Widespread habitat loss leads to ecosystem-scale decrease in trophic function

Natural and anthropogenic disturbances have led to rapid declines in the amount and quality of available habitat in many ecosystems. Many studies have focused on how habitat loss has affected the composition and configuration of habitats, but there have been fewer studies that investigate how this loss affects ecosystem function. We investigated how a large-scale seagrass die-off altered the distribution of energetic resources of three seagrass-associated consumers with varied resource use patterns. Using long-term benthic habitat monitoring data and resource use data from Bayesian stable isotope mixing models, we generated energetic resource landscapes (E-scapes) annually between 2007 and 2019. E-scapes link the resources being used by a consumer to the habitats that produce those resources to calculate a habitat resource index as a measurement of energetic quality of the landscape. Overall, our results revealed that following the die-off there was a reduction in trophic function across all species in areas affected by the die-off event, but the response was species-specific and dependent on resource use and recovery patterns. This study highlights how habitat loss can lead to changes in ecosystem function. Incorporating changes in ecosystem function into models of habitat loss could improve understanding of how species will respond to future change.

Renal Outcomes Following Transcatheter Mitral Valve Repair - Analysis of COAPT Trial Data

The prevalence of valvular heart disease in the United States has been estimated at 4.2-to-5.6 million, with mitral regurgitation (MR) being the most common lesion. Significant MR is associated with heart failure (HF) and death if left untreated. When HF is present, renal dysfunction (RD) is common and is associated with worse outcomes (ie, it is a marker of HF disease progression). Additionally, a complex interplay exists in patients with HF who also have MR, as this combination further impairs renal function, and the presence of RD further worsens prognosis and often limits guideline-directed management and therapy (GDMT). This has important implications in secondary MR because GDMT is the standard of care. However, with the development of minimally invasive transcatheter mitral valve repair, mitral transcatheter edge-to-edge repair (TEER) has become a new treatment option for secondary MR that is now incorporated into current guidelines published in 2020 that listed mitral TEER as a class 2a recommendation (moderate recommendation with benefit >> risk) as an addition to GDMT in a subset of patients with left ventricular ejection fraction <50%. The Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation (COAPT) trial, which demonstrated favorable outcomes in secondary MR by adding mitral TEER to GDMT versus GDMT alone, was the evidence base for these guidelines. Considering these guidelines and the understanding that concomitant RD often limits GDMT in secondary MR, there is emerging research studying the renal outcomes from the COAPT trial. This review analyzes this evidence, which could further influence current decision-making and future guidelines.

Trophic ontogeny of a generalist predator is conserved across space

Consumers can influence ecological patterns and processes through their trophic roles and contributions to the flow of energy through ecosystems. However, the diet and associated trophic roles of consumers commonly change during ontogeny. Despite the prevalence of ontogenetic variation in trophic roles of most animals, we lack an understanding of whether they change consistently across local populations and broad geographic gradients. We examined how the diet and trophic position of a generalist marine predator varied with ontogeny across seven broadly separated locations (~ 750 km). We observed a high degree of heterogeneity in prey consumed without evidence of spatial structuring in this variability. However, compound-specific isotope analysis of amino acids revealed remarkably consistent patterns of increasing trophic position through ontogeny across local populations, suggesting that the roles of this generalist predator scaled with its body size across space. Given the high degree of diet heterogeneity we observed, this finding suggests that even though the dietary patterns differed, the underlying food web architecture transcended variation in prey species across locations for this generalist consumer. Our research addresses a gap in empirical field work regarding the interplay between stage-structured populations and food webs, and suggests ontogenetic changes in trophic position can be consistent in generalist consumers.

Prothrombin Complex Concentrate vs Plasma for Post-Cardiopulmonary Bypass Coagulopathy and Bleeding: A Randomized Clinical Trial

Importance

Post-cardiopulmonary bypass (CPB) coagulopathy and bleeding are among the most common reasons for blood product transfusion in surgical practices. Current retrospective data suggest lower transfusion rates and blood loss in patients receiving prothrombin complex concentrate (PCC) compared with plasma after cardiac surgery.

Objective

To analyze perioperative bleeding and transfusion outcomes in patients undergoing cardiac surgery who develop microvascular bleeding and receive treatment with either PCC or plasma.

Design, Setting, and Participants

A single-institution, prospective, randomized clinical trial performed at a high-volume cardiac surgical center. Patients were aged 18 years or older and undergoing cardiac surgery with CPB. Patients undergoing complex cardiac surgical procedures (eg, aortic replacement surgery, multiple procedures, or repeated sternotomy) were preferentially targeted for enrollment. During the study period, 756 patients were approached for enrollment, and 553 patients were randomized. Of the 553 randomized patients, 100 patients met criteria for study intervention.

