Brain death and postmortem organ donation: Report of a questionnaire from the CENTER-TBI study

Background: We aimed to investigate the extent of the agreement on practices around brain death and postmortem organ donation. Methods: Investigators from 67 Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study centers completed several questionnaires (response rate: 99%). Results: Regarding practices around brain death, we found agreement on the clinical evaluation (prerequisites and neurological assessment) for brain death determination (BDD) in 100% of the centers. However, ancillary tests were required for BDD in 64% of the centers. BDD for nondonor patients was deemed mandatory in 18% of the centers before withdrawing life-sustaining measures (LSM). Also, practices around postmortem organ donation varied. Organ donation after circulatory arrest was forbidden in 45% of the centers. When withdrawal of LSM was contemplated, in 67% of centers the patients with a ventricular drain in situ had this removed, either sometimes or all of the time. Conclusions: This study showed both agreement and some regional differences regarding practices around brain death and postmortem organ donation. We hope our results help quantify and understand potential differences, and provide impetus for current dialogs toward further harmonization of practices around brain death and postmortem organ donation

A void-based description of compaction and segregation in flowing granular materials

Guided by the kinematical treatment of vacancies in theories for solid-state diffusion, we develop a theory for compaction and segregation in flowing granular materials. This theory leads to a partial differential equation for the macroscopic motion of the material coupled to a system of partial differential equations for the volume fractions of the individual particle types. When segregation is ignored, so that the focus is compaction, the latter system is replaced by a scalar partial differential equation that closely resembles equations arising in theories of traffic flow. To illustrate the manner in which the theory describes compaction and segregation, we present three explicit solutions. In particular, for an arbitrary loosely packed mixture of small and large particles in a fixed container under the influence of gravity, we show that a layer of large particles forms at the free surface and grows with time, while a closely packed mixture of large and small particles forms and grows from the base of the container; the final solution, attained in finite time, consists of a layer of closely packed large particles above a closely packed mixed state. At the mundane level of everyday experience, this solution at least qualitatively explains why in a container of mixed nuts, Brazil nuts are generally found at the top.published or submitted for publicationis peer reviewe