Microsurgery costs and outcome

Reliable information on cost and value in microsurgery is not readily available in the literature. Driving factors for cost, determinants of complications, and cost-reduction strategies have not been elucidated in this population, despite such progress in other areas of medicine. Clearly, the time-consuming and costly nature of this endeavor demands that appropriate indications and patient management be delineated; to operate proactively in this cost-conscious time, financial and outcome determinations are critical. One hundred seven consecutive free-tissue transfers performed from 1991 to 1994 by a single microsurgeon were studied. Retrospective chart review for clinical parameters was combined with analysis of hospital costs and professional charges. Operating room and anesthesia costs were based on a microcost analysis of actual operating room time, materials, labor, and overhead. Other patient level costs were generated by Transition 1, a hospital cost-accounting system. The following issues were addressed: (1) flap survival; (2) total costs and length of stay for all free flaps; (3) payments received from various insurers; (4) breakdown of operating room costs by labor, supplies, and overhead; (5) breakdown of inpatient costs by category; (6) additional costs of complications and takebacks; (7) factors associated with complications and flap takebacks; and (8) cost-reduction strategies. Mean free flap operating room costs (exclusive of professional fees) ranged among case types from $4439 to $6856 and were primarily a function of operating room times. Elective patient cases lasted a mean 440 minutes. There was a large disparity in reimbursement: private insurers covered hospital costs (not charges) completely, whereas Medicare paid 79 percent and Medicaid only 64 percent. Length of stay, operative procedures, and complications had the greatest influence on inpatient costs in this group of free flap patients. Potential cost savings as a result of possible practice changes (e.g., shortening intensive care unit stays and avoiding staged operations) can be predicted. This analysis has caused a revision in these institutions' practice patterns and lays the foundation for planned outcome studies in this population.     

Measuring the costs of reproduction

The measurement of costs of reproduction is of interest because such costs are generally assumed by life history theory. There is some controversy concerning how to measure costs: common methods include experimental manipulations of life history, such as preventing some individuals from reproducing, or estimates of genetic correlations. These two methods often yield similar results, suggesting that one can serve as a substitute for the other. There are now experiments which demonstrate that there are different mechanisms underlying the response to an experimental manipulation versus a genetic correlation, so the two methods are not equivalent in estimating costs.     

Mapping the economic costs and benefits of conservation

Resources for biodiversity conservation are severely limited, requiring strategic investment. Understanding both the economic benefits and costs of conserving ecosystems will help to allocate scarce dollars most efficiently. However, although cost-benefit analyses are common in many areas of policy, they are not typically used in conservation planning. We conducted a spatial evaluation of the costs and benefits of conservation for a landscape in the Atlantic forests of Paraguay. We considered five ecosystem services (i.e., sustainable bushmeat harvest, sustainable timber harvest, bioprospecting for pharmaceutical products, existence value, and carbon storage in aboveground biomass) and compared them to estimates of the opportunity costs of conservation. We found a high degree of spatial variability in both costs and benefits over this relatively small (~3,000 km²) landscape. Benefits exceeded costs in some areas, with carbon storage dominating the ecosystem service values and swamping opportunity costs. Other benefits associated with conservation were more modest and exceeded costs only in protected areas and indigenous reserves. We used this cost-benefit information to show that one potential corridor between two large forest patches had net benefits that were three times greater than two otherwise similar alternatives. Spatial cost-benefit analysis can powerfully inform conservation planning, even though the availability of relevant data may be limited, as was the case in our study area. It can help us understand the synergies between biodiversity conservation and economic development when the two are indeed aligned and to clearly understand the trade-offs when they are not.     

Marginal costs and benefits.

