General Anesthesia 2
Terms
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- Clinical Stages of Anesthesia
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Stage 1: Interfered synaptic transmission in spinothalamic tract -> analgesia
Stage 2: blockade of inhibitory pathways -> excitement, disinhibition, irregular respiration, vomiting
Stage 3: Depression of ascending pathways in reticular activating system -> unconsciousness, muscle relaxation
Stage 4: depression of medullary vital centers - Minimum Alveolar Conc. (MAC)
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conc of anesthetic at 1 atm that produces immobility in 50% in response to painful stimulus
Decreased MAC: hypothermia, hypthyroidism, alcohol intox, age, sedatives - Inhaled Anesthetics
- decrease BP (except NO2) b/c decrease periph vasc resistance, increase HR
- Isoflurane
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Mechanism: activate GABA receptor
Clinical Use: not used much - Desflurane
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similar to isoflurane
less soluble, so higher inspired conc. required
Side effects: irritating to airway, increased BP and HR - Sevoflurane
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solubility between isoflurane and desflurane
mild odor, mask inductions - Nitrous oxide
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Mechanism: NMDA glutamate inhibitor, high MAC requires other drugs, low solubility
Side Effects: inhibits methionine synthase -> >12-24hrs depress bone marrow and fetal tissue - Intravenous Anesthetics
- Mechanism: activate GABA receptor, most are short acting due to redistribution
- Thiopental
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Most commonly used barbiturate
significant cardiac depression at high dose - Etomidate
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less cardiac depression, but pain on injection
decreased cortisol and aldosterone - Midazolam
- benzodiazepine for anxiolysis and sedation
- Propofol
- Standard induction drug for general anesthesia
- Ketamine
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NMDA receptor blockade
maintains or stimulates respiration - Neostigmine
- reverse effect of paralyzing drugs