Interventions

Patients with excessive microvascular bleeding, a prothombin time (PT) greater than 16.6 seconds, and an international normalized ratio (INR) greater than 1.6 were randomized to receive treatment with either PCC or plasma. The PCC dose was 15 IU/kg or closest standardized dose; the plasma dose was a suggested volume of 10 to 15 mL/kg rounded to the nearest unit.

Main Outcomes and Measures

The primary outcome was postoperative bleeding (chest tube output) from the initial postsurgical intensive care unit admission through midnight on postoperative day 1. Secondary outcomes were PT/INR, rates of intraoperative red blood cell (RBC) transfusion after treatment, avoidance of allogeneic transfusion from the intraoperative period to the end of postoperative day 1, postoperative bleeding, and adverse events.

Results

One hundred patients (mean [SD] age, 66.8 [13.7] years; 61 [61.0%] male; and 1 [1.0%] Black, 1 [1.0%] Hispanic, and 98 [98.0%] White) received the study intervention (49 plasma and 51 PCC). There was no significant difference in chest tube output between the plasma and PCC groups (median [IQR], 1022 [799-1575] mL vs 937 [708-1443] mL). After treatment, patients in the PCC arm had a greater improvement in PT (effect estimate, -1.37 seconds [95% CI, -1.91 to -0.84]; P < .001) and INR (effect estimate, -0.12 [95% CI, -0.16 to -0.07]; P < .001). Fewer patients in the PCC group required intraoperative RBC transfusion after treatment (7 of 51 patients [13.7%] vs 15 of 49 patients [30.6%]; P = .04); total intraoperative transfusion rates were not significantly different between groups. Seven (13.7%) of 51 patients receiving PCCs avoided allogeneic transfusion from the intraoperative period to the end of postoperative day 1 vs none of those receiving plasma. There were no significant differences in postoperative bleeding, transfusions, or adverse events.

Conclusions and Relevance

The results of this study suggest a similar overall safety and efficacy profile for PCCs compared with plasma in this clinical context, with fewer posttreatment intraoperative RBC transfusions, improved PT/INR correction, and higher likelihood of allogeneic transfusion avoidance in patients receiving PCCs.

Trial Registration

ClinicalTrials.gov Identifier: NCT02557672.

The impacts of mangrove range expansion on wetland ecosystem services in the southeastern United States: Current understanding, knowledge gaps, and emerging research needs

Climate change is transforming ecosystems and affecting ecosystem goods and services. Along the Gulf of Mexico and Atlantic coasts of the southeastern United States, the frequency and intensity of extreme freeze events greatly influence whether coastal wetlands are dominated by freeze-sensitive woody plants (mangrove forests) or freeze-tolerant grass-like plants (salt marshes). In response to warming winters, mangroves have been expanding and displacing salt marshes at varying degrees of severity in parts of north Florida, Louisiana, and Texas. As winter warming accelerates, mangrove range expansion is expected to increasingly modify wetland ecosystem structure and function. Because there are differences in the ecological and societal benefits that salt marshes and mangroves provide, coastal environmental managers are challenged to anticipate the effects of mangrove expansion on critical wetland ecosystem services, including those related to carbon sequestration, wildlife habitat, storm protection, erosion reduction, water purification, fisheries support, and recreation. Mangrove range expansion may also affect wetland stability in the face of extreme climatic events and rising sea levels. Here, we review the current understanding of the effects of mangrove range expansion and displacement of salt marshes on wetland ecosystem services in the southeastern United States. We also identify critical knowledge gaps and emerging research needs regarding the ecological and societal implications of salt marsh displacement by expanding mangrove forests. One consistent theme throughout our review is that there are ecological trade-offs for consideration by coastal managers. Mangrove expansion and marsh displacement can produce beneficial changes in some ecosystem services, while simultaneously producing detrimental changes in other services. Thus, there can be local-scale differences in perceptions of the impacts of mangrove expansion into salt marshes. For very specific local reasons, some individuals may see mangrove expansion as a positive change to be embraced, while others may see mangrove expansion as a negative change to be constrained.

Use of plasma late on cardiopulmonary bypass in patients undergoing left ventricular assist device implantation

Coagulopathy is common during left ventricular assist device (LVAD) implantation, treatment of which can be challenging given the often-limited ability for the right ventricle to accommodate volume transfusion after device initiation with 20% to 40% of patients developing right ventricular failure (RVF). Transfusion of plasma late on cardiopulmonary bypass (CPB) combined with ultrafiltration may replace clotting factors while reducing volume administration. We compared outcomes in patients undergoing LVAD implantation receiving plasma on CPB and ultrafiltration with traditional transfusion practices. Co-primary outcomes needed for blood product transfusion in the first 6 and 24 hours after CPB. Secondary outcomes included metrics of morbidity and mortality. 396 patients were analyzed (59 plasma on CPB). Patients receiving plasma on CPB had a greater volume of blood products transfused (3764 vs. 2741 mL first 6 hours; 6059 vs. 4305 mL first 24 hours) in unadjusted analysis. In adjusted analysis, plasma transfusion on CPB with ultrafiltration had no significant effect on the primary outcomes of blood products given in the first 6 hours (estimated effect size 982 [-428, 2392] mL, P = .17) and 24 hours (estimated effect size 1076 [-904, 3057] mL, P = .29). Patients receiving plasma on CPB were more likely on either vasopressors or inotropes at 24 hours after ICU admission (P = .01), however, indices of coagulopathy and RVF were similar between groups. While prospective studies would be necessary to definitively evaluate the clinical utility of this strategy, no signal for benefit was observed suggesting plasma should not be used for this purpose.

