Minimally invasive approaches increase postoperative complications in obese patients undergoing pancreaticoduodenectomy during the initial development period: a propensity score matching study.

BACKGROUND: Obesity increases surgical risks in various abdominal surgeries and its impact on open pancreaticoduodenectomy (OPD) and minimally invasive pancreaticoduodenectomy (MIPD) remains unknown. This study aimed to compare the surgical outcomes of OPD and MIPD in obese and non-obese patients by propensity score matching (PSM) analysis during the implementation of MIPD. METHODS: We retrospectively reviewed all pancreaticoduodenectomies from December 2014 to May 2021. Obesity was defined as body mass index > 25 kg/m2 according to World Health Organization International Obesity Task Force. PSM was used to minimize the selection bias of MIPD. RESULTS: Among 462 pancreaticoduodenectomies (339 OPDs, 123 MIPDs), there were 313 patients in the non-obese group (MIPD: 78, OPD: 235) and 149 patients in the obese group (MIPD: 45, OPD: 104). After PSM, there were 70 MIPD/106 OPD patients in the non-obese group and 38 MIPD/54 OPD patients in the obese group. The obese MIPD patients had more fluid collection (36.8% vs 9.8%, p = 0.002), a higher Clavien-Dindo (CD) grade (p = 0.007), more major complications (42.1% vs 14.8%, p = 0.004), and longer operative times (306 min vs 264 min, p < 0.001) than the obese OPD patients. The non-obese MIPD patients had lower CD grades (p = 0.02), longer operative times (294 vs 264 min, p < 0.001), and less blood loss (100 mL vs 200 mL) than the non-obese OPD patients. MIPD was a strong predictor of major complication (CD ≥ 3) in obese patients (odds ratio 3.11, 95% CI: 1.40-6.95, p = 0.005). CONCLUSIONS: Minimally invasive approaches deteriorate the CD grade, fluid collection, and major complications in obese patients undergoing pancreaticoduodenectomy during the initial development period. Non-obese patients may benefit from MIPD over OPD in terms of less blood loss and lower CD grades. The impact of BMI on MIPD should be considered when assessing the surgical risks.

Fabrication of multicomponent polymer nanostructures containing PMMA shells and encapsulated PS nanospheres in the nanopores of anodic aluminum oxide templates.

Multi-component polymer nanomaterials have attracted great attention because of their applications in areas such as biomedicine, tissue engineering, and organic solar cells. The precise control over the morphologies of multi-component polymer nanomaterials, however, is still a great challenge. In this work, the fabrication of poly(methyl methacrylate)(PMMA)/poly-styrene (PS) nanostructures that contain PMMA shells and encapsulated PS nanospheres is studied. The nanostructures are prepared using a triple solution wetting method with anodic aluminum oxide (AAO) templates. The nanopores of the templates are wetted sequentially by PS solutions in dimethylformamide (DMF), PMMA solutions in acetic acid, and water. The compositions and morphologies of the nanostructures are controlled by the interactions between the polymers, solvents, and AAO walls. This work not only presents a feasible method to prepare multi-component polymer nanomaterials, but also leads to a better understanding of polymer-solvent interactions in confined geometries.

Curved polymer nanodiscs by wetting nanopores of anodic aluminum oxide templates with polymer nanospheres.

Although nanostructures with diverse morphologies have been fabricated, it is still a great challenge to prepare anisotropic two-dimensional (2-D) nanostructures, especially non-planar disc-like nanostructures. In this work, we develop a simple method to prepare curved polymer nanodiscs with regular sizes by wetting polymer nanospheres in the nanopores of anodic aluminum oxide (AAO) templates. Polystyrene (PS) nanospheres are first fabricated by using a non-solvent-assisted template wetting method. By annealing the PS nanospheres in the nanopores of AAO templates, curved PS nanodiscs can be produced. The length and morphology of the curved PS nanodiscs can be controlled by the wetting conditions such as the annealing temperatures and times. For some stacked nanospheres, the annealing process can result in the formation of helix-like nanostructures. To demonstrate the universality of this work, this approach is also applied to poly(methyl methacrylate) (PMMA), another common polymer, and similar results are obtained.

Porous polymer nanostructures fabricated by the surface-induced phase separation of polymer solutions in anodic aluminum oxide templates.

We study the formation of porous polymer nanostructures fabricated by the surface-induced phase separation of polymer solutions in anodic aluminum oxide (AAO) templates. Poly(methyl methacrylate) (PMMA) and tetrahydrofuran (THF) are used to investigate the evolution process of the surface-induced phase separation. With the longer immersion time of the AAO template in the polymer solution, the size of the solvent-rich droplet is increased by the coarsening process, resulting in the formation of porous polymer nanostructures. The coarsening mechanism is further evaluated by changing the experimental parameters including the immersion time, the polymer concentration, the polymer molecular weight, and the solvent quality. Under conditions in which polymer solutions have higher viscosities, the coarsening process is slowed down and the formation of the porous nanostructures is prohibited. The prevention of the porous nanostructures can also be realized by adding water to the PMMA/THF solution before the immersion process.

Effect of nonsolvent on the formation of polymer nanomaterials in the nanopores of anodic aluminum oxide templates.

We study the effect of nonsolvent on the formation of polymer nanomaterials in the nanopores of porous templates. Water (nonsolvent) is added into a poly (methyl methacrylate) (PMMA) solution in dimethylformamide (DMF) confined in the nanopores of an anodic aluminum oxide (AAO) template. Water forms a wetting layer on the pore wall and causes the PMMA solution to be isolated in the center of the nanopore, resulting in the formation of PMMA nanospheres or nanorods after the solvent is evaporated. The formation of the polymer nanomaterials induced by nonsolvent is found to be driven by the Rayleigh-instability-type transformation. Without adding the nonsolvent, PMMA chains precipitate on the walls of the nanopores after the solvent is evaporated, and PMMA nanotubes are obtained.