Estimación de la incertidumbre en la medición de hidrocarburos aromáticos en el análisis de muestras de agua por microextracción en fase sólida automático y cromatografía de gases con detección selectiva de masas

Muchas decisiones importantes se basan en los resultados de análisis químicos, es el caso de la estimación de rendimientos ó de verificación de especificaciones o límites legales de materiales. Debido a esto cada vez hay mayor presión sobre los químicos para demostrar la calidad de sus resultados y su aptitud para el uso. Uno de los principales parámetros metrológicos que demuestra esta capacidad, es la incertidumbre de la medición. Su estimación no es una tarea fácil debido a los múltiples factores que influyen en su cálculo, para lo cual se requiere un buen conocimiento en metrología y de algunos conceptos estadísticos. En este estudio se evaluó la incertidumbre en el análisis de Hidrocarburos Aromáticos Policíclicos en muestras de agua natural y potable, en un método para el prestador del servicio de agua potable en el Valle de Aburrá (Colombia), que utiliza la técnica depreparación de muestra por microextracción en fase sólida (SPME) automática por inmersión, y su posterior separación y detección por cromatografía de gases con detector selectivo de masas. Este trabajo da respuesta a este requisito, establecido en la norma ISO-IEC 17025 para la acreditación de laboratorios de ensayo. Palabras clave: Incertidumbre (U), microextracción en fase sólida (SPME), cromatografía de gases-detector selectivo de masas (GC-MS), Hidrocarburos Aromáticos Policíclicos (HAP). ABSTRACTMany important decisions are based on the results of chemical analyses as in the case of calculating yields of a reaction or in the verification of specifications or legally allowed limits of certain materials. Thus, there is increasing pressure on chemists to demonstrate the quality of their results and the adequacy of these for their use. One of the main metrological parameters used to demonstrate this capability is the uncertainty of a measurement. Theestimation of uncertainty is not an easy task due to the many factors influencing its calculation, and requires a sound knowledge of metrology and statistical concepts. In this work, the uncertainty in the analysis of polycyclic aromatic hydrocarbons (PAHs) in samples of natural and potable water was determined for the service provider ofdrinking water in the Valle de Aburrá (Colombia), using a method based on the technique of automatic Solid Phase Micro Extraction (SPME) by immersion for sample preparation, followed by separation and analysis by gas chromatography with a selective mass detector. This corresponds to the requirements for test laboratory certification according to the specification ISO-IEC 17025. Keywords: Uncertainty (U), solid phase micro extraction (SPME), gas chromatography-mass spectrometry (GCMS), Polycyclic Aromatic Hydrocarbons (PAHs)

Evolution over Time of Ventilatory Management and Outcome of Patients with Neurologic Disease∗

OBJECTIVES: To describe the changes in ventilator management over time in patients with neurologic disease at ICU admission and to estimate factors associated with 28-day hospital mortality. DESIGN: Secondary analysis of three prospective, observational, multicenter studies. SETTING: Cohort studies conducted in 2004, 2010, and 2016. PATIENTS: Adult patients who received mechanical ventilation for more than 12 hours. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among the 20,929 patients enrolled, we included 4,152 (20%) mechanically ventilated patients due to different neurologic diseases. Hemorrhagic stroke and brain trauma were the most common pathologies associated with the need for mechanical ventilation. Although volume-cycled ventilation remained the preferred ventilation mode, there was a significant (p < 0.001) increment in the use of pressure support ventilation. The proportion of patients receiving a protective lung ventilation strategy was increased over time: 47% in 2004, 63% in 2010, and 65% in 2016 (p < 0.001), as well as the duration of protective ventilation strategies: 406 days per 1,000 mechanical ventilation days in 2004, 523 days per 1,000 mechanical ventilation days in 2010, and 585 days per 1,000 mechanical ventilation days in 2016 (p < 0.001). There were no differences in the length of stay in the ICU, mortality in the ICU, and mortality in hospital from 2004 to 2016. Independent risk factors for 28-day mortality were age greater than 75 years, Simplified Acute Physiology Score II greater than 50, the occurrence of organ dysfunction within first 48 hours after brain injury, and specific neurologic diseases such as hemorrhagic stroke, ischemic stroke, and brain trauma. CONCLUSIONS: More lung-protective ventilatory strategies have been implemented over years in neurologic patients with no effect on pulmonary complications or on survival. We found several prognostic factors on mortality such as advanced age, the severity of the disease, organ dysfunctions, and the etiology of neurologic disease

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally