Prevention of ischemic complications during aneurysm surgery

Ischemic complications during aneurysm surgery are a frequent cause of postoperative infarctions and new neurological deficits. In this article, we discuss imaging and neurophysiological tools that may help the surgeon to detect intraoperative ischemia. The strength of intraoperative digital subtraction angiography (DSA) is the full view of the arterial and venous vessel. DSA is the gold standard in complex and giant aneurysms, but due to certain disadvantages, it cannot be considered standard of care. Microvascular Doppler sonography is probably the fastest diagnostic tool and can quickly aid diagnosis of large vessel occlusions. Intraoperative indocyanine green videoangiography is the best tool to assess flow in perforating and larger arteries, as well as occlusion of the aneurysm sac. Intraoperative neurophysiological monitoring with somatosensory and motor evoked potentials indirectly measures blood flow by recording neuronal function. It covers all causes of intraoperative ischemia, provided that ischemia occurs in the brain areas under surveillance. However, every method has advantages and disadvantages. No single method is superior to the others in every aspect. Therefore, it is very important for the neurosurgeon to know the strengths and weaknesses of each tool in order to have them available, to know how to use them for each individual situation, and to be ready to apply them within the time window for reversible cerebral ischemia.

Temporal and small-scale spatial variation in grassland productivity, biomass quality, and nutrient limitation

Characterization of spatial and temporal variation in grassland productivity and nutrition is crucial for a comprehensive understanding of ecosystem function. Although within-site heterogeneity in soil and plant properties has been shown to be relevant for plant community stability, spatiotemporal variability in these factors is still understudied in temperate grasslands. Our study aimed to detect if soil characteristics and plant diversity could explain observed small-scale spatial and temporal variability in grassland productivity, biomass nutrient concentrations, and nutrient limitation. Therefore, we sampled 360 plots of 20 cm × 20 cm each at six consecutive dates in an unfertilized grassland in Southern Germany. Nutrient limitation was estimated using nutrient ratios in plant biomass. Absolute values of, and spatial variability in, productivity, biomass nutrient concentrations, and nutrient limitation were strongly associated with sampling date. In April, spatial heterogeneity was high and most plots showed phosphorous deficiency, while later in the season nitrogen was the major limiting nutrient. Additionally, a small significant positive association between plant diversity and biomass phosphorus concentrations was observed, but should be tested in more detail. We discuss how low biological activity e.g., of soil microbial organisms might have influenced observed heterogeneity of plant nutrition in early spring in combination with reduced active acquisition of soil resources by plants. These early-season conditions are particularly relevant for future studies as they differ substantially from more thoroughly studied later season conditions. Our study underlines the importance of considering small spatial scales and temporal variability to better elucidate mechanisms of ecosystem functioning and plant community assembly.

Health promotion attitudes and practices of Texas nurse practitioners

The purpose of this descriptive cross-sectional survey was to examine the health promotion attitudes and practices of Texas nurse practitioners and to evaluate the applicability of the Theory of Reasoned Action and the Theory of Planned Behavior as a theoretical model to guide nurse practitioner health promotion research. A questionnaire developed to elicit responses regarding demographic information, practice characteristics, behavior, behavior intention, attitudes toward health promotion, subjective norm and perceived behavioral control for health promotion practices was mailed to the home address of 727 Texas nurse practitioners. The majority of the 442 respondents reported positive attitudes toward health promotion. Texas nurse practitioners provide health promotion for more than 50% of their patients. Significant barriers to the provision of health promotion cited by Texas nurse practitioners were lack of time, lack of reimbursement and lack of patient desire to change behavior. The findings of this study support the use of the Theory of Reasoned Action and the Theory of Planned Behavior in nurse practitioner research. ^

A Tort for Risk and Endogenous Bankruptcy

Conventional tort law bars victims of exposure to a toxic substance from filing suit until they actually develop symptoms of illness. Practically speaking, this rule often bars recovery due to bankruptcy and causal uncertainty. One solution is to allow victims to file at exposure for expected damages (a tort for risk). The trade-off is that such a rule may trigger a race to file among exposure victims, thereby itself inducing bankruptcy. This paper characterizes the conditions under which such a race will occur in equilibrium and examines the implications for social welfare.

