Observer-Based Time-Variant Spacing Policy for a Platoon of Non-Holonomic Mobile Robots.

This paper presents a navigation strategy for a platoon of n non-holonomic mobile robots with a time-varying spacing policy between each pair of successive robots at the platoon, such that a safe trailing distance is maintained at any speed, avoiding the robots getting too close to each other. It is intended that all the vehicles in the formation follow the trajectory described by the leader robot, which is generated by bounded input velocities. To establish a chain formation among the vehicles, it is required that, for each pair of successive vehicles, the (i+1)-th one follows the trajectory executed by the former i-th one, with a delay of τ(t) units of time. An observer is proposed to estimate the trajectory, velocities, and positions of the i-th vehicle, delayed τ(t) units of time, consequently generating the desired path for the (i+1)-th vehicle, avoiding numerical approximations of the velocities, rendering robustness against noise and corrupted or missing data as well as to external disturbances. Besides the time-varying gap, a constant-time gap is used to get a secure trailing distance between each two successive robots. The presented platoon formation strategy is analyzed and proven by using Lyapunov theory, concluding asymptotic convergence for the posture tracking between the (i+1)-th robot and the virtual reference provided by the observer that corresponds to the i-th robot. The strategy is evaluated by numerical simulations and real-time experiments.

Increased Mutation Rate Is Linked to Genome Reduction in Prokaryotes.

The evolutionary processes that drive variation in genome size across the tree of life remain unresolved. Effective population size (Ne) is thought to play an important role in shaping genome size [1-3]-a key example being the reduced genomes of insect endosymbionts, which undergo population bottlenecks during transmission [4]. However, the existence of reduced genomes in marine and terrestrial prokaryote species with large Ne indicate that genome reduction is influenced by multiple processes [3]. One candidate process is enhanced mutation rate, which can increase adaptive capacity but can also promote gene loss. To investigate evolutionary forces associated with prokaryotic genome reduction, we performed molecular evolutionary and phylogenomic analyses of nine lineages from five bacterial and archaeal phyla. We found that gene-loss rate strongly correlated with synonymous substitution rate (a proxy for mutation rate) in seven of the nine lineages. However, gene-loss rate showed weak or no correlation with the ratio of nonsynonymous/synonymous substitution rate (dN/dS). These results indicate that genome reduction is largely associated with increased mutation rate, while the association between gene loss and changes in Ne is less well defined. Lineages with relatively high dS and dN, as well as smaller genomes, lacked multiple DNA repair genes, providing a proximate cause for increased mutation rates. Our findings suggest that similar mechanisms drive genome reduction in both intracellular and free-living prokaryotes, with implications for developing a comprehensive theory of prokaryote genome size evolution.

Ocean currents promote rare species diversity in protists.

Oceans host communities of plankton composed of relatively few abundant species and many rare species. The number of rare protist species in these communities, as estimated in metagenomic studies, decays as a steep power law of their abundance. The ecological factors at the origin of this pattern remain elusive. We propose that chaotic advection by oceanic currents affects biodiversity patterns of rare species. To test this hypothesis, we introduce a spatially explicit coalescence model that reconstructs the species diversity of a sample of water. Our model predicts, in the presence of chaotic advection, a steeper power law decay of the species abundance distribution and a steeper increase of the number of observed species with sample size. A comparison of metagenomic studies of planktonic protist communities in oceans and in lakes quantitatively confirms our prediction. Our results support that oceanic currents positively affect the diversity of rare aquatic microbes.

Modeling the COVID-19 epidemic in Okinawa

We analyze current data on the COVID-19 spreading in Okinawa, Japan. We find that the initial spread is characterized by a doubling time of about 5 days. We implement a model to forecast the future spread under different scenarios. The model predicts that, if significant containment measures are not taken, a large fraction of the population will be infected with COVID-19, with the peak of the epidemic expected at the end of May and intensive care units having largely exceeded capacity. We analyzed scenarios implementing strong containment measures, similar to those imposed in Europe. The model predicts that an immediate implementation of strong containment measures (on the 19th of April) will significantly reduce the death count. We assess the negative consequences of these measures being implemented with a delay, or not being sufficiently stringent.