E-scape: Consumer-specific landscapes of energetic resources derived from stable isotope analysis and remote sensing

Energetic resources and habitat distribution are inherently linked. Energetic resource availability is a major driver of the distribution of consumers, but estimating how much specific habitats contribute to the energetic resource needs of a consumer can be problematic. We present a new approach that combines remote sensing information and stable isotope ecology to produce maps of energetic resources (E-scapes). E-scapes project species-specific resource use information onto the landscape to classify areas based on energetic importance. Using our E-scapes, we investigated the relationship between energetic resource distribution and white shrimp distribution and how the scale used to generate the E-scape mediated this relationship. E-scapes successfully predicted the size, abundance, biomass, and total energy of a consumer in salt marsh habitats in coastal Louisiana, USA at scales relevant to the movement of the consumer. Our E-scape maps can be used alone or in combination with existing models to improve habitat management and restoration practices and have potential to be used to test fundamental movement theory.

The Success of a Simulation-Based Transesophageal Echocardiography Course for Liver Transplant Anesthesiologists

INTRODUCTION

Transesophageal echocardiography (TEE) is increasingly used for intraoperative management during orthotopic liver transplantation. Proficient TEE use requires skill and knowledge to accurately assess the hemodynamic status and guide clinical management. Currently there are no TEE educational tracks specifically focused on perioperative liver transplant management and barriers to obtaining basic certification exist.

METHODS

A 4-hour simulation-based learning (SBL) course was provided to improve liver transplant anesthesiologist TEE knowledge and skill. Learners received training and education using a TEE simulator in small groups focusing on basic image acquisition, relevant anatomy, hemodynamic calculations, and pathology germane to the liver transplant period. Knowledge assessment and survey responses were assessed at the beginning and completion of the course. Learners completed TEE examinations with simulated pathology during high-fidelity simulations following the course.

RESULTS

Seventeen anesthesiologists completed the course. The median baseline knowledge assessment score was 55.0% (37-70). The median postcourse knowledge assessment score improved to 95.0% (94-100) (P < .001). All anesthesiologists were able to identify TEE pathology during high-fidelity simulation. Survey responses yielded significant median score improvement in all areas assessed using a 5-point Likert scale.

CONCLUSIONS

A small group, simulation TEE course delivered over 4 hours can increase knowledge and skill in TEE use for liver transplant anesthesiologists.

Impact of nutritional status on prevalence of left ventricular hypertrophy in children undergoing liver transplant

OBJECTIVE

We sought to (1) determine the prevalence of cardiac changes in patients with ESLD awaiting OLT (2) determine relationship between nutritional indices and cardiac changes.

METHODS

Retrospective review of transthoracic ECHO, clinical and nutritional information of pediatric patients evaluated for OLT. ECHO was analyzed for LVH, defined as LVMI > 95 g/m^2.7 and/or RWT > 0.42. These findings were correlated with age, ESLD etiology, growth and nutritional parameters as well as pre- and post-OLT.

RESULTS

Sixty-five patients were included, all had normal left ventricular systolic function. Nine patients (14%) had LVMI > 95 g/m^2.7 , five patients (8%) had RWT > 0.42, none met both criteria. None had thickened interventricular septal wall. Fourteen patients (20%) had significant left ventricular dilation. Nutritional deprivation was modestly present-weight under third percentile in 22%, length under third percentile in 24%, and both weight and length under third percentile in 17%. There were 12 patients (17%) with MUAC below two standard deviations for age; of these one had an elevated LVMI and another had an RWT > 0.42.

CONCLUSIONS

In this contemporary cross-sectional evaluation, a smaller proportion of patients with ESLD had LVH in contrast to prior studies. Despite a comparable disease burden, our cohort had better nutritional status. Though there was a trend between nutritional and LVH indices, this correlation may be better assessed prospectively in a larger cohort.

