Anesthesia 3
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Anesthesia 3

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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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Anesthesia 3 Anesthesia 3 Presentation Transcript

  • ANESTHESIA Claro M. Isidro md
  • Anesthesia
    • Loss of consciousness
    • Analgesia
    • Adequate muscle relaxation
    Analgesia
    • Loss of sensation to pain
  • Types of Anesthetics :
    • General Anesthetics
      • Reversible loss of consciousness
      • Loss of CNS activity
    • Local Anesthetics
      • No loss of consciousness
      • Reversible loss of pain sensation
  • GENERAL ANESTHETICS:
    • INHALATIONAL ANESTHETICS
    • INTRAVENOUS ANESTHETICS
  • 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
    • 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:
    • Pharmacokinetics:
    • absorption (uptake)
    • distribution
    • metabolism
    • elimination  lungs
    • Principal objective:
    • To achieve a constant and optimal brain partial pressure of the inhaled anesthetic
    GENERAL ANESTHETICS:
    • 2 PHASES:
          • Pulmonary Phase
          • Circulatory Phase
    GENERAL ANESTHETICS: UPTAKE
    • 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
  • GENERAL ANESTHETICS: SOLUBILITY Partition Coefficient Blood:Gas Brain:Blood Soluble Methoxyflurane 12 2 Intermediate Halothane 2.4 1.9 Enflurane 1.9 1.5 Isoflurane 1.4 1.6 Poorly soluble Nitrous Oxide 0.46 1.1 Desflurane 0.42 1.3 Sevoflurane 0.59 1.7
    • As a rule, the more soluble an anesthetic in the blood the more of it must be dissolved to raise the partial pressure.
    • 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
  • 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
    • 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:
  • 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
  • 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
  • Halothane
    • 2 bromo-111 triflouroethane
    • is a non ether derivative ( an ethane)
    • vapor is pleasant to smell and non-irritating
    • can cause a dose dependent reduction of arterial blood pressure due to:
    • 1.    Direct depression of the myocardium
    • 2. The normal baroreceptor mediated tachycardia in response to hypotension is obtunded
    • sensitizes the myocardium to catecholamines leading to cardiac arrhythmia’s
    • causes a dose related reduction in the ventilatory response to carbon dioxide
    • produce adequate muscle relaxation
    • has no toxic effect on the kidneys
    • Repeated  administration over a short period of time has been implicated to produce halothane hepatitis
    • another dreaded complication is malignant hyperthermia, which is characterized by the following:
    • 1. Rapid rise in body temperature
    • 2. massive increase in oxygen consumption
    • 3. increase production of carbon dioxide
    • Cardiotoxic, Hepatotoxic but not Nephrotoxic
  • Enflurane
    • 2 chloro-112 trifluroethyl difluromethyl ether
    • an halogenated ether derivative
    • produce mild stimulation of salivation and bronchial
    • cause dose dependent myocardial depression similar to that of halothane
    • sensitizes the myocardium to the effect of catcholamines , no unusual effect on the GIT
    • muscle relaxation is greater than that of halothane
    • contraindicated in patient with seizure disorder because it cause CNS irritability in high doses
    • the free fluoride radical a metabolite of enflurane has been implicated to its renal toxicity so it is contraindicated in patient with renal disorder
    • Cadiotoxic, Nephrotoxic but not Hepatotoxic
  • Isoflurane
    • 1 chloro-222 trifluroethyl difluromethyl ether
    • an halogenated ether derivative
    • the chemical and physical properties are similar to those of its isomer enflurane
    • does not sensitize the myocardium to the effect of cathecholamines
    • cerebral blood flow is increased while the cerebral metabolism is reduced
    • produce adequate muscle relaxation
    • less nephrotoxic than enflurane
    • less hepatotoxic than halothane
    • agent of choice for cardiac surgery
    • non Cardiotoxic, non Hepatotoxic, non Nephrotoxic
    • Least vicerotoxic
  • Methoxyflurane
    • 2,2dichloro- 1,1 difluroethyl methyl ether
    • it is clear, colorless liquid with sweet fruity odor
    • non flammable and non explosive in air
    • most potent of the inhalational anesthetic
    • induction of anesthesia is slow due to its high solubility coefficient
    • respiratory and cardiovascular depression is generally similar to that of halothane
    • sensitize the myocardium to the effects of catecholamines