Bet-hedging strategies in expanding populations.

In ecology, species can mitigate their extinction risks in uncertain environments by diversifying individual phenotypes. This observation is quantified by the theory of bet-hedging, which provides a reason for the degree of phenotypic diversity observed even in clonal populations. Bet-hedging in well-mixed populations is rather well understood. However, many species underwent range expansions during their evolutionary history, and the importance of phenotypic diversity in such scenarios still needs to be understood. In this paper, we develop a theory of bet-hedging for populations colonizing new, unknown environments that fluctuate either in space or time. In this case, we find that bet-hedging is a more favorable strategy than in well-mixed populations. For slow rates of variation, temporal and spatial fluctuations lead to different outcomes. In spatially fluctuating environments, bet-hedging is favored compared to temporally fluctuating environments. In the limit of frequent environmental variation, no opportunity for bet-hedging exists, regardless of the nature of the environmental fluctuations. For the same model, bet-hedging is never an advantageous strategy in the well-mixed case, supporting the view that range expansions strongly promote diversification. These conclusions are robust against stochasticity induced by finite population sizes. Our findings shed light on the importance of phenotypic heterogeneity in range expansions, paving the way to novel approaches to understand how biodiversity emerges and is maintained.

Povidone iodine in wound healing: A review of current concepts and practices.

BACKGROUND: Of the many antimicrobial agents available, iodophore-based formulations such as povidone iodine have remained popular after decades of use for antisepsis and wound healing applications due to their favorable efficacy and tolerability. Povidone iodine's broad spectrum of activity, ability to penetrate biofilms, lack of associated resistance, anti-inflammatory properties, low cytotoxicity and good tolerability have been cited as important factors, and no negative effect on wound healing has been observed in clinical practice. Over the past few decades, numerous reports on the use of povidone iodine have been published, however, many of these studies are of differing design, endpoints, and quality. More recent data clearly supports its use in wound healing. METHODS: Based on data collected through PubMed using specified search criteria based on above topics and clinical experience of the authors, this article will review preclinical and clinical safety and efficacy data on the use of povidone iodine in wound healing and its implications for the control of infection and inflammation, together with the authors' advice for the successful treatment of acute and chronic wounds. RESULTS AND CONCLUSION: Povidone iodine has many characteristics that position it extraordinarily well for wound healing, including its broad antimicrobial spectrum, lack of resistance, efficacy against biofilms, good tolerability and its effect on excessive inflammation. Due to its rapid, potent, broad-spectrum antimicrobial properties, and favorable risk/benefit profile, povidone iodine is expected to remain a highly effective treatment for acute and chronic wounds in the foreseeable future.

Eco-evolutionary Model of Rapid Phenotypic Diversification in Species-Rich Communities.

Evolutionary and ecosystem dynamics are often treated as different processes -operating at separate timescales- even if evidence reveals that rapid evolutionary changes can feed back into ecological interactions. A recent long-term field experiment has explicitly shown that communities of competing plant species can experience very fast phenotypic diversification, and that this gives rise to enhanced complementarity in resource exploitation and to enlarged ecosystem-level productivity. Here, we build on progress made in recent years in the integration of eco-evolutionary dynamics, and present a computational approach aimed at describing these empirical findings in detail. In particular we model a community of organisms of different but similar species evolving in time through mechanisms of birth, competition, sexual reproduction, descent with modification, and death. Based on simple rules, this model provides a rationalization for the emergence of rapid phenotypic diversification in species-rich communities. Furthermore, it also leads to non-trivial predictions about long-term phenotypic change and ecological interactions. Our results illustrate that the presence of highly specialized, non-competing species leads to very stable communities and reveals that phenotypically equivalent species occupying the same niche may emerge and coexist for very long times. Thus, the framework presented here provides a simple approach -complementing existing theories, but specifically devised to account for the specificities of the recent empirical findings for plant communities- to explain the collective emergence of diversification at a community level, and paves the way to further scrutinize the intimate entanglement of ecological and evolutionary processes, especially in species-rich communities.