Decision makers are interested in measuring the costs and benefits of various interventions, and sometimes they are presented with the average costs and benefits of alternative interventions and asked to compare these. Usually a newer intervention is being compared with an existing one, and the most appropriate comparison is not of average costs (and benefits) but of the extra--or marginal--costs (and benefits) of the new intervention. Reanalysis of the cost effectiveness ratio of biochemical screening of all women for Down''s syndrome compared with age based screening shows that the marginal cost effectiveness of biochemical screening is 47,786 pounds, compared with an average cost effectiveness of 37,591 pounds. It may sometimes be difficult or costly to calculate marginal costs and benefits, but this should be done whenever possible.     

Parabiotic ants: the costs and benefits of symbiosis

1. Mutualisms are important drivers of co‐evolution and speciation. However, they typically imply costs for one or both partners. Each partner consequently tries to maximise benefits and minimise costs. Mutualisms can therefore develop towards commensalism or parasitism if one partner fails to provide sufficient benefits. This is particularly likely in diffuse interactions, where multiple species can associate with each other. If costs and benefits of a species vary with the identity of the partner species, this may result in a geographical mosaic of co‐evolution. 2. In the present study, inter‐specific interactions in two parabiotic associations of ants were studied (Hymenoptera: Formicidae). One Crematogaster species was associated with one of two closely related Camponotus species. We assessed cost and benefits by studying behavioural interactions, foraging behaviour, and nest defence in the associations. 3. While parabioses had been shown to be mutualistic, evidence was found for exploitation and aggressive competition between species. In spite of apparent costs of being exploited, we found no benefits for one partner (Crematogaster). The magnitude of potential costs to Crematogaster varied between the two Camponotus species. 4. We conclude that the cost/benefit ratio for Crematogaster varies between the two Camponotus partners, and between environmental conditions. Parabiosis can thus fluctuate between mutualism, commensalism, and parasitism, with Crematogaster being the species that may have higher costs than benefits. 5. We suggest that geneflow in the Crematogaster population hinders local adaptation to the resulting mosaic of locally varying selection pressures. This study demonstrates how diffuse interactions and environmental variation can result in a complex of local selection pressures.     

Optimal life histories and the age-specific costs of reproduction

Increases in reproduction at a given age may carry costs measured as reductions in subsequent survival and/or future fertility. Such costs generate constraints within which natural selection may mould life histories to maximize fitness. In this paper, I derive expressions predicting the age-specific costs of reproduction conditional on the maximization of fitness. Survival costs should, on this hypothesis, vary as the inverse of the reproductive value curve; fertility costs should vary as the ratio of successive terms in the stable age distribution. For many organisms, this means that survival costs should increase markedly with age, while fertility costs should be nearly age-invariant. Data on such age-specific costs is scarce, but that which is available (mainly for humans) agrees with these predictions.     

Linking signal fidelity and the efficiency costs of communication

The handicap principle has been the overarching framework to explain the evolution and maintenance of communication. Yet, it is becoming apparent that strategic costs of signalling are not the only mechanism maintaining signal honesty. Rather, the fidelity of detecting signals can itself be strongly selected. Specifically, we argue that the fidelity of many signals will be constrained by the investment in signal generation and reception by the signaller and perceiver, respectively. Here, we model how investments in signal fidelity influence the emergence and stability of communication using a simple theoretical framework. The predictions of the model indicate that high‐cost communication can be stable whereas low‐cost intermediates are generally selected against. This dichotomy suggests that the most parsimonious route to the evolution of communication is for initial investment in communicative traits to be driven by noncommunicative functions. Such cues can appeal to pre‐existing perceptual biases and thereby stimulate signal evolution. We predict that signal evolution will vary between systems in ways that can be linked to the economics of communication to the two parties involved.     

