Regional Anesthesia

Fatiş AltındaşDept. of Anesthesiology

Regional anesthesia - Definition Renders a specific area of the body, e.g. foot, arm, lower extremities insensating to stimulus of surgery or other instrumentation

Eliminates sensation in a limited region of the body

Interferes with impulse transmission in peripheral or spinal cord nerves

There is no loss of consciousness

Benefits of Regional Anesthesia Benefits of Regional Anesthesia

Provide anesthesia for a surgical procedure Provide anesthesia for a surgical procedure Unsurpassed quality of analgesia postUnsurpassed quality of analgesia post--operatively or during labor and deliveryoperatively or during labor and deliveryReduction in stress responseReduction in stress responseImproves regional blood flowImproves regional blood flowDiagnosis or therapy for patients with chronic Diagnosis or therapy for patients with chronic pain syndromespain syndromes

Regional anesthesia - typesCentral neuraxial blockade

EpiduralSpinal

Peripheral nerve blockminor: single nervemajor: multiple nerves or plexus

InfiltrationTopical

skinmucous membranes

Central Blocks: Spinal, Epidural

These blocks are also known neuroaxial anesthesiaPerforming as a single injection or with a catheter to allow intermittent boluses or continuous infusion

The principal site of action for central blocks is the nerve rootsInjecting local anesthetic into CSF or the epidural space

Anatomy of the vertebral column

Spinal cord and its nerve roots lie within the vertebral columnSpinal cord extends from the foramen magnum to level of L1 in adults and L3 in children

Spinal cord

Spinal cord is covered by meningesPia materArachnoid materDura mater

CSF is contained between the pia and arachnoid materin the subarachnoid space

Indications: Uses

Central blocks may be used for nearlyany procedure below the neckAs a primary anesthetic technique

Lower abdominal, inguinalUrogenital, rectalLower extremity surgery

Indications-cont.The choice of anesthesia is determined bythe patients

Discussing risks and benefitsObtaining informed consentSuitability of the technique for the type of surgeryThe surgeon’s preferenceThe experience of the anesthetistPhysiologic and mental state

Contraindications

AbsoluteInfection at the site of injectionPatient refusalCoagulopathy or bleedingdiathesisSevere hypovolemiaIncreased ICPSevere aortic stenosisSevere mitral stenosis

RelativeSepsisUncooperative patientPreexisting neurologicdeficits

Demyelinating lesionsSevere spinal deformity

Technical considerationsThey should only be performed in facility where all the equipment anddrugs needed for intubation andresuscitation are immediatelyavailableMonitoring for surgical anesthesia is the same as for general anesthesia

Blood pressure, heart rate , pulseoximetry

CentralCentral BlocksBlocks-- SpinalSpinal

AdvantagesAdvantagesTechnicallyTechnically easyeasy (LP (LP techniquetechnique))HighHigh successsuccess rate, rate, rapidrapid onsetonset

DisadvantagesDisadvantages““highhigh spinalspinal””hypotensionhypotension duedue toto sympatheticsympathetic blockblockpost dural post dural puncturepuncture headacheheadache

Central Blocks- Epidural

Performing at the cervical, thoracic, lumbar or sacral levels.Widely used for surgical anesthesia, obstetric analgesia, postoperativepain control and chronic painmanagement

Epidural anesthesia is slower in onset(10-20 minutes)It is not as intense as spinalanesthesia

Effects of central blocks

Sempathetic blockadeVasodilationHypotension

Sensory blockadeInterrupts both somatic and visceral painfulstimuli

Motor blockade

Advantages of central blocks

Morbidity –and mortality may be reducedby neuroaxial blockade

Incidence of venous thrombosisPulmonary embolismCardiac complications in high risk patientsBleeding and transfusion requirementsPneumonia and respiratory depression

Complications of neuroaxial blocks

Range from bothersome to cripplingand life-threatiningResult from medication introduced orthe needle used to perform theprocedure

Complications-cont.

NeedleBackacheHeadacheNerve injuryVascular injuryInfection

Medication=LAHigh blokadeSystemic toxicityLocal toxicityInfection

Plexus BlockadeInjectionInjection of of locallocal anestheticanesthetic adjacentadjacent toto a a plexusplexus, , e.g e.g cervicalcervical, , brachialbrachial oror lumbarlumbar plexusplexusUsesUses: : surgicalsurgical anesthesiaanesthesia oror postpost--operativeoperativeanalgesiaanalgesia in in thethe distributiondistribution of of thethe plexusplexusProceduresProcedures on on thethe armarm, , shouldershoulder, , trunktrunk oror legslegsAdvantagesAdvantages: : largelarge areaarea of of anesthesiaanesthesia withwithrelativelyrelatively smallsmall dosedose of of agentagent

DisadvantagesDisadvantages: : -- technicallytechnically complexcomplex, , potentialpotential forfortoxicitytoxicity andand neuropathyneuropathy

Brachial plexusC5 through C8 andT1Anesthesia of theshoulder and upperextremity

Topical AnesthesiaApplicationApplication of of locallocal anestheticanesthetic toto mucousmucousmembranemembrane -- corneacornea, , nasalnasal/oral /oral mucosamucosaUsesUses : : -- awakeawake oral oral oror nasalnasal intubationintubation, , superficialsuperficial surgicalsurgical procedureprocedure

AdvantagesAdvantages : : technicallytechnically easyeasyminimal minimal equipmentequipment

DisadvantagesDisadvantages : : potentialpotential forfor largelarge dosesdoses leadingleading toto toxicitytoxicity

