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Anesthesia 3

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Anesthesia 3

  1. 1. ANESTHESIA Claro M. Isidro md
  2. 2. Anesthesia <ul><li>Loss of consciousness </li></ul><ul><li>Analgesia </li></ul><ul><li>Adequate muscle relaxation </li></ul>Analgesia <ul><li>Loss of sensation to pain </li></ul>
  3. 3. Types of Anesthetics : <ul><li>General Anesthetics </li></ul><ul><ul><li>Reversible loss of consciousness </li></ul></ul><ul><ul><li>Loss of CNS activity </li></ul></ul><ul><li>Local Anesthetics </li></ul><ul><ul><li>No loss of consciousness </li></ul></ul><ul><ul><li>Reversible loss of pain sensation </li></ul></ul>
  4. 4. GENERAL ANESTHETICS: <ul><li>INHALATIONAL ANESTHETICS </li></ul><ul><li>INTRAVENOUS ANESTHETICS </li></ul>
  5. 5. STAGES OF GENERAL ANESTHESIA (Guedel) <ul><li>Stage I: Analgesia </li></ul><ul><li>Stage II: Excitement/ Delirium </li></ul><ul><li>Stage III: Surgical Anesthesia </li></ul><ul><ul><li>Plane I: reg. breathing  loss of eye movement </li></ul></ul><ul><ul><li>Plane II  initiation of IC muscle paralysis </li></ul></ul><ul><ul><li>Plane III:  completion ICM paralysis </li></ul></ul><ul><ul><li>Plane IV:  diaphragmatic paralysis </li></ul></ul><ul><li>Stage IV: Medullary Paralysis </li></ul>
  6. 6. <ul><li>Pharmacokinetics: </li></ul><ul><li>tension (partial pressure) in the brain  depth </li></ul><ul><li>tension in this tissues  rate of induction and recovery </li></ul><ul><li>Flow of anesthetic during induction: </li></ul><ul><li>Anesthesia  Lungs  Arterial  Brain & </li></ul><ul><li>machine blood tissues </li></ul>GENERAL ANESTHETICS:
  7. 7. <ul><li>Pharmacokinetics: </li></ul><ul><li>absorption (uptake) </li></ul><ul><li>distribution </li></ul><ul><li>metabolism </li></ul><ul><li>elimination  lungs </li></ul><ul><li>Principal objective: </li></ul><ul><li>To achieve a constant and optimal brain partial pressure of the inhaled anesthetic </li></ul>GENERAL ANESTHETICS:
  8. 8. <ul><li>2 PHASES: </li></ul><ul><ul><ul><ul><li>Pulmonary Phase </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Circulatory Phase </li></ul></ul></ul></ul>GENERAL ANESTHETICS: UPTAKE
  9. 9. <ul><li>Pulmonary Phase </li></ul><ul><ul><ul><li>Concentration of the anesthetic agent in the inspired gas </li></ul></ul></ul><ul><ul><ul><li>Pulmonary ventilation </li></ul></ul></ul><ul><ul><ul><li>Transfer of anesthetic gases from alveoli to blood </li></ul></ul></ul><ul><ul><ul><ul><li>solubility of the agent </li></ul></ul></ul></ul><ul><ul><ul><ul><li>rate of pulmonary blood flow </li></ul></ul></ul></ul><ul><ul><ul><ul><li>partial pressure in the alveoli and mixed venous blood </li></ul></ul></ul></ul>GENERAL ANESTHETICS: UPTAKE
  10. 10. 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
  11. 11. <ul><li>As a rule, the more soluble an anesthetic in the blood the more of it must be dissolved to raise the partial pressure. </li></ul>
  12. 12. <ul><li>Pulmonary Phase </li></ul><ul><ul><ul><li>Concentration of the anesthetic agent in the inspired gas </li></ul></ul></ul><ul><ul><ul><li>Pulmonary ventilation </li></ul></ul></ul><ul><ul><ul><li>Transfer of anesthetic gases from alveoli to blood </li></ul></ul></ul><ul><ul><ul><ul><li>solubility of the agent </li></ul></ul></ul></ul><ul><ul><ul><ul><li>rate of pulmonary blood flow </li></ul></ul></ul></ul><ul><ul><ul><ul><li>partial pressure in the alveoli and mixed venous blood </li></ul></ul></ul></ul>GENERAL ANESTHETICS: UPTAKE
  13. 13. GENERAL ANESTHETICS: UPTAKE <ul><li>Circulatory or Distribution Phase </li></ul><ul><ul><ul><li>Solubility </li></ul></ul></ul><ul><ul><ul><ul><li>tissue:blood solubility coefficient </li></ul></ul></ul></ul><ul><ul><ul><li>Tissue Blood Flow </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Vessel-Rich group – 75% of CO </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Muscle Group – 3% </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Fatty Group – 2% </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Vessel-Poor group - <1% </li></ul></ul></ul></ul></ul><ul><ul><ul><li>Partial Pressure of Gas in Arterial Blood and Tissues </li></ul></ul></ul>
