General and Local Anesthetics

Local Anesthetic (Single Target)

Mode of Action

  • Reversible Inhibition of Action Potential
    • Inhibits Depolarization causing relaxation and prevents sodium from entering
  • Sodium Channel

Side Effects

  • CNS Stimulation

    • Causing Tremor
    • Euphoria

  • Seizures (Due to High Dosage)

  • Example

    • Ester (RCOOR)

    • Short Acting Local Anesthetic

      • Procaine
      • 1st synthetic local anesthetic
      • Chloroprocaine
      • Addition of a functional group Chlorine

    • Intermediate Acting Local Anesthetic

      • Cocaine
      • 1st natural local anesthetic
      • Inhibits Epinephrine or Alpha 1 causing Vasoconstriction
      • Benzocaine

    • Long Acting

      • Tetracaine

    • Amides (RCO)

    • Intermediate Acting Local Anesthetic

      • Lidocaine

      • Most Widely used Anesthetic

      • Prilocaine

      • Congener of Lidocaine

      • Converted into a metabolite called O-Toludine

        • O-Toludine is carcinogenic that causes Methemoglobinemia, that reduces the oxygen carrying capacity of the blood

      • EMLA = Eutectic Mixture Local Anesthetic

      • Specifically Lidocaine

        • This are mixtures that are given as topical administration
        • This is use for children who are afraid in injections

    • Long Acting Local Anesthetic

      • Bupivacaine

      • Causes Cardiotoxic

        • Causes Arrythmia

      • Levobupivacaine

      • Less Cardiotoxic

      • Use for Epidural Anesthesia

        • Pain and Labor during pregnancy

      • Administered Intrathecaly in the spinal cord

      • Ropivacaine

      • Less potent and High Dose

        • Causing less cardiotoxic effect

General Anesthesia

  • Stage 1
    • Induction/Analgesia
    • Removing the pain of the patient
    • The patient is aware or awake
  • Stage 2
    • Delirium/Disinhibition
    • Avoid this stage
    • Causes severe depolarization
    • Causes muscle excitation
  • Stage 3
    • Surgical Anesthesia
    • No Pain
    • Unconscious
    • Relax
    • No muscle movement
  • Stage 4
    • Medullary Depression
    • Avoid this stage
    • Causes Respiratory Depression
      • Patient cant breath
    • Causes Cardiovascular Depression

Goal of Anesthesia

  • Unconsiousness
  • Analgesia
  • Amnesia
  • Skeletal muscle relaxation
  • Loss of muscle reflexes

Mode of Action of Anesthesia

  • Stimulate GABA A-Chloride
  • Inhibits Sodium Influx
    • Causing depolarization
  • Inhibits Calcium Influx
    • To prevent inducing depolarization or muscle movement

Concepts of Anesthesia

  • Minimum Alveolar Concentration

    • Minimum concentration of an inhaled anesthetic at 1atm that prevents skeletal movement
    • Determines the Potency
    • High Minimum Alveolar Concentration
      • Low Potency
      • Nitrous Oxide
    • Low Minimum Alveolar Concentration
      • High Potency
      • Most Potent Halothane

  • Blood-Gas Partition Coefficient

    • Solubility of inhalation anesthetics in blood
    • High Blood/Gas Ratio increases the solubility in the blood
    • Causes Slow Onset and Recovery
    • High Blood/Gas Ratio
    • Halothane
      • Most Potent
    • Low Blood/Gas Ratio
    • Desflurane
      • Less Potent

NonHalogenated Drugs

  • Nitrous Oxide

    • Produce more analgesia
    • No Cardiovascular and Respiratory Depression
    • For minor surgery and dental surgery

  • Adverse Effect

    • Megaloblastic Anemia
    • Deficiency of B12 and B9
    • Causes mild euphoria
    • A feeling of great happiness or well-being

Halogenated Anesthetic (Inhalational Anesthetics)

  • Halothane

    • Most Potent
    • High Blood/Gas Ratio
    • Slow Onset and Recovery
    • Sensitize the heart to catecholamines
    • Hepatoxicity
    • Malignant hyperthermia or the fast rise of body
    • Treatment is Danthrolene

  • Enflurane and Isoflurane

    • Rapid induction and recovery
    • Less metabolic degradation
    • Produce little arrhythmia
    • Causes more respiratory depression
    • Enflurane is used in Asthmatics
    • Isoflurane is used for Neurosurgery

  • Desflurane and Sevoflurane

    • 1st line to be administered
    • Has the most rapid rate of induction and recovery
    • Desuflurane can cause irritation in the respiratory tract
    • Sevoflurane is close to an ideal anesthetic
    • Has pleasant odor
    • Low Blood Solubility
    • Less Arrhythmogenic
      • Causes a strong or irregular heart beat (palpitations), chest pain, or shortness of breath

Parenteral Anesthetics (Intravenous Anesthetics)

  • Barbiturates (Activate GABA) (Changes the opening of Chloride) (More chloride causes hyperpolarization)
    • Thiopental
    • Methohexital
  • Benzodiazepines (Activate GABA) (Changes the opening of Chloride) (More chloride causes hyperpolarization)
    • Midazolam
  • Opioids
    • Fentanyl
    • Fentanyl + Droperidol + Nitrous Oxide
      • For Neuroleptic Anesthesia
  • Propofol (Fospropofol)
    • Milk of Amnesia
    • Default induction Anesthetic
  • Etomidate
    • Rapid Induction to induce Anesthesia for conscious sedation
    • No Cardiovascular Risk
  • Ketamine
    • Avoid
    • Addictive
    • Blocks N-methyl-d-aspartate receptors
    • Receptor for Glutamate
    • Produces Dissociative Anesthesia
    • Causes Psychedelic
      • Dissociate from reality
      • Affects mood and perception

Inhalational Anesthetics