Have outcomes following colectomy in the United States improved over time?

BACKGROUND: There has been tremendous effort to improve quality following colorectal surgery, including the proliferation of minimally invasive techniques, enhanced recovery protocols, and surgical site infection prevention bundles. While these programs have demonstrated improved postoperative outcomes at the institutional level, it is unclear whether similar benefits are present on a national scale. METHODS: American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) Targeted Colectomy data from 2012 to 2020 were used to identify patients undergoing minimally invasive surgery (MIS) or open partial colectomy (CPT 44140, 44204) or low anterior resection (CPT 44145, 44207). Chronological cohorts as well as annual trends in 30-day postoperative outcomes including surgical site infection, venous thromboembolism, and length of stay were assessed using both univariable and multivariable regression analyses. RESULTS: 261,301 patients, 135,876 (52 â€‹%) female, with a median age of 62 (IQR 53-72) were included. Across all years, MIS partial colectomy was the most common procedure (37 â€‹%), followed by MIS low anterior resection (27 â€‹%), open partial colectomy (24 â€‹%), and open low anterior resection (12 â€‹%). MIS increased from 59 â€‹% in 2012-2014 to 66 â€‹% in 2018-2020 (p â€‹< â€‹0.001). During this same period, postoperative length of stay decreased from a median of 5 days (IQR 4-7) in 2012-2014 to 4 days (IQR 3-6) in 2018-2020 (p â€‹< â€‹0.001). Superficial surgical site infections decreased from 5.5 â€‹% in 2012-2014 to 2.9 â€‹% in 2018-2020 (p â€‹< â€‹0.001). Deep surgical site infections similarly decreased from 1.1 â€‹% to 0.4 â€‹% between these periods (p â€‹< â€‹0.001). Pulmonary embolism also decreased from 0.6 â€‹% to 0.5 â€‹% between periods (p â€‹= â€‹0.02). 30-day mortality was unchanged at 1.7 â€‹% between 2012-2014 and 2018-2020 (p â€‹= â€‹0.40). After adjustment for ACS NSQIP estimated probability of morbidity and mortality, undergoing a colectomy in 2020 compared to 2012 was associated with a 14 â€‹% decrease in postoperative length of stay (p â€‹< â€‹0.001). CONCLUSIONS: Between 2012 and 2020, significant improvements in postoperative outcomes after colectomy were observed in the United States. These results support the positive impact that the widespread adoption of quality improvement initiatives is having on colorectal patient care nationally.

Frailty and Suicidality in Older Adults: A Mini-Review and Synthesis.

The prevalence of frailty, which is significantly associated with late-life suicidality, increases with age in older adults. This review addresses the compiled evidence on the relationship between suicidality and frailty within older populations, explores the latest findings, weighs the effectiveness of various intervention strategies, and outlines potential future investigations in this area. Growing evidence suggests that identifying and addressing risk factors, including mood disorders, prior suicide attempts, poor physical health, and social isolation/problems can decrease the risk of late-in-life suicide. Various studies have shown that interventions such as diet improvements, cognitive training, psychosocial programs, and depression medication could reduce the severity of frailty and suicidality, with physical exercise being the most effective intervention. Combined programs with multiple interventions can have an even greater impact on combating depression, lowering risk of falls, and improving gait speed in older adults.

An extensible lattice Boltzmann method for viscoelastic flows: complex and moving boundaries in Oldroyd-B fluids.

 Most biological fluids are viscoelastic, meaning that they have elastic properties in addition to the dissipative properties found in Newtonian fluids. Computational models can help us understand viscoelastic flow, but are often limited in how they deal with complex flow geometries and suspended particles. Here, we present a lattice Boltzmann solver for Oldroyd-B fluids that can handle arbitrarily shaped fixed and moving boundary conditions, which makes it ideally suited for the simulation of confined colloidal suspensions. We validate our method using several standard rheological setups and additionally study a single sedimenting colloid, also finding good agreement with the literature. Our approach can readily be extended to constitutive equations other than Oldroyd-B. This flexibility and the handling of complex boundaries hold promise for the study of microswimmers in viscoelastic fluids.