  14. 14. <ul><li>RECOVERY and EMERGENCE </li></ul><ul><ul><li>Factors affecting rate of Elimination </li></ul></ul><ul><ul><ul><li>SOLUBILITY IN BLOOD & TISSUE </li></ul></ul></ul><ul><ul><ul><li>BLOOD FLOW </li></ul></ul></ul><ul><li>Flow of anesthetic during elimination: </li></ul><ul><li>Tissue/  Blood  Lungs  Anesthesia </li></ul><ul><li>Brain Machine </li></ul>GENERAL ANESTHETICS:
  15. 15. Ideal Characteristics of Inhalational Anesthetics: <ul><li>Rapid & pleasant induction & recovery </li></ul><ul><li>Rapid changes in depth of anesthesia </li></ul><ul><li>Adequate relaxation of smooth muscle </li></ul><ul><li>Wide margin of safety </li></ul><ul><li>Absence of toxic effect </li></ul>
  16. 16. INHALATIONAL ANESTHETICS <ul><li>GASEOUS ANESTHETIC: </li></ul><ul><ul><ul><li>NITROUS OXIDE </li></ul></ul></ul><ul><ul><ul><li>CYCLOPROPANE </li></ul></ul></ul><ul><li>VOLATILE ANESTHETIC: </li></ul>A. Halogenated B. Non Halogenated 1. Halothane 1. Ether 2. Enflurane 2. Chloroform 3. Isoflurane 4. Methoxyflurane 5. Sevoflurane 6. Desflurane
  17. 17. Halothane <ul><li>2 bromo-111 triflouroethane </li></ul><ul><li>is a non ether derivative ( an ethane) </li></ul><ul><li>vapor is pleasant to smell and non-irritating </li></ul><ul><li>can cause a dose dependent reduction of arterial blood pressure due to: </li></ul><ul><li>1.    Direct depression of the myocardium </li></ul><ul><li>2. The normal baroreceptor mediated tachycardia in response to hypotension is obtunded </li></ul><ul><li>sensitizes the myocardium to catecholamines leading to cardiac arrhythmia’s </li></ul><ul><li>causes a dose related reduction in the ventilatory response to carbon dioxide </li></ul><ul><li>produce adequate muscle relaxation </li></ul><ul><li>has no toxic effect on the kidneys </li></ul>
  18. 18. <ul><li>Repeated  administration over a short period of time has been implicated to produce halothane hepatitis </li></ul><ul><li>another dreaded complication is malignant hyperthermia, which is characterized by the following: </li></ul><ul><li>1. Rapid rise in body temperature </li></ul><ul><li>2. massive increase in oxygen consumption </li></ul><ul><li>3. increase production of carbon dioxide </li></ul><ul><li>Cardiotoxic, Hepatotoxic but not Nephrotoxic </li></ul>
  19. 19. Enflurane <ul><li>2 chloro-112 trifluroethyl difluromethyl ether </li></ul><ul><li>an halogenated ether derivative </li></ul><ul><li>produce mild stimulation of salivation and bronchial </li></ul><ul><li>cause dose dependent myocardial depression similar to that of halothane </li></ul><ul><li>sensitizes the myocardium to the effect of catcholamines , no unusual effect on the GIT </li></ul><ul><li>muscle relaxation is greater than that of halothane </li></ul><ul><li>contraindicated in patient with seizure disorder because it cause CNS irritability in high doses </li></ul><ul><li>the free fluoride radical a metabolite of enflurane has been implicated to its renal toxicity so it is contraindicated in patient with renal disorder </li></ul><ul><li>Cadiotoxic, Nephrotoxic but not Hepatotoxic </li></ul>
  20. 20. Isoflurane <ul><li>1 chloro-222 trifluroethyl difluromethyl ether </li></ul><ul><li>an halogenated ether derivative </li></ul><ul><li>the chemical and physical properties are similar to those of its isomer enflurane </li></ul><ul><li>does not sensitize the myocardium to the effect of cathecholamines </li></ul><ul><li>cerebral blood flow is increased while the cerebral metabolism is reduced </li></ul><ul><li>produce adequate muscle relaxation </li></ul><ul><li>less nephrotoxic than enflurane </li></ul><ul><li>less hepatotoxic than halothane </li></ul><ul><li>agent of choice for cardiac surgery </li></ul><ul><li>non Cardiotoxic, non Hepatotoxic, non Nephrotoxic </li></ul><ul><li>Least vicerotoxic </li></ul>
