Local Anesthesia Flashcards
Local anesthesia
loss of sensation limited to local area or region of body
Local anesthetic
drugs that block generation and propagation of nerve impulses that result in REVERSIBLE REGIONAL LOSS OF FUNCTION
Three main types of local anesthesia
TOPICAL
PERINEURAL INFILTRATION
NERVE BLOCK
Perineural Advantage
EASE OF DELIVERY - specific area to be anesthetized
Nerve Block Advantage
LESS DRUG REQUIRED to block larger areas distal to injection site
Spinal Block
advantages?
injection of agent INTO CSF IN LUMBAR REGION OF SUBARACHNOID SPACE
more reliable block
minimal disruption of respiratory and cardiovascular block
Epidural block
injection of agent INTO EXTRADURAL SPACE
less reliable than spinal block
Local anesthetic MOA
BLOCKADE OF VOLTAGE GATED SODIUM CHANELS
decrease generation and conduction of action potentials
4 sites of action of local anesthetics
BIOTOXINS
LIDOCAINE
BENZOCAINE
COMBO OF 2 AND 3
Local anesthetics end in
Amides have
Esters have
-caine
two i’s
one i
Amides
longer half life
longer duration of action
METABOLIZED IN LIVER
Esters
short plasma half life
short duration of action
Fiber size effect on local anesthetic onset and recovery
Increase fiber = increase Cm - blocks B fibers first then A-alpha last
Cm
Cm - minimum anesthetic concentration
Site of deposition on local anesthetic onset and recovery
anesthesia occurs FIRST AT OUTER FIBERS as the drugs moves down concentration gradient
pH effect on local anesthetic onset and recovery
Increase pH = DECREASE Cm
Nerve stimulation rate effect on local anesthetic onset and recovery
higher frequency nerves are MORE SENSITIVE
Calcium concentration effect on local anesthetic onset and recovery
increase Ca = INCREASE Cm
Addition of vasoconstrictors effect on local anesthetic onset and recovery
REDUCES LA TOXICITY
BUT NEVER INJECT LA with vasoconstrictor into AREAS WITH END ARTERIOLES - can cause gangrene or sloughing off of tissues
Factors affecting Reversal
Dilution by ECF
Absorption into circulation
Redistribution
Use of vasoconstrictors
Amides metabolized by
Esters metabolized by
LIVER –> half life can be altered with individuals with hepatic problems
PLASMA –> PABA moiety –> can cause side effects
Potential Adverse Effect of LA
Hypersensitivity –MOST COMMONLY TO METHYLPARABEN
Systemic Toxicity – LESS LIKELY WITH ESTERS
Bupivicaine systemic toxicity
CARDIAC EFFECTS can cause complete cardiac collapse and death
Treatment for LAST
INTERVENOUS EMULSION OR INTRALIPID
forms a lipid sink
Lidocaine Important Notes
REFERENCE STANDARD FOR MOST ANESTHETICS
CAN BE GIVEN TOPICALLY AND INJECTED
Bupivicaine Important Notes
AGENT OF CHOICE FOR EPIDURAL INFUSION
EXCELLENT SPINAL ANESTHETIC
Articaine Important notes
DENTAL ANESTHETIC
Cocaine Important Notes
CURRENT USE FOR TOPICAL ANESTHETIC FOR ENT
Benzocaine Important Notes
TOPICAL ONLY due to enhanced lipid solubility
Chloroprocaine Important Notes
EPIDURAL AGENT FOR LABOR ANESTHESIA due to lower risk of systemic toxicity
Exparel Liposome Important Notes
BUPIVICAINE ENCASED IN LIPID
better relief
EMLA
eutectic mixture of local anesthetics
TAC
tetracaine, adrenaline, and cocaine
neurolytics
agents that are not reversible
Topical Local Anesthetics General Rule
TOPICALS TOO TOXIC FOR INJECTION
