Is prosthesis retention effective for chronic infections in hip arthroplasties? A systematic literature review.

The success rate of prosthesis removal as the standard approach to manage chronic infection in hip arthroplasties (HA) is 80-90 %. The effectiveness of prosthesis retention, with or without surgical debridement, to treat patients with chronic HA infection (symptom duration of more than 4 weeks) has not been well established, whereas this strategy is sometimes used in clinical practice. This study aimed to explore the cumulative incidence of failure of chronic HA infections treated with prosthesis retention, with or without debridement. A systematic literature review was conducted in accordance with the methods described in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Studies concerning patients with chronically infected HA treated with prosthesis retention were included. The primary outcome was the cumulative risk of failure. We searched the MEDLINE, Embase, and Cochrane databases up to April 2014. The database searches provided a total of 1,213 studies for potential inclusion in the review. Six relevant studies were finally identified, corresponding to 29 patients included. Their treatments consisted of prosthesis retention with debridement. This strategy failed for 14 out of these 29 patients after a 1-year follow-up. The failure rate of the prosthesis retention approach associated to debridement for chronic infection in HA is 48.3 % in this review. Debridement and prosthesis retention in association with prolonged antimicrobial treatment may be an advantageous alternative to arthroplasty exchange for frail patients. The difficulty in finding relevant studies illustrates the challenges of interpreting the existing literature for the management of chronic prosthetic joint infection (PJI).

The features of infectious diseases departments and anti-infective practices in France and Turkey: a cross-sectional study.

The aim of this study was to assess the infectious diseases (ID) wards of tertiary hospitals in France and Turkey for technical capacity, infection control, characteristics of patients, infections, infecting organisms, and therapeutic approaches. This cross-sectional study was carried out on a single day on one of the weekdays of June 17-21, 2013. Overall, 36 ID departments from Turkey (n = 21) and France (n = 15) were involved. On the study day, 273 patients were hospitalized in Turkish and 324 patients were followed in French ID departments. The numbers of patients and beds in the hospitals, and presence of an intensive care unit (ICU) room in the ID ward was not different in both France and Turkey. Bed occupancy in the ID ward, single rooms, and negative pressure rooms were significantly higher in France. The presence of a laboratory inside the ID ward was more common in Turkish ID wards. The configuration of infection control committees, and their qualifications and surveillance types were quite similar in both countries. Although differences existed based on epidemiology, the distribution of infections were uniform on both sides. In Turkey, anti-Gram-positive agents, carbapenems, and tigecycline, and in France, cephalosporins, penicillins, aminoglycosides, and metronidazole were more frequently preferred. Enteric Gram-negatives and hepatitis B and C were more frequent in Turkey, while human immunodeficiency virus (HIV) and streptococci were more common in France (p < 0.05 for all significances). Various differences and similarities existed in France and Turkey in the ID wards. However, the current scene is that ID are managed with high standards in both countries.

Homologous human blood protein separation using immobilized metal affinity chromatography: protein C separation from prothrombin with application to the separation of factor IX and prothrombin.

Protein C (PC) is a natural anticoagulant and antithrombotic present in human blood at a concentration of 4 microg/mL. Its deficiency can result in excessive clotting and thrombosis. Protein C can be obtained from human blood plasma; however, there are other coagulant proteins in blood, including prothrombin (factor II), which is present in relatively large amounts and is one of the most active components. Protein C and prothrombin are homologous proteins with similar biochemical features; therefore, immunoaffinity chromatography is used for their separation. However, this technology is very expensive, protein C recovery and activity is low, and contamination problems with mouse antibody are likely. Immobilized metal affinity chromatography (IMAC) utilizes the protein metal-binding properties for protein separation. Protein C has twelve surface-accessible histidines, which are the major metal-binding groups for IMAC separation. After investigating metal ion-binding properties of protein C, we used an IDA-Cu column to separate protein C and prothrombin. Following protein adsorption to the column, prothrombin was washed out using a sodium phosphate buffer containing 2 mM imidazole and protein C was recovered with 15 mM imidazole in the buffer. The mild elution condition allows a high protein C activity and a high recovery. Also, this technology introduces no immunoglobulins, and it is relatively inexpensive. IMAC could replace the immunoaffinity technology for the large-scale separation of protein C from blood plasma Cohn Fraction IV-1. In addition, this work demonstrates a significant application of this technology for the separation of factor IX from prothrombin. Prothrombin has proven to be a harmful contaminant in factor IX cocktails that have been administered to humans in the treatment of hemophilia B.