Local/Field Anesthesia =Infiltration

ApplicationApplication of of locallocal subcutaneouslysubcutaneously totoanesthetizeanesthetize distaldistal nervenerve endingsendingsUsesUses: : -- SuturingSuturing, , minorminor superficialsuperficial surgerysurgery, , linelineplacementplacement, , moremore extensiveextensive surgerysurgery withwithsedationsedationAdvantagesAdvantages: : -- minimal minimal equipmentequipment, , technicallytechnicallyeasyeasy, , rapidrapid onsetonset

DisadvantagesDisadvantages: : -- potentialpotential forfor toxicitytoxicity ifif largelarge fieldfield

Bier Block

InjectionInjection of of locallocal anestheticanesthetic intravenouslyintravenouslyforfor anesthesiaanesthesia of an of an extremityextremityUsesUses -- anyany surgicalsurgical procedureprocedure on an on an extremityextremityAdvantagesAdvantages: : -- technicallytechnically simplesimple, minimal , minimal equipmentequipment, , rapidrapid onsetonset

DisadvantagesDisadvantages: : -- durationduration limitedlimited bybytolerancetolerance of of tourniquettourniquet painpain, , toxicitytoxicity

Peripheral nerve blockInjectingInjecting locallocal anestheticanesthetic nearnear thethe coursecourseof a of a namednamed nervenerveUsesUses: : -- SurgicalSurgical proceduresprocedures in in thethedistributiondistribution of of thethe blockedblocked nervenerveAdvantagesAdvantages: : -- relativelyrelatively smallsmall dosedose of of locallocal anestheticanesthetic toto covercover largelarge areaarea; ; rapidrapidonsetonset

DisadvantagesDisadvantages: : -- technicaltechnical complexitycomplexity, , neuropathyneuropathy

LocalLocal AnestheticsAnesthetics -- DefinitionDefinition

A A substancesubstance whichwhichreversiblyreversibly inhibitsinhibits nervenerveconductionconduction whenwhen appliedapplieddirectlydirectly toto tissuestissues at at nonnon--toxictoxic concentrationsconcentrations

Local Anesthetics

Mechanism of action is by reversibly blocking sodium channels to prevent depolarizationAnesthetic enters on axioplasmic side and attaches to receptor in middle of channel

Local Anesthetics

Linear molecules that have a lipophilic and hydrophilic end (ionizable)

low pH-- more in ionized state and unable to cross membraneadding sodium bicarb-- more in non-ionized state

Local Anesthetics

Two groups: esters and amidesesters metabolized by plasma cholinesteraseamides metabolized by cytochrome p-450

LocalLocal anestheticsanesthetics -- ClassesClasses

EstersEsters

CocaineCocaineChloroprocaineChloroprocaineProcaineProcaineTetracaineTetracaine

AmidesAmides

BupBupiivacainevacaineLLiidocainedocaineRopRopiivacainevacaineEtEtiidocainedocaineMepMepiivacainevacaine

LocalLocal anestheticsanesthetics -- DurationDuration

DeterminedDetermined byby rate of rate of eliminationelimination of of agentagentfromfrom site site injectedinjectedFactorsFactors includeinclude lipidlipid solubilitysolubility, , dosedose givengiven, , bloodblood flowflow at site, at site, additionaddition of of vasoconstrictorsvasoconstrictors ((doesdoes not not reliablyreliably prolongprolongallall agentsagents))SomeSome techniquestechniques allowallow multiplemultiple injectionsinjectionsoverover time time toto increaseincrease durationduration, e.g. , e.g. epiduralepidural cathetercatheter

PrecautionsEpinephrine combinations should not be used where circulation may be compromised by vasoconstriction

fingerstoesearsnosepenis

LocalLocal AnestheticsAnesthetics -- AllergyAllergyTrueTrue allergyallergy is is veryvery rarerareMostMost reactionsreactions areare resultedresulted fromfromester ester classclassEster Ester hydrolysishydrolysis (normal (normal metabolismmetabolism) ) leadsleads toto formationformation of of PABAPABA

LocalLocal AnestheticsAnesthetics –– ToxicityToxicity

TissueTissue toxicitytoxicityRareRareOccursOccurs ifif administeredadministered in in highhigh enoughenoughconcentrationsconcentrations ((greatergreater thanthan thosethose usedusedclinicallyclinically) ) UsuallyUsually relatedrelated toto preservativespreservatives addedadded totosolutionsolution

Systemic toxicityRelatedRelated toto bloodblood levellevel of of drugdrug

AbsoluteAbsolute overdoseoverdoseAccidentally intravascular injection

AllAll LA LA produceproduce a a similarsimilar picturepicture of of toxicitytoxicityDegreeDegree of of disturbancesdisturbances causedcaused byby toxicitytoxicity

PotencyPotency of of drugsdrugs: : lipidlipid solubilitysolubilityPharmacokineticsPharmacokinetics propertiesproperties

TheThe rate of rate of riserise of of plasmaplasma levelslevelsTheThe peakpeak levellevelTheThe fractionfraction of of unboundunbound drugdrug in in thethe circulationcirculation

0

5

10

15

20

25

30

Lign

ocai

nepl

asm

aco

nc. (

mcg

/mL)

Toxic effects

CVS depression

Respiratory arrest

Coma=CNS collapsConvulsionsUnconciousnessMuscular twitchingTinnitusVisual disturbanceLigthheadednessNumbness of tongue + Metallic taste

Prevention and Treatment of Toxicity

Primarily from intravascular injection or excessive dose -- anticipation

aspirate often with slow injectionask about CNS toxicityhave monitoring availableprepare with resuscitative equipment, CNS-depressant drugs, cardiovascular drugsABC’s

Treatment of Toxicity

Hoping without disability