LOCAL ANESTHETICS - PowerPoint

							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