Application of near-IR time-resolved spectroscopy and frequency response analysis for deep vein thrombosis detection.

Frequency response analysis is applied to analyze NIR-TRS spectra in a tissue model with a simulated thrombus. The value changes in parameters obtained from frequency response analysis are correlated with heterogeneity position in three dimensions. The goal of this research is to noninvasively localize deep vein thrombosis in the human leg through the use of this novel combination.

Probabilistic modeling of oxygen transport in brain tissue.

A three-dimensional model of a subregion of the microcirculation was developed. The model employed parallel probabilistic distributions of reaction and convection of oxygen. A Green's function solution to oxygen transport in this system was derived and applied in a series of dynamic solutions on a minicomputer. Results include the transient response of oxygen tension at grid points throughout the system and a correlation of the oxygen demand and surplus supply. Results clearly represent anticipated oxygen partial pressure behavior trends of a countercurrent flow system and in pertinent ways compared favorably with the results obtained by previous investigators. The technique is conservative and employs from 2,000 to 3,600 time steps to achieve precision of seven significant figures. Excellent stability was observed as well. The simulation provides a reliable means to represent the transient response of oxygen partial pressure in a three-dimensional system. Case studies show effects of changing arterial oxygen partial pressure as well as the importance in this system of the convection of dissolved oxygen. It is concluded that the system adequately simulates the anticipated broad profiles of a probabilistically distributed system and provides a rather original insight into neuronal viability through a correlation of oxygen supply and demand. Adaptation of such a complex, dynamic, three-dimensional stimulation to a minicomputer is a step toward simulation of more sophisticated geometries.

Beyond reliability and validity: analysis of selected quality-of-life instruments for use in palliative care.

The purpose of this study was to review quality-of-life instruments for their potential usefulness in the palliative care setting. Conceptualizations of quality of life throughout history, and contemporary conceptualizations of quality of life were briefly discussed. The specific conceptualizations of six quality-of-life measurement tools (the Medical Outcomes Study Short-Form Health Survey [SF-36], the European Organization for Research and Treatment of Cancer [EORTC] QLQ-C30, the Quality of Life Index [QLI], the Hospice Quality of Life Index [HQLI], the McGill Quality of Life Questionnaire [MQOL], and the Missoula-VITAS Quality of Life Index [MVQOLI]) were evaluated. The origins, target populations, acceptability of individual items, completion time, number of questions, type of response format, and type of scoring of each instrument were discussed, and evidence of the instruments' reliability, validity, and responsiveness were reviewed. The researcher or clinician should consider all of these factors when choosing the quality-of-life instrument that best fits the purpose.

Modeling oxygen transport: development of methods and current state.

Many investigators have contributed to the quantitative understanding of oxygen transport to tissue. Computers continue to improve in speed and architecture thus allowing more sophisticated modeling approaches to be employed. This paper highlights the development of a unique computational strategy, the B-W-K method, that was developed to handle large simulations on small computers. It has proven to be very effective for the solution of large-scale problems in oxygen transport to tissue.

The genesis of ISOTT. International Society on Oxygen Transport to Tissue.

