induction recovery concentration = partial pressure x solubility tissue
TRANSCRIPT
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Induction
Recovery
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Concentration = Partial pressure x Solubilitytissue
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Pulmonary ventilation
Respiratory rate Vtidal – Vdead space
Anesthetic concentration
Blood-gas partition coefficient
Concentration effect Second gas effect
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Table 1 Characteristics of Inhalational Anesthetics
Anesthetics MAC
(% of 1 atm)
Oil:Gas Partition
Coefficient
Blood:Gas Partition
Coefficient
Desflurane 7.0 19 0.42
Ether 1.9 65 12
Enflurane 1.7 98 1.9
Halothane 0.75 225 2.3
Isoflurane 1.2 98 1.4
Methoxyflurane 0.16 825 13
Nitrous oxide 105 1.4 0.47
Sevoflurane 2.0 53 0.63
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Pulmonary ventilation
Concentration effect Second gas effect Respiratory rate
Vtidal – Vdead space
Anesthetic concentration
Blood-gas partition coefficient
Pulmonary blood flow Gradient of Parterial / Pvenous
Cardiac output
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Anesthetic concentration Pulmonary ventilation Concentration effect Second gas effect
Blood-gas partition coefficient
Tissue blood flow Gradient of Parterial / PTissue
•Redistribution
•Diffusion hypoxia
Pulmonary blood flow Gradient of Parterial / Pvenous
Cardiac output
Tissue-Blood partition coefficient
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Stages of Ether Anesthesia
Stage I Analgesia Clouding Spinal cord sensory neurons
(Substantia gelatinosa)
Stage II Delirium
(Excitement)
Loss of consciousness
Hypersensitive
small Golgi type interneurons
excitatory neurons
Stage III Surgical anesthesia
Loss of somatic pain Ascending pathway of recticular activating systemSpinal reflex
Stage IV Medullary depression
Loss of visceral pain Medulla
(respiratory, cardiovascular center)
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Anesthetics MAC
(% of 1 atm)
Oil:Gas Partition
Coefficient
Blood:Gas Partition
Coefficient
Desflurane 7.0 19 0.42
Ether 1.9 65 12
Enflurane 1.7 98 1.9
Halothane 0.75 225 2.3
Isoflurane 1.2 98 1.4
Methoxyflurane 0.16 825 13
Nitrous oxide 105 1.4 0.47
Sevoflurane 2.0 53 0.63
Table 1 Characteristics of Inhalational Anesthetics
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Stages of Ether Anesthesia
Stage I Analgesia Clouding Spinal cord sensory neurons
(Substantia gelatinosa)
Stage II Delirium
(Excitement)
Loss of consciousness
Hypersensitive
small Golgi type interneurons
excitatory neurons
Stage III Surgical anesthesia
Loss of somatic pain Ascending pathway of recticular activating systemSpinal reflex
Stage IV Medullary depression
Loss of visceral pain Medulla
(respiratory, cardiovascular center)
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Mechanisms of Action
Lipid bilayer-Meyer and Overton Theory Membrane fluidity Membrane expansion
Voltage-gated ion channels Na+
K+
GIRK TASK, TREK: 2P, pH-sensitive, open rectifier
Ca+2
Ligand-gated ion channels NMDA nACh Glycine 5HT3 GABAA
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TASK-1
Activated by inhalational anesthetics (0.1-0.4 mM)
Two pore background K+ channels
pH-sensitive, pHo <7, channels close
Open rectifier, instaneous activation No time dependence
Slight outward rectification
TASK-2 might also be the target Time-dependent outward rectifier
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TREK-1
Activated by inhalational anesthetics (higher) pH-sensitive, pHi <7, channels open
Outward rectification
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Gaseous anesthetics Nitrous oxide (N2O)
Volatile anesthetics Ether Chloroform Halothane Enflurane Isoflurane Desflurane Sevoflurane
Inhalational Anesthetics
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Nitrous Oxide
Benefits No CV side effect Rapid induction Second gas effect
Harms Weak potency Diffusion hypoxia Megaloblastic anemia N2O pockets formed in
closed spaces Occluded middle ear Pneumothorax Embolism Pneumoencephaly Obstructed intestine
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Nitrous OxideNormal
N2
N2
N2
N2O
Blood vessel Blood vessel
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Nitrous Oxide
Benefits No CV side effect Rapid induction Second gas effect
Harms Weak potency Diffusion hypoxia Megaloblastic anemia N2O pockets formed in
