anesthetics - ANESTHETIC S Dr.Shadi- Sarahroodi Pharm.D...

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Unformatted text preview: ANESTHETIC S Dr.Shadi- Sarahroodi Pharm.D & PhD PUBLISHED BY for more lectures General Anesthetics Signs and Stages of Anesthesia (Somewhat Signs related to the response from Diethyl Ether): related 1. Stage I—Analgesia 2. Stage II—Excitement 3. Stage III—Surgical anesthesia 4. Stage IV—Medullary paralysis for more lectures Patient Factors in Selection of Patient Anesthesia Anesthesia Liver and kidney Respiratory system Cardiovascular system Nervous system Pregnancy for more lectures Summary of anesthetics for more lectures MOA modulating ligand-gated modulating ion channels activating GABA activating channels (hyperpolarizing cells) blocking excitatory blocking receptors (like NMDAreceptors glutamate receptors). glutamate for more lectures for more lectures Inhalation Anesthetics Modern inhalation anesthetics are nonflammable, Modern nonexplosive nonexplosive nitrous oxide nitrous halothane, desflurane, enflurane, isoflurane, halothane, sevoflurane, and methoxyflurane (easily vaporized liquid halo-genated hydrocarbons) liquid for more lectures Inhalation Anesthetics ether [which is highly flammable] chloroform [which has toxic properties] chloroform are no longer used as general anesthetics for more lectures important concepts minimal alveolar concentration (MAC) minimal blood:gas partition coefficient for more lectures MAC(minimal alveolar concentration) concentration of anesthetic agent that renders concentration 50% of patients immobile during surgery 50% tthis is measured as the percentage of the his agent in inspired air agent MAC is a direct measure of the potency of a MAC drug drug iinfluenced by the age and physiologic state of nfluenced age the patient and by the presence of other w for more lectures pharmacologic agents for more lectures blood:gas partition coefficient solubility of the agent in blood solubility and is a measure of how quickly the inhalation and anesthetic will equilibrate between lungs and blood and ultimately the target site in the brain blood llow blood:gas coefficient (e.g., desflurane) ow equilibrate quickly equilibrate lower the blood:gas coefficient ffaster aster the induction and the faster the recovery the for more lectures for more lectures speed of induction of speed anesthetic effects anesthetic Solubility Inspired gas partial pressure-high partial high pressure in the lungs rapid achievement pressure off anesthetic levels in the blood o Ventilation rate Pulmonary blood flow—high pulmonary blood high flows onset of anesthesia is reduced. flows for more lectures Alveolar Blood Concentration for more lectures Anesthetic Blood: Gas Partition Coefficient Minimum Alveolar Concentration (%)* Metabolism Nitrous oxide 0.47 >100 None Desflurane 0.42 6.5 <0.1% Sevoflurane 0.69 2.0 2-5% (fluoride) Isoflurane 1.40 1.4 <2% Enflurane 1.80 1.7 8% Halothane 2.30 0.75 >40% 12 0.16 >70% (fluoride) Methoxyflurane for more lectures ELIMINATION redistribution of the drug from the brain to the redistribution blood and elimination of the drug through the blood lungs. lungs. for more lectures desflurane, sevoflurane llow blood ow solubility shorter recovery solubility for more lectures EFFECTS OF INHALED EFFECTS ANESTHETICS ANESTHETICS CNS effects: CNS decrease brain metabolic rate. decrease reduce vascular resistance increase reduce cerebral blood flow. High concentrations of enflurane may cause High enflurane spike-and-wave activity and muscle twitching, nitrous oxide has low anesthetic potency (ie, a nitrous high MAC), it exerts marked analgesic and analgesic for more lectures amnestic actions. amnestic EFFECTS OF INHALED EFFECTS ANESTHETICS ANESTHETICS Cardiovascular effects decrease arterial blood pressure moderately Enflurane and halothane: myocardial Enflurane depressants iisoflurane, desflurane, and sevoflurane: soflurane, peripheral vasodilation Nitrous oxide: less likely to lower blood Nitrous pressure pressure for more lectures EFFECTS OF INHALED EFFECTS ANESTHETICS ANESTHETICS Respiratory effects: dose-dependent decrease in tidal volume and dose-dependent minute ventilation iincrease in arterial ncrease minute CO2 tension CO Bronchodilation except desflurane(pulmonary Bronchodilation irritant). for more lectures Toxicities Halothane: Postoperative hepatitis (rarely) (formation of reactive metabolites that cause direct toxicity or initiate immune-mediated responses.) Methoxyflurane, enflurane and sevoflurane: Methoxyflurane, Fluoride release renal insuffi-ciency Fluoride renal nitrous oxide: megaloblastic anemia anesthetics + neuromuscular blockers anesthetics malignant hyperthermia : (Susceptible patients) (Susceptible mutations in the gene loci corresponding to the ryanodine receptor (RyRl) mutations Dantrolene for more lectures for more lectures Intravenous Anesthetics Intravenous BARBITURATES: Thiopental and methohexital BARBITURATES: BENZODIAZEPINES: Midazolam BENZODIAZEPINES: KETAMINE OPIOIDS: Morphine and fentanyl OPIOIDS: PROPOFOL ETOMIDATE for more lectures 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 Redistribution of Thiopental for more lectures BENZODIAZEPINES The onset of its CNS effects is slower than that The onset off thiopental o fflumazenil, accelerates recovery from lumazenil, midazolam and other benzodiazcpines. midazolam for more lectures KETAMINE dissociative anesthesia patient remains conscious patient marked catatonia, analgesia, and amnesia. phencyclidine (PCP) cardiovascular stimulant iincrease in intracranial pressure. ncrease disorientation, excitation, and hallucinations disorientation, occur during recovery occur for more lectures OPIOIDS Morphine and fentanyl Morphine Intravenous opioids :chest wall rigidity Respiratory depression Respiratory Neuroleptanesthesia (state of analgesia and amnesia): fentanyl Neuroleptanesthesia is used with droperidol and nitrous oxide. is Alfentanil and remifentanil (NEW) for more lectures PROPOFOL Rapid as the intravenous barbiturates antiemetic prolonged sedation prolonged marked hypotension during induction of marked anesthesia anesthesia Total body clearance is greater than hepatic Total blood flow, suggesting elimination includes other mechanisms in addition to metabolism by for more lectures liver enzymes. liver ETOMIDATE rapid induction rapid minimal change in cardiac function minimal minimal change in respiratory rate minimal not analgesic cause pain and myoclonus on injection and cause nausea postoperatively nausea Prolonged administration may cause adrenal Prolonged suppression. for more lectures suppression. for more lectures for more lectures PUBLISHED BY for more lectures ...
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