anesthetics n.
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  1. ANESTHETICS Dr.Shadi- Sarahroodi Pharm.D & PhD PUBLISHED BY for more lectures

  2. General Anesthetics Signs and Stages of Anesthesia (Somewhat related to the response from Diethyl Ether): • Stage I—Analgesia • Stage II—Excitement • Stage III—Surgical anesthesia • Stage IV—Medullary paralysis for more lectures

  3. Patient Factors in Selection of Anesthesia • Liver and kidney • Respiratory system • Cardiovascular system • Nervous system • Pregnancy for more lectures

  4. Summary of anesthetics for more lectures

  5. MOA • modulating ligand-gated ion channels • activating GABA channels (hyperpolarizing cells) • blocking excitatory receptors (like NMDA-glutamate receptors). for more lectures

  6. for more lectures

  7. Inhalation Anesthetics • Modern inhalation anesthetics are nonflammable, nonexplosive • nitrous oxide • halothane, desflurane, enflurane, isoflurane, sevoflurane, and methoxyflurane (easily vaporized liquid halo-genated hydrocarbons) for more lectures

  8. Inhalation Anesthetics • ether [which is highly flammable] • chloroform [which has toxic properties] • are no longer used as general anesthetics for more lectures

  9. important concepts • minimal alveolar concentration (MAC) • blood:gas partition coefficient for more lectures

  10. MAC(minimal alveolar concentration) • concentration of anesthetic agent that renders 50% of patients immobile during surgery • this is measured as the percentage of the agent in inspired air • MAC is a direct measure of the potency of a drug • influenced by the age and physiologic state of the patient and by the presence of other pharmacologic agents for more lectures

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  12. blood:gas partition coefficient • solubility of the agent in blood • and is a measure of how quickly the inhalation anesthetic will equilibrate between lungs and blood and ultimately the target site in the brain • low blood:gas coefficient (e.g., desflurane) equilibrate quickly • lower the blood:gas coefficient faster the induction and the faster the recovery for more lectures

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  14. speed of induction of anesthetic effects • Solubility • Inspired gas partial pressure-high partial pressure in the lungs rapid achievement of anesthetic levels in the blood • Ventilation rate • Pulmonary blood flow—high pulmonary blood flows onset of anesthesia is reduced. for more lectures

  15. Alveolar Blood Concentration for more lectures

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  17. elimination • redistribution of the drug from the brain to the blood and elimination of the drug through the lungs. for more lectures

  18. desflurane, sevoflurane low blood solubility shorter recovery for more lectures

  19. effects of inhaled anesthetics • CNS effects: • decrease brain metabolic rate. • reduce vascular resistance increase cerebral blood flow. • High concentrations of enflurane may cause spike-and-wave activity and muscle twitching, • nitrous oxide has low anesthetic potency (ie, a high MAC), it exerts marked analgesic and amnestic actions. for more lectures

  20. effects of inhaled anesthetics • Cardiovascular effects • decrease arterial blood pressure moderately • Enflurane and halothane: myocardial depressants • isoflurane, desflurane, and sevoflurane: peripheral vasodilation • Nitrous oxide: less likely to lower blood pressure for more lectures

  21. effects of inhaled anesthetics • Respiratory effects: • dose-dependent decrease in tidal volume and minute ventilation increase in arterial CO2 tension • Bronchodilation except desflurane(pulmonary irritant). for more lectures

  22. Toxicities • Halothane: Postoperative hepatitis (rarely) (formation of reactive metabolites that cause direct toxicity or initiate immune-mediated responses.) • Methoxyflurane, enflurane and sevoflurane: Fluoride release renal insuffi­ciency • nitrous oxide: megaloblastic anemia • anesthetics + neuromuscular blockers (Susceptible patients): malignant hyperthermia mutations in the gene loci corresponding to the ryanodine receptor (RyRl) Dantrolene for more lectures

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  24. Intravenous Anesthetics • Barbiturates: Thiopental and methohexital • Benzodiazepines: Midazolam • ketamine • Opioids: Morphine and fentanyl • propofol • etomidate for more lectures

  25. Barbiturates • high lipid solubility rapid entry into the brain surgical anesthesia in one circulation time (< 1 min). • short surgical procedures • hepatic metabolism • respiratory and circulatory depressants • depress cerebral blood flow • decrease intracranial pressure. for more lectures

  26. Redistribution of Thiopental for more lectures

  27. Benzodiazepines • The onset of its CNS effects is slower than that of thiopental • flumazenil, accelerates recovery from midazolam and other benzodiazcpines. for more lectures

  28. ketamine • dissociative anesthesia • patient remains conscious • marked catatonia, analgesia, and amnesia. • phencyclidine (PCP) • cardiovascular stimulant • increase in intracranial pressure. • disorientation, excitation, and hallucinations occur during recovery for more lectures

  29. opioids • Morphine and fentanyl • Intravenous opioids :chest wall rigidity • Respiratory depression • Neuroleptanesthesia(state of analgesia and amnesia):fentanyl is used with droperidol and nitrous oxide. • Alfentanil and remifentanil (NEW) for more lectures

  30. propofol • Rapid as the intravenous barbiturates • antiemetic • prolonged sedation • marked hypotension during induction of anesthesia • Total body clearance is greater than hepatic blood flow, suggesting elimination includes other mechanisms in addition to metabolism by liver enzymes. for more lectures

  31. etomidate • rapid induction • minimal change in cardiac function • minimal change in respiratory rate • not analgesic • cause pain and myoclonus on injection and nausea postoperatively • Prolonged administration may cause adrenal suppression. for more lectures

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  34. PUBLISHED BY for more lectures