Hydrodynamic mobility reversal of squirmers near flat and curved surfaces.

Self-propelled particles have been experimentally shown to orbit spherical obstacles and move along surfaces. Here, we theoretically and numerically investigate this behavior for a hydrodynamic squirmer interacting with spherical objects and flat walls using three different methods of approximately solving the Stokes equations: The method of reflections, which is accurate in the far field; lubrication theory, which describes the close-to-contact behavior; and a lattice Boltzmann solver that accurately accounts for near-field flows. The method of reflections predicts three distinct behaviors: orbiting/sliding, scattering, and hovering, with orbiting being favored for lower curvature as in the literature. Surprisingly, it also shows backward orbiting/sliding for sufficiently strong pushers, caused by fluid recirculation in the gap between the squirmer and the obstacle leading to strong forces opposing forward motion. Lubrication theory instead suggests that only hovering is a stable point for the dynamics. We therefore employ lattice Boltzmann to resolve this discrepancy and we qualitatively reproduce the richer far-field predictions. Our results thus provide insight into a possible mechanism of mobility reversal mediated solely through hydrodynamic interactions with a surface.

A lattice Boltzmann model for squirmers.

The squirmer is a simple yet instructive model for microswimmers, which employs an effective slip velocity on the surface of a spherical swimmer to describe its self-propulsion. We solve the hydrodynamic flow problem with the lattice Boltzmann (LB) method, which is well-suited for time-dependent problems involving complex boundary conditions. Incorporating the squirmer into LB is relatively straightforward, but requires an unexpectedly fine grid resolution to capture the physical flow fields and behaviors accurately. We demonstrate this using four basic hydrodynamic tests: two for the far-field flow-accuracy of the hydrodynamic moments and squirmer-squirmer interactions-and two that require the near field to be accurately resolved-a squirmer confined to a tube and one scattering off a spherical obstacle-which LB is capable of doing down to the grid resolution. We find good agreement with (numerical) results obtained using other hydrodynamic solvers in the same geometries and identify a minimum required resolution to achieve this reproduction. We discuss our algorithm in the context of other hydrodynamic solvers and present an outlook on its application to multi-squirmer problems.

Toward Understanding of Self-Electrophoretic Propulsion under Realistic Conditions: From Bulk Reactions to Confinement Effects.

Active matter concerns itself with the study of particles that convert energy into work, typically motion of the particle itself. This field saw a surge of interest over the past decade, after the first micrometer-sized, man-made chemical motors were created. These particles served as a simple model system for studying in a well-controlled manner complex motion and cooperative behavior as known from biology. In addition, they have stimulated new efforts in understanding out-of-equilibrium statistical physics and started a revolution in microtechnology and robotics. Concentrated effort has gone into realizing these ambitions, and yet much remains unknown about the chemical motors themselves. The original designs for self-propelled particles relied on the conversion of the chemical energy of hydrogen peroxide into motion via catalytic decomposition taking place heterogeneously over the surface of the motor. This sets up gradients of chemical fields around the particle, which allow it to autophorese. That is, the interaction between the motor and the heterogeneously distributed solute species can drive fluid flow and the motor itself. There are two basic designs: the first relies on redox reactions taking place between the two sides of a bimetal, for example, a gold-platinum Janus sphere or nanorod. The second uses a catalytic layer of platinum inhomogeneously vapor-deposited onto a nonreactive particle. For convenience's sake, these can be referred to as redox motors and monometallic half-coated motors, respectively. To date, most researchers continue to rely on variations of these simple, yet elegant designs for their experiments. However, there is ongoing debate on the exact way chemical energy is transduced into motion in these motors. Many of the experimental observations on redox motors were successfully modeled via self-electrophoresis, while for half-coated motors there has been a strong focus on self-diffusiophoresis. Currently, there is mounting evidence that self-electrophoresis provides the dominant contribution to the observed speeds of half-coated motors, even if the vast majority of the reaction products are electroneutral. In this Account, we will summarize the most common electrophoretic propulsion model and discuss its strengths and weaknesses in relation to recent experiments. We will comment on the possible need to go beyond surface reactions and consider the entire medium as an "active fluid" that can create and annihilate charged species. This, together with confinement and collective effects, makes it difficult to gain a detailed understanding of these swimmers. The potentially dominant effect of confinement is highlighted on the basis of a recent study of an electro-osmotic pump that drives fluid along a substrate. Detailed analysis of this system allows for identification of the electro-osmotic driving mechanism, which is powered by micromolar salt concentrations. We will discuss how our latest numerical solver developments, based on the lattice Boltzmann method, should enable us to study collective behavior in systems comprised of these and other electrochemical motors in realistic environments. We conclude with an outlook on the future of modeling chemical motors that may facilitate the community's microtechnological ambitions.

