The equilibrium constant, K3, of aqueous homolysis of peroxynitrous acid into hydroxyl and nitrogen dioxide free radicals was estimated to be 5 x 10(-10) M. This value was derived from a thermodynamic cycle by use of the experimentally known delta fH degree(ONOO-,aq) = -10.8 kcal/mol and the enthalpy of ionic dissociation of ONOOH(aq), delta H degree 1 = 0 kcal/mol, as well as of the entropy of gaseous ONOOH, S degree(ONOOH,g) = 72 eu. Furthermore we assumed the entropy of hydration of ONOOH, delta S degree 2, to be -25 eu, a value closely bracketed by the hydration entropies of analogous substances. The rate constant of radical recombination of OH. with NO2. to yield ONOOH, k-3, was resimulated from experimental data and found to be ca. 5 x 10(9) M-1 s-1. Together with the estimated K3, this yields the homolysis rate constant k3 = 2.5 s-1. This value is close to 0.5 s-1, the rate constant of formation of a reactive intermediate during the isomerization of peroxynitrous acid to nitrate. Our thermodynamic estimate is therefore consistent with substantial amounts of OH. and NO2. free radicals being formed in this process. The thermodynamic implications for the carbon dioxide/peroxynitrite system are also discussed.

Carbon Dioxide↗

PubMed1997

Resource support and heart patient recovery.

This prospective study examines the effects of resources utilized by myocardial infarction (MI) and coronary artery bypass (BY) patients in the recovery process. The resource support model incorporates formal (institutionalized) and semi-formal (mutual aid) services along with informal assistance (social networks). Patient interview data were collected on 147 MI and 159 BY patients at hospitalization and at 3 months. Sociodemographic, illness and resource data were obtained, and hospital records were abstracted. Two outcomes were evaluated: activity limitations and work capacity. Bivariate and multivariate analyses were used to assess individual and resource effects. Multivariate analyses revealed that, for MI patients, a higher level of activity prior to hospitalization and a shorter hospital stay were significantly related to recovery. A smaller social network with greater frequency of contact enhanced recovery. For BY patients, recovery was significantly associated with higher social class higher level of activity prior to hospitalization and fewer health care visits. Outcome based on work capacity revealed that MI patients who were younger in age, male sex and who had fewer prescribed medications were more likely to recover. By patients had a similar pattern as that observed for MI patients in terms of age and sex. Co-morbidity had a negative effect on recovery. Those with less affective informal support were more likely to have recovered. The resource support model employed in this prospective study proved to have mixed results. However, the model may be a useful multifactorial framework for examining the effects on patient recovery over a longer duration.

Activities of Daily Living↗

PubMed1996