Eluding catastrophic shifts.

Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences.

Quenched disorder forbids discontinuous transitions in nonequilibrium low-dimensional systems.

Quenched disorder affects significantly the behavior of phase transitions. The Imry-Ma-Aizenman-Wehr-Berker argument prohibits first-order or discontinuous transitions and their concomitant phase coexistence in low-dimensional equilibrium systems in the presence of random fields. Instead, discontinuous transitions become rounded or even continuous once disorder is introduced. Here we show that phase coexistence and first-order phase transitions are also precluded in nonequilibrium low-dimensional systems with quenched disorder: discontinuous transitions in two-dimensional systems with absorbing states become continuous in the presence of quenched disorder. We also study the universal features of this disorder-induced criticality and find them to be compatible with the universality class of the directed percolation with quenched disorder. Thus, we conclude that first-order transitions do not exist in low-dimensional disordered systems, not even in genuinely nonequilibrium systems with absorbing states.

El desarrollo nuclear pacífico y las “3 S” (‘safety’, ‘security’ y ‘safeguards’) / Peaceful nuclear development and the three "s" ('safety', 'security'and 'safeguards')

RESUMEN Se debería consensuar una solución global para un conmensurado control internacional tanto de los materiales nucleares y radiactivos que permita garantizar que el desarrollo pacífico nuclear no ocasione daños a la humanidad. El concepto de régimen internacional de seguridad está obnubilado por la confusa semántica de sus partes: los conceptos ingleses ‘safeguards’, ‘safety’ y ‘security’, y los de materiales nucleares y radiactivos. El objetivo es garantizar, mediantesafeguards apropiadas la no diversión de materiales nucleares hacia actividades no pacíficas.; prevenir mediante security apropiada, la posesión no autorizada o uso ilegal o malévolo de materiales nucleares y radiactivos; y cerciorar, mediante safety apropiada, que el uso de materiales nucleares y radiactivos no causará daño a personas y al ambiente. Security se debe entender como una parte integral de safeguards y de safety, porque los materiales que son secure no son necesariamente safeguarded or safe y los materiales no pueden ser safeguarded or safe al menos que sean secure. Security es una condición necesaria pero no suficiente para safeguards y safety; es una condición importante, pero subsidiaria de safeguards y safety. Se concluye sugiriendo un Tratado Internacional para el Control (‘safeguards’, ‘safety’ y ‘security’) del Desarrollo Pacífico de la Energía Nuclear y sus Subproductos que regule claramente las obligaciones y penalidades de las Partes, el que basándose en los acuerdos existentes debería ser claro, lógico, racional, fundado, metódico, sistemático, universal, equitativo, ecuánime, imparcial, justo y no discriminatorio.

ABSTRACT We should agree on a comprehensive solution for a commensurate international control of both nuclear and radioactive material designed to ensure that peaceful nuclear development will not cause harm to the human race. The concept international security system is clouded by the confusing semantics of its parts: the English concepts ‘safeguards’, ‘safety’ and ‘security’, on one hand, and nuclear and radioactive materials on the other hand. The objectives should be: to ensure, through appropriate safeguards, that nuclear materials are not diverted to non-peaceful purposes; to prevent, through appropriate security, the unauthorized possession or use, illegal or malicious, of nuclear and radioactive materials; and, to ensure, through appropriate safety, that the use of nuclear and radioactive material will not cause harm to people and the environment. Security must be understood as an integral part of safeguards and safety, because materials that are secure are not necessarily safeguarded or safe, and materials may not be safeguarded or safe unless they are secure. Security is a necessary but not sufficient condition for safeguards and safety; security is an important but subsidiary condition of safeguards and safety; security is necessary but not sufficient to ensure nuclear control via safeguards and safety. In conclusion an International Treaty for the Control (‘safeguards’, ‘safety’ and ‘security’) of the Peaceful Development of Nuclear Energy and its Byproducts is proposed. It should clearly regulate the obligations and (non-compliance) penalties of the Parties, and, based on existing agreements, should be clear, logical, rational, fundamental, methodical, systematic, universal, equitable, impartial, fair and non discriminatory.