Analysis of the ESC/EACTS 2020 Atrial Fibrillation Guidelines With Perioperative Implications

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia worldwide, with an individual lifetime risk of approximately 37% in the United States. Broadly defined as a supraventricular tachyarrhythmia with disorganized atrial activation, AF results in an increased risk of stroke, heart failure, valvular heart disease, and impaired quality of life, and confers a significant burden on the health of individuals and society. AF in the perioperative setting is common and a significant source of perioperative morbidity and mortality worldwide. The latest iteration of the European Society of Cardiology AF guidelines published in 2020 provide the clinician a valuable road map for the management of this arrythmia. This expert review will comprehensively analyze the 2020 European Society of Cardiology guidelines and provide perioperative management tools for the clinician.

Pulmonary artery sheath hematoma

Dissection of the ascending aorta (AA) represents a life-threatening condition typically treated by emergent surgical repair. A rare, potential complication of AA dissection is pulmonary artery (PA) sheath hematoma. Due to the presence of a common adventitial layer between the proximal AA and the PA, dissection can propagate between both vessels, potentially compromising the PA lumen. The resultant acute narrowing of the PA lumen may abruptly increase right ventricular (RV) afterload. Recognition of PA sheath hematoma is important; when seen on echocardiography it is suggestive of AA dissection and has the potential to result in RV hypertension and dysfunction if significant PA compression occurs.

Individual Repeatability of Locomotor Kinematics and Swimming Performance in a Gymnotiform Swimmer

AbstractGymnotiform swimming is a specialized form of swimming wherein thrust is produced by the ribbonlike motion of an elongate anal fin, while the body is held relatively stiff. This form of swimming has been extensively examined in relation to the biomechanics of thrust production, the kinematics of the anal fin, and neuromuscular control, whereas few studies have examined whole-animal performance parameters of this swimming mode. The goals of this research were to (1) assess the maximum abilities and repeatability of two swimming performance measures, sprinting and prolonged swimming, which would indicate that these performance measures in a gymnotiform swimmer may be a target for selection, similar to body-caudal fin-swimming fish; (2) examine how a gymnotiform swimmer modulates swimming speed; and (3) determine whether modulatory behavior is consistent across different-sized fish and within individuals across time. Sprinting and prolonged swimming were examined in black ghost knifefish (Apteronotus albifrons; N=15), multiple times on the same day, and were measured again 4 wk later. Sprinting ability was measured by chasing a fish down a photocell-lined racetrack and obtaining the fastest speed between any 8-cm span. Prolonged swimming abilities were measured in a constant acceleration test (U_cat) in a Brett-style swim tunnel by measuring the maximum speed the fish could attain against a steadily increasing water velocity. We determined frequency, wavelength, and amplitude of the anal fin sine wave in fish swimming at different speeds during the U_cat trials. We found repeatable measures of sprint speed and U_cat performance over short (day) and medium (4 wk) time periods for both tests. Neither sprint nor U_cat performance was significantly dependent on size, suggesting that the primary driver of performance variation was individual differences in physiology. Most modulation of swimming speed occurred through changes in the frequency of the wave train processing down the anal fin, with only modest changes to the wavelength and minimal changes to amplitude. Finally, we compare our measures of swimming performance in this gymnotiform swimmer to published values of body-caudal fin swimmers to demonstrate that this form of locomotion results in comparable sprint and constant-acceleration values.

Not All Nitrogen Is Created Equal: Differential Effects of Nitrate and Ammonium Enrichment in Coastal Wetlands

Excess reactive nitrogen (N) flows from agricultural, suburban, and urban systems to coasts, where it causes eutrophication. Coastal wetlands take up some of this N, thereby ameliorating the impacts on nearshore waters. Although the consequences of N on coastal wetlands have been extensively studied, the effect of the specific form of N is not often considered. Both oxidized N forms (nitrate, NO3-) and reduced forms (ammonium, NH4+) can relieve nutrient limitation and increase primary production. However, unlike NH4+, NO3- can also be used as an electron acceptor for microbial respiration. We present results demonstrating that, in salt marshes, microbes use NO3- to support organic matter decomposition and primary production is less stimulated than when enriched with reduced N. Understanding how different forms of N mediate the balance between primary production and decomposition is essential for managing coastal wetlands as N enrichment and sea level rise continue to assail our coasts.

Acute Severe Functional Mitral Regurgitation After Non-Mitral Valve Cardiac Surgery-Left Ventricular Dyssynchrony as a Potential Mechanism

Functional mitral regurgitation (MR) describes valve leakage in the absence of disease or damage to the mitral leaflets or subvalvular apparatus. Significant, new functional MR after cardiopulmonary bypass (CPB) may result from a number of intraoperative processes, including left ventricular (LV) ischemia and enlargement, left atrial enlargement secondary to increased filling pressure, and systolic anterior motion of the mitral valve after mitral repair. Assessment of new MR after CPB is important because it may direct hemodynamic maneuvers or prompt reinitiation of CPB if surgical intervention is deemed necessary. Described extensively in the electrophysiology literature but underreported as a cause of MR after CPB, LV dyssynchrony represents another possible mechanism of functional MR, in which resynchronization of conduction via pacing maneuvers may prove beneficial. Herein, a series of 4 patients in whom new MR was found after non-mitral valve cardiac surgery in the setting of normal LV systolic function is presented, and LV dyssynchrony is proposed as a major contributing factor. The findings suggested that the concomitant observation of new or worsened functional MR, together with normal global and regional LV systolic function, should lead the clinician to consider ventricular dyssynchrony as a possible cause. Attempts to improve or alter ventricular conduction should be considered before contemplating a return to CPB for mitral valve intervention.