The pill and the rising costs of fertility control

Abstract

Until recently it seemed obvious that oral contraception greatly reduced the costs of fertility control. Anxiety about effectiveness was removed, and the inconvenience and displeasure associated with coitus‐related contraception was bypassed. These advantages doubtless led to the sharp rise in pill use during the 1960's in the United States. The 197O's, however, appear to have ushered in a different calculus regarding the pill. Not only has the trend in pill use leveled off, but suspicions have arisen that the net costs to women of practicing this form of birth control are higher than was previously believed. It now appears that significant costs to health may exist and that people are increasingly evincing concern about these physiological consequences. In this paper, the trend in use of oral contraception is examined briefly. Then, a short summary of some of the health risks apparently involved in use of the pill is presented. Finally, the main body of the paper provides information on public attitudes toward the pill over the decade 1966–76.     

The pill and the rising costs of fertility control

Until recently it appeared as if oral contraception greatly reduced the costs of fertility control. The advantages of effectiveness and the convenience of this method in preference to coitus-related contraception led to the dramatic increase in oral contraceptive (OC) use during the 1960s in the U.S. The trend in the 1970s is different. OC use has leveled off, and suspicions have arisen that the net costs to women of using this form of birth control are higher than was previously believed. Discontinuation rates by women who have been on OCs have increased despite major improvement in the chemistry of the OC in recent years. In view of the evidence concerning the apparent risks to health associated with OCs, the current trend is not surprising. The range of major diseases for which the relative risk is higher among OC users seems to be broadening, and, as a consequence, the cumulative absolute risk overall of these diseases may be very much higher than was believed when only selected thromboembolic entities seemed to be involved. In order to obtain the public's view about the safety of OCs, 1500 voting age adults have been questioned in national surveys since 1966. 34% of the respondents in 1976 said that they believed the OC to be safe, but 47% of this group meant that it is as safe as aspirin. 34% ranked it as being somewhat less safe than aspirin. Their answers indicate that over time there had been increasing anxiety about the safety of the OC, but no general sense of panic. Even among those who felt it is unsafe, only a minority are willing to label it as "really dangerous."     

Premeiotic endomitosis and the costs and benefits of asexual reproduction

Different patterns of development can influence the strength and direction of selection of a trait. Here, it is shown how this may be the case for asexual reproduction in which eggs (animals) or spores (plants) inherit the maternal chromosome number through a precursor cell undergoing an endoduplication of its chromosomes prior to meiotic reduction. Asexuality involving premeiotic endoduplication (APE) has a wide but uneven distribution among animals and plants. It is argued that different patterns of egg and spore production and differences in when endoduplication occurs, together with differences in breeding structure (dioecious vs. hermaphroditic) and reproductive strategy (e.g. spawning vs. vivipary), can result in APE being associated with fecundity costs that can result in an overall cost of sex or in an overall cost of asex or in APE being selectively neutral relative to sex. There is a lack of a close correlation between the taxonomic distribution of APE and its potential costs and benefits however, possible causes of which are explored. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 487–495.     

Regulatory control and the costs and benefits of biochemical noise

Experiments in recent years have vividly demonstrated that gene expression can be highly stochastic. How protein concentration fluctuations affect the growth rate of a population of cells is, however, a wide-open question. We present a mathematical model that makes it possible to quantify the effect of protein concentration fluctuations on the growth rate of a population of genetically identical cells. The model predicts that the population's growth rate depends on how the growth rate of a single cell varies with protein concentration, the variance of the protein concentration fluctuations, and the correlation time of these fluctuations. The model also predicts that when the average concentration of a protein is close to the value that maximizes the growth rate, fluctuations in its concentration always reduce the growth rate. However, when the average protein concentration deviates sufficiently from the optimal level, fluctuations can enhance the growth rate of the population, even when the growth rate of a cell depends linearly on the protein concentration. The model also shows that the ensemble or population average of a quantity, such as the average protein expression level or its variance, is in general not equal to its time average as obtained from tracing a single cell and its descendants. We apply our model to perform a cost-benefit analysis of gene regulatory control. Our analysis predicts that the optimal expression level of a gene regulatory protein is determined by the trade-off between the cost of synthesizing the regulatory protein and the benefit of minimizing the fluctuations in the expression of its target gene. We discuss possible experiments that could test our predictions.