Effect of patient transfer on outcomes after open repair of ruptured abdominal aortic aneurysms.

Patients with ruptured abdominal aortic aneurysms (RAAAs) benefit from treatment in high-volume facilities. This study explored the effect of patient transfer on outcomes and the relationship between hemodynamic status and mortality. We performed a retrospective review of 83 consecutive patients who had open repair for RAAA at a single tertiary facility. The patients were divided into two groups based on arrival in the local emergency department, "local" (n = 44) versus "transfer" (n = 39) from an outside institution, and into three categories of hemodynamic status: (a) no obtainable blood pressure, "pulseless"; (b) requiring vasopressor support, "pressors"; and (c) no vasopressor support, "no pressors." Thirty-day mortality was 21.4%. There was no difference in mortality between the local (18.2%) and transfer (25.6%) patients (p = .41). There were no deaths during transfer. There was no difference in the hemodynamic status of the transfer versus the local group (p = .34). The mortality by category was pulseless, 100% (3 of 3); pressors, 71.4% (10 of 14); and no pressors, 7.6% (5 of 66) (p < .0001). Actuarial survival was 66%, 64%, and 62% at 1, 3, and 5 years, respectively. Patient transfer does not adversely affect mortality after RAAA repair. Patients without a palpable pulse and those requiring hemodynamic support have a significantly higher mortality.

Endovascular repair of ruptured abdominal aortic aneurysms: systematic literature review.

Endovascular repair is increasingly used for ruptured abdominal aortic aneurysms (RAAAs). This study estimated the mortality rate for this approach. A review of 307 publications in English was performed. Thirty-four publications representing 1,200 patients with RAAA were deemed appropriate for analysis by weighted least squares regression. Of the 1,200 patients, 531 (44.3%) underwent endovascular aneurysm repair (EVAR). The average age was 74 years, and 13% were female. Aortouni-iliac grafts were used in 49.4% of patients, and 50.6% received bifurcated grafts. The technical success rate was 94.9%, with a mortality rate of 30.2%. The ratio of endovascular cases to the total number of cases strongly predicted the mortality rate (weighted coefficient -0.378, p< .0003). The mortality rate following EVAR of RAAA is 30%. A 3.8% reduction in mortality was found for each 10% increase in the percentage of ruptures repaired endovascularly at each center. These results are suggestive of a learning curve.

Ascending and transverse aortic arch repair: the impact of glomerular filtration rate on mortality.

BACKGROUND: Recent studies have described the importance of renal glomerular filtration rate (GFR) as a determinant of perioperative mortality in patients with aneurysms that involve the thoracoabdominal and abdominal aorta. We studied the impact of GFR on mortality following repair of ascending and arch aneurysms. METHODS: Between February 1991 and August 2006, we performed 994 repairs of the ascending and transverse aortic arch. Nine hundred twenty patients had evaluable data for this study. Sixty-two percent were men (566/920); mean age was 65 years (range 17-89). We estimated the GFR using the Cockcroft-Gault equation. Mean preoperative serum creatinine was 1.2 +/- 0.9 mg/dl, mean GFR was 77 +/- 37 mL/min. Renal function data were arrayed in quartiles for univariate analysis and kept continuous for multivariable analyses. Multivariable analyses assessed demographics, extent of disease, acuity of presentation, and renal function measured by both creatinine and GFR. RESULTS: Overall 30-day mortality was 10.8% (99/920). In univariate analyses, GFR (P < 0.0001), serum creatinine (P < 0.0003), coronary artery disease (P > 0.03), acute dissection (P < 0.03), emergency presentation (P < 0.002), age (P < 0.009), pump time (P < 0.0001), cross-clamp time, (P < 0.03) and circulatory arrest time (P < 0.003) were associated with increased mortality. By multivariable analyses, only GFR (P < 0.0001), pump time (P < 0.0001), emergency status (P < 0.002) were significant independent risk factors for mortality. CONCLUSIONS: Preoperative renal function as defined by GFR was the most significant predictor of mortality during repairs of the ascending and transverse aortic arch. The use of GFR provides better preoperative risk stratification during these repairs than creatinine alone.