closed spaces Occluded middle ear Pneumothorax Embolism Pneumoencephaly Obstructed intestine
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Halothane Enflurane Isoflurane Desflurane Sevoflurane
Analgesia +/- + + + +
Muscle relaxation - + ++ ++ ++
Fast Induction - + ++ ++++ ++
Potency ++++ +++/- +++ +/- ++
Metabolism ++++ ++ +/- - ++(+)
Airway irritation + + - +/- -
Nausea, vomiting + - - - -
Malignant Hyperthermia + + - - -
Arrhythmia +++ ++ +/- +/- -
Hypotension + + + + +
Cardiac output decrease ++ ++ - - -
Hepatic toxicity ++ + - - +/-
Renal toxicity ++ ++ - - +/-
dantrolene
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Malignant hyperthermia
Genetic susceptibility:
1 in 15,000 to 50,000
Failure of Ca2+ uptake by sarcoplastic recticulum in
skeletal muscle, genetic mutation of ryanodine
receptors
Treatment with dantrolene
Incidence if coadministration with succinylcholine
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Halothane Enflurane Isoflurane Desflurane Sevoflurane
Analgesia +/- + + + +
Muscle relaxation - + ++ ++ ++
Fast Induction - + ++ ++++ ++
Potency ++++ +++/- +++ +/- ++
Metabolism ++++ ++ +/- - ++(+)
Airway irritation + + - +/- -
Nausea, vomiting + - - - -
Malignant Hyperthermia + + - - -
Arrhythmia +++ ++ +/- +/- -
Hypotension + + + + +
Cardiac output decrease ++ ++ - - -
Hepatic toxicity ++ + - - +/-
Renal toxicity ++ ++ - - +/-
Seizure
F-
Cough
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Intravenous Anesthetics
Barbiturates Thiopental (Pentothal)
Methohexital (Brietal)
Thiamylal (Surital)
Benzodiazepines Diazepam (Valium)
Lorazepam (Ativan)
Midazolam (Dormicum)
Dissociate anestheticKetamine (Ketaral)
Etomidate (Hypnomidate)
Propofol (Diprivan)Butyrophenones
Droperidol
OpioidsFentanyl
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Ultrashort Barbiturates GABAA-Cl- current
Contraindication Porphyria Shock Respirator not available
Pain threshold Laryngeal spasm Unpurpose movement
Thiopental Redistribution Slow recovery Short t1/2
Methohexital Rapid recovery Hiccup
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Benzodiazepines GABAA-Cl- current
Diazepam Amnesia Reflex No analgesic action Endoscopy,Cardiocatheter respiration CV function
Midazolam More rapid onset Shorter duration More potent Water soluble Antidote: flumazenil Emergency room
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Ketamine NMDA receptor blocker
Dissociation anesthesia Sedation Analgesic CV stimulation Muscle tone Nightmare Trauma, Emergency, Radiotherapy
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Etomidate GABA uptake inhibitor
Onset rapid (< 5min), redistribution No CV and respiratory depression No analgesia Nausea vomiting, myoclonic twitch Adrenocortical supprssion Sedative-hypnotic in ICU Used in hypovolumic shock, Burn trama
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Propofol GABA uptake inhibitor
Rapid psychomotor recovery Unpurpose movement Allergic reaction Antiemetic Not suggested in obstetrical procedures Respiratory and cardiovascular depression
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Neuroleptic Analgesia
Droperidol D2 receptor blocker
Antiemetic Antianxiety, Indifference motor activity
Antifibrilation Anticonvusion
Diagnosis only when used alone
Extrapyramidal dyskinesia
Fentanyl Opioid receptor agonist Nausea vomitting
Skeletal muscle rigidity
Analgesia
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Premedication of Anesthesia
Benzodiazepine: Diazepam
Barbiturates: Secobarbital, Phenobarbital
Narcotics: Meperidine, Morphine
Anticholinergics: Atropine, scopolamine
Antihistamines: H1 antagonists, H2 antagonists
Antiemetics: Benzquinamide, Odansetron, diphenhydramine, metocloprmide
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Mechanism of Action: GABAA receptor
TM2 segment of 21 subunit of GABAA receptor
Binding site different to that of GABA
Potentiating GABA effect at low concentrations
Directly inducing GABA current at high concentrations
Preventing GABAA receptor desensitization
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Discovery of Inhalational Anesthetics
1842 Crawford W. Long Surgeon
1844 Horace Wells Dentist1846 Willium T. G.
MortonCharles J. Jackson
Mr. ifs
N2O
Ether
Time: 1846, October 16Place: Massachusetts General HospitalSurgeon: John Collins Warren
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Concentration Effect
N2O (blood/gas =0.5)
40 % 20 %
0.2 * 40 % = 8 %
80 % 40 %
0.4 * 80 % = 32 %
Palveola Pblood