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19 Cards in this Set
- Front
- Back
Meaning of Anesthesia
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insensible or without feeling
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Effects of general anesthesia
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* Reversible CNS depression
* Absence of awareness (unconsciousness) * No recall of events at conscious level (amnesia) * Insensitivity to pain (analgesia) * Muscle relaxation * Diminished motor response to noxious stimuli (immobility) |
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What are the 4 stages of anesthesia?
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1. Stage I = stage of voluntary movement
2. Stage II = stage of delirium or involuntary movement 3.Stage III = surgical anesthesia 4.Stage IV = CNS extremely depressed, respiration ceases • Weak or imperceptible HR, absent reflexes, acutely dilated eyes, loss of mm. tone |
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What occurs during Stage I anesthesia?
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*stage of voluntary movement*
* From time of drug administration to loss of consciousness * Tachycardia, hypertension, irregular resp rate, reflexes intact, salivation, muscle tone present |
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What occurs during Stage II anesthesia?
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*stage of delirium or involuntary movement*
* Loss of voluntary control (excitement stage) * Irregular resp rate, salivation less, reflexes present but depressed, nystagmus (esp. horses and cows) |
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What occurs during Stage III anesthesia?
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**surgical anesthesia**
* Unconsciousness with progressive depression of reflexes * Progressive bradycardia, progressive resp depression, minimal mm. tone |
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What occurs during Stage IV anesthesia?
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* CNS extremely depressed, respiration ceases*
* Weak or imperceptible HR, absent reflexes, acutely dilated eyes, loss of mm. tone |
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Why is anesthetic solubility in blood and body tissues such an important factor?
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* Determines rate of uptake and distribution
* Determines rate of induction and subsequent recovery * Solubility in lipid is closely related to anesthetic potency; tendency to dissolve influences management and admin. |
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What is the solubility coefficient?
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extent to which gas will dissolve in a given solvent
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What is the partial coefficient?
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* Conc. ratio of anesthetic in 2 solvent phases
* Describes affinity of an anesthetic for one phase compared to another phase of that solvent (describes how the anesthetic partitions itself between 2 phases at equilibrium) |
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Anesthetic uptake is influenced by what?
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1. Solubility
2. CO 3. Difference in anesthetic PP between alveoli and venous blood |
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What is the blood/gas partition coefficient?
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The ratio of an anesthetic in the safe phase (blood & gas)
* Basically how it will partition itself between the two phases (affinity) |
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What does it mean if an anesthetic has a low blood/gas PC?
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o Low – wants to pass thru blood to CNS so causes induction faster (recovery faster too)
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What does it mean if an anesthetic has a high blood/gas PC?
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High – wants to stay in blood so diffusion takes longer
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Sequence of events: how anesthetics enter the body?
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1.Vaporizer
2, Lungs 3. Blood 4. CNS (brain/spinal cord) |
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How does CO affect induction of anesthesia?
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• Increased CO means decreased time for diffusion from inspired air to blood = slower induction
* Decreased CO means increased time for blood-gas exchange= faster induction |
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When does the largest gradient between alveolar and venous PP occur?
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Largest gradient between alveolar and venous PP occurs during induction
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MAC
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minimum alveolar conc. of anesthetic that anesthetizes 50% of patients
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How is anesthetic potency determined?
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Anesthetic potency = 1/MAC
(sevoflurane MAC > Isoflurane MAC = isoflurane is more potent) |