Electron spin resonance study of phosphorus-nitroxides from 1,3-additions of silicon-phosphorus reagents to nitrones.

This article explores a new, convenient route to beta-phosphorus nitroxides. Specifically, the reaction sequence involves the novel 1,3-addition of trimethylsilyl phosphites (e.g. diethyl) or trimethylsilyl phosphines (e.g. diphenyl) to aldo-nitrones [e.g. alpha-phenyl-N-tert-butylnitrone (PBN) or 5,5-dimethyl-l-pyrroline-N-oxide (DMPO)] or keto-nitrones [e.g. 2-ethyl-5,5-dimethyl-1 pyrroline-N-oxide (2-Et-DMPO) or 2-phenyl-5,5-dimethyl-l-pyrroline-N-oxide (2-Ph-DMPO)] to form alpha-phosphityl- or alpha-phosphinyl-O-silylhydroxylamines. Acidic hydrolysis provides the corresponding hydroxylamines that are easily oxidized to the title beta-phosphorus-nitroxides. ESR spectroscopic analysis revealed some very large beta-phosphorus hyperfine splittings (i.e. in excess of 5 mT). For this reason and their remarkable stability (persistence) some of these nitroxides show promise as integral components in new, improved weak-field dynamic nuclear polarization (DNP) magnetometers.

Technical and economic feasibility of reusing disposable perfusion cannulas.

OBJECTIVE(S): The reuse of disposable devices is a potential source of significant cost savings to hospitals. Venous and arterial perfusion cannulas under new and reused conditions were selected to identify the clinical, safety, technical, logistic, and economic issues that must be addressed to realize these savings. METHODS: Single- and dual-stage venous and arterial cannulas from two manufacturers were tested when new, after initial clinical use, and after a single clinical use plus up to nine simulated reuses. Reuse was simulated by end-to-end bending, coupling and uncoupling of the connectors, and by two 1-hour soaks in plasma at 4 degrees and 40 degrees C, respectively. Cannulas were decontaminated and then processed by a peracetic acid-based liquid chemical sterilization system after each use/reuse. Sterilization was validated by eliminating Bacillus subtilis spores from the cannulas on each of five consecutive cycles. Cannulas were tested for physical changes, functional integrity, biocompatibility, and in vivo performance in sheep. A cost analysis was also performed. RESULTS: Sterilization was successfully achieved. Mechanical changes were less than 20% on all variables studied and were undetectable by experienced cardiac surgeons in selective evaluation. No clinically important differences were found between new and reused cannulas, even after nine simulated reuses. Reusing cannulas four times would reduce the cost per procedure from $53 to $19 (64%). CONCLUSIONS: Preliminary data suggest that the perfusion cannulas tested can be safely and efficaciously used five times. Limited reuse of these disposable cannulas is technically feasible and cost-effective. Cannula reuse would result in a small incremental savings; however, with more expensive devices and higher-volume sterilization procedures, the savings could be considerably greater. This program provides a model for evaluation of other single-use medical devices for reuse.

Technical and economic feasibility of reusing disposable perfusion cannulae.

The reuse of disposable devices is a potential source of significant cost savings to hospitals. Venous and arterial perfusion cannulae under new and reused conditions were selected to identify the clinical, safety, technical, logistic, and economic issues that must be addressed to realize these savings. Single- and dual-stage venous and arterial cannulae from two manufacturers were tested when new, after initial clinical use, and after a single clinical use plus up to nine simulated reuses. Reuse was simulated by end-to-end bending, coupling and uncoupling the connectors, and by two 1-hour soaks in plasma at 4 degrees C and 40 degrees C, respectively. Cannulae were decontaminated and then sterilized by a peracetic acid based liquid chemical sterilization system following each use/reuse. Sterilization was validated by eliminating Bacillus subtilis spores from the cannulae on each of five consecutive cycles. Cannulae were tested for physical changes, functional integrity, biocompatibility, and in vivo performance in sheep. A cost minimization analysis was also performed. No clinically important differences were found between new and reused cannulae, even after nine simulated reuses. Mechanical changes were less than 20% on all variables studied and were undetectable by experienced cardiac surgeons in selective evaluation. Sterilization was successfully achieved. Reusing cannulae for times would reduce the cost per procedure from $53 to $19 (64%). Perfusion cannulae tested can be safely and efficaciously used five times. This study suggests that reuse would result in a small incremental savings; however, with more expensive devices and higher-volume sterilization procedures, the savings could be exponentially greater. Although this study demonstrates that it may be technically feasible and cost-effective to reuse disposable cannulae, the U.S. Food and Drug Administration does not sanction the reuse of disposable cannulae.

Spin trapping study in the lungs and liver of F344 rats after exposure to ozone.