The International Society on Oxygen Transport to Tissue (ISOTT) was founded in April, 1973 by Drs. Duane F. Bruley and Haim I. Bicher. Dr. Bruley first wanted to sponsor an international symposium on oxygen transport to tissue to highlight the research activity between his group at Clemson University in Clemson, South Carolina and Dr. Melvin H. Knisely's group at the Medical College of South Carolina in Charleston, South Carolina. At the same time it was hoped to honor Dr. Knisely for his ingenious development of the Quartz Rod Crystal technique for observing blood flow in-vivo. In discussions with Dr. Knisely's wife, Verona, it was decided to sponsor a meeting that was jointly held at Clemson and Charleston. When Dr. Bicher returned from an extended trip abroad, he agreed to join the effort and he organized the program from the Medical College while Dr. Bruley handled all arrangements at Clemson University. After getting an overwhelming response to their initial call for papers from the international community, Drs. Bruley and Bicher made the decision to found an International Society. They then decided on a name, developed the society logo, assigned a mission, developed a charter, sketched the by-laws, and selected charter members to comprise the first international committee. The unique characteristics of the new society were to include a focus on inter and cross-disciplinary research involving theoretical and experimental investigations of oxygen transport to tissue. The intent was to bring life scientists and engineers together to examine the many complex phenomena of normal tissue growth and maintenance as well as tissue survival and repair under pathological conditions. Drs. Bruley and Bicher solicited Dr. Melvin Knisley as an honorary first President of the Society. At the meeting April 22-28, in Charleston/Clemson the first elected president was determined to be Dr. Melvin H. Kinsely. It was decided that in alternate years the meeting would be held in the United States and otherwise in Europe or Asia. The society has met around the world and is now celebrating its 25th Anniversary.

Approximate-analytical solution of the diffusion, convection and reaction problem in homogeneous media.

In convex homogeneous domains, the diffusion, convection and reaction (DCR) problem may be solved by applying Green's function solution technique. When this technique is applied, the solution to the DCR problem consists of the sum of a set of integrals whose integrands involve the Green's function. The Green's function is singular at the upper limit of the time integral and is nonuniformly convergent at the boundaries of the domain. Due to this behaviour, numerical evaluation of the integrals is prohibitively expensive and in some cases, the integrals are incorrectly evaluated. The method presented in this work circumvents all the difficulties inherent with the numerical quadrature of the intergrals and in preliminary case studies (in rectangular coordinates) has reduced the required computation time by up to five orders of magnitude while increasing the accuracy of the results by as much as eight orders of magnitude. The method involves transforming the function in the integrand, which multiplies the Green's function, into a series of Legendre polynomials. The integral of the product of the Green's function and Legendre polynomials can be evaluated analytically. This produces both a rapid and accurate evaluation of the integral and subsequently the solution to the DCR problem.

A mathematical model applying the random-walk method to the environment of a neuron.

A mathematical model describing the supply and demand relationships existing in the environment of a brain cell (neuron of the cerebral cortex) was developed. The stochastic random-walk technique was applied to the representation and solution of the system which consisted of a neuron being supplied with nutrients by an adjoining capillary. The random-walk method incorporated a uniformly generated random number which was weighted by the normal distribution curve to determine the random walk of a molecule. The resultant weighted value was designated as defining the motion of any particular species in space. The distribution curve was a function of diffusivity and time. The method allowed the tracking of individual molecules as they proceeded through the metabolic reactions in the cell. Oxygen, glucose, carbon dioxide and lactate were selected as the primary components of study, since they represent the major input and output parameters of metabolism inside the cell. The consumption and/or production of these components were dependent on probability values assigned to each metabolic reaction into which they entered. The solution of the model was based on the number of molecules existing in the tissue as a function of PO2, (partial pressure of oxygen), glucose level, etc. The model was very sensitive to perturbations of metabolic scheme parameters and to PO2 levels in the capillary. The model predicted an excess of O2, (oxygen) in the tissue. The effects of edema on intercapillary distances as well as changes in the size and number of mitochondria within the neuron were examined using the model.(ABSTRACT TRUNCATED AT 250 WORDS)

The transport of oxygen, glucose, carbon dioxide and lactic acid in the human brain: mathematical models.

