The accuracy of pulse oximetry in emergency department patients with severe sepsis and septic shock: a retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>Pulse oximetry is routinely used to continuously and noninvasively monitor arterial oxygen saturation (SaO₂) in critically ill patients. Although pulse oximeter oxygen saturation (SpO₂) has been studied in several patient populations, including the critically ill, its accuracy has never been studied in emergency department (ED) patients with severe sepsis and septic shock. Sepsis results in characteristic microcirculatory derangements that could theoretically affect pulse oximeter accuracy. The purposes of the present study were twofold: 1) to determine the accuracy of pulse oximetry relative to SaO2 obtained from ABG in ED patients with severe sepsis and septic shock, and 2) to assess the impact of specific physiologic factors on this accuracy.</p> <p>Methods</p> <p>This analysis consisted of a retrospective cohort of 88 consecutive ED patients with severe sepsis who had a simultaneous arterial blood gas and an SpO₂value recorded. Adult ICU patients that were admitted from any Calgary Health Region adult ED with a pre-specified, sepsis-related admission diagnosis between October 1, 2005 and September 30, 2006, were identified. Accuracy (SpO₂- SaO₂) was analyzed by the method of Bland and Altman. The effects of hypoxemia, acidosis, hyperlactatemia, anemia, and the use of vasoactive drugs on bias were determined.</p> <p>Results</p> <p>The cohort consisted of 88 subjects, with a mean age of 57 years (19 - 89). The mean difference (SpO₂- SaO₂) was 2.75% and the standard deviation of the differences was 3.1%. Subgroup analysis demonstrated that hypoxemia (SaO₂< 90) significantly affected pulse oximeter accuracy. The mean difference was 4.9% in hypoxemic patients and 1.89% in non-hypoxemic patients (p < 0.004). In 50% (11/22) of cases in which SpO₂was in the 90-93% range the SaO2 was <90%. Though pulse oximeter accuracy was not affected by acidoisis, hyperlactatementa, anemia or vasoactive drugs, these factors worsened precision.</p> <p>Conclusions</p> <p>Pulse oximetry overestimates ABG-determined SaO₂by a mean of 2.75% in emergency department patients with severe sepsis and septic shock. This overestimation is exacerbated by the presence of hypoxemia. When SaO₂needs to be determined with a high degree of accuracy arterial blood gases are recommended.</p

Contribution of Efflux to the Emergence of Isoniazid and Multidrug Resistance in Mycobacterium tuberculosis

Multidrug resistant (MDR) tuberculosis is caused by Mycobacterium tuberculosis resistant to isoniazid and rifampicin, the two most effective drugs used in tuberculosis therapy. Here, we investigated the mechanism by which resistance towards isoniazid develops and how overexpression of efflux pumps favors accumulation of mutations in isoniazid targets, thus establishing a MDR phenotype. The study was based on the in vitro induction of an isoniazid resistant phenotype by prolonged serial exposure of M. tuberculosis strains to the critical concentration of isoniazid employed for determination of drug susceptibility testing in clinical isolates. Results show that susceptible and rifampicin monoresistant strains exposed to this concentration become resistant to isoniazid after three weeks; and that resistance observed for the majority of these strains could be reduced by means of efflux pumps inhibitors. RT-qPCR assessment of efflux pump genes expression showed overexpression of all tested genes. Enhanced real-time efflux of ethidium bromide, a common efflux pump substrate, was also observed, showing a clear relation between overexpression of the genes and increased efflux pump function. Further exposure to isoniazid resulted in the selection and stabilization of spontaneous mutations and deletions in the katG gene along with sustained increased efflux activity. Together, results demonstrate the relevance of efflux pumps as one of the factors of isoniazid resistance in M. tuberculosis. These results support the hypothesis that activity of efflux pumps allows the maintenance of an isoniazid resistant population in a sub-optimally treated patient from which isoniazid genetically resistant mutants emerge. Therefore, the use of inhibitors of efflux should be considered in the development of new therapeutic strategies for preventing the emergence of MDR-TB during treatment

Cultural otherness and disaster news: the influence of western discourses on Japan in US and UK news coverage of the 2011 Great East Japan Disaster

The Great East Japan Disaster of 2011 provides an important case study to evaluate how western media cover Japan. Employing a critical discourse analysis of coverage in The New York Times, The Guardian and The Observer this article seeks to examine how Japan and the disaster-affected communities of Tohoku were represented through the context of this disaster. The analysis revealed the presence of a cultural framework, enacted during the response phase of the disaster news cycle to explain how people in Japan were coping in the aftermath of the disaster, which was premised on a discourse of cultural otherness. The textual elements that underwrote this discourse included a tendency to draw on stereotypes and in the way culture was employed to provide context to individual stories. The analysis also acknowledges how forms of bias circulated through other discourses, in particular when covering the nuclear crisis at Fukushima. The article argues that this discourse of cultural otherness is, in part, attributable to the features of disaster journalism, rather than a lack of familiarity on the part of journalists with the cultural context