Anesthesia
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  • The concentration of inhaled anesthetic in the inspired gas has a direct effect on both the maximum tension that can be achieved in the alveoli and rate of increase of its tension in the arterial blood. Increasing the anesthetic concentration in the inspired gases will speed up the rate of induction of anesthesia by increasing the delivery of anesthetic into the alveoli that will result to a rapid rise in alveolar tension of anesthetic. This rapid rise in tension of anestheic in the alveolus will promote the transfer of anesthetic from alveoli to blood resulting to increase in arterial or blood tension or concentration of anesthetic. So that the tension or concentration of anesthetic in the blood approaches that of the inspired gas mixture.
  • The concentration of inhaled anesthetic in the inspired gas has a direct effect on both the maximum tension that can be achieved in the alveoli and rate of increase of its tension in the arterial blood. Increasing the anesthetic concentration in the inspired gases will speed up the rate of induction of anesthesia by increasing the delivery of anesthetic into the alveoli that will result to a rapid rise in alveolar tension of anesthetic. This rapid rise in tension of anestheic in the alveolus will promote the transfer of anesthetic from alveoli to blood resulting to increase in arterial or blood tension or concentration of anesthetic. So that the tension or concentration of anesthetic in the blood approaches that of the inspired gas mixture.
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Transcript

  • 1. ANESTHESIA
  • 2. Anesthesia
    • Loss of consciousness
    • Analgesia
    • Adequate muscle relaxation
    Analgesia
    • Loss of sensation to pain
  • 3. Types of Anesthetics :
    • General Anesthetics
      • Reversible loss of consciousness
      • Loss of CNS activity
    • Local Anesthetics
      • No loss of consciousness
      • Reversible loss of pain sensation
  • 4. GENERAL ANESTHETICS:
    • INHALATIONAL ANESTHETICS
    • INTRAVENOUS ANESTHETICS
  • 5. STAGES OF GENERAL ANESTHESIA (Guedel)
    • Stage I: Analgesia
    • Stage II: Excitement/ Delirium
    • Stage III: Surgical Anesthesia
      • Plane I: reg. breathing  loss of eye movement
      • Plane II  initiation of IC muscle paralysis
      • Plane III:  completion ICM paralysis
      • Plane IV:  diaphragmatic paralysis
    • Stage IV: Medullary Paralysis
  • 6.
    • Pharmacokinetics:
    • tension (partial pressure) in the brain  depth
    • tension in this tissues  rate of induction and recovery
    • Flow of anesthetic during induction:
    • Anesthesia  Lungs  Arterial  Brain &
    • machine blood tissues
    GENERAL ANESTHETICS:
  • 7.
    • Pharmacokinetics:
    • absorption (uptake)
    • distribution
    • metabolism
    • elimination  lungs
    • Principal objective:
    • To achieve a constant and optimal brain partial pressure of the inhaled anesthetic
    GENERAL ANESTHETICS:
  • 8.
    • 2 PHASES:
          • Pulmonary Phase
          • Circulatory Phase
    GENERAL ANESTHETICS: UPTAKE
  • 9.
    • Pulmonary Phase
        • Concentration of the anesthetic agent in the inspired gas
        • Pulmonary ventilation
        • Transfer of anesthetic gases from alveoli to blood
          • solubility of the agent
          • rate of pulmonary blood flow
          • partial pressure in the alveoli and mixed venous blood
    GENERAL ANESTHETICS: UPTAKE
  • 10.
    • As a rule, the more soluble an anesthetic in the blood the more of it must be dissolved to raise the partial pressure.
  • 11.
    • Pulmonary Phase
        • Concentration of the anesthetic agent in the inspired gas
        • Pulmonary ventilation
        • Transfer of anesthetic gases from alveoli to blood
          • solubility of the agent
          • rate of pulmonary blood flow
          • partial pressure in the alveoli and mixed venous blood
    GENERAL ANESTHETICS: UPTAKE
  • 12. GENERAL ANESTHETICS: UPTAKE
    • Circulatory or Distribution Phase
        • Solubility
          • tissue:blood solubility coefficient
        • Tissue Blood Flow
            • Vessel-Rich group – 75% of CO
            • Muscle Group – 3%
            • Fatty Group – 2%
            • Vessel-Poor group - <1%
        • Partial Pressure of Gas in Arterial Blood and Tissues
  • 13.
