Download LOCAL ANESTHETICS

Dr .Rupak Bhattarai
 A local anesthetic is an agent that interrupts pain
impulses in a specific region of the body without a loss
of patient consciousness. Normally, the process is
completely reversible--the agent does not produce any
residual effect on the nerve fiber.
History
 The first local anesthetic was Cocaine which was isolated
from coca leaves by Albert Niemann in Germany in the
1860s. The very first clinical use of Cocaine was in 1884 by
Sigmund Freud who used it to wean a patient from
morphine addiction. It was Freud and his colleague Karl
Kollar who first noticed its anesthetic effect. Kollar first
introduced it to clinical ophthalmology as a topical ocular
anesthetic. Also in 1884, Dr. William Stewart Halsted was
the first to describe the injection of cocaine into a sensory
nerve trunk to create surgical anesthesia.
TYPES OF LOCAL ANESTHESIA
AMIDES:
 Bupivacaine(Marcaine)
 Etidocaine(Duranest)
 Lidocaine(Xylocaine)
 Mepivacaine(Carbocaine)
 Prilocaine(Citanest)
 Ropivacaine
Esters:
 Chloroprocaine .(Nesacaine)
 Cocaine.
 Procaine.
 Tetracaine .(Pontocaine)
Clinical Uses
Esters
 Benzocaine:Topical
 Chloroprocaine : Epidural,Infiltration,Peripheral nerve
block.
 Cocaine : Topical
 Procaine : Spinal, Infiltration,Peripheral nerve block.
 Tetracaine : Spinal,Topical
Amides:
 Bupivacaine: Epidural,Spinal,Infiltration,Peripheral
nerve block.
 Lidocaine: Epidural, Spinal,Infiltration,Peripheral
nerve block, Intravenous, Topical.
 Mepivacaine: Epidural,Infiltration,Peripheral nerve
block.
 Prilocaine : Peripheral nerve block(Dental).
 Ropivacaine : Epidural, Spinal,Infiltration,Peripheral
Nerve block.
Mechanism of Action
 Local anesthetics work to block nerve conduction by
reducing the influx of sodium ions into the nerve
cytoplasm.
 Sodium ions cannot flow into the neuron, thus the
potassium ions cannot flow out, thereby inhibiting the
depolarization of the nerve.
Local Anesthetics
 Mechanism of action is by reversibly blocking sodium
channels to prevent depolarization
 Anesthetic enters on axioplasmic side and attaches to
receptor in middle of channel
Local Anesthetic Toxicity
 Central nervous system
 initially-- lightheadedness, dizziness, tinnitus,
visual change
 later-- drowsiness, disorientation, slurred speech,
loss of consciousness, convulsions
 finally-- respiratory depression
 Cardiovascular
 Myocardial depression and vasodilation-- hypotension
and circulatory collapse
 Allergic reactions-- rare (less than 1%)
 preservatives or metabolites of esters
 rash, bronchospasm
Prevention and Treatment of
Toxicity
 Primarily from intravascular injection or excessive dose
-- anticipation
 aspirate often with slow injection
 ask about CNS toxicity
 have monitoring available
 prepare with resuscitative equipment, CNS-depressant
drugs, cardiovascular drugs
 ABC’s
Types of Local Anesthesia
 Local Infiltration (Local Anesthesia). Local
infiltration occurs when the nerve endings in the skin
and subcutaneous tissues are blocked by direct contact
with a local anesthetic, which is injected into the
tissue. Local infiltration is used primarily for surgical
procedures involving a small area of tissue (for
example, suturing a cut).
Topical Block
 . A topical block is accomplished by applying the
anesthetic agent to mucous membrane surfaces and in that
way blocking the nerve terminals in the mucosa. This
technique is often used during examination procedures
involving the respiratory tract. The anesthetic agent is
rapidly absorbed into the bloodstream. The topical block
easily anesthetizes the surface of the cornea (of the eye)
and the oral mucosa.
Surface Anesthesia
 This type of anesthesia is accomplished by the
application of a local anesthetic to skin. Surface
anesthesia is used to relieve itching, burning, and
surface pain (for example, as seen in minor sunburns)
Nerve Block
 In this type of anesthesia, a local anesthetic is injected
around a nerve that leads to the operative site. Usually
more concentrated forms of local anesthetic solutions
are used for this type of anesthesia.
Epidural Anesthesia
 This type of anesthesia is accomplished by injecting a
local anesthetic into the Epidural space.
 The Epidural space is one of the coverings of the spinal
cord.
Spinal Anesthesia
 In spinal anesthesia, the local anesthetic is injected
into the subarachnoid space.
Vasoconstrictors
 Vasoconstrictors decrease the rate of vascular absorption
which allows more anesthetic to reach the nerve
membrane and improves the depth of anesthesia.
 1:200,000 epinephrine appears to be the best
vasoconstrictor