Dosing some medications in amount of drug per square meter of body surface area *(BSA) instead of body mass takes into account the metabolic and drug elimination differences among patients. BSA dosing is often used for anti-cancer (chemotherapy) drugs. ----- Original Message ----- From: Bill Potts To: [email protected] ; 'U.S. Metric Association' Cc: [email protected] ; 'Gentry, Elizabeth' Sent: 02 January, 2011 11:34 Subject: RE: [USMA:49395] powers of ten--becoming an exponent proponent
I agree with you, Paul. And, for the grade level at which exponents should be taught, that seems about right. The one thing that puzzles me is the milligrams per square meter dosage. I can only think of this being used for some kind of skin cream, which leads to the question of how one easily determines a patient's skin area. I have to assume, though, that an approximation is probably close enough and that order-of-magnitude errors are unlikely. :o) Bill ------------------------------------------------------------------------------ From: [email protected] [mailto:[email protected]] On Behalf Of Paul Trusten Sent: Sunday, January 02, 2011 08:40 To: U.S. Metric Association Cc: [email protected]; [email protected]; Gentry, Elizabeth Subject: [USMA:49395] powers of ten--becoming an exponent proponent The previous discussion of Zimbabwe currency in the article in question (http://news.yahoo.com/s/ap/20110102/ap_on_re_af/af_zimbabwe_numbers_game ) reminded me that part of our problem in accepting metrication in the U.S. is that we Americans are not yet proponents of exponents. We tend to limit the teaching of exponents to a small part of our mathematics education and don't apply that education to the practical subject of measurement. When I stop to consider the metric system, I sense that I am returning to eighth-grade algebra, when I should have learned something about exponents much earlier than that. At least to me, facility in exponential notation makes the meanings of the SI prefixes easier to understand and manipulate. I don't know what it's like in metric countries, but, here in the land of the foot and the mile, even the simplest application of exponents in connection with SI falls on innumerate ears. For example, in pharmacy I have yet to hear one of my colleagues look at the symbol m2 and pronounce it "square meter." They will pronounce it "meters squared," which may be good as an exponential statement but, I think, bad as a measurement unit. Some (usually outside of pharmacy) can't even get that far, and will state a dose of 50 mg/m2 as "50 milligrams emm two," reading it out to me with difficulty, not knowing what it means. Pharmacists use common sense and can interpret, based on the drug being ordered, that 50 milligrams per square meter is what was meant, but if two people are communicating purely on the basis of the expression being used, with nothing else to refer to, who knows? From the resulting confusion, we may get a medical Gimli Glider. I remember, in the fourth grade (which, for me, was 50 years ago), learning "decimal places," and learning the "millions place" and the "thousands place," but at that time, those places were never connected to the concept of bases and exponential notation. Had that been done for us,I think we could have adapted to the metric system the very next day and become metric citizens. As I mentioned, I haven't been in the fourth grade for 50 years, and the timing of the study of exponents may have changed since then (big grin). I'd be interested in what the teachers on this list think of the above. So, my question is:: to what extent do you think a thorough grounding in exponential notation in the early years of mathematics education (2nd, 3rd grade?) would improve the ability of the U.S. to go metric? Paul T.