    • nephrotoxicity and hepatotoxicity are the major disadvantage
    • most toxic of the inhalational anesthetic
    • Cardiotoxic, Hepatotoxic, and Nephrotoxic
  • Desflurane
    • a fluorinated methyl ethyl ether that differ from isoflurane only by substitution of a fluoride atom from chlorine
    • can produce a dose related decrease in blood pressure and cardiac output
    • non Cardiotoxic, non Hepatotoxic, non Nephrotoxic
    • Sevoflurane
    • also a fluorinated methyl ethyl ether
    • not irritating to the airways
    • cardivascular effect is similar to isoflurane
  • Non Hologenated
    • Ether
    • first anesthetic discovered
    • seldom use today because of its flammability and explosive property
    • Chloroform
    • no longer use today because of liver toxicity
    • non explosive and non flammable
    • has rapid induction and recovery
  • Gaseous Anesthetics
    • Nitrous Oxide
    • sweet smelling, non irritating, colorless gas
    • the only inorganic gas in common use possessing anesthetic properties
    • potent analgesic but a weak anesthetic in the sense that it does not produce adequate muscular relaxation
    • ventilatory drive is not affected
    • little or no cardiovascular effect
    • Cyclopropane
    • explosive and flammable property
  • 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
    • BARBITURATES
    • the most commonly use barbiturates is the ultra short acting thiopental
    • following a single IV anesthetic dose of thiopental unconsciousness occur after 10-20 seconds and returns in 20-30 minutes
    • poor analgesic and may even increase the sensitivity to pain (hyperalgesia) when administered in inadequate amounts.
    • Not irritating to the respiratory tract
    • Cerebral blood flow and cerebral metabolic rate are reduced
    • Produce a dose related depression of respiration and circulation
    • Agent of choice for induction of anesthesia in patient with increased intracranial pressure and hypertension
    • Contraindicated in patient with acute intermittent porphyria and hypotension
    INTRAVENOUS ANESTHETICS
  • Benzodiazepines (Diazepam)
    • first introduced for the treatment of anxiety
    • rapidly absorbed from the GIT after oral administration
    • hypnosis and unconsciousness may be produced with large doses
    • cause amnesia in 50% of patients characteristically Anterograde type
    • may cause moderate depression of circulation and respiration
    • they are not analgesic and it is necessary to combine several drugs to achieve surgical levels of anesthesia
    • Ketamine HCl
    • used for induction of dissociative anesthesia
    • a sensation of dissociation is noticed within 15 seconds and unconsciousness becomes apparent within another 30 seconds and lasts for some 40 minutes
    • intense analgesia and amnesia are established rapidly
    • muscular relaxation is poor
    • cardiovascular and respiratory system are stable
    • drug of choice for induction of anesthesia in children and hypotensive patients
    • contraindicated in patients with hypertension because it increase sympathetic activity
    • can cause increase intraocular pressure
    • contraindicated in patient with glaucoma
  • Propofol
    • 2,6 Diisoprophylpenol
    • produces anesthesia at a rate similar to that of barbiturates
    • cause marked decrease in systemic blood pressure during induction
    • post operative vomiting is less common and may have anti-emetic property
    • hypersensitivity is less common
  • 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
    • MOA: block nerve conduction
    • Structure:
      • aromatic group (Hydrophobic lipophilic)
      • amide group (hydrophilic)
        • tertiary amine or secondary amine
      • intermediate chain
        • Ester or Amide
    LOCAL ANESTHETICS
  • 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
    • METABOLISM:
      • Ester  plasma and liver esterases
      •  metabolite: PABA
      • Amide  liver
    • EXCRETION:
    • kidneys
    LOCAL ANESTHETICS
    • ROUTES OF ADMINISTRATION:
      • Topical
      • Local Infiltration
      • Nerve Block
      • Spinal or Intrathecal injection
      • Epidural
      • Caudal
    LOCAL ANESTHETICS
  • LOCAL ANESTHETICS
    • ESTERS:
    • Cocaine
    • Procaine
    • Chloroprocaine
    • Tetracaine
    • AMIDES:
    • Lidocaine
    • Bupivacaine
    • Mepivacaine
    • Dibucaine
    • Prilocaine
    • Etidocaine
    • May also be classified into
    • Short acting – cocaine, procaine
    • Intermediate acting – lidocaine, mepivacaine, dibucaine, prilocaine
    • Long acting – tetracaine, bupivacaine, etidocaine
  •  
    • 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