Mathematical models of the transport of oxygen, glucose, carbon dioxide and lactic acid in the human brain have been developed and solved for both steady-state and dynamic cases which include normal conditions, arterial and venous hypoxia, reduced flow and hematocrit, hypocapnia, reduced glucose and transient arterial upsets. Results indicate that local concentration deficits of oxygen and/or glucose and excesses of lactic acid can exist within the system described by the models and therefore possibly could exist in the tissues of the human brain under similar conditions.

Changes in tissue oxygenation and acidity induced by localized microwave hyperthermia and hematoporphyrin phototherapy, an update.

Changes in tumor tissue oxygenation and acidity were determined using ultramicroelectrodes, and presented in histogram fashion. The effect of Hyperthermia and Hpd photo-therapy were tested. It was found that both modalities affect tumor microcirculation, causing a marked drop in oxygen availability. Tissue pH is decreased by Hyperthermia, but not by phototherapy. These effects are long lasting, at least for 24 hours after treatment.

A computer simulation of simultaneous heat and oxygen transport during heterogeneous three dimensional tumor hyperthermia.

Hyperthermia is a developing modelity for the treatment of cancer. This therapy is occasionally used by itself, however, usually it is used as an adjuvate with chemo or radiation therapy. The mechanism for this treatment is based on the fact that cancer cells are heated preferentially by heat application due to lower vascularity in the tumor tissue as compared with the surrounding normal tissue and that, when used with radiation therapy or chemo therapy, higher oxygen partial pressure in the tumor results in increased tumor cell damage. Appropriate mathematical models and their real time prediction of oxygen and temperature profiles could be very helpful in achieving optimal results via hyperthermia and to avoid possible danger which might occur during the treatment. Because of the complexity and the heterogeneous nature of physiological system, it is necessary to include heterogeneous properties in the mathematical models for them to be useful for biomedical calculations. Of course, it is much more difficult to solve mathematically the heterogeneous system than the homogeneous one. In this paper, the importance of the implementation of heterogeneities in the heat and mass transport for biological system mathematical modelling is discussed. Results of a three dimensional computer simulation of mass and heat transfer in tumor tissue with different capillary geometries during hyperthermia are demonstrated. The method used for the computer simulation is a deterministic/probabilistic technique, Williford-Bruley calculational strategy.

Computer modeling of tumor hyperthermia (a dynamic lumped parameter model).

The thermal behavior of normal and neoplastic tissue is modeled by a set of coupled ordinary differential equations. The equations lump the tissue and tumor into individual compartments, so that the equations are time dependent. These equations represent an initial step in the development of a comprehensive model which may be used in studying the dynamics and control of the system under normo- and hyperthermic conditions.

Gel compression considerations for chromatography scale-up for protein C purification.

This work is to establish theoretical and experimental relationships for the scale-up of Immobilized Metal Affinity Chromatography (IMAC) and Immuno Affinity Chromatography for the low cost production of large quantities of Protein C. The external customer requirements for this project have been established for Protein C deficient people with the goal of providing prophylactic patient treatment. Deep vein thrombosis is the major symptom for protein C deficiency creating the potential problem of embolism transport to important organs, such as, lung and brain. Gel matrices for protein C separation are being analyzed to determine the relationship between the material properties of the gel and the column collapse characteristics. The fluid flow rate and pressure drop is being examined to see how they influence column stability. Gel packing analysis includes two considerations; one is bulk compression due to flow rate, and the second is gel particle deformation due to fluid flow and pressure drop. Based on the assumption of creeping flow, Darcy's law is being applied to characterize the flow through the gel particles. Biot's mathematical description of three-dimensional consolidation in porous media is being used to develop a set of system equations. Finite difference methods are being utilized to obtain the equation solutions. In addition, special programs such as finite element approaches, ABAQUS, will be studied to determine their application to this particular problem. Experimental studies are being performed to determine flow rate and pressure drop correlation for the chromatographic columns with appropriate gels. Void fraction is being measured using pulse testing to allow Reynolds number calculations. Experimental yield stress is being measured to compare with the theoretical calculations. Total Quality Management (TQM) tools have been utilized to optimize this work. For instance, the "Scatter Diagram" has been used to evaluate and select the appropriate gels and operating conditions via Taguchi techniques. Targeting customer requirements under the structure of TQM represents a novel approach to graduate student research in an academic institution which is designed to simulate an industrial environment.