Collective Voluntary Agreements and the Production of Less Polluting Products

Recently, some industries have collectively agreed not to produce models that do not meet an energy efficiency (and hence an environmental) standard. This paper presents a simple model that can be used to examine a voluntary collective agreement to limit or completely eliminate the low efficiency model of a given product (e.g., a low efficiency washing machine). We show that, when there is competition between firms, a collective agreement to limit or even eliminate production of the polluting model can actually increase profits for all firms in the industry. This suggests that a collective agreement of this type might actually be beneficial to firms, while at the same time improving environmental quality. However, the implicit enforcement that comes from the public nature of the commitment is necessary to ensure this outcome. This suggests that, by promoting such agreements, policymakers may be able to achieve substantial environmental gains with relatively little inducement. The impact on social welfare will then depend on whether these gains are sufficiently large to offset consumer losses from reductions in product variety and the associated price increases.

A Bargaining Model of Holdouts and Takings

The holdout problem is commonly cited as the justification for eminent domain, but the nature of the problem is not well understood. This paper models the holdout problem in a bargaining framework, where a developer seeks to acquire several parcels of land for a large-scale development. We show that in the absence of eminent domain, holdouts are inevitable, threatening costly delay. However, if the developer has the power to use eminent domain to acquire the land from holdouts, all sellers will bargain, thus avoiding delay. An offsetting cost is that owners may negotiate prices below their true value, possibly resulting in excessive transfer of land to the developer.

Punishing the Innocent along with the Guilty: The Economics of Individual versus Group Punishment

Standard models of law enforcement involve the apprehension and punishment of a single suspect, but in many contexts, punishment is actually imposed on an entire group known to contain the offender. The advantages of .group punishment. are that the offender is punished with certainty and detection costs are saved. The disadvantage is that innocent individuals are punished. We compare individual and group punishment when social welfare depends on fairness, and when it depends on deterrence. We show that group punishment may dominate in the former case if the detection technology is ineffective but never in the latter case. We discuss our results in the context of several examples.

A Note on Optimal Care by Wealth-Constrained Injurers

This paper clarifies the relationship between an injurer's wealth level and his care choice by highlighting the distinction between monetary and non-monetary care. When care is non-monetary, wealth-constrained injurers generally take less than optimal care, and care is increasing in their wealth level under both strict liability and negligence. In contrast, when care is monetary, injurers may take too much or too little care under strict liability, and care is not strictly increasing in injurer wealth. Under negligence, the relationship between injurer care and wealth is similar in the two formulations. However, when litigation costs are added to the model, the relationship between injurer care and wealth becomes non-monotonic under both liability rules.

Do Exposure Suits Produce a 'Race to File'? An Economic Analysis of a Tort for Risk

Conventional tort law does not allow victims of exposure to a toxic substance to seek compensation until they develop actual symptoms of illness. This may effectively bar recovery because at the time the illness arises, injurers may be judgment proof. One possible response is to allow a tort for risk that allows victims to seek expected damages at the time of exposure. However, critics charge that this could create a 'race to file' wherein victims rush to file suit to ensure that they will get a share of the injurer's limited assets. We show that such a race may or may not occur in equilibrium, and that when it does occur, not all victims choose to file at exposure if bankruptcy is an inevitable result. If bankruptcy is not inevitable, it is possible that a tort for risk will trigger bankruptcy, although a no-bankruptcy equilibrium always exists and Paretodominates the bankruptcy equilibrium. We examine the consequences of the various tort-for-risk equilibria on the compensation of exposure victims, litigation costs, and injurer care.

Nonpoint Pollution Control: Inducing First-best Outcomes through the Use of Threats

In this paper we develop a simple economic model to analyze the use of a policy that combines a voluntary approach to controlling nonpoint-source pollution with a background threat of an ambient tax if the voluntary approach is unsuccessful in meeting a pre-specified environmental goal. We first consider the case where the policy is applied to a single farmer, and then extend the analysis to the case where the policy is applied to a group of farmers. We show that in either case such a policy can induce cost-minimizing abatement without the need for farm-specific information. In this sense, the combined policy approach is not only more effective in protecting environmental quality than a pure voluntary approach (which does not ensure that water quality goals are met) but also less costly than a pure ambient tax approach (since it entails lower information costs). However, when the policy is applied to a group of farmers, we show that there is a potential tradeoff in the design of the policy. In this context, lowering the cutoff level of pollution used for determining total tax payments increases the likely effectiveness of the combined approach but also increases the potential for free riding. By setting the cutoff level equal to the target level of pollution, the regulator can eliminate free riding and ensure that cost-minimizing abatement is the unique Nash equilibrium under which the target is met voluntarily. However, this cutoff level also ensures that zero voluntary abatement is a Nash equilibrium. In addition, with this cutoff level the equilibrium under which the target is met voluntarily will not strictly dominate the equilibrium under which it is not. We show that all results still hold if the background threat instead takes the form of reducing government subsidies if a pre-specified environmental goal is not met.