Applying multi-phase DES approach for modelling the patient journey through accident and emergency departments

Accident and Emergency departments (A&ED) are in charge of providing access to patients requiring urgent acute care. A&ED are difficult to model due to the presence of interactions, different pathways and the multiple outcomes that patients may undertake depending on their health status. In addition, public concern has focused on the presence of overcrowding, long waiting times, patient dissatisfaction and cost overruns associated with A&ED. There is then a need for tackling these problems through developing integrated and explicit models supporting healthcare planning. However, the studies directly concentrating on modelling the A&EDs are largely limited. Therefore, this paper presents the use of a multi-phase DES framework for modelling the A&ED and facilitating the assessment of potential improvement strategies. Initially, the main components, critical variables and different states of the A&ED are identified to correctly model the entire patient journey. In this step, it is also necessary to characterize the demand in order to categorize the patients into pipelines. After this, a discrete-event simulation (DES) model is developed. Then, validation is conducted through the 2-sample t test to demonstrate whether the model is statistically comparable with the real-world A&ED department. This is followed by the use of Markov phase-type models for calculating the total costs of the whole system. Finally, various scenarios are explored to assess their potential impact on multiple outcomes of interest. A case study of a mixed-patient environment in a private A&E department is provided to validate the effectiveness of the multi-phase DES approach

Myocardial energy depletion and dynamic systolic dysfunction in hypertrophic cardiomyopathy

Evidence indicates that anatomical and physiological phenotypes of hypertrophic cardiomyopathy (HCM) stem from genetically mediated, inefficient cardiomyocyte energy utilization, and subsequent cellular energy depletion. However, HCM often presents clinically with normal left ventricular (LV) systolic function or hyperkinesia. If energy inefficiency is a feature of HCM, why is it not manifest as resting LV systolic dysfunction? In this Perspectives article, we focus on an idiosyncratic form of reversible systolic dysfunction provoked by LV obstruction that we have previously termed the 'lobster claw abnormality' — a mid-systolic drop in LV Doppler ejection velocities. In obstructive HCM, this drop explains the mid-systolic closure of the aortic valve, the bifid aortic pressure trace, and why patients cannot increase stroke volume with exercise. This phenomenon is characteristic of a broader phenomenon in HCM that we have termed dynamic systolic dysfunction. It underlies the development of apical aneurysms, and rare occurrence of cardiogenic shock after obstruction. We posit that dynamic systolic dysfunction is a manifestation of inefficient cardiomyocyte energy utilization. Systolic dysfunction is clinically inapparent at rest; however, it becomes overt through the mechanism of afterload mismatch when LV outflow obstruction is imposed. Energetic insufficiency is also present in nonobstructive HCM. This paradigm might suggest novel therapies. Other pathways that might be central to HCM, such as myofilament Ca2+ hypersensitivity, and enhanced late Na+ current, are discussed

Do orthopaedic journals provide high-quality evidence for clinical practice?

BACKGROUND: In the hierarchy of research designs, randomized controlled trials and meta-analyses are considered to be evidence of the highest grade, and scientific journals are the main source of scientific information. METHODS: Using the National Library of Medicine Medline database, all randomized controlled trials and meta-analyses from 1966 to 1999 were retrieved from the journals indexed in the core list of the Science Citation Index in 1999, dedicated primarily to orthopaedics. The abstracts of the articles were reviewed independently by each author and classified by the year, journal name and subject. RESULTS: The total number of articles was 36,293, of which only 671 were randomized controlled trials (1.85%) and 12 were meta-analyses (0.03%). Although there was a progressively increasing trend for randomized controlled trials, more than half of them (81.9%) were published in four journals. Of the randomized controlled trials, 66% was about arthroplasty, and hip and knee arthroplasties covered 90.7%. CONCLUSION: Although the number of randomized controlled trials and meta-analyses is tending to increase, the conclusion of this study is that the high-quality evidence provided by the major orthopaedic journals is quite low, and more randomized controlled trials and meta-analyses are needed for evidence-based orthopaedic practice

Antibiotic-impregnated xenografts in the treatment of chronic osteomyelitic cavities. Seven cases followed for 3 to 5 years

We describe seven patients with chronic osteomyelitis which developed in 3 following operation and in 4 after trauma. The treatment consisted of removal of dead tissue and filling the resulting cavities with gentamicin-impregnated xenografts. No antibiotics were used postoperatively. Urine gentamicin levels were above 0.5 μg/ml for 8 days. The patients were followed up for at least 3.5 years and neither clinical nor laboratory signs of infection were detected. These results lead us the conclusion that gentamicin-impregnated xenografts may have a place in the treatment of chronic osteomyelitis

Effects of three different biochars amendment on water retention of silty loam and loamy soils

A greenhouse experiment was conducted to investigate the effects of three biochar types on available water contents (AWC) of sandy loam and loamy soils. Two soil types, three different biochar types (BT), five biochar rates (BR) and five fertilizer levels (FR) were included in the study. The biochar types were produced from rice husk (RB), bean harvest residue (BB) and corn cobs (CB). All of the biochar types were either saturated with nutrient rich dairy effluent (DE) or kept unsaturated, while the soils with no addition of biochar types were regarded as control treatment. Winter wheat (Triticum aestivum L.) was grown for two seasons and soil sampling was done following each harvest. The mineral fertilizers were applied at the beginning of each season, while biochar types were applied only at the beginning of the experiment. Soil samples were analyzed for total porosity, water contents at field capacity and permanent wilting point, and thereby AWC was calculated. Soil type, BT, BR and FR had significant effect on water retention and total porosity. In both soil types, total porosity was significantly lower at higher BRs than control. The addition of different biochar types continually increased the AWC both in sandy loam and loamy soils, though the effect was more obvious in the loamy soils. However, comparing the water retention with 2.0 and 3.0% BR relative to the control in the first season, the increase rate of AWC was much higher in sandy loam soil compared to loamy soil. The aging of all three biochar types in second season caused to increase in AWC at a rate of 19.9% in RB, 6.0% in CB and 6.1% in BB. The results revealed that all biochar types used in this experiment can be utilized to improve AWC in both sandy loam and loamy soils. © 2018 Elsevier B.V