Intraoperative skeletal muscle ischemia contributes to risk of renal dysfunction following thoracoabdominal aortic repair.

OBJECTIVE: Renal dysfunction is among the most commonly occurring morbidities following descending thoracic and thoracoabdominal aortic repair. We hypothesized that myoglobin nephrotoxicity might arise from leg ischemia caused by femoral artery cannulation, which is required for distal aortic perfusion. Lacking complete historical laboratory data on myoglobinemia, we studied somatosensory evoked potential (SSEP) changes in the leg (a functional marker of leg ischemia), as a surrogate predictor of acute postoperative renal failure. METHODS: Intraoperative leg SSEP function and preoperative glomerular filtration rate (GFR - an essential covariate) were available for 299 patients. Change in SSEP was defined as 10% increase in latency or 50% decrease in amplitude. Postoperative renal dysfunction was 1mg/dl/day increase in creatinine for 2 days, clinical diagnosis of ARF or need for dialysis postoperatively. RESULTS: Change in SSEP in the cannulated leg occurred in 108/299 (36%) of cases intraoperatively. All recovered normal SSEP function at decannulation. Patients with SSEP changes had 41/108 (38%) postoperative renal failure compared to 49/191 (26%) without (odds ratio 1.8, p<0.03). Modeled with GFR, aneurysm extent, and chronic obstructive pulmonary disease (COPD), SSEP changes had an adjusted odds ratio of 1.9, p<0.03. Pre-op GFR was also a highly significant predictor of postoperative renal failure (OR 0.98/ml; p<0.0001). CONCLUSION: This is the first study to show a relationship between intraoperative leg ischemia and postoperative renal failure. It provides epidemiological evidence that the ischemic leg may be an important contributor to rhabdomyolysis-like renal morbidity after thoracoabdominal aortic surgery.

Risk factors for impaired wound healing in sirolimus-treated renal transplant recipients.

AIM: As sirolimus has been implicated in impaired wound healing, the aim of this study was to evaluate risk factors for wound complications after renal transplantation in patients treated with this drug de novo. METHODS: This single center retrospective review of wound complications included 194 renal transplant recipients, all of whom received sirolimus immunosuppression in combination with reduced doses of cyclosporine (CsA) and corticosteroids de novo. A wound complication was defined as an infection, incisional hernia, or lymphocele. RESULTS: The overall incidence of wound complications within the first year post-transplantation was 36% (n = 70) including infection in 12% (n = 23), lymphocele formation in 18% (n = 34), and incisional hernia in 18% (n = 34) of patients. Seventeen patients suffered more than one wound complication. A multivariate analysis showed that independent risk factors for the development of wound complications were recipients over the age of 40 yr (odds ratio 2.536, p = 0.011), subjects with body mass index (BMI) >26 (odds ratio 2.498, p = 0.027) and especially BMI >30 (odds ratio 3.738, p = 0.007), the use of thymoglobulin for induction immunosuppression (odds ratio 3.627, p = 0.002), and a cumulative dose of sirolimus of at least 35 mg by post-transplant day 4 (odds ratio 2.694, p = 0.023). African-American (odds ratio 0.139, p < 0.001) or Hispanic recipients (odds ratio 0.337, p = 0.014) were less likely to experience a wound problem than Caucasian recipients. CONCLUSION: A number of potentially modifiable risk factors independently increase the incidence of wound complications among renal transplant recipients receiving sirolimus-based immunosuppression de novo.

