Comparison of the Parameters of the Exergoeconomic Environmental Analysis of Two Combined Cycles of Three Pressure Levels with and without Postcombustion.

Nowadays, in Mexico, most of the installed electricity generation capacity corresponds to combined cycles, representing 37.1%. For this reason, it is important to maintain these cycles in good operating conditions, with the least environmental impacts. An exergoeconomic and environmental analysis is realized to compare the operation of the combined cycle, with and without postcombustion, with the comparison of exergoeconomic and environmental indicators. With the productive structure of the energy system, the process of formation of the final products and the residues are identified, and an allocation criterion is also used to impute the formation cost of residue to the productive components related to its formation. This criterion considers the irreversibilities generated in each productive component that participates in the formation of a residue. The compositions of pollutant gases emitted are obtained, and their environmental impact is determined. The unit exergoeconomic cost of the power output in the gas turbine is lower in the combined cycle with postcombustion, indicating greater efficiency in the process of obtaining this energy stream, and the environmental indicators of global warming, smog formation and acid rain formation are higher in the combined cycle with postcombustion, these differences being 5.22%, 5.53% and 5.30%, respectively.

Randomized, Placebo-Controlled Trial of Dobutamine for Low Superior Vena Cava Flow in Infants.

OBJECTIVE: To gather information for a future confirmatory trial of dobutamine (DB) for circulatory impairment (ie, low superior vena cava [SVC] flow). STUDY DESIGN: A total of 127 infants born at < 31 weeks gestational age were serially scanned from birth to 96 hours after birth. The infants were randomly assigned to 2 groups and were treated with DB (stepwise dose increase, 5-10-15-20 µg/kg/min) or placebo if they had an SVC flow < 41 mL/kg/min within the first 24 hours after birth. The primary outcome measures were the achievement and maintenance of an SVC flow ≥ 41 mL/kg/min. Secondary outcome measures were the short-term evolution of clinical and biochemical variables, near-infrared spectroscopy, cranial Doppler ultrasound, and clinical outcomes. RESULTS: SVC flow increased throughout the first 96 hours for the entire cohort. All of the randomized infants (n = 28) except 2 achieved and maintained an SVC flow ≥ 41 mL/kg/min after intervention; however, the infants treated with DB (n = 16) showed a higher heart rate and improved base excess compared with those treated with placebo (n = 12). Low SVC flow was associated with low gestational age (P = .02) and poor condition at birth (P = .02). Low SVC flow significantly increased the risk of severe ischemic events (OR, 13; 95% CI, 2.4-69.2; P < .01). CONCLUSION: This exploratory trial demonstrates a tendency toward improved short-term clinical and biochemical perfusion variable outcomes in infants with low SVC flow treated with DB. TRIAL REGISTRATION: ClinicalTrials.gov (NCT01605279) and the European Clinical Trials Database (EurodraCT 2009-010901-35).

New time-frequency method for cerebral autoregulation in newborns: predictive capacity for clinical outcomes.

OBJECTIVE: To describe an alternative analysis in the frequency-domain of the temporal relationship between 2 biological signals and evaluate the method's predictive capacity for classifying infants at risk for an adverse outcome. STUDY DESIGN: We studied 54 infants (mean gestational age 27 weeks) with invasive mean arterial blood pressure monitoring. The bivariate autoregressive spectral coherence (BiAR-COH) method and the spectral coherence methods were used to analyze the relationship between spontaneous changes in mean arterial blood pressure and the near-infrared tissue oxygenation index. RESULTS: The mean postnatal age at the beginning and end of the autoregulation study was 6.0 (3.0) and 29.0 (7.5) hours, respectively. The BiAR-COH was superior to the spectral coherence in predicting low superior vena cava (SVC) flow (≤ 41 mL/kg per minute), with an area under the receiver operating characteristic curve of 0.84 (95% CI, 0.77-0.90; P < .001). The BiAR-COH threshold for identifying low SVC flow was 0.577, with 0.8 sensitivity and 0.76 specificity. After adjusting for the repeated measures effect (multiple epochs) in a given patient, the averaged BiAR-COH per patient and averaged COH per patient were calculated as the average value per patient. The pBiAR-COH (but not the pCOH) was associated with intraventricular hemorrhage grades 3 and 4 and predicted mortality. CONCLUSIONS: The BiAR-COH classifier identifies low SVC flow infants who are at risk for brain hypoperfusion. The BiAR-COH is superior to frequency domain methods in predicting adverse outcomes in infants.

