transient and reversible loss of transient and reversible loss of sensation in circumscribed sensation in circumscribed region of the bodyregion of the body

Page 4: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

History of local anaesthesiaHistory of local anaesthesia

iin 1884, n 1884, cocainecocaine was first was first used as a local used as a local anaesthetic to immobilize anaesthetic to immobilize a patient's eye for eye a patient's eye for eye surgery bysurgery by Carl KollerCarl Koller

Carl Ludwig SchleichCarl Ludwig Schleich is is the pioneer of the pioneer of infiltrationinfiltration anaesthesia anaesthesia in 1892in 1892

(1857 - 1944)

(1859-1922)

Page 5: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

Mechanismm and action of LAMechanismm and action of LA

these drugs bind selectively to the these drugs bind selectively to the

intracellular surface of sodium channels intracellular surface of sodium channels and block entry of sodium into the and block entry of sodium into the cellcell block the depolarisation block the depolarisation

LA LA bind more readily to bind more readily to NaNa++ channels in channels in inactivated stateinactivated state - - onset of neuronal onset of neuronal blockade is faster in neurons that are blockade is faster in neurons that are rapidly firingrapidly firing ((statestate--dependent blockadedependent blockade))

Page 6: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút
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EEffect of pHffect of pH

LALA are weak are weak bases bases ((hydrochloride salt hydrochloride salt == water- water-solublesoluble))

only the only the ununionisedionised molecule diffuses molecule diffuses readily readily across cell membranesacross cell membranes

aacidosiscidosis (in (in inflammationinflammation)) partly partly reduces the reduces the action of action of LALA - - most of the most of the LALA is ionised is ionised && therefore unable to cross the cell membrane therefore unable to cross the cell membrane

Page 9: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

Mechanismm and action of LA – Mechanismm and action of LA – cont.cont.

Actions on various nerve fibersActions on various nerve fibers LA block conduction LA block conduction in small diameter nerv fibers more in small diameter nerv fibers more

readily when in large fibersreadily when in large fibers

Fibers CFibers C (under 1 (under 1 m, unmyelinated postgaglionic m, unmyelinated postgaglionic and somatic)-and somatic)-autonomic paralysisautonomic paralysis, loss of the , loss of the sensation of itch and tickle pain sensation of itch and tickle pain

Fibers BFibers B (1-3 (1-3 m, myelinated preganglionic ) m, myelinated preganglionic ) autonomic paralysis.autonomic paralysis.

Fibers AFibers A (1-20 (1-20 m, myelinated, somatic, motor and m, myelinated, somatic, motor and some somatic)- sceletal muscle relaxation, loss of some somatic)- sceletal muscle relaxation, loss of thermal and tactil sansation, thermal and tactil sansation, proprioceptive lossproprioceptive loss, loss , loss of sharp pain.of sharp pain.

Page 10: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

Mechanismm and action of LA – Mechanismm and action of LA – cont.cont.

Metabolism of LAMetabolism of LA estersesters are primarily inactivated are primarily inactivated in plasmain plasma

by hydrolysis (pseudocholinesterase)by hydrolysis (pseudocholinesterase) - they generally have a relatively short half-- they generally have a relatively short half-

life in the bodylife in the body - in spinal fluid (absence of esterase activity) - in spinal fluid (absence of esterase activity)

duration of anaesthesia is extendedduration of anaesthesia is extended

amidesamides are metabolized are metabolized by liverby liver microsomes microsomes

- metabolites are excreted by urine- metabolites are excreted by urine - liver disease - liver disease cumulation of drugs cumulation of drugs

higher risk of toxicityhigher risk of toxicity

Page 11: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

PharmacokineticsPharmacokinetics

LA should act locallyLA should act locally

the duration of action of all agents is prolonged by the duration of action of all agents is prolonged by the addition ofthe addition of adrenalineadrenaline when used forwhen used for infiltration anaesthesia infiltration anaesthesia && peripheral nerve peripheral nerve blocksblocks

aadrenalinedrenaline also increases the duration ofalso increases the duration of extradural anaesthesia extradural anaesthesia when added to when added to procaine, mepivacaine procaine, mepivacaine && li liddocaineocaine but does not but does not alter markedly the duration of action of extradural alter markedly the duration of action of extradural prilocaine, bupivacaineprilocaine, bupivacaine or or etidocaineetidocaine

Page 12: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

Vasoconstrictors in local Vasoconstrictors in local anaesthesiaanaesthesia

- to slow absorption- to slow absorption

- to prolong the local action- to prolong the local action

- to decrease toxicity- to decrease toxicity

Page 13: Local anaesthetics Local anaesthetics Anton Kohút Anton Kohút

PharmacokineticsPharmacokinetics(p(practical ractical ppoint oint ))

aadrenaline 1:1000 contains 1 g of drenaline 1:1000 contains 1 g of adrenaline per 1000adrenaline per 1000 ml solution i.e. ml solution i.e. 1mg/ml1mg/ml

tto prepare a 1 in 200o prepare a 1 in 200 000 solution the 000 solution the

1:1000 must be diluted 200 times1:1000 must be diluted 200 times

tthis is achieved by taking 0.1ml (= his is achieved by taking 0.1ml (= 0.1mg) 0.1mg) & & adding 19.9 ml of adding 19.9 ml of LALA solution solution

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PharmacokineticsPharmacokinetics((adrenalineadrenaline

contraindicationscontraindications)) adrenalineadrenaline nevernever be used for infiltration be used for infiltration around around

end-arteriesend-arteries i.e. penis, ring block of fingers or i.e. penis, ring block of fingers or other areas with a terminal vascular supply other areas with a terminal vascular supply (ischaemia, necrosis)(ischaemia, necrosis)

in patients with in patients with diabetesdiabetes && CV diseasesCV diseases::hypertensionhypertension

severe atherosclerosissevere atherosclerosis

hearth failure hearth failure

after IMafter IM

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Methods of aplication of Methods of aplication of LALA

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Mode of application of LA

topical (surface)

infiltration

plexus block

epidural (extradural) spinal (subarachnoid)

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Methods of aplication of LAMethods of aplication of LA1. Surface anaesthesia1. Surface anaesthesia- the LA solution is applied directly to the mucosal - the LA solution is applied directly to the mucosal

surface: nose and mouth, bronchial tree, oesophagus surface: nose and mouth, bronchial tree, oesophagus or genitourinary tractor genitourinary tract

- LA can be absorbed into the circulation following - LA can be absorbed into the circulation following topical aplication to mucous (mainly tracheobronchial topical aplication to mucous (mainly tracheobronchial tree) tree) risk of toxicityrisk of toxicity

- relatively high doses are often used - relatively high doses are often used tetracaine (2%), tetracaine (2%), lidocaine (2-10%), cocaine (1-4%)lidocaine (2-10%), cocaine (1-4%)

2. Infiltration anaesthesia2. Infiltration anaesthesia- LA are injected directly into the tissues to reach fine - LA are injected directly into the tissues to reach fine

nerve branches and sensory nerve terminalsnerve branches and sensory nerve terminals- most frequently used LA - most frequently used LA lidocaine (0.5-1%), lidocaine (0.5-1%),

procaine (0.5-1%), bupivacaine (0.125-0.25%)procaine (0.5-1%), bupivacaine (0.125-0.25%)

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Methods of aplication of LA – Methods of aplication of LA – cont.cont.3. 3. Nerve-block anaesthesiaNerve-block anaesthesia- LA are injected close to the appropriate - LA are injected close to the appropriate nerve trunksnerve trunks - -

widely used methods widely used methods much less anesthetics are needed much less anesthetics are needed ::-procaine (0.5-1%), lidocaine (1-2%), mepivacaine (1-3%), -procaine (0.5-1%), lidocaine (1-2%), mepivacaine (1-3%), bupivacaine (0.25-0.75%) are usedbupivacaine (0.25-0.75%) are used

4. Spinal and epidural anaesthesia4. Spinal and epidural anaesthesia spinal (subdural) anaesthesiaspinal (subdural) anaesthesia - LA is injected into the - LA is injected into the

lumbar subarachnoid space, which contains cerebrospinal lumbar subarachnoid space, which contains cerebrospinal fluid, fluid,

epidural anaesthesiaepidural anaesthesia - LA is injected just outside the dura - LA is injected just outside the dura into a narrow space between the dura and the bony spinal into a narrow space between the dura and the bony spinal canalcanal

- advantage- advantage relatively small doses of LA are needed relatively small doses of LA are needed --unwanted effectsunwanted effects in spinal anaesthesia are: in spinal anaesthesia are:

vasodilatation, vasodilatation, bradykardia, bradykardia, marked fall in arterial marked fall in arterial pressurepressure

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Side effects of LASide effects of LA

CNSCNS- all LA cause stimulation of CNS: - restlessness - all LA cause stimulation of CNS: - restlessness

and tremor and tremor tremor can progress to convulsion tremor can progress to convulsion- further increasing the dose - further increasing the dose CNS depression CNS depressionmain threat for life comes from respiratory main threat for life comes from respiratory

depressiondepression- cocaine has different effect on CNS - cocaine has different effect on CNS doses doses

lower than convulsive produce marked euphorialower than convulsive produce marked euphoria

Treatment:Treatment: restoration of normal ventilation and circulationrestoration of normal ventilation and circulation diazepamdiazepam in prevention and treatment of in prevention and treatment of

seizuresseizures

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Side effects of LA – cont.Side effects of LA – cont.Cardiovascular systemCardiovascular system- myocardial depression and vasodilatation- myocardial depression and vasodilatation- vasodilatation - vasodilatation partly direct effect on vascular smooth partly direct effect on vascular smooth

muscle and partly inhibition of sympathetic nevous muscle and partly inhibition of sympathetic nevous system (centrally)system (centrally)

- this combined effect - this combined effect marked fall in blood pressure marked fall in blood pressure- cocaine - cocaine inhibition of adrenaline re-uptake inhibition of adrenaline re-uptake tachycardia, tachycardia,

vasoconstriction and increase of arterial pressurevasoconstriction and increase of arterial pressure

Effects of vasoconstrictorsEffects of vasoconstrictorslocal ischemia, anxiety, tachycardia, hypertensionlocal ischemia, anxiety, tachycardia, hypertensionContraindications of vasoconstrictorsContraindications of vasoconstrictors hypertension, atherosclerosis, thyreotoxicosis, congestive hypertension, atherosclerosis, thyreotoxicosis, congestive

heart failureheart failure

Allergy Allergy - - esters. There is not cross-esters. There is not cross-reactivity with the amides.reactivity with the amides.

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diclofenac, felbinac, ibuprofen, diclofenac, felbinac, ibuprofen, ketoprofen, piroxicam, naproxen, ketoprofen, piroxicam, naproxen,

flurbiprofen and others.flurbiprofen and others.