Healthcare professionals often face clinical and ethical challenges when charged with making decisions related to provision or lack of provision of artificial nutrition and hydration. The intent of this review is to supply a framework of clinical practices, ethical principles, legal precedents, and professional guidelines that will impart information and can assist decision making regarding artificial nutrition and hydration. Comprehensive understanding of the theory and practice of informed consent for competent adults, decisionally incompetent adults, and minors is necessary for making valid clinical judgments and for guiding patients and their families or surrogates in choosing options related to initiating, withholding, or withdrawing artificial nutrition and hydration. The framework offered in this review can serve as a basis for evaluation of appropriateness of artificial nutrition and hydration in 3 common conditions in which decision making is particularly challenging: terminal illness, advanced dementia, and a persistent vegetative state. The framework facilitates guidance for institutional policy makers and individual nutrition support professionals dealing with situations in which personal values often create ethical dilemmas related to artificial nutrition and hydration and its utility.
A comparison of hyperfine coupling constants obtained by electron-nuclear double resonance spectroscopy of in vitro monomer chlorophyll and bacteriochlorophyll free radicals with those of the photoesr (electron spin resonance) signal associated with light conversion in photosynthesis provides convincing support for the special pair model for the in vivo photo-reaction center. The special pair model for photo-active chlorophyll predicts that the esr line shape will be narrowed by a factor 1/A/2 relative to monomer Chl at, and that each and every electronnuclear hyperfine (hf) coupling constant in a special pair will be reduced by a factor of 1/2 relative to the monomer coupling constants. A comparison of hf splittings measured in both in vivo and in vitro chlorophyll free radicals is thus a considerably more rigorous test of the special pair proposal. Because chlorophyll free radical esr signals, especially in vivo, do not show hf structures that permit extraction of hf coupling constants, we have had resort to electron-nuclear double resonance (endor) spectroscopy, a high resolution extension of esr first discovered by G. Feher (22), which in combination with organisms and chlorophylls of unnatural isotopic composition makes assignment of the endor spectrum and hf coupling constants possible. MATERIALS AND METHODSInstrumentation. Endor spectra were recorded at 10'K and 108'K on a modified Varian E-700 spectrometer.Production of Chlorophyll Free Radicals. In vitro free radicals were usually generated in 10-4 10-1 M Chl solutions in thoroughly degassed C2H2C12-C2H302H by chemical oxidation with minimal amounts of iodine (23), ferric chloride, or zinc tetraphenylporphyrin free radical (24).In vivo free radicals for endor were generated in packed whole cells, chromatophores, chloroplasts, and reaction center preparations by careful titration with KFe(CN)6. The esr and endor signals produced by this chemical method are indistinguishable from the photo-induced signal in bacteria (16) and green algae and thus are believed to have the same origin.
The preparation of hair for the determination of elements is a critical component of the analysis procedure. Open-beaker, closed-vessel microwave, and flowthrough microwave digestion are methods that have been used for sample preparation and are discussed. A new digestion method for use with inductively coupled plasma-mass spectrometry (ICP-MS) has been developed. The method uses 0.2 g of hair and 3 mL of concentrated nitric acid in an atmospheric pressure-low-temperature microwave digestion (APLTMD) system. This preparation method is useful in handling a large numbers of samples per day and may be adapted to hair sample weights ranging from 0.08 to 0.3 g. After digestion, samples are analyzed by ICP-MS to determine the concentration of Li, Be, B, Na, Mg, Al, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, Se, Rb, Sr, Zr, Mo, Pd, Ag, Cd, Sn, Sb, I, Cs, Ba, Pt, Au, Hg, Tl, Pb, Bi, Th, and U. Benefits of the APLTMD include reduced contamination and sample handling, and increased precision, reliability, and sample throughput.
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