Open abdomen in liver transplantation.

INTRODUCTION: Damage control laparotomy with vacuum assisted closure (VAC) is used for selective cases in trauma. In liver transplantation, VAC has also been applied for management of intra-operative hemorrhage. The primary objective was to evaluate peri-operative blood loss and blood product utilization in VAC compared to primary abdominal closure (PAC) at the index transplant operation. METHODS: Retrospective review of all adults undergoing deceased donor liver transplantation (2007-2011) at a single center tertiary care institution. RESULTS: 201 deceased donor liver transplantations were performed, with 167 PAC and 34 VAC cases. Intra-operative blood loss (4.4L vs 10.7L), cell saver return (1399 ml vs 3998 ml), FFP (7.6U vs 15.9U) and PLT requirements (8.5U vs 18.3U), were all significantly elevated in VAC compared to PAC. VAC patients had significantly increased RBC, FFP, PLT, and total volume requirements during initial ICU admission. 30 PAC cases required on demand laparotomy and most commonly for post-operative bleeding. CONCLUSION: In liver transplantation, application of VAC secondary to massive intra-operative exsanguination was safely utilized. Further evaluation is required to identify long-term morbidity and mortality.

Fast volumetric integral-equation solver for acoustic wave propagation through inhomogeneous media.

Elements are described of a volumetric integral-equation-based algorithm applicable to accurate large-scale simulations of scattering and propagation of sound waves through inhomogeneous media. The considered algorithm makes possible simulations involving realistic geometries characterized by highly subwavelength details, large density contrasts, and described in terms of several million unknowns. The algorithm achieves its competitive performance, characterized by O(N log N) solution complexity and O(N) memory requirements, where N is the number of unknowns, through a fast and nonlossy fast Fourier transform based matrix compression technique, the adaptive integral method, previously developed for solving large-scale electromagnetic problems. Because of its ability of handling large problems with complex geometries, the developed solver may constitute an efficient and high fidelity numerical simulation tool for calculating acoustic field distributions in anatomically realistic models, e.g., in investigating acoustic energy transfer to the inner ear via nonairborne pathways in the human head. Examples of calculations of acoustic field distribution in a human head, which require solving linear systems of equations involving several million unknowns, are presented.

Fast volumetric integral-equation solver for high-contrast acoustics.

An approach for solving volumetric integral equations in acoustics, applicable to problems involving large density contrasts, is described. While the conventional Lippmann-Schwinger integral equations become under such circumstances ill conditioned, the proposed approach reformulates them and casts them into an equivalent system of well-conditioned surface and volume integral equations. The corresponding fast solver [utilizing stiffness matrix compression based on fast Fourier transforms and characterized by O(N log N) solution complexity and storage requirements, where N is the number of unknowns] was enhanced to incorporate the proposed formulation. Features of the solution method and of the solver are illustrated on representative examples of numerically large problems.