Tricuspid Regurgitation in Congestive Heart Failure: Management Strategies and Analysis of Outcomes

Tricuspid regurgitation is a notable aspect of congestive heart failure and is linked with worse outcomes if untreated. Functional tricuspid regurgitation commonly is seen in patients with heart failure, particularly in patients presenting for surgical management, such as those for mechanical cardiac assist device implantation. This review aims to study the published data related to the surgical management of tricuspid regurgitation in the cardiac surgical population comprehensively.

Assessment of food web recovery following restoration using resource niche metrics

The primary goal of habitat restoration is to recover the ecological structure, function, and services of natural ecosystems lost due to disturbance. Post-restoration success typically focuses on the return of a desired habitat type, consumer species composition, or abundance relative to a reference site. However, how energy flow responds to habitat restoration has not been widely studied, and there is a need to develop a better understanding of how energy flows through a restored vs reference ecosystem following restoration. We tested recently developed niche metrics as a tool to assess the degree of recovery of ecosystem energy flow and evaluate the success of habitat restoration. Using published stable isotope values from six systems, one to three years post-restoration, we used Bayesian mixing models to quantify resource use by consumers to generate food web hypervolumes for restored and reference habitats in each ecosystem and to quantify similarity in resource use between restored and reference systems. Our analysis showed that there were differences in restoration success at each restoration project between the restored and reference food webs, but two general patterns emerged in the early stages following restoration. Restoration efforts that restore biogenic habitats display lower levels of recovery of food web function than those that only restore abiotic habitat structural. Restoration increases the variability in basal resource use of consumers in food webs that rely heavily on one basal resource, while in food webs that relied on multiple basal resources consumers decrease variability in basal resource use. Our results demonstrate that hypervolume analysis is a powerful tool that can be used to quantify energy flow, the recovery of food web function, and measure restoration success.

Red Blood Cell Disorders: Perioperative Considerations for Patients Undergoing Cardiac Surgery

Disorders affecting red blood cells (RBCs) are uncommon yet have many important physiologic considerations for patients undergoing cardiac surgery. RBC disorders can be categorized by those that are congenital or acquired, and further by disorders affecting the RBC membrane, hemoglobin, intracellular enzymes, or excessive RBC production. A foundational understanding of the physiologic derangement for these disorders is critical when considering perioperative implications and optimization, strategies for cardiopulmonary bypass, and the rapid recognition and treatment if complications occur. This review systematically outlines the RBC disorders of frequency and relevance with an emphasis on how the disorder affects normal physiologic processes, a review of the literature related to the disorder, and the implications and recommendations for patients undergoing cardiac surgery.

BioTIME: A database of biodiversity time series for the Anthropocene

MOTIVATION

The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.

MAIN TYPES OF VARIABLES INCLUDED

The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.

SPATIAL LOCATION AND GRAIN

BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2).

TIME PERIOD AND GRAIN

BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.

MAJOR TAXA AND LEVEL OF MEASUREMENT

BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.

SOFTWARE FORMAT

.csv and .SQL.

The Invention and Early History of the N-Localizer for Stereotactic Neurosurgery

Nearly four decades after the invention of the N-localizer, its origin and history remain misunderstood. Some are unaware that a third-year medical student invented this technology. The following conspectus accurately chronicles the origin of the N-localizer, presents recently discovered evidence that documents its history, and corrects misconceptions related to its origin and early history.

Oxygen consumption rate v. rate of energy utilization of fishes: a comparison and brief history of the two measurements

Accounting for energy use by fishes has been taking place for over 200 years. The original, and continuing gold standard for measuring energy use in terrestrial animals, is to account for the waste heat produced by all reactions of metabolism, a process referred to as direct calorimetry. Direct calorimetry is not easy or convenient in terrestrial animals and is extremely difficult in aquatic animals. Thus, the original and most subsequent measurements of metabolic activity in fishes have been measured via indirect calorimetry. Indirect calorimetry takes advantage of the fact that oxygen is consumed and carbon dioxide is produced during the catabolic conversion of foodstuffs or energy reserves to useful ATP energy. As measuring [CO2 ] in water is more challenging than measuring [O2 ], most indirect calorimetric studies on fishes have used the rate of O2 consumption. To relate measurements of O2 consumption back to actual energy usage requires knowledge of the substrate being oxidized. Many contemporary studies of O2 consumption by fishes do not attempt to relate this measurement back to actual energy usage. Thus, the rate of oxygen consumption (M˙O2 ) has become a measurement in its own right that is not necessarily synonymous with metabolic rate. Because all extant fishes are obligate aerobes (many fishes engage in substantial net anaerobiosis, but all require oxygen to complete their life cycle), this discrepancy does not appear to be of great concern to the fish biology community, and reports of fish oxygen consumption, without being related to energy, have proliferated. Unfortunately, under some circumstances, these measures can be quite different from one another. A review of the methodological history of the two measurements and a look towards the future are included.