    • RECOVERY and EMERGENCE
      • Factors affecting rate of Elimination
        • SOLUBILITY IN BLOOD & TISSUE
        • BLOOD FLOW
    • Flow of anesthetic during elimination:
    • Tissue/  Blood  Lungs  Anesthesia
    • Brain Machine
    GENERAL ANESTHETICS:
  • 14. Ideal Characteristics of Inhalational Anesthetics:
    • Rapid & pleasant induction & recovery
    • Rapid changes in depth of anesthesia
    • Adequate relaxation of smooth muscle
    • Wide margin of safety
    • Absence of toxic effect
  • 15. INHALATIONAL ANESTHETICS
    • GASEOUS ANESTHETIC:
        • NITROUS OXIDE
        • CYCLOPROPANE
    • VOLATILE ANESTHETIC:
    A. Halogenated B. Non Halogenated 1. Halothane 1. Ether 2. Enflurane 2. Chloroform 3. Isoflurane 4. Methoxyflurane 5. Sevoflurane 6. Desflurane
  • 16. INHALATIONAL ANESTHETICS
    • GASEOUS ANESTHETIC:
        • NITROUS OXIDE
        • CYCLOPROPANE
    • VOLATILE ANESTHETIC:
    A. Halogenated B. Non Halogenated 1. Halothane 1. Ether 2. Enflurane 2. Chloroform 3. Isoflurane 4. Methoxyflurane 5. Sevoflurane 6. Desflurane
  • 17. Properties of a Desirable Local Anesthetic
    • should not be irritating to tissues
    • should not cause permanent damage to nerves
    • have low systemic toxicity
    • must be effective
    • should have rapid onset but long duration of action
  • 18.
    • MOA: block nerve conduction
    • Structure:
      • aromatic group (Hydrophobic lipophilic)
      • amide group (hydrophilic)
        • tertiary amine or secondary amine
      • intermediate chain
        • Ester or Amide
    LOCAL ANESTHETICS
  • 19. Structure
    • CH 2 -CH 3
    • NH 2 O-O-CH 2 -CH 2 -N
    • O CH 2 -CH 3
    • Aromatic grp Alkyl Amide grp
    • Lipophilic chain Hydrophilic
  • 20.
    • METABOLISM:
      • Ester  plasma and liver esterases
      •  metabolite: PABA
      • Amide  liver
    • EXCRETION:
    • kidneys
    LOCAL ANESTHETICS
  • 21.
    • ROUTES OF ADMINISTRATION:
      • Topical
      • Local Infiltration
      • Nerve Block
      • Spinal or Intrathecal injection
      • Epidural
      • Caudal
    LOCAL ANESTHETICS
  • 22. LOCAL ANESTHETICS
    • ESTERS:
    • Cocaine
    • Procaine
    • Chloroprocaine
    • Tetracaine
    • AMIDES:
    • Lidocaine
    • Bupivacaine
    • Mepivacaine
    • Dibucaine
    • Prilocaine
    • Etidocaine
  • 23.
    • May also be classified into
    • Short acting – cocaine, procaine
    • Intermediate acting – lidocaine, mepivacaine, dibucaine, prilocaine
    • Long acting – tetracaine, bupivacaine, etidocaine
  • 24.
    • 1. Hepatotoxic agent a. Isoflurane
    • 2. Nephrotoxic agent b. Barbiturate
    • 3. Cardiotoxic agent c. Enflurane
    • 4. Thiopental d. Halothane
    • 5. Flammable agent e. Ether
    • Amide LA b. Esther LA
    • 6. Lidocaine
    • 7. Tetracaine
    • 8. Cocaine
    • 9. Bupivacaine
    • 10. Etidocaine