  21. 21. Methoxyflurane <ul><li>2,2dichloro- 1,1 difluroethyl methyl ether </li></ul><ul><li>it is clear, colorless liquid with sweet fruity odor </li></ul><ul><li>non flammable and non explosive in air </li></ul><ul><li>most potent of the inhalational anesthetic </li></ul><ul><li>induction of anesthesia is slow due to its high solubility coefficient </li></ul><ul><li>respiratory and cardiovascular depression is generally similar to that of halothane </li></ul><ul><li>sensitize the myocardium to the effects of catecholamines </li></ul><ul><li>nephrotoxicity and hepatotoxicity are the major disadvantage </li></ul><ul><li>most toxic of the inhalational anesthetic </li></ul><ul><li>Cardiotoxic, Hepatotoxic, and Nephrotoxic </li></ul>
  22. 22. Desflurane <ul><li>a fluorinated methyl ethyl ether that differ from isoflurane only by substitution of a fluoride atom from chlorine </li></ul><ul><li>can produce a dose related decrease in blood pressure and cardiac output </li></ul><ul><li>non Cardiotoxic, non Hepatotoxic, non Nephrotoxic </li></ul><ul><li>Sevoflurane </li></ul><ul><li>also a fluorinated methyl ethyl ether </li></ul><ul><li>not irritating to the airways </li></ul><ul><li>cardivascular effect is similar to isoflurane </li></ul>
  23. 23. Non Hologenated <ul><li>Ether </li></ul><ul><li>first anesthetic discovered </li></ul><ul><li>seldom use today because of its flammability and explosive property </li></ul><ul><li>Chloroform </li></ul><ul><li>no longer use today because of liver toxicity </li></ul><ul><li>non explosive and non flammable </li></ul><ul><li>has rapid induction and recovery </li></ul>
  24. 24. Gaseous Anesthetics <ul><li>Nitrous Oxide </li></ul><ul><li>sweet smelling, non irritating, colorless gas </li></ul><ul><li>the only inorganic gas in common use possessing anesthetic properties </li></ul><ul><li>potent analgesic but a weak anesthetic in the sense that it does not produce adequate muscular relaxation </li></ul><ul><li>ventilatory drive is not affected </li></ul><ul><li>little or no cardiovascular effect </li></ul><ul><li>Cyclopropane </li></ul><ul><li>explosive and flammable property </li></ul>
  25. 25. INHALATIONAL ANESTHETICS <ul><li>GASEOUS ANESTHETIC: </li></ul><ul><ul><ul><li>NITROUS OXIDE </li></ul></ul></ul><ul><ul><ul><li>CYCLOPROPANE </li></ul></ul></ul><ul><li>VOLATILE ANESTHETIC: </li></ul>A. Halogenated B. Non Halogenated 1. Halothane 1. Ether 2. Enflurane 2. Chloroform 3. Isoflurane 4. Methoxyflurane 5. Sevoflurane 6. Desflurane
  26. 26. <ul><li>BARBITURATES </li></ul><ul><li>the most commonly use barbiturates is the ultra short acting thiopental </li></ul><ul><li>following a single IV anesthetic dose of thiopental unconsciousness occur after 10-20 seconds and returns in 20-30 minutes </li></ul><ul><li>poor analgesic and may even increase the sensitivity to pain (hyperalgesia) when administered in inadequate amounts. </li></ul><ul><li>Not irritating to the respiratory tract </li></ul><ul><li>Cerebral blood flow and cerebral metabolic rate are reduced </li></ul><ul><li>Produce a dose related depression of respiration and circulation </li></ul><ul><li>Agent of choice for induction of anesthesia in patient with increased intracranial pressure and hypertension </li></ul><ul><li>Contraindicated in patient with acute intermittent porphyria and hypotension </li></ul>INTRAVENOUS ANESTHETICS
  27. 27. Benzodiazepines (Diazepam) <ul><li>first introduced for the treatment of anxiety </li></ul><ul><li>rapidly absorbed from the GIT after oral administration </li></ul><ul><li>hypnosis and unconsciousness may be produced with large doses </li></ul><ul><li>cause amnesia in 50% of patients characteristically Anterograde type </li></ul><ul><li>may cause moderate depression of circulation and respiration </li></ul><ul><li>they are not analgesic and it is necessary to combine several drugs to achieve surgical levels of anesthesia </li></ul>
