Question 1
Question
What does lipid theory say?
Answer
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When the concentration of general anaesthetic exceeds 0.05mM, anaesthesia is induced as a result of a lipid volume increase of 0.4%. The lipid expansion interferes with nerve impulse conduction and thus anaesthesia is induced.
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When the concentration of general anaesthetic exceeds 0.5mM, anaesthesia is induced as a result of a lipid volume increase of 0.4%. The lipid expansion interferes with nerve impulse conduction and thus anaesthesia is induced.
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When the concentration of general anaesthetic exceeds 0.5mM, anaesthesia is induced as a result of a lipid volume increase of 4%. The lipid expansion interferes with nerve impulse conduction and thus anaesthesia is induced.
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When the concentration of general anaesthetic exceeds 0.1mM, anaesthesia is induced as a result of a lipid volume increase of 0.4%. The lipid expansion interferes with nerve impulse conduction and thus anaesthesia is induced.
Question 2
Question
What can reverse lipid theory?
Question 3
Question
What is protein theory?
Answer
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A concentration of general anaesthetic that reaches 0.05mM leads to a lipid volume increase of 0.4% which induces anaesthesia. This is because the increase in lipid volume interferes with conduction of nerve impulses.
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Lipid solubility of general anaesthetics is required for the general anaesthetic to reach a hydrophobic pocket on a channel protein. Channel proteins targeted are usually ion channels like GABA, K+ or nAchR.
Question 4
Question
Optical isomers of GA have the same lipid solubility and the same potency.
Question 5
Question
What are the inhibitory responses caused by general anaesthetics?
Answer
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Opening of K+ channels (efflux)
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Increase GABA activity
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Inhibit excitatory channels such as nAchR
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Increase glutaminergic activity
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Opening of K+ channels (influx)
Question 6
Question
What is meant by the cut-off phenomenon?
Answer
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The lipid solubility of a GA (and thus its potency) increases with the number of carbons in a GA but after a certain point (usually >11 carbons) the GA's potency abruptly declines.
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After a certain high dose of GA, the patients condition rapidly deteriorates.
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The general anaesthetic stops working after a certain period of time.
Question 7
Question
GA have a large therapeutic window.
Question 8
Question
The minimum alveolar concentration effectively describes what?
Answer
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The more lipid soluble a GA is, the lower the concentration required in inspired air.
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The more lipid soluble a GA is, the higher the concentration required in inspired air.
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The less lipid soluble a GA is, the lower the concentration required in inspired air.
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The less lipid soluble a GA is, the higher the concentration required in inspired air.
Question 9
Question
What increases transfer of GA to the alveoli?
Answer
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Increased concentration of GA
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Increased rate and depth of breathing
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Decreased concentration of GA
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Decreased rate and depth of breathing
Question 10
Question
A higher blood:gas partition coefficient means that the GA is highly soluble in blood.
Question 11
Question
A GA with a high blood:gas partition coefficient will travel to the brain much quicker than one with a lower blood:gas partition coefficient.
Question 12
Question
Why would pulmonary blood flow increase help with absorption of GA when GA concentration in the body is initially low?
Answer
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It maintains a high, favourable concentration gradient for the absorption of GA from the lungs into the blood, therefore increasing speed of induction.
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It helps to increase blood flow to the brain to increase the concentration of general anaesthetic in the desired place.
Question 13
Question
What tissue has a high tissue:blood partition coefficient?
Answer
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Adipose tissue
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Muscle tissue
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Brain tissue
Question 14
Question
Overall, what is evidence for lipid theory?
Question 15
Question
Overall, what is evidence for protein theory?
Question 16
Question
GA is usually metabolised by the body and excreted in the urine.
Question 17
Question
Both blood:gas and tissue:blood partition coefficients are inversely proportional to the speed of induction of GA.
Question 18
Question
What is an advantage of using halothane?
Answer
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Potent and fast acting
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Pleasant odour
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Less liver damage
Question 19
Question
What is a disadvantage of sevoflurane?
Answer
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Liver toxicity
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Bad smell
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Possible seizures
Question 20
Question
Intravenous GA is usually used for induction.
Question 21
Question
Intravenously administered thiopental and propofol act at which receptors?
Answer
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GABA-a receptors
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GABA-b receptors
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NMDA
Question 22
Question
Intravenously administered ketamine act at what receptors?
Question 23
Question
Adjuncts are used to enhance the potency of a GA.
Question 24
Question
Give some examples of adjuncts used for GA administration.
Answer
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Anxiolytics
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Anti-depressants
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Anti-psychotics
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Anti-emetics
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Muscle relaxants