Moving charged particles in lattice Boltzmann-based electrokinetics.

The motion of ionic solutes and charged particles under the influence of an electric field and the ensuing hydrodynamic flow of the underlying solvent is ubiquitous in aqueous colloidal suspensions. The physics of such systems is described by a coupled set of differential equations, along with boundary conditions, collectively referred to as the electrokinetic equations. Capuani et al. [J. Chem. Phys. 121, 973 (2004)] introduced a lattice-based method for solving this system of equations, which builds upon the lattice Boltzmann algorithm for the simulation of hydrodynamic flow and exploits computational locality. However, thus far, a description of how to incorporate moving boundary conditions into the Capuani scheme has been lacking. Moving boundary conditions are needed to simulate multiple arbitrarily moving colloids. In this paper, we detail how to introduce such a particle coupling scheme, based on an analogue to the moving boundary method for the pure lattice Boltzmann solver. The key ingredients in our method are mass and charge conservation for the solute species and a partial-volume smoothing of the solute fluxes to minimize discretization artifacts. We demonstrate our algorithm's effectiveness by simulating the electrophoresis of charged spheres in an external field; for a single sphere we compare to the equivalent electro-osmotic (co-moving) problem. Our method's efficiency and ease of implementation should prove beneficial to future simulations of the dynamics in a wide range of complex nanoscopic and colloidal systems that were previously inaccessible to lattice-based continuum algorithms.

Role of geometrical shape in like-charge attraction of DNA.

While the phenomenon of like-charge attraction of DNA is clearly observed experimentally and in simulations, mean-field theories fail to predict it. Kornyshev et al. argued that like-charge attraction is due to DNA's helical geometry and hydration forces. Strong-coupling (SC) theory shows that attraction of like-charged rods is possible through ion correlations alone at large coupling parameters, usually by multivalent counterions. However for SC theory to be applicable, counterion-counterion correlations perpendicular to the DNA strands need to be sufficiently small, which is not a priori the case for DNA even with trivalent counterions. We study a system containing infinitely long DNA strands and trivalent counterions by computer simulations employing varying degrees of coarse-graining. Our results show that there is always attraction between the strands, but its magnitude is indeed highly dependent on the specific shape of the strand. While discreteness of the charge distribution has little influence on the attractive forces, the role of the helical charge distribution is considerable: charged rods maintain a finite distance in equilibrium, while helices collapse to close contact with a phase shift of π, in full agreement with SC predictions. The SC limit is applicable because counterions strongly bind to the charged sites of the helices, so that helix-counterion interactions dominate over counterion-counterion interactions. Thus DNA's helical geometry is not crucial for like-charge DNA attraction, but strongly enhances it, and electrostatic interactions in the strong-coupling limit are sufficient to explain this attraction.