RegionalRegional Anesthesia: AnAnesthesia: AnIntroductionIntroduction

Jason Ramirez, MDJason Ramirez, MD

Associate Director Acute Pain ServiceAssociate Director Acute Pain Service

University HospitalUniversity Hospital

March 2007March 2007

ObjectivesObjectives

•• Understand the basic mechanism of actionUnderstand the basic mechanism of actionfor local anestheticsfor local anesthetics

•• Understand the difference betweenUnderstand the difference betweenneuraxial and peripheral nerve blocksneuraxial and peripheral nerve blocks

•• Be able to name some of the benefits andBe able to name some of the benefits andrisks associated with regional anesthesiarisks associated with regional anesthesia

•• Be familiar with some of the commonBe familiar with some of the commonregional techniques used at Universityregional techniques used at UniversityHospitalHospital

Local Anesthetics: Cornerstone ofLocal Anesthetics: Cornerstone ofRegional AnesthesiaRegional Anesthesia

•• Temporary blockade of neuronalTemporary blockade of neuronaltransmission when local anesthetics (LAs)transmission when local anesthetics (LAs)injected near nerve fibersinjected near nerve fibers

•• Results in motor and sensory blockadeResults in motor and sensory blockade•• Dilute concentrations of LAs can provideDilute concentrations of LAs can provide

sensory blockade while preserving motorsensory blockade while preserving motorfunctionfunction

Motor and Sensory BlockadeMotor and Sensory Blockade

Mechanism of ActionMechanism of Action

•• Mechanism of ActionMechanism of Action•• Local Anesthetics cross nerve membranesLocal Anesthetics cross nerve membranes

where they stop axonal conductionwhere they stop axonal conduction•• Local Anesthetics exist in 2 formsLocal Anesthetics exist in 2 forms

•• the unionized weak base form the unionized weak base form ……..LA..LA•• crosses nerve membranescrosses nerve membranes

•• The ionized formThe ionized form……..........................LAH..........................LAH++

•• binds NA channels preventingbinds NA channels preventingdepolarizationdepolarization

Mechanism of ActionMechanism of Action

•• Unionized form.. LA.. crosses nerve membraneUnionized form.. LA.. crosses nerve membrane•• Becomes ionized .. Becomes ionized .. LAHLAH++.. and blocks sodium channels.. and blocks sodium channels

Local Anesthetic StructureLocal Anesthetic Structure

CH3

NH

CH3

C CH2 N

C2H5

O

C2H5

Aromatic Ring

Intermediate Chain Tertiary

Amine

Local Anesthetic StructureLocal Anesthetic Structure

•• Determines Local Anesthetic Class and MetabolismDetermines Local Anesthetic Class and Metabolism

NH C CH2

O

Intermediate Chain

Types of Regional AnesthesiaTypes of Regional Anesthesia

•• Neuraxial AnesthesiaNeuraxial Anesthesia•• Local anesthetic is injected into the neuraxisLocal anesthetic is injected into the neuraxis•• Site of action is at the nerve rootSite of action is at the nerve root•• Results motor and/or sensory block whichResults motor and/or sensory block which

follows a dermatomal patternfollows a dermatomal pattern•• Includes epidural and spinal anesthesiaIncludes epidural and spinal anesthesia

•• Peripheral Nerve BlockadePeripheral Nerve Blockade•• LA injected near peripheral nervesLA injected near peripheral nerves•• Resulting block follows the innervation of eachResulting block follows the innervation of each

particular nerveparticular nerve

Why Regional Anesthesia?Why Regional Anesthesia?

•• Benefits of a Regional TechniqueBenefits of a Regional Technique

•• avoidance of general anesthesiaavoidance of general anesthesia•• no airway instrumentationno airway instrumentation•• no risk of malignant hyperthermiano risk of malignant hyperthermia•• less risk of post-op nausea and vomitingless risk of post-op nausea and vomiting

Benefits ContinuedBenefits Continued

•• decreased incidence of DVT, PEdecreased incidence of DVT, PE•• decreased amount of intraoperativedecreased amount of intraoperative

blood lossblood loss•• improved pain control and patientimproved pain control and patient

satisfactionsatisfaction•• less opioid useless opioid use•• earlier ambulation and improvedearlier ambulation and improved

rehabilitation outcomesrehabilitation outcomes

Risks of Regional AnesthesiaRisks of Regional Anesthesia

•• Block FailureBlock Failure•• Direct Tissue DamageDirect Tissue Damage

•• hematoma formationhematoma formation•• direct nerve traumadirect nerve trauma•• damage to other organs or structuresdamage to other organs or structures

•• Local EffectsLocal Effects•• nerve toxicitynerve toxicity

Risks ContinuedRisks Continued

•• Systemic EffectsSystemic Effects•• Allergic reactionsAllergic reactions•• Excessive or high blockExcessive or high block

•• hypotensionhypotension•• bradycardiabradycardia•• loss of airwayloss of airway

•• Local anesthetic toxicityLocal anesthetic toxicity•• seizuresseizures•• CV collapseCV collapse

Neuraxial AnesthesiaNeuraxial Anesthesiaspinal and epiduralspinal and epidural

•• Results in dermatomal pattern ofResults in dermatomal pattern ofblockadeblockade

Epidural and SpinalEpidural and Spinal

•• epidural catheter placement for laborepidural catheter placement for laboranalgesiaanalgesia

Epidural Catheter PlacementEpidural Catheter Placement

Peripheral Nerve Blockade at thePeripheral Nerve Blockade at theUniversity HospitalUniversity Hospital

•• Common Block ProceduresCommon Block Procedures•• Popliteal FossaPopliteal Fossa•• Sciatic NerveSciatic Nerve•• Femoral NerveFemoral Nerve•• Lumbar PlexusLumbar Plexus•• Brachial PlexusBrachial Plexus

•• Interscalene, SupraclavicularInterscalene, Supraclavicular•• Infraclavicular, AxillaryInfraclavicular, Axillary

Peripheral Nerve BlockadePeripheral Nerve Blockade

•• Single injection popliteal nerve blockSingle injection popliteal nerve blockfor foot and ankle surgeryfor foot and ankle surgery

Peripheral Nerve BlockadePeripheral Nerve Blockade

•• Sciatic nerve block for LE surgerySciatic nerve block for LE surgery

Peripheral Nerve BlockPeripheral Nerve Block

•• Femoral Nerve block for post-op painFemoral Nerve block for post-op paincontrol following knee surgerycontrol following knee surgery

Peripheral Nerve BlockadePeripheral Nerve Blockade•• Psoas compartment block placing LAPsoas compartment block placing LA

into the lumbar plexusinto the lumbar plexus•• Utilized in hip replacement surgeryUtilized in hip replacement surgery

Peripheral Nerve BlockadePeripheral Nerve Blockade

•• Interscalene approach to the brachialInterscalene approach to the brachialplexusplexus

•• Used in shoulder replacement andUsed in shoulder replacement androtator cuff repairrotator cuff repair

ReferencesReferences

• Rathmell, Regional Anesthesia The Requisites In Anesthesiology,2004

• Morgan, Clinical Anesthesiology 3rd Ed, 2002

• New York School of Regional Anesthesia Website, NYSORA.com• Google Images Search links

• http://mywebpages.comcast.net/epollak/PSY255_pix/PSY255_pix.htm

• adam.about.com/surgery/100195.htm• http://www.apsf.org/resource_center/newsletter/2005/fall/epidu

ral.jpg• http://www.thegooddrugsguide.com/gallery/images/c_coca_lea

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