Load-dependent surface nanomechanical properties of poly-HEMA hydrogels in aqueous medium.

The mechanical properties of hydrogels are of importance in many applications, including scaffolds and drug delivery vehicles where the release of drugs is controlled by water transport. While the macroscopic mechanical properties of hydrogels have been reported frequently, there are less studies devoted to the equally important nanomechanical response to local load and shear. Scanning probe methods offer the possibility to gain insight on surface nanomechanical properties with high spatial resolution, and thereby provide fundamental insights on local material property variations. In this work, we investigate the local response to load and shear of poly(2-hydroxyethyl methacrylate) hydrogels with two different cross-linking densities submerged in aqueous solution. The response of the hydrogels to purely normal loads, as well as the combined action of load and shear, was found to be complex due to viscoelastic effects. Our results show that the surface stiffness of the hydrogel samples increased with increasing load, while the tip-hydrogel adhesion was strongly affected by the load only when the cross-linking density was low. The combined action of load and shear results in the formation of a temporary sub-micrometer hill in front of the laterally moving tip. As the tip pushes against such hills, a pronounced stick-slip effect is observed for the hydrogel with low cross-linking density. No plastic deformation or permanent wear scar was found under our experimental conditions.

Association Between Race and Case Fatality Rate in Hospitalizations for Sepsis.

BACKGROUND: Differentiating whether disparities in outcomes for sepsis among racial groups are due to differences in hospital care versus pre-hospitalization factors is an important step in developing effective strategies to reduce these disparities. As such, we examined the association between race and case fatality rates among hospitalizations for sepsis. METHODS: This was a case-control study of hospitalizations for sepsis in all acute-care, non-federal California hospitals during 2011. The association between hospital mortality and race was examined using hierarchical logistic regression analysis. RESULTS: Among 131,831 hospitalizations for sepsis, the unadjusted case fatality rates were 15.1 % in whites, 14.0 % in blacks, 13.8 % in Hispanics, and 16.2 % in Asians (P < 0.001). Compared to whites, the odds of hospital mortality was 0.84 (95 % CI 0.79-0.89) for blacks, 0.88 (95 % CI 0.84-0.92) for Hispanics, and 0.93 (95 % CI 0.87-0.98) for Asians after controlling for patient, healthcare systems, and hospital-level factors. There was no difference in the variability of sepsis mortality across hospitals between racial groups. The range of case fatality rates for sepsis among hospitals was 8.3-22.9 % for whites, 9.1-20.5 % for blacks, 7.0-19.1 % for Hispanics, and 10.0-23.0 % for Asians. CONCLUSION: Case fatality rates for sepsis hospitalizations are lower in minority racial groups in California. Future studies and interventions that seek to reduce racial disparities in sepsis need to focus on pre-hospitalization factors that contribute to population-level racial differences in sepsis outcomes.

Volume of fluids administered during resuscitation for severe sepsis and septic shock and the development of the acute respiratory distress syndrome.

PURPOSE: The purpose of this study was to examine the association between the volume of intravenous (IV) fluids administered in the resuscitative phase of severe sepsis and septic shock and the development of the acute respiratory distress syndrome (ARDS). MATERIALS AND METHODS: This was a retrospective cohort study of adult patients admitted with severe sepsis and septic shock at a large academic public hospital. The relationship between the volume of IV fluids administered and the development of ARDS was examined using multivariable logistic regression analysis. RESULTS: Among 296 patients hospitalized for severe sepsis and septic shock, 75 (25.3%) developed ARDS. After controlling for confounding variables, there was no significant association between the volume of IV fluids administered in the first 24 hours of hospitalization and the development of ARDS (odds ratio [OR], 1.05; 95% confidence interval [CI], 0.95-1.18). Serum albumin (OR, 0.52; 95% CI, 0.31-0.87) and Acute Physiology and Chronic Health Evaluation II score (OR, 1.08; 95% CI, 1.04-1.13) on admission were the most informative covariates for the development of ARDS in the regression model. CONCLUSIONS: For patients hospitalized for severe sepsis and septic shock, fluid administration to improve end-organ perfusion should remain the top priority in early resuscitation despite the potential risk of inducing ARDS.