The Origin and History of the N-Localizer for Stereotactic Neurosurgery

Nearly four decades after the invention of the N-localizer, its origin and history remain misunderstood. Some are unaware that a third-year medical student invented this technology. The following conspectus accurately chronicles the origin and early history of the N-localizer and corrects some misconceptions related to both.

Hypoxia tolerance variance between swimming and resting striped bass Morone saxatilis

Individual striped bass Morone saxatilis were each exposed in random order to aquatic hypoxia (10% air saturation) either while swimming at 50% of their estimated critical swimming speed (Ucrit ) or while at rest until they lost equilibrium. Individuals were always less tolerant of hypoxia when swimming (P < 0.01); the average fish was over five times more tolerant to the same hypoxia exposure when not swimming. There was no relationship between an individual's rank order of hypoxia tolerance (HT) under the two flow regimes, suggesting that different factors determine an individual's HT when at rest than when swimming.

Acute kidney injury after open ventral hernia repair: an analysis of the 2005-2012 ACS-NSQIP datasets

PURPOSE

Acute kidney injury (AKI) is a serious postoperative complication, negatively impacting mortality rates, extending length of stay, and raising hospital costs. The purpose of this study was to examine AKI following open ventral hernia repair (OVHR) using a large, heterogeneous database to determine the incidence and identify risk factors for this complication.

METHODS

Using the 2005-2012 ACS-NSQIP database, patients undergoing open ventral hernia repair were identified by CPT codes. Patients with acute kidney injury within 30 days of surgery were compared to controls by multivariate logistic regression across preoperative and intraoperative characteristics.

RESULTS

Of 48,629 open ventral hernia repair patients identified in the dataset, AKI developed in 1.4% (681 patients). Multivariate logistic regression determined a number of factors associated with AKI. These include WHO Class III obesity (OR = 2.57, p < 0.001), history of cardiovascular disease (OR = 1.81, p < 0.001), diabetes (OR = 1.29, p = 0.028), hypoalbuminemia (OR = 1.42, p = 0.004), and chronic kidney disease (for a baseline GFR of 60-89 mL/min/1.73 m2, OR = 1.62, p = 0.001; for 30-59 mL/min/1.73 m2, OR = 2.25, p < 0.001; for 15-29 mL/min/1.73 m2, OR = 4.96, p < 0.001). Intraoperative factors include prolonged operative time (for ≥1 SD above the mean, OR = 1.68, p = 0.002; for ≥2SD above the mean, OR = 2.76, p < 0.001) and intraoperative transfusion (OR = 2.44, p < 0.001).

CONCLUSIONS

Patients with a history of obesity, chronic kidney disease, cardiovascular history, diabetes, and hypoalbuminemia are at increased risk for AKI when undergoing OVHR. Intraoperative variables such as prolonged operative times and blood transfusions may also suggest increased risk. Preoperative identification of patients with these characteristics and perioperative hemodynamic stabilization are important first steps to minimize this complication.

Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ (13)C and δ (15)N)

Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ¹³C and δ¹⁵N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ¹⁵N values in nearly all comparisons. Ethanol also had strong effects on the δ¹³C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and corresponding low levels of mass loss with a substantial change in the isotope value of the sample. Regardless of mechanism, it was evident that accounting for offsets caused by different preservation methods was not possible using the standard correction. Caution is warranted when interpreting the results from specimens stored in either ethanol or salt, especially when using those from multiple preservation techniques. We suggest the use of ice as the preferred preservation technique for muscle tissue when conducting stable isotope analysis as it is widely available, inexpensive, easy to transport and did not impart a significant offset in measured isotopic values. Our results provide additional evidence that preservation effects on stable isotope analysis can be highly contextual, thus requiring their effects to be measured and understood for each species and isotopic ratio of interest before addressing research questions.