Changes in tumor tissue oxygenation during microwave hyperthermia: clinical relevance.

As previously described (Bicher 1981) TpO2 and blood flow increase in tumor as temperature increases until 41 degrees C and decrease thereafter (microcirculation "breaking point"). In the present clinical study using O2 microelectrodes this response was reproduced in over 54 treatment sessions. However, it was found that as treatment progresses (patients are treated for one hour 10 times, twice weekly, and concomitantly receive 4000 rads of ionizing radiation) the initial increase of blood flow and TpO2 is reduced and there is immediate decrease in tissue oxygenation. A correlation between microvascular tumor physiological changes and tumor treatment responses is being developed.

Identification of viable regions in "in vitro" spheroidal tumors: a mathematical investigation.

In the treatment of solid tumors by hyperthermia, a major question is how to obtain an a priori knowledge of which tumors can be effectively treated with this modality. The key question is; given a solid tumor, what parameters in the various regions of the tumor, need to be measured so that a tumor-tissue model can provide a meaningful real time simulation of the hyperthermic treatment. This paper addresses the former question as a mathematical investigation, and the latter as a consequence of the former.

A stochastic model for the transport of oxygen to brain tissue.

Material balances around a small, but finite volume element have formed the basis for previous mathematical models describing the transport of oxygen in the brain microcirculation. Seeking a model which would be both simple and versatile, a stochastic model was proposed based on the assumption that oxygenation of the brain can be described quantitatively by simulating the activity of only one erythrocyte and the oxygen molecules surrounding it. Compared with existing deterministic models, the capillary space-average oxygen partial pressure profiles were in close agreement. Tissue tensions were decidedly different.

Autonomic and pharmacological control of oxygen autoregulation mechanisms in brain tissue.

The effect of several agents active on autonomic nervous system functions was tested on brain oxygen autoregulation parameters. It was found that atropine, propranolol and isproterenol had no influence on the measured parameters. Phenoxybenzamine, tolazoline and dibenamine all suppress autoregulation. In an additional experimental series, a phenoxybenzamine infusion was given during O2 breathing. The infusion induced a marked rise in TpO2. It is concluded that an alpha-adrenergic mechanism is part of the autoregulation process, and its pharmacological blockade could be used to raise TpO2 levels in brain with O2 breathing at normal atmospheric pressure. Also, the increase in brain TpO2 induced by 95% O2 - 5% CO2 breathing seems to be blocked by alpha-adrenolytic drugs.

Chromatographic process identification for protein C purification using frequency response analysis.

Frequency response analysis is applied for the analysis of liquid chromatography output of protein separation. Reduced data from simple chromatograms suggest that various Bode plot parameters, magnitude ratios, phase shift, the steady state gain, break frequency, and system order in the frequency domain, can be used to gain phenomenological insights on the system. Such an approach is advantageous because the validity of the model can be checked for two plots, the magnitude ratio vs. frequency and the phase shift vs. frequency, as compared to a single plot in the time domain. This approach also provides a useful empirical-tool which can be quantifiably used for process validation and scale-up, especially for immunoaffinity and immobilized metal affinity chromatographic systems used for protein C purification.