Sorry. Will it help if I suggest that vapor pressure of a material like TF changes with temperature, specifically increases with temperature?
Go back to Item V and make another choice.
Incorrect: The high boiling point of BF shows that it would not be a gas at standard temperature and pressure; hence, unlike cyclopropane, which is, BF would not be stored under pressure in steel tanks. As a matter of fact, BF has a melting point of 25°C. Needless to say, the same reasoning would apply to consideration of BF in comparison to nitrous oxide, the other anesthetic gas.
Go back to Item I and select another choice.
Sorry, wrong choice. Perhaps you'd better review Question IV to refresh your memory about the relationships among Pa, Ps and measured potency. In analyzing the data for Item X, remember that we've established that the concentration-latency curves for BF, TF, and MF are parallel. Maybe it would help to draw sketch-graphs of the curves for the agents.
Go back and make another choice in Item X.
Too bad; you'll have to try again. The rate limiting factor in onset of anesthesia with materials that act as general anesthetics do is the solubility of the agent in the blood. You'll probably remember now that rate of onset of anesthesia and relative solubility in the blood are related inversely to each other.
Go back to Item VII and make a different choice.
Too bad; you may have forgotten that the square roots of both molecular weight and vapor density are inversely related to the diffusion constant, and that diffusion rate will vary with diffusion constant, concentration difference, and area through which diffusion occurs. If the last two are viewed as the same for BF and ether (one lung's worth of area!) then it follows that....
Go back to Item VI and try again.
Quite the contrary. The ventricle beating at such a rate, under the impetus of regular stimuli from the SA node, spends so much of its time in either controlled contraction or in a refractory state, so to speak, that there is little opportunity for the slow inherent rhythmicity of the ventricle to be manifest.
I'd suggest that a look into your textbook of physiology might help clear up points such as those.
Try another choice among those in Item XIII.
Sorry, wrong choice. If the partial pressure of material in the inspired air required to produce anesthesia is proportional to the vapor pressure of the material (and it is; generally, Pa = PsK) and potency is inversely related to partial pressure for anesthesia or dose (as by definition it is), then BF should be more potent than either MF or ether. In Item I, by the way, it came out that BF might require some special treatment to volatilize it, but that's another question.
Go back to Item IV and choose again.
Very good and very true. Wouldn't you like to go back to Item XVIII and see if there are any more true answers?
Sorry, ether was readily given in an open system although it could be given in a closed system. TF, like halothane, might well require the aid of a volatilizer or vaporizer because of its relatively high boiling point. In practice, halothane is given in a closed system that contains a carefully and finely calibrated vaporizer that permits precise adjustment of the dose of this potent agent.
Go back to Item I and try again.
Perfectly correct. Halothane is one of the clinically useful general anesthetic agent - let's not debate the clinical role, if any, of ethanol - to undergo substantial biotransformation in the body. What are the names of the others?
Some things, I fear, are facts to be learned: either there's no figuring them out from first principles, or reasoning them out is more trouble than just remembering!
Now try Item XV.
Very good, you've chosen correctly. Not only do halothane and chloroform "sensitize" the heart to epinephrine-induced arrhythmias, the Freons do it too. One of the hazards of inhaling aerosol propellants to achieve euphoria (probably more appropriately called self-induced Stage I anesthesia, when we discuss it) is sudden death not unlikely caused by cardiac arrhythmia, which itself might be caused by the halogenated hydrocarbon propellant, such as a Freon. See, for example, JAMA 214: 81, 1970; JAMA 219: 33, 1972, and Arch. Environ. Health 22: 265, 1971. By the way, what drug(s) should prevent occurrence of the arrhythmias we're talking about?
Early in the history of chloroform anesthesia, sudden death occurring during induction was not just a tragic technical, professional problem; the knowledge that such deaths occurred worked against public acceptance of general anesthesia as a desirable medical procedure.
Now go on to Item XIII.
Very good. You're aware that "moment-to moment" control is simply a reflection of the rate at which depth of anesthesia can be increased or decreased by changing the concentration of anesthetic agent in the inspired air. Moment-to-moment control is a miniature of induction and recovery from anesthesia. The old rules apply and since, of all the agent in the table, BF has the lowest water/gas solubility coefficient, moment-to-moment control would be greatest with BF.
Go on to Item X.