Breaking wind to survive: fishes that breathe air with their gut

Several taxonomically disparate groups of fishes have evolved the ability to extract oxygen from the air with elements of their gut. Despite perceived difficulties with balancing digestive and respiratory function, gut air breathing (GAB) has evolved multiple times in fishes and several GAB families are among the most successful fish families in terms of species numbers. When gut segments evolve into an air-breathing organ (ABO), there is generally a specialized region for exchange of gases where the gut wall has diminished, vascularization has increased, capillaries have penetrated into the luminal epithelium and surfactant is produced. This specialized region is generally separated from digestive portions of the gut by sphincters. GAB fishes tend to be facultative air breathers that use air breathing to supplement aquatic respiration in hypoxic waters. Some hindgut breathers may be continuous, but not obligate air breathers (obligate air breathers drown if denied access to air). Gut ABOs are generally used only for oxygen uptake; CO₂ elimination seems to occur via the gills and skin in all GAB fishes studied. Aerial ventilation in GAB fishes is driven primarily by oxygen partial pressure of the water (PO₂) and possibly also by metabolic demand. The effect of aerial ventilation on branchial ventilation and the cardiovascular system is complex and generalizations across taxa or ABO type are not currently possible. Blood from GAB fishes generally has a low blood oxygen partial pressure that half saturates haemoglobin (p50) with a very low erythrocytic nucleoside triphosphate concentration [NTP]. GAB behaviour in nature depends on the social and ecological context of the animal as well as on physiological factors.

Invention of the N-localizer for stereotactic neurosurgery and its use in the Brown-Roberts-Wells stereotactic frame

The N-localizer, which facilitates computed tomography-guided stereotactic surgery, was invented in the late 1970s by a medical student who built a prototype stereotactic frame to test the concept. Initial experiments using the prototype frame were soon followed by surgery in humans using the Brown-Roberts-Wells stereotactic frame.

Compartment pressure measurements have poor specificity for compartment syndrome in the traumatized limb

BACKGROUND

Osseofascial compartment syndrome is defined by ischemic necrosis of muscle caused by elevated pressure within fascial compartments. The diagnosis can be made either clinically or through compartment pressure measurements. Compartment pressure above 30 mm Hg was traditionally used as the threshold for diagnosis of compartment syndrome, but was challenged due to a high number of false-positive results. Perfusion pressure (diastolic blood pressure - compartment pressure) <30 mm Hg came to be promoted as a confirmatory diagnostic test.

OBJECTIVE

The objective of this article is to review the specificity of perfusion pressure for compartment syndrome in the acutely traumatized limb.

DISCUSSION

Perfusion pressure has been shown to generate false-positive results in 18-84% of patients with tibial fractures. Two studies showed that not a single patient with measurements qualifying for fasciotomy actually needed the procedure.

CONCLUSION

Both absolute compartment pressure and tissue perfusion pressure generate a high rate of false-positive results in the acutely traumatized limb. An alternative diagnostic test or process is needed to prevent overtreatment. In the meantime, emergency medicine and orthopedic surgery textbooks and guidelines should promote awareness of the limitations of the test.

Local skull trephination before transfer is associated with favorable outcomes in cerebral herniation from epidural hematoma

OBJECTIVES

The patient with epidural hematoma and cerebral herniation has a good prognosis with immediate drainage, but a poor prognosis with delay to decompression. Such patients who present to nonneurosurgical hospitals are commonly transferred without drainage to the nearest neurosurgical center. This practice has never been demonstrated to be the safest approach to treating these patients. A significant minority of emergency physicians (EPs) have advised and taught bedside burr hole drainage or skull trephination before transfer for herniating patients. The objective of this study was to assess the effect of nonneurosurgeon drainage on neurologic outcome in patients with cerebral herniation from epidural hematoma.

METHODS

A structured literature review was performed using EMBASE, the Cochrane Library, and the Emergency Medicine Abstracts database.

RESULTS

No evidence meeting methodologic criteria was found describing outcomes in patients transferred without decompressive procedures. For patients receiving local drainage before transfer, 100% had favorable outcomes.

CONCLUSIONS

Although the total number of patients is small and the population highly selected, the natural history of cerebral herniation from epidural hematoma and the best available evidence suggests that herniating patients have improved outcomes with drainage procedures before transport.

Peak shift as a function of multiple schedules of reinforcement

Pigeons were trained to respond to two stimuli on the wavelength continuum, 550 nm and 570 nm, each correlated with an independent schedule of reinforcement. The multiple schedule component in effect during 550 nm (S1) was always a variable-interval 1-min. During the 570-nm stimulus (S2) the second component of the schedule was either variable-interval 30-sec, 1-min, 2-min, 5-min, or extinction for different groups of birds. Generalization gradients were obtained after this training, with the following results: (1) response rate to S1 during training was related to the reinforcement frequency associated with S2; the distribution of responding during generalization testing was a function of the schedules of reinforcement used during training and the response rates they produced. Decreases in the relative frequency of reinforcement correlated with S2 resulted in increases in the distribution shift of responses away from S2 during generalization testing.

