Peroxynitrates are responsible for global scale transport of reactive nitrogen. Recent laboratory observations suggest that they may also play an important role in delivery of nutrients to plant canopies. We measured eddy covariance fluxes of total peroxynitrates (ΣPNs) and three individual peroxynitrates (APNs ≡ PAN + PPN + MPAN) over a ponderosa pine forest during the Biosphere Effects on AeRosols and Photochemistry EXperiment 2009 (BEARPEX 2009). Concentrations of these species were also measured at multiple heights above and within the canopy. While the above-canopy daytime concentrations are nearly identical for ΣPNs and APNs, we observed the downward flux of ΣPNs to be 30–60% slower than the flux of APNs. The vertical concentration gradients of ΣPNs and APNs vary with time of day and exhibit different temperature dependencies. These differences can be explained by the production of peroxynitrates other than PAN, PPN, and MPAN within the canopy (presumably as a consequence of biogenic VOC emissions) and upward fluxes of these PN species. The impact of this implied peroxynitrate flux on the interpretation of NO_x fluxes and ecosystem N exchange is discussed.

In critical care, the specific, structured approach to patient care known as a time-limited trial has been promoted in the literature to help patients, surrogate decision makers, and clinicians navigate consequential decisions about life-sustaining therapy in the face of uncertainty. Despite promotion of the time-limited trial approach, a lack of consensus about its definition and essential elements prevents optimal clinical use and rigorous evaluation of its impact. The objectives of this American Thoracic Society Workshop Committee were to establish a consensus definition of a time-limited trial in critical care, identify the essential elements for conducting a time-limited trial, and prioritize directions for future work. We achieved these objectives through a structured search of the literature, a modified Delphi process with 100 interdisciplinary and interprofessional stakeholders, and iterative committee discussions. We conclude that a time-limited trial for patients with critical illness is a collaborative plan among clinicians and a patient and/or their surrogate decision makers to use life-sustaining therapy for a defined duration, after which the patients response to therapy informs the decision to continue care directed toward recovery, transition to care focused exclusively on comfort, or extend the trials duration. The plans 16 essential elements follow four sequential phases: consider, plan, support, and reassess. We acknowledge considerable gaps in evidence about the impact of time-limited trials and highlight a concern that if inadequately implemented, time-limited trials may perpetuate unintended harm. Future work is needed to better implement this defined, specific approach to care in practice through a person-centered equity lens and to evaluate its impact on patients, surrogates, and clinicians.

Background and Rationale: ICU clinicians regularly care for patients who lack capacity, an applicable advance directive, and an available surrogate decision-maker. Although there is no consensus on terminology, we refer to these patients as "unrepresented." There is considerable controversy about how to make treatment decisions for these patients, and there is significant variability in both law and clinical practice.Purpose and Objectives: This multisociety statement provides clinicians and hospital administrators with recommendations for decision-making on behalf of unrepresented patients in the critical care setting.Methods: An interprofessional, multidisciplinary expert committee developed this policy statement by using an iterative consensus process with a diverse working group representing critical care medicine, palliative care, pediatric medicine, nursing, social work, gerontology, geriatrics, patient advocacy, bioethics, philosophy, elder law, and health law.Main Results: The committee designed its policy recommendations to promote five ethical goals: 1) to protect highly vulnerable patients, 2) to demonstrate respect for persons, 3) to provide appropriate medical care, 4) to safeguard against unacceptable discrimination, and 5) to avoid undue influence of competing obligations and conflicting interests. These recommendations also are intended to strike an appropriate balance between excessive and insufficient procedural safeguards. The committee makes the following recommendations: 1) institutions should offer advance care planning to prevent patients at high risk for becoming unrepresented from meeting this definition; 2) institutions should implement strategies to determine whether seemingly unrepresented patients are actually unrepresented, including careful capacity assessments and diligent searches for potential surrogates; 3) institutions should manage decision-making for unrepresented patients using input from a diverse interprofessional, multidisciplinary committee rather than ad hoc by treating clinicians; 4) institutions should use all available information on the patient's preferences and values to guide treatment decisions; 5) institutions should manage decision-making for unrepresented patients using a fair process that comports with procedural due process; 6) institutions should employ this fair process even when state law authorizes procedures with less oversight.Conclusions: This multisociety statement provides guidance for clinicians and hospital administrators on medical decision-making for unrepresented patients in the critical care setting.

Background

The erosion of the early mortality advantage of elective endovascular aneurysm repair (EVAR) compared with open repair of abdominal aortic aneurysm remains without a satisfactory explanation.

Methods

An individual-patient data meta-analysis of four multicentre randomized trials of EVAR versus open repair was conducted to a prespecified analysis plan, reporting on mortality, aneurysm-related mortality and reintervention.

Results

The analysis included 2783 patients, with 14 245 person-years of follow-up (median 5·5 years). Early (0-6 months after randomization) mortality was lower in the EVAR groups (46 of 1393 versus 73 of 1390 deaths; pooled hazard ratio 0·61, 95 per cent c.i. 0·42 to 0·89; P = 0·010), primarily because 30-day operative mortality was lower in the EVAR groups (16 deaths versus 40 for open repair; pooled odds ratio 0·40, 95 per cent c.i. 0·22 to 0·74). Later (within 3 years) the survival curves converged, remaining converged to 8 years. Beyond 3 years, aneurysm-related mortality was significantly higher in the EVAR groups (19 deaths versus 3 for open repair; pooled hazard ratio 5·16, 1·49 to 17·89; P = 0·010). Patients with moderate renal dysfunction or previous coronary artery disease had no early survival advantage under EVAR. Those with peripheral artery disease had lower mortality under open repair (39 deaths versus 62 for EVAR; P = 0·022) in the period from 6 months to 4 years after randomization.

Conclusion

The early survival advantage in the EVAR group, and its subsequent erosion, were confirmed. Over 5 years, patients of marginal fitness had no early survival advantage from EVAR compared with open repair. Aneurysm-related mortality and patients with low ankle : brachial pressure index contributed to the erosion of the early survival advantage for the EVAR group. Trial registration numbers: EVAR-1, ISRCTN55703451; DREAM (Dutch Randomized Endovascular Aneurysm Management), NCT00421330; ACE (Anévrysme de l'aorte abdominale, Chirurgie versus Endoprothèse), NCT00224718; OVER (Open Versus Endovascular Repair Trial for Abdominal Aortic Aneurysms), NCT00094575.