Proximal reoperations after repaired acute type A aortic dissection.

BACKGROUND: Concerned with the associated risks of proximal reoperation, some have proposed an aggressive approach of aortic root replacement during emergent repair of acute type A aortic dissection. Because few data exist regarding late reoperations, we report outcomes of proximal reoperation after repaired type A aortic dissection. METHODS: Between January 1991 and March 2006, 63 patients underwent reoperation after previous repair for acute type A aortic dissection. Procedures performed at reoperation included ascending (94%, 59 of 63), total arch (62%, 39 of 63), elephant trunk (56%, 35 of 63), aortic valve replacement (38%, 24 of 63), aortic root (27%, 17 of 63), and coronary artery bypass graft (8%, 5 of 63). Preoperative, operative, and postoperative variables were analyzed retrospectively with regard to early and late mortality. RESULTS: Thirty-day mortality was 11.1% (7 of 63). No strokes occurred. Incidence of renal failure, respiratory failure, and bleeding was 6% (4 of 63), 23% (15 of 63), and 6% (4 of 63), respectively. Mean time from initial repair to reoperation was 69 months (range, 1 to 258). Procedure performed (root versus ascending/resuspension) at initial repair did not affect the time to reoperation (p > 0.05). Median follow-up was 40 months; and 1-, 5-, and 10-year survival was 82%, 74%, and 62%, respectively. Multivariate predictors of late mortality were prior coronary artery bypass graft surgery (odds ratio = 6.5, p < 0.003), bypass time (odds ratio = 3.6, p < 0.02), and renal dysfunction (odds ratio = 3.7, p < 0.05). CONCLUSIONS: Proximal reoperations for repaired acute type A aortic dissection can be performed with acceptable early and late mortality. The concern for proximal reoperation should not dictate the initial procedure choice during acute type A aortic dissection. Continued clinical and radiographic surveillance of repaired type A aortic dissection is warranted.

Successful descending thoracic aortic aneurysm repair during a twin pregnancy: case report and literature review.

A 28-year-old woman in the first trimester of a twin pregnancy presented with a symptomatic descending thoracic aortic aneurysm. We report our experience in managing a descending thoracic aortic aneurysm in this patient.

Optimization of aortic arch replacement: two-stage approach.

BACKGROUND: Aneurysms of the aortic arch seldom occur alone. They usually involve the ascending aorta. Occasionally, the aneurysm also involves the descending thoracic or thoracoabdominal aorta. We advocate a staged approach for repair of these extensive aortic aneurysms, with the ascending and arch generally being repaired in the first stage and the descending thoracic or thoracoabdominal aorta being repaired in the second stage. METHODS: Between February 1991 and December 2005, we repaired aneurysms of the ascending, arch, descending thoracic, and thoracoabdominal aorta in 2120 patients. Of these, 254 (12.0%) involved the ascending, arch, and descending aorta (extensive aortic aneurysm). A first-stage repair was done in 254 patients, and 115 returned for a second-stage repair for a total of 369 procedures performed. RESULTS: First-stage 30-day mortality was 6.3% (16/254), with the glomerular filtration rate (GFR) exceeding 70 mL/min in 2.9% of patients and less than 70 mL/min in 10.5% (p < 0.03). Second-stage 30-day mortality was 9.6% (11/115), with GFR exceeding 70 mL/min in 4.9% and less than 70 mL/min in 9.8% (not significant). The incidence of postoperative stroke for the first stage was 2.0% (5/254), and the rate of neurologic deficit (paraplegia and paraparesis) was .9% (1/115) in the second stage. The mortality for the interval of 31 days to 6 weeks after the first-stage operation was 2.9% (7/238). CONCLUSIONS: Aneurysms involving the transverse arch with extensive involvement of the ascending and descending thoracic or thoracoabdominal aorta can be effectively repaired using the two-stage technique with acceptable morbidity and mortality. GFR correlates to surgical outcome in the first-stage repair. After the first stage, prompt treatment of the remaining segment of aorta is crucial to success.

