Identifying Factors Predicting Kidney Graft Survival in Chile Using Elastic-Net-Regularized Cox's Regression.

Background and Objectives: We developed a predictive statistical model to identify donor-recipient characteristics related to kidney graft survival in the Chilean population. Given the large number of potential predictors relative to the sample size, we implemented an automated variable selection mechanism that could be revised in future studies as more national data is collected. Materials and Methods: A retrospective multicenter study was conducted to analyze data from 822 adult kidney transplant recipients from adult donors between 1998 and 2018. To the best of our knowledge, this is the largest kidney transplant database to date in Chile. A procedure based on a cross-validated regularized Cox regression using the Elastic Net penalty was applied to objectively identify predictors of death-censored graft failure. Hazard ratios were estimated by adjusting a multivariate Cox regression with the selected predictors. Results: Seven variables were associated with the risk of death-censored graft failure; four from the donor: age (HR = 1.02, 95% CI: 1.00-1.03), male sex (HR = 0.64, 95% CI: 0.46-0.90), history of hypertension (HR = 1.49, 95% CI: 0.98-2.28), and history of diabetes (HR = 2.04, 95% CI: 0.97-4.29); two from the recipient: years on dialysis log-transformation (HR = 1.29, 95% CI: 0.99-1.67) and history of previous solid organ transplantation (HR = 2.02, 95% CI: 1.18-3.47); and one from the transplant: number of HLA mismatches (HR = 1.13, 95% CI: 0.99-1.28). Only the latter is considered for patient prioritization in deceased kidney allocation in Chile. Conclusions: A risk model for kidney graft failure was developed and trained for the Chilean population, providing objective criteria which can be used to improve efficiency in deceased kidney allocation.

Grid-wide assessment of varying re-regulation storage capacity for hydropeaking mitigation.

Hydropeaking affects downstream ecosystems and water uses. We assessed the effect of small re-regulation reservoirs (RRR) located downstream of hydropower plants to mitigate the impact of hydropeaking operations, in terms of the tradeoffs between flashiness of flows and power system cost. The study is performed on a hypothetical power system composed by one reservoir hydropower plant, one coal-fired plant, one diesel-fired plant, and one wind power plant. Hourly operations within a weekly horizon by each plant are prescribed by a system-wide cost-minimization model. Operations are constrained by minimum flows (MIF) and maximum ramping rates (MRR). The model was run for selected weeks, representative of the four seasons and three water year types. Results show that MIF and MRR constraints can achieve improvements in the flashiness of flows, from Richard-Baker index above 0.8 down to less than 0.1. However, without a RRR, these constraints can cause a power system cost increase of up to 70% with respect to the unconstrained case. The strongest effect on power system costs is observed under the dry hydrologic scenario. The cost increase is also significant in the summer weeks of the two normal scenarios. A half-hour capacity RRR keeps the cost increase below 8% and further reduces the flashiness to values below 0.1, on average for the dry scenarios. RRR storage capacities of one and 2 h can further reduce the cost increase below 5%, with flashiness as low as 0.01. No significant improvement is observed beyond this RRR size. In synthesis, this study shows that small re-regulation reservoirs, with capacities up to 2-h detention time, are a promising alternative for hydropeaking control at low power system cost.

Association Among ICU Congestion, ICU Admission Decision, and Patient Outcomes.

OBJECTIVES: To employ automated bed data to examine whether ICU occupancy influences ICU admission decisions and patient outcomes. DESIGN: Retrospective study using an instrumental variable to remove biases from unobserved differences in illness severity for patients admitted to ICU. SETTING: Fifteen hospitals in an integrated healthcare delivery system in California. PATIENTS: Seventy thousand one hundred thirty-three episodes involving patients admitted via emergency departments to a medical service over a 1-year period between 2008 and 2009. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A third of patients admitted via emergency department to a medical service were admitted under high ICU congestion (more than 90% of beds occupied). High ICU congestion was associated with a 9% lower likelihood of ICU admission for patients defined as eligible for ICU admission. We further found strong associations between ICU admission and patient outcomes, with a 32% lower likelihood of hospital readmission if the first inpatient unit was an ICU. Similarly, hospital length of stay decreased by 33% and likelihood of transfer to ICU from other units-including ICU readmission if the first unit was an ICU-decreased by 73%. CONCLUSIONS: High ICU congestion is associated with a lower likelihood of ICU admission, which has important operational implications and can affect patient outcomes. By taking advantage of our ability to identify a subset of patients whose ICU admission decisions are affected by congestion, we found that, if congestion were not a barrier and more eligible patients were admitted to ICU, this hospital system could save approximately 7.5 hospital readmissions and 253.8 hospital days per year. These findings could help inform future capacity planning and staffing decisions.

Replacing quarantine of COVID-19 contacts with periodic testing is also effective in mitigating the risk of transmission.

The quarantine of identified close contacts has been vital to reducing transmission rates and averting secondary infection risk before symptom onset and by asymptomatic cases. The effectiveness of this contact tracing strategy to mitigate transmission is sensitive to the adherence to quarantines, which may be lower for longer quarantine periods or in vaccinated populations (where perceptions of risk are reduced). This study develops a simulation model to evaluate contact tracing strategies based on the sequential testing of identified contacts after exposure as an alternative to quarantines, in which contacts are isolated only after confirmation by a positive test. The analysis considers different number and types of tests (PCR and lateral flow antigen tests (LFA)) to identify the cost-effective testing policies that minimize the expected infecting days post-exposure considering different levels of testing capacity. This analysis suggests that even a limited number of tests can be effective at reducing secondary infection risk: two LFA tests (with optimal timing) avert infectiousness at a level that is comparable to 14-day quarantine with 80-90% adherence, or equivalently, 7-9 day quarantine with full adherence (depending on the sensitivity of the LFA test). Adding a third test (PCR or LFA) reaches the efficiency of a 14-day quarantine with 90-100% adherence. These results are robust to the exposure dates of the contact, test sensitivity of LFA and alternative models of viral load evolution, which suggests that simple testing rules can be effective for improving contact tracing in settings where strict quarantine adherence is difficult to implement.