Human Cytomegalovirus US28: a functionally selective chemokine binding receptor

Chemokines are small cytokines that are part of a large family of molecules that bind to G-protein coupled receptors, which, as a family, are the most widely targeted group of molecules in the treatment of disease. Chemokines are critical for recruiting and activating the cells of the immune system during inflammation especially during viral infections. However, a number of viruses including the large herpes virus human cytomegalovirus (HCMV) encode mechanisms to impede the effects of chemokines or has gained the ability to use these molecules to its own advantage. The Human Cytomegalovirus (HCMV)-encoded chemokine receptor US28 is the best characterized of the four unique chemokine receptor-like molecules found in the HCMV genome. US28 has been studied as an important virulence factor for HCMV-mediated vascular disease and, more recently, in models of HCMV-associated malignancy. US28 is a rare multi-chemokine family binding receptor with the ability to bind ligands from two distinct chemokine classes. Ligand binding to US28 activates cell-type and ligand-specific signaling pathways leading to cellular migration, which is an important example of receptor functional selectivity. Additionally, US28 has been demonstrated to constitutively activate phospholipase C (PLC) and NF-kB signaling pathways. Understanding the structure/function relationships between US28, its ligands and intracellular signaling molecules will provide essential clues for effective pharmacological targeting of this multifunctional chemokine receptor.

Individual variation and repeatability in aerobic and anaerobic swimming performance of European sea bass, Dicentrarchus labrax

Studies of inter-individual variation in fish swimming performance may provide insight into how selection has influenced diversity in phenotypic traits. We investigated individual variation and short-term repeatability of individual swimming performance by wild European sea bass in a constant acceleration test (CAT). Fish were challenged with four consecutive CATs with 5 min rest between trials. We measured maximum anaerobic speed at exhaustion (U(CAT)), gait transition speed from steady aerobic to unsteady anaerobic swimming (U(gt)), routine metabolic rate (RMR), post-CAT maximum metabolic rate (MMR), aerobic scope and recovery time from the CATs. Fish achieved significantly higher speeds during the first CAT (U(CAT)=170 cm s(-1)), and had much more inter-individual variation in performance (coefficient of variation, CV=18.43%) than in the subsequent three tests (U(CAT)=134 cm s(-1); CV=7.3%), which were very repeatable among individuals. The individual variation in U(CAT) in the first trial could be accounted for almost exclusively by variation in anaerobic burst-and-coast performance beyond U(gt). The U(gt) itself varied substantially between individuals (CV=11.4%), but was significantly repeatable across all four trials. Individual RMR and MMR varied considerably, but the rank order of post-CAT MMR was highly repeatable. Recovery rate from the four CATs was highly variable and correlated positively with the first U(CAT) (longer recovery for higher speeds) but negatively with RMR and aerobic scope (shorter recovery for higher RMR and aerobic scope). This large variation in individual performance coupled with the strong correlations between some of the studied variables may reflect divergent selection favouring alternative strategies for foraging and avoiding predation.

The clinical differentiation of cerebellar infarction from common vertigo syndromes

This article summarizes the emergency department approach to diagnosing cerebellar infarction in the patient presenting with vertigo. Vertigo is defined and identification of a vertigo syndrome is discussed. The differentiation of common vertigo syndromes such as benign paroxysmal positional vertigo, Meniere's disease, migrainous vertigo, and vestibular neuritis is summarized. Confirmation of a peripheral vertigo syndrome substantially lowers the likelihood of cerebellar infarction, as do indicators of a peripheral disorder such as an abnormal head impulse test. Approximately 10% of patients with cerebellar infarction present with vertigo and no localizing neurologic deficits. The majority of these may have other signs of central vertigo, specifically direction-changing nystagmus and severe ataxia.

The obesity-hypoventilation syndrome and respiratory failure in the acute trauma patient

BACKGROUND

The Emergency Department experience, for many patients, involves procedures and therapies that can compromise ventilation. In the acute trauma patient, these include spinal immobilization, supine positioning, and the administration of sedative and analgesic medications. Patients with the obesity-hypoventilation syndrome have a syndrome distinct from mere obesity, and are more sensitive to these insults.

OBJECTIVE

To describe a case of respiratory failure in a patient with the obesity-hypoventilation syndrome resulting from injuries and therapies that in any other patient would not be expected to cause respiratory failure.

CASE REPORT

A 59-year-old woman suffered a mechanical fall, fractured her T6 vertebral body and right proximal humerus, and, after spinal immobilization and the administration of routine doses of opioid analgesics, suffered significant hypoxemia and respiratory acidosis. Reversal agents were ineffective, but non-invasive mechanical ventilation restored adequate respiration.

CONCLUSION

Although obesity-hypoventilation syndrome occurs in only a minority of morbidly obese patients, it is important because the consequences of respiratory failure can be severe if not recognized and anticipated. Such patients will not be able to adequately increase ventilation in response to mounting hypercapnia. The condition is easily addressed through non-invasive ventilation.