  28. 28. <ul><li>Ketamine HCl </li></ul><ul><li>used for induction of dissociative anesthesia </li></ul><ul><li>a sensation of dissociation is noticed within 15 seconds and unconsciousness becomes apparent within another 30 seconds and lasts for some 40 minutes </li></ul><ul><li>intense analgesia and amnesia are established rapidly </li></ul><ul><li>muscular relaxation is poor </li></ul><ul><li>cardiovascular and respiratory system are stable </li></ul><ul><li>drug of choice for induction of anesthesia in children and hypotensive patients </li></ul><ul><li>contraindicated in patients with hypertension because it increase sympathetic activity </li></ul><ul><li>can cause increase intraocular pressure </li></ul><ul><li>contraindicated in patient with glaucoma </li></ul>
  29. 29. Propofol <ul><li>2,6 Diisoprophylpenol </li></ul><ul><li>produces anesthesia at a rate similar to that of barbiturates </li></ul><ul><li>cause marked decrease in systemic blood pressure during induction </li></ul><ul><li>post operative vomiting is less common and may have anti-emetic property </li></ul><ul><li>hypersensitivity is less common </li></ul>
  30. 30. Properties of a Desirable Local Anesthetic <ul><li>should not be irritating to tissues </li></ul><ul><li>should not cause permanent damage to nerves </li></ul><ul><li>have low systemic toxicity </li></ul><ul><li>must be effective </li></ul><ul><li>should have rapid onset but long duration of action </li></ul>
  31. 31. <ul><li>MOA: block nerve conduction </li></ul><ul><li>Structure: </li></ul><ul><ul><li>aromatic group (Hydrophobic lipophilic) </li></ul></ul><ul><ul><li>amide group (hydrophilic) </li></ul></ul><ul><ul><ul><li>tertiary amine or secondary amine </li></ul></ul></ul><ul><ul><li>intermediate chain </li></ul></ul><ul><ul><ul><li>Ester or Amide </li></ul></ul></ul>LOCAL ANESTHETICS
  32. 32. Structure <ul><li>CH 2 -CH 3 </li></ul><ul><li>NH 2 O-O-CH 2 -CH 2 -N </li></ul><ul><li>O CH 2 -CH 3 </li></ul><ul><li>Aromatic grp Alkyl Amide grp </li></ul><ul><li>Lipophilic chain Hydrophilic </li></ul>
  33. 33. <ul><li>METABOLISM: </li></ul><ul><ul><li>Ester  plasma and liver esterases </li></ul></ul><ul><ul><li>  metabolite: PABA </li></ul></ul><ul><ul><li>Amide  liver </li></ul></ul><ul><li>EXCRETION: </li></ul><ul><li>kidneys </li></ul>LOCAL ANESTHETICS
  34. 34. <ul><li>ROUTES OF ADMINISTRATION: </li></ul><ul><ul><li>Topical </li></ul></ul><ul><ul><li>Local Infiltration </li></ul></ul><ul><ul><li>Nerve Block </li></ul></ul><ul><ul><li>Spinal or Intrathecal injection </li></ul></ul><ul><ul><li>Epidural </li></ul></ul><ul><ul><li>Caudal </li></ul></ul>LOCAL ANESTHETICS
  35. 35. LOCAL ANESTHETICS <ul><li>ESTERS: </li></ul><ul><li>Cocaine </li></ul><ul><li>Procaine </li></ul><ul><li>Chloroprocaine </li></ul><ul><li>Tetracaine </li></ul><ul><li>AMIDES: </li></ul><ul><li>Lidocaine </li></ul><ul><li>Bupivacaine </li></ul><ul><li>Mepivacaine </li></ul><ul><li>Dibucaine </li></ul><ul><li>Prilocaine </li></ul><ul><li>Etidocaine </li></ul>
  36. 36. <ul><li>May also be classified into </li></ul><ul><li>Short acting – cocaine, procaine </li></ul><ul><li>Intermediate acting – lidocaine, mepivacaine, dibucaine, prilocaine </li></ul><ul><li>Long acting – tetracaine, bupivacaine, etidocaine </li></ul>
  37. 38. <ul><li>1. Hepatotoxic agent a. Isoflurane </li></ul><ul><li>2. Nephrotoxic agent b. Barbiturate </li></ul><ul><li>3. Cardiotoxic agent c. Enflurane </li></ul><ul><li>4. Thiopental d. Halothane </li></ul><ul><li>5. Flammable agent e. Ether </li></ul><ul><li>Amide LA b. Esther LA </li></ul><ul><li>6. Lidocaine </li></ul><ul><li>7. Tetracaine </li></ul><ul><li>8. Cocaine </li></ul><ul><li>9. Bupivacaine </li></ul><ul><li>10. Etidocaine </li></ul>

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