Ordering sequential competitions to reduce order relevance: Soccer penalty shootouts.

In sequential competitions, the order in which teams take turns may have an impact on performance and the outcome. Previous studies with penalty shootouts have shown mixed evidence of a possible advantage for the first shooting team. This has led to some debate on whether a change in the rules of the game is needed. This work contributes to the debate by collecting an extensive dataset of shootouts which corroborates an advantage for the first shooter, albeit with a smaller effect than what has been documented in previous research. To evaluate the impact of alternative ordering of shots, we model shootouts as a probability network, calibrate it using the data from the traditional ordering, and use the model to conduct counterfactual analysis. Our results show that alternating the team that shoots first in each round would reduce the impact of ordering. These results were in part developed as supplement to field studies to support the International Football Association Board's (IFAB) consideration of changing the shooting order.

Effect of Autonomic Responses After Isometric Training at Different Intensities on Obese People.

BACKGROUND: Arterial hypertension is among the leading causes of mortality worldwide. The primary non-pharmacological management of arterial hypertension is isometric grip training, which has shown better results than pharmacological methods; however, it has not been thoroughly studied in large muscle groups. OBJECTIVE: This study compared the pressor response of isometric exercise training at different intensities, in large groups versus small muscle groups, in sedentary eutrophic and overweight people aged 20-29 years. METHODS: A sample of 93 people (57 people with excess weight and 36 people of normal weight) participated in isometric training for 5 days, subdivided into leg press vs. handgrip strength, with different intensities for each subgroup (30 and 50%, 1 RM). Before and after the 5 training days, Heart Rate Variability (HRV) and systolic and diastolic blood pressure, BSBP-BDBP and PSBP-PDBP, were measured to evaluate the state of sympathetic activation at rest and pressor response. RESULTS: Changes with significant differences (p <0.05) in terms of pre-post training measurements in the eutrophic group were the BSBP-PSBP variables at 30% and 50% 1 RM for manual isometric grip strength. In the excess weight group, the only significant change was the PSBP variable in handgrip strength at 30% 1 RM. It should be noted that in all cases, blood pressure values reduced. CONCLUSION: Isometric strength exercises in large and small muscle groups show a tendency to reduce blood pressure values; however, the isometric handgrip force at 30% 1 RM shows statistically significant reductions in blood pressure values.

Assessing the effect of fish size on species distribution model performance in southern Chilean rivers.

Despite its theoretical relationship, the effect of body size on the performance of species distribution models (SDM) has only been assessed in a few studies, and to date, the evidence shows unclear results. In this context, Chilean fishes provide an ideal case to evaluate this relationship due to their short size (fishes between 5 cm and 40 cm) and conservation status, providing evidence for species at the lower end of the worldwide fish size distribution and representing a relevant management tool for species conservation. We assessed the effect of body size on the performance of SDM in nine Chilean river fishes, considering the number of records, performance metrics, and predictor importance. The study was developed in the Bueno and Valdivia basins of southern Chile. We used a neural network modeling algorithm, training models with a cross-validation scheme. The effect of fish size on selected metrics was assessed using linear models and beta regressions. While no relationship between fish size and the number of presences was found, our results indicate that the model specificity increases with fish size. Additionally, the predictive importance of Riparian Vegetation and Within-Channel Structures variables decreases for larger species. Our results suggest that the relationship between the grain of the dataset and the home range of the species could bias SDM, leading in our case, to overprediction of absences. We also suggest that evolutionary adaptation to low slopes among Chilean fishes increases the relevance of riparian vegetation in the SDMs of smaller species. This study provides evidence on how species size may bias SDM, which could potentially be corrected by adjusting the model grain.

Recomendaciones generales en cirugía oncológica de cabeza y cuello durante la pandemia COVID-19 / General recommendations in head and neck oncologic surgery during COVID-19 pandemic

Resumen Durante la pandemia COVID-19, el enfrentamiento sanitario nacional e internacional ha enfocado sus esfuerzos en disminuir los riesgos inherentes del paciente oncológico. Existe un reforzamiento del enfoque resolutivo en los casos oncológicos críticos que requieren tratamiento precoz, evitando la exposición innecesaria al SARS-CoV-2 en los casos electivos y/o diferibles. Así como también, consideraciones de seguridad según riesgo para los cirujanos de cabeza y cuello acorde con la evidencia disponible hasta la fecha. Estas medidas tienen por objetivo evitar la exposición al virus y disminuir el uso de insumos limitados, enfocando nuestros esfuerzos en el tratamiento quirúrgico crítico.

During the COVID-19 pandemic, the national and international health confrontation has focused its efforts on reducing the inherent risk of cancer patients. There is a strengthening in the resolutions of critical oncological cases that require early treatment, avoiding unnecessary exposure to SARS-CoV-2 in elective or deferrable cases. And also, risk-based safety considerations for head and neck surgeons consistent with the evidence available to date. These actions aim to avoid exposure to the virus and decrease the use of limited supplies, focusing our efforts on critical surgical treatment.