Management of distal femoral and popliteal arterial injuries: an update.

BACKGROUND: The management of combined arterial and musculoskeletal injuries to the lower extremity remains controversial, particularly with regard to the initial order of intervention and the use of intravascular shunting. In this study, we review the contemporary management and outcome of patients treated for acute traumatic distal femoropopliteal arterial injuries. METHODS: From January 2001 to January 2006, we repaired 57 acute traumatic lower-extremity arterial injuries in a level 1 trauma center. Our approach was to perform surgical revascularization without intraluminal shunting as soon as the arterial injury was recognized. There were 44 men (77%). Mean age was 31 years (range, 5-68). The mechanism of injury was blunt in 42 of 57 (74%) patients. Vascular reconstruction was achieved by using an autogenous saphenous vein graft in 52 of 57 (91%), a vein patch in 3 of 57 (5%), or primarily in 2 of 57 (4%) patients. RESULTS: The limb-salvage rate was 92% (53/57). Thirty-six patients (63%) had associated orthopedic fixation: 12 of 36 (33%) before and 24 of 36 (67%) after revascularization. Twenty-one of 57 patients (37%) had vascular repair only without orthopedic fixation. Thirty-four patients (60%) required fasciotomy. Four patients had subsequent above-knee amputation: 3 because of wound complications despite successful revascularization and 1 because of failed revascularization. There were no complications related to the arterial repairs that were performed before orthopedic fixation. CONCLUSION: Our study shows that arterial reconstruction for acute traumatic lower-limb injuries results in a good limb-salvage rate. We advocate prompt vascular repair before orthopedic intervention for combined vascular and skeletal injuries of the lower extremity, without using intravascular shunting.

Glomerular filtration rate is superior to serum creatinine for prediction of mortality after thoracoabdominal aortic surgery.

BACKGROUND: Clinically evident renal disease (dialysis, history of renal insufficiency, or serum creatinine >2.0 mg/dL) is a known risk factor for mortality after thoracoabdominal aortic aneurysm repair. We extended this concept to the questions of whether subclinical renal disease is also a risk factor and how best to identify subclinical disease. We hypothesized that the glomerular filtration rate (GFR) would be a more sensitive determinant of renal function than serum creatinine alone. METHODS: Between 1991 and 2004, we repaired 1106 thoracoabdominal aortic aneurysms and descending thoracic aortic aneurysms. The median age was 67 years. There were 400 (36%) women and 706 (64%) men. We estimated GFR by using the Cockcroft-Gault equation. We divided baseline serum creatinine and baseline GFR into quartiles and estimated the association of the quartiles with 30-day postoperative mortality by chi2 testing. We further subdivided the population into patients with and without clinically evident renal disease and repeated the analysis in the patients without clinically apparent disease (n = 869). RESULTS: Clinically apparent renal disease was highly associated with 30-day mortality (odds ratio, 3.2; P < .0001). In all patients, serum creatinine quartile and GFR quartile were also both highly significantly associated with 30-day mortality (P < .0001). In patients without clinically apparent renal disease, both creatinine and GFR predicted additional mortality, but GFR was a much stronger predictor (P < .02 for creatinine vs < .0001 for GFR). In these patients, mortality ranged from 5% in the best GFR quartile to 27% in the worst. Taken as continuous variables in logistic regression equations, serum creatinine had no discrimination in patients without clinical disease (P = .73), whereas GFR remained strong (P < .0001). CONCLUSIONS: Preoperative renal function is an important determinant of early mortality even in patients without clinically evident disease. Estimated GFR is a much more powerful determinant of mortality risk than serum creatinine alone.