Clinical, biochemical, and neuroimaging findings predict long-term neurodevelopmental outcome in symptomatic congenital cytomegalovirus infection.

OBJECTIVE: To evaluate clinical, biochemical, and neuroimaging findings as predictors of neurodevelopmental outcome in patients with symptomatic congenital cytomegalovirus (CMV). STUDY DESIGN: The study cohort comprised 26 patients with symptomatic congenital CMV born between 1993 and 2009 in a single center. Absolute and weight deficit-adjusted head circumference were considered. Cerebrospinal fluid (CSF) investigations included standard cytochemical analysis, determination of beta2-microglobulin (ß2-m), neuron-specific enolase, and CMV DNA detection. Neuroimaging was classified according to a validated scoring system comprising calcifications, ventriculomegaly, and atrophy, with findings graded from 0 to 3. Systematic long-term neurodevelopmental assessment included motor function, cognition, behavior, hearing, vision, and epilepsy. Sequelae were graded as mild/absent, moderate, or severe; adverse outcome was defined as death or moderate to severe disability. RESULTS: Three children died. The mean age at follow-up of the survivors was 8.7 ± 5.3 years (range, 19 months to 18.0 years). Neonatal findings showing a significant association with adverse outcome were relative microcephaly, CSF ß2-m concentrations, and grade 2-3 neuroimaging abnormalities (P < .05). Receiver operator characteristic curve analysis indicated that the most accurate single factor for predicting unfavorable outcome was CSF ß2-m >7.9 mg/L (area under the curve, 0.84 ± 0.08; sensitivity, 69%; specificity, 100%). The combination of CSF ß2-m >7.9 mg/L and moderate-severe neuroimaging alterations improved predictive ability (area under the curve, 0.92 ± 0.06; sensitivity, 87%; specificity, 100%). CONCLUSION: Adjusted head circumference, CSF ß2-m level, and neuroimaging studies have prognostic significance for neurodevelopmental outcome in newborns with congenital CMV. A combination of early findings improves the predictive value.

Segundo Consenso Clínico de la Sociedad Iberoamericana de Neonatología: manejo hemodinámico del recién nacido / Second Clinical Consensus of the Ibero-American Society of Neonatology: hemodynamic management of newborns

Este trabajo informa acerca del proceso y los resultados del Segundo Consenso Clínico de la SIBEN (Sociedad Iberoamericana de Neonatología), en el cual 80 neonatólogos de 23 países fueron invitados a participar y colaborar. Se desarrollaron varias preguntas de importancia clínico-fisiológica sobre el manejo hemodinámico del recién nacido. Los participantes fueron distribuidos en grupos, facilitando así la interacción y el trabajo conjunto, con la consigna de responder de tres a cinco preguntas mediante el análisis de bibliografía y factores locales. El Grupo de Consenso se reunió en Mar del Plata, Argentina, donde se llevaron a cabo diversas ponencias, debates y presentaciones. En total participaron 54 neonatólogos de 21 países, con el objetivo de desarrollar un consenso sobre aspectos que incluyeron conceptos y definiciones de inestabilidad hemodinámica, la fisiopatología del cuadro de compromiso hemodinámico, las estrategias terapéuticas recomendadas y el monitoreo hemodinámico. Se espera que esta experiencia internacional sirva como una iniciativa útil tanto para la búsqueda de futuros consensos como para reducir las disparidades existentes entre los tratamientos y resultados de los diferentes países de la Región.

This study reports on the process and results of the Second Clinical Consensus of the Ibero-American Society of Neonatology. Eighty neonatologists from 23 countries were invited to collaborate and participate in the event. Several questions of clinical-physiological importance in the hemodynamic management of newborns were addressed. Participants were divided into groups to facilitate interaction and teamwork, with instructions to respond to three to five questions by analyzing the literature and local factors. Meeting in Mar del Plata, Argentina, the Consensus Group served as a form for various presentations and discussions. In all, 54 neonatologists from 21 countries attended, with the objective of reaching a consensus on such matters as concepts and definitions of hemodynamic instability, the physiopathology of hemodynamic compromise, recommended therapy strategies, and hemodynamic monitoring. It is hoped that this international experience will serve as a useful initiative for future consensus building and reduction of the existing disparities among the countries of the Region in terms of treatment and outcomes.