Fischer 344 rats were injected with the spin traps C-phenyl N-tert-butyl nitrone (PBN, 150 mg/kg bw, ip) or 4-pyridine-N-oxide N-tert-butyl nitrone (POBN, 775 mg/kg bw, ip), and exposed to clean air or 2 ppm ozone for two hours. The presence of spin adducts was determined by electron paramagnetic resonance (EPR) spectroscopy of chloroform extracts of lung and liver homogenates. No significant levels of adducts were detected in the lungs of air control animals. Benzoyl N-tert-butyl aminoxyl, attributed to direct reaction of ozone with PBN, and tert-butyl hydroaminoxyl, the scission product of the hydroxyl adduct of PBN, were detected in the lungs of ozone exposed rats. EPR signals for carbon-centred alkoxyl and alkyl adducts were also detected with PBN in the lungs and liver of animals exposed to ozone. With POBN, only carbon-centred alkyl radicals were detected. Senescent, 24 months old rats were found to retain about twice more 14C-PBN in blood, heart and lungs by comparison to juvenile, 2 months old animals. Accordingly, the EPR signals were generally stronger in the lungs of the senescent rats by comparison to juvenile rats. Together, the observations were consistent with the previously proposed notion that a significant flux of hydrogen peroxide produced from the reaction of ozone with lipids of the extracellular lining, or from activated macrophages in the lungs could be a source of biologically relevant amounts of hydroxyl radical.

Maternity care and outcomes in a high-risk service: the North Central Bronx Hospital experience.

The maternity service of the North Central Bronx Hospital, a New York City municipal hospital for the medically indigent, has demonstrated that good maternal and infant outcomes can be obtained in an unselected population of disadvantaged women by using obstetric interventions only when medically indicated. Approximately 70 percent of the mothers cared for in the service are considered at risk or high risk. Of the 3287 deliveries in 1988, 86.1 percent were performed by the midwives on staff. Midwives were the primary providers of prenatal, intrapartum, and postpartum care for all low-risk mothers, and comanaged with the attending obstetricians the care of all high-risk mothers. The cesarean section rate was 11.8 percent, and the rate of instrumental delivery was 0.3 percent, with minimal use of oxytocin augmentation (6.4%). Among the 3323 infants delivered in 1988, the last full year before an obstetric residency program was established, the rate of those requiring special or intensive care was 11.1 percent, and neonatal mortality was 9.2 per 1000 live births for all birth weights and 3.7 per 1000 for infants over 1000 g. The experience gained from 10 years and over 25,000 births suggests that the maternity care of both high- and low-risk mothers could be improved by minimizing obstetric intervention whenever possible.

Structure identification of free radicals by ESR and GC/MS of PBN spin adducts from the in vitro and in vivo rat liver metabolism of halothane.

Free radicals were detected from the in vitro metabolism of halothane (rat liver microsomes) by the PBN spin trapping method. The detected radical species include the 1-chloro-2,2,2-trifluoro-1-ethyl radical (I), as determined by mass spectral analysis, and lipid-type radicals assigned by high resolution ESR spectroscopy with the use of d14-deuterated PBN. The lipid-derived radicals are a carbon-centred radical with the partially assigned structure CH2R and an oxygen-centred radical of the OR' type. From the mass spectral analysis of the spin adduct mixture there is also evidence for a halocarbon double adduct of PBN of the type I-PBN-I.

Synthesis and purification of 5,5-dimethyl-1-pyrroline-N-oxide for biological applications.

General procedures for the synthesis and purification of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and its synthetic intermediates for electron paramagnetic resonance (EPR) spin trapping is described. The synthetic methods are not new per se and are based on Todd's original scheme (1959). In contrast to his account, however, we provide a detailed description of the numerous procedures and precautions necessary to obtain DMPO of very high 'chemical' and (most importantly) 'EPR' purity for use in biological spin trapping.

Detection of free radicals generated from the in vitro metabolism of carbon tetrachloride using improved ESR spin trapping techniques.

The spin trapping chemistry of carbon tetrachloride has been previously investigated in rat liver, both in vitro and in vivo. In addition to the trichloromethyl radical, both a 'carbon-centered' and an 'oxygen-centered' radical have been detected in vitro. These spin adducts have been assigned to 'lipid' and 'lipid oxyl' radicals. However, no specific structural characterization has been provided to date. The spin trapping chemistry of this system was reinvestigated with the use of deuterated alpha-phenyl N-tert-butyl nitrones to obtain better spectral resolution. Results indicate that the PBN trapped carbon-centered lipid radical is of a primary alkyl type.

The cultural warping of childbirth.

PIP: The higher incidence of fetal, neonatal, and maternal deaths in the U.S. than in other developed countries is due to the unphysiological practices adopted during childbirth and the lack of emotional support offered to mothers in labor. American mothers must be educated to a ccept a certain amount of inconvenience and discomfort in order to have a delivery more conducive to the good health of themselves and their babies. These supportive efforts are known to reduce the need for obstetrical medication and obstetrical intervention during labor and birth. It is not necessary that normal childbirth be performed in hospitals with physicians; nurse midwives can provide much of the predelivery support and care. Medication during labor and delivery increases the risks to both mother and child. Breast feeding must be actively encouraged in order to reduce the incidence of infant mortality and to offer emotional support for the postpartum mother. Other U.S. obstetrical practices which warp the childbirth experience in this country include elective induction of labor, separation of the mother from her family during delivery and the immediate postpartum period, and chemical stimulation of labor.^ieng