Leopold Pleva

Anaerobic metabolism associated with traumatic hemorrhagic shock monitored by microdialysis of muscle tissue is dependent on the levels of hemoglobin and central venous oxygen saturation: a prospective, observational study

BackgroundTraumatic hemorrhagic shock resulting in tissue hypoxia is a significant cause of morbidity and mortality in polytraumatized patients. Early identification of tissue hypoxia is possible with microdialysis. The aim of this study was to determine the correlation between a marker of tissue hypoxia (L/P; lactate to pyruvate ratio) and selected parameters of systemic oxygen delivery (Hb; hemoglobin) and oxygen extraction (ScvO2; central venous oxygen saturation). We also investigated the severity of tissue hypoxia over the course of care.MethodsAdult patients with traumatic hemorrhagic shock were enrolled in this prospective, observational study. Microdialysis of the peripheral muscle tissue was performed. Demographic data and timeline of care were collected. Tissue lactate, pyruvate, glycerol, glucose levels, hemoglobin, serum lactate and oxygen saturation of the central venous blood (ScvO2) levels were also measured.ResultsThe L/P ratio trend may react to changes in systemic hemoglobin levels with a delay of 7 to 10 hours, particularly when systemic hemoglobin levels are increased by transfusion. Decrease in tissue L/P ratio may react to increase in ScvO2 with a delay of up to 10 hours, and such a decrease may signify elimination of tissue hypoxia after transfusion. We also observed changes in the L/P trend in the 13 hours preceding a change in the hemoglobin level. Fluid administration, which is routinely used as a first-line treatment of hypovolemic shock, can cause hemodilution and decreased hemoglobin. When ScvO2 decreases, increase in L/P ratio may precede the ScvO2 trend by 10 or 11 hours. An increase in the L/P ratio is an early warning sign of insufficient tissue oxygenation and should lead to intensive observation of hemoglobin levels, ScvO2 and other hemodynamic parameters. Patients who were treated more rapidly had lower maximal L/P values and a lower degree of tissue ischemia.ConclusionThe L/P ratio is useful to identify tissue ischemia and can estimate the effectiveness of fluid resuscitation. An increase in the L/P ratio is an early warning sign of inadequate tissue oxygenation and should lead to more detailed hemodynamic and laboratory monitoring. This information cannot usually be obtained from global markers.

Finite Element Modelling of T-Plate for Treatment of Distal Radius

Distal radius fractures are the most frequent type of injury in the upper limbs. This paper analyses a new locking compression plate for osteosynthesis. The plate, made of Ti6Al4V or stainless steel, is used for the internal fixation of distal radius fractures by open reposition. The bone (with a fracture of 23–C1 AO classification), together with the plate and angularly stable screws, was exposed to axial tension/compression and bending quasi-dynamic overloading. The material properties of bone can be described with sufficient accuracy for individual bone parts using a homogeneous isotropic material model. In order to provide an adequate description of reality, the bone model was divided into two types of osseous tissues, i.e. cortical (compact—substantia compacta) and spongy (cancellous—substantia spongiosa) tissues. Other bone models based on the theory of elastic (Winkler’s) foundations were also used. Variant calculations (i.e. numerical simulations) were carried out for fused bone (i.e. successful treatment) and non-fused bone. The safety factor was evaluated with regard to the minimum yield strength of the material. The situation of maximum loading on non-fused bone is an extreme state in which the fracture fails to heal and the patient places excessive stress on the limb. From this biomechanical perspective, the analysed new locking compression plate with its angularly stable screws can be considered safe for the treatment of distal radius fractures.

Ring Fixators in Traumatology (An Engineering Point of View)

This article focuses on ring (Ilizarov) external fixators in traumatology and orthopedics. External fixators are used in the treatment of complicated fractures, bone shortening and lengthening, corrections of angular deformities, and similar applications. An engineering/biomechanical point of view represents an essential perspective when taking account of the recommendations of medical specialists, designing materials for fixator components, developing surface treatment methods, optimizing design concepts, and conducting experimental verification. The article presents practical experience and results gained during cooperation between medical specialists and engineers (an overview of applicable materials, design, laboratory experiments, Finite Element Modeling).

Locking Compression Plate for Distal Tibia Fractures

This article represents a multidisciplinary approach to biomechanics (engineering + medicine) in the field of distal tibia fractures. The objective of the present study was to carry out a strength and reliability assessment of a medial plate for the treatment of distal tibia fractures. This was performed via numerical modelling (FEM) and experimental methods (compression test and Electronic Speckle Pattern Interferometry – ESPI method). The plate is used for internal fixation in orthopaedics and traumatology. Analyses were performed for non-fused bone with comminuted fracture in the distal metaphysis (i.e. unsuccessful treatment, where all loads in the metaphysis are carried by the plate). An anatomical tibia model (based on CT images in Mimics software) was used for FE analysis. In the experiments, the bone was replaced with a shaped piece of spruce wood (based on Mimics software) and the plate was loaded until its failure (major plastic deformation). Numerical and experimental results were evaluated and compared.

Study of Fracture Feature of Titanium Based Alloys for Biocompatible Implants after Removal from Human Body

The study of microstructure and fracture surfaces was performed on specimens of reconstruction plate, reconstruction nail and elastic nail. The composition and phase analysis of microstructure was performed by scanning electron microscope (SEM) JEOL JSM - 6490LV equipped with EDS INCA X - ACT probe. Examination of fracture surfaces by SEM confirmed that damage was not simply due to fatigue but contained evidence of corrosion and mechanical fretting as well.

Passive motion splint applied in traumatology and ortopaedics

Tento clanek se zabýva analýzou pasivni kolenni motodlahy sloužici k rehabilitaci pacientů po operacich a urazech. Pasivni motodlahy se použivaji pro urychleni lecby, obnovu pohyblivosti kloubů a zamezeni komplikacim způsobených imobilizaci. Cilem je řeseni kinematických, dynamických, deformacnich a pevnostnich parametrů pro motodlahu “Artromot K1 Comfort”.