You are perfectly right. This problem has a solution that's a variation on our old theme of Pa = PsK, that the partial pressure of the gas or vapor required to produce anesthesia is proportional to the vapor pressure of the material (see Question IV). A similar relationship applies when effects other than anesthesia are under consideration. For production of anesthesia, the proportionality constant is about 0.05, for all agents; for production of Stage IV anesthesia - respiratory arrest from the agent alone - the proportionality constant is about 0.12. The vapor pressures of nitrous oxide is so great that the partial pressure predicted (from the product of vapor pressure and 0.12) to cause respiratory arrest is greater than 760 mmHg: at atmospheric pressure, there's no room in the inspired gas mixture for both the requisite amount of drug and sufficient oxygen to prevent anoxia. Of course, one could always give anesthesia with this agent under hyperbaric conditions... if one wanted to produce Stage IV anesthesia! The "safety" of nitrous oxide, under the usual conditions of drug administration, is at least in part an inevitable consequence of its low boiling point and high vapor pressure. Cyclopropane doesn't qualify, physicochemically speaking; its vapor pressure - although it is a gas at standard temperature and pressure - is low, as gases go, and cyclopropane, in the presence of a concentration of oxygen adequate to prevent anoxia, can readily produce Stage IV anesthesia.
Remember that many inert gases, such as xenon, for example, can produce anesthesia from Stage I through Stage IV when given under hyperbaric conditions. SCUBA divers recognized this, too, after unfortunate accidents resulted from breathing the inert gas nitrogen under conditions of high partial pressures.
Observe, that if P1 is the partial pressure of gas required to produce Stage IV anesthesia, a lethal effect, P1/Pa is a sort of "therapeutic index". Then P1/Pa = .12 Ps/.05 Ps for any agent; Ps "cancels out", and we see that every anesthetic agent (i.e. regardless of its vapor pressure, fugacity, thermodynamic activity, or whatever) has a "therapeutic index" of about 2.4. It happens to be true, experimentally, and seems likely to remain true for agents of this type.
O.K., now on to Item XVII.
Sorry, one of the other choices is correct. I assume you're using the known relation between vapor pressure and partial pressure to produce anesthesia in analyzing this item and that you aren't confusing "potency" and "dose".
Go back to Item IV and try to analyze the data again, and make another choice.
I'm afraid you've made a wrong choice. Not all of these undergo biotransformation to any degree in the body. I think you should refresh your memory on this topic by reference to your text, then,
Back to Item XIV and make another choice.
Stop! There are several things wrong about this choice. Non-polar compounds such as these give no evidence of acting on receptors as they're usually defined. The probabilistic model suggests that the general effect of such agents as these is greatest on the longest neurone chains. The probabilistic model describes what happens to transmission of information through neurone chains after the function of individual cells has been altered, and, hence, is not concerned with the cellular mechanism by which the change was brought about.
Go back to Item II and select another choice.
Sorry, moment-to-moment control would be least with ether. Since moment-to-moment control is so much related to problems of rate in induction and recovery from anesthesia, I suggest you go back to Item IX.
No. Are you really satisfied that only two of these effects would be produced by the mechanisms suggested? Go back to Item XVIII and be adventurous and daring: Try choice e.
Sorry, all of these agents can produce respiratory arrest - i.e. Stage IV anesthesia - under the conditions given.
Back to Item XVI and make another choice.
Very true; the perfect choice
Go on to Item XX
Correct; Pauling is responsible for originating the theory. See Science 134: 15, 1961 and Anesth. and Analges. 43: 1, 1964.
Might not another choice or two be correct as well? Go back to Item XX and try again.
Correct, when he wasn't studying the epidemiology of cholera or taking the handle from the Broad Street pump, Snow was busy being, probably, the first professional anesthesiologist; Queen Victoria used his services during several of her obstetrical deliveries.
Incidentally, Benjamin Ward Richardson (Richardson's Law: anesthetic potencies of aliphatic alcohols are inversely related to their water solubilities) also combined an interest in anesthesiology with an interest in epidemiology! Do you think this is anything more than coincidence?
You might be interested in Keys, T. E., The History of Surgical Anesthesia, Dover Publications, 1963.
But might one or another choice also be correct?
Go back to Item XX and have another try.
Of course, the first successful public demonstration of surgical anesthesia is summarized by the triad of Morton-Ether-Boston. But might another choice be equally correct?
Perfectly correct; not every "first" in anesthesiology happened in Boston. Might another choice be equally correct?
Go back to Item XX and choose again.
Completely correct at last! (Do read the comments for the other choices to Item XX... if you have not done so already)... and this is the end of the program.