Association of baseline frailty and age with postoperative outcomes in metastatic brain tumor patients.

BACKGROUND: The impact of baseline frailty status versus that of chronological age on surgical outcomes of metastatic brain tumor patients remains largely unknown. The present study aimed to evaluate this relationship for preoperative risk stratification using a large national database. METHODS: The National Surgical Quality Improvement Program database was queried to extract data of metastatic brain tumor patients who underwent surgery between 2015 and 2019 (n=5,943). Univariate and multivariate analyses were performed to assess the effect of age and modified frailty index-5 (mFI-5) on mortality, major complications, unplanned readmission and reoperation, extended length of stay (eLOS), and non-home discharge. RESULTS: Both univariate and multivariate analyses demonstrated that frailty status was significantly predictive of 30-day mortality, major complications, eLOS, and non-home discharge. Although increasing age was also a significant predictor of eLOS and discharge to non-home destination, effect sizes were smaller compared with frailty. CONCLUSIONS: The present study, based on analysis of data from a large national registry, shows that frailty, when compared with age, is a superior predictor of postoperative outcomes in metastatic brain tumor patients. A future prospective study, namely a randomized controlled trial, would be beneficial in helping to corroborate the findings of this retrospective study.

Early turbulence and pulsatile flows enhance diodicity of Tesla's macrofluidic valve.

Microfluidics has enabled a revolution in the manipulation of small volumes of fluids. Controlling flows at larger scales and faster rates, or macrofluidics, has broad applications but involves the unique complexities of inertial flow physics. We show how such effects are exploited in a device proposed by Nikola Tesla that acts as a diode or valve whose asymmetric internal geometry leads to direction-dependent fluidic resistance. Systematic tests for steady forcing conditions reveal that diodicity turns on abruptly at Reynolds number [Formula: see text] and is accompanied by nonlinear pressure-flux scaling and flow instabilities, suggesting a laminar-to-turbulent transition that is triggered at unusually low [Formula: see text]. To assess performance for unsteady forcing, we devise a circuit that functions as an AC-to-DC converter, rectifier, or pump in which diodes transform imposed oscillations into directed flow. Our results confirm Tesla's conjecture that diodic performance is boosted for pulsatile flows. The connections between diodicity, early turbulence and pulsatility uncovered here can inform applications in fluidic mixing and pumping.

Flow Rectification in Loopy Network Models of Bird Lungs.

We demonstrate flow rectification, valveless pumping, or alternating to direct current (AC-to-DC) conversion in macroscale fluidic networks with loops. Inspired by the unique anatomy of bird lungs and the phenomenon of directed airflow throughout the respiration cycle, we hypothesize, test, and validate that multiloop networks exhibit persistent circulation or DC flows when subject to oscillatory or AC forcing at high Reynolds numbers. Experiments reveal that disproportionately stronger circulation is generated for higher frequencies and amplitudes of the imposed oscillations, and this nonlinear response is corroborated by numerical simulations. Visualizations show that flow separation and vortex shedding at network junctions serve the valving function of directing current with appropriate timing in the oscillation cycle. These findings suggest strategies for controlling inertial flows through network topology and junction connectivity.