Tackling a Post-COVID-19 Cholecystectomy Waiting List: Are We Meeting the Challenge?

Background and Objectives: The COVID-19 pandemic has led to a tremendous backlog in elective surgical activity. Our hospital trust adopted an innovative approach to dealing with elective waiting times for cholecystectomy during the recovery phase from COVID-19. This study aimed to evaluate trends in overall cholecystectomy activity and the effect on waiting times. Materials and Methods: A prospective observational study was undertaken, investigating patients who received a cholecystectomy at a large United Kingdom hospital trust between February 2021 and February 2022. There were multiple phased strategies to tackle a 533-patient waiting list: private sector, multiple sites including emergency operating, mobile theatre, and seven-day working. The correlation of determination (R2) and Kruskal-Wallis analysis were used to evaluate trends in waiting times across the study period. Results: A total of 657 patients underwent a cholecystectomy. The median age was 49 years, 602 (91.6%) patients had an ASA of 1-2, and 494 (75.2%) were female. A total of 30 (4.6%) patients were listed due to gallstone pancreatitis, 380 (57.8%) for symptomatic cholelithiasis, and 228 (34.7%) for calculous cholecystitis. Median waiting times were reduced from 428 days (IQR 373-508) to 49 days (IQR 34-96), R2 = 0.654, p < 0.001. For pancreatitis specifically, waiting times had decreased from a median of 218 days (IQR 139-239) to 28 (IQR 24-40), R2 = 0.613, p < 0.001. Conclusions: This study demonstrates the methodology utilised to safely and effectively tackle the cholecystectomy waiting list locally. The approach utilised here has potential to be adapted to other units or similar operation types in order to reduce elective waiting times.

100 W, tunable in-band thulium fiber amplifier pumped by incoherently combined 1.9 µm fiber lasers.

We detail the design and performance of a high efficiency in-band pumped thulium fiber amplifier operating at the 100 W level. Using a novel pumping architecture based on three incoherently combined thulium fiber oscillators at 1904 nm and a seed laser tunable from 1970-1990 nm, efficient amplification is demonstrated in a high dopant concentration 25/65/250 µm thulium fiber. Here we use the 65 µm pedestal surrounding the core as a pump cladding to increase the cladding to core overlap and improve the overall pump absorption. Up to 89% slope efficiency is obtained with ∼100 W output power at 1990 nm. These results indicate that in-band pumping is a viable route to circumvent the thermal limitations associated with 793 nm diode pumping and provide a pathway for development of multi-kW laser sources in the 2 µm spectral window.

Numerical simulation of steady-state thermal blooming with natural convection.

This work investigates steady-state thermal blooming of a high-energy laser in the presence of laser-driven convection. While thermal blooming has historically been simulated with prescribed fluid velocities, the model introduced here solves for the fluid dynamics along the propagation path using a Boussinesq approximation to the incompressible Navier-Stokes equations. The resultant temperature fluctuations were coupled to refractive index fluctuations, and the beam propagation was modeled using the paraxial wave equation. Fixed-point methods were used to solve the fluid equations as well as to couple the beam propagation to the steady-state flow. The simulated results are discussed relative to recent experimental thermal blooming results [Opt. Laser Technol.146, 107568 (2022) OLTCAS0030-399210.1016/j.optlastec.2021.107568], with half-moon irradiance patterns matching for a laser wavelength at moderate absorption. Higher energy lasers were simulated within an atmospheric transmission window, with the laser irradiance exhibiting crescent profiles.

Single-centre review of the management of intra-thoracic oesophageal perforation in a tertiary oesophageal unit: paradigm shift, short- and long-term outcomes over 15 years.

BACKGROUND: Oesophageal perforation is an uncommon surgical emergency associated with high morbidity and mortality. The timing and type of intervention is crucial and there has been a major paradigm shift towards minimal invasive management over the last 15 years. Herein, we review our management of spontaneous and iatrogenic oesophageal perforations and assess the short- and long-term outcomes. METHODS: We performed a retrospective review of consecutive patients presenting with intra-thoracic oesophageal perforation between January 2004 and Dec 2020 in a single tertiary hospital. RESULTS: Seventy-four patients were identified with oesophageal perforations: 58.1% were male; mean age of 68.28 ± 13.67 years. Aetiology was spontaneous in 42 (56.76%), iatrogenic in 29 (39.2%) and foreign body ingestion/related to trauma in 3 (4.1%). The diagnosis was delayed in 29 (39.2%) cases for longer than 24 h. There was change in the primary diagnostic modality over the period of this study with CT being used for diagnosis for 19 of 20 patients (95%). Initial management of the oesophageal perforation included a surgical intervention in 34 [45.9%; primary closure in 28 (37.8%), resection in 6 (8.1%)], endoscopic stenting in 18 (24.3%) and conservative management in 22 (29.7%) patients. On multivariate analysis, there was an effect of pathology (malignant vs. benign; p = 0.003) and surgical treatment as first line (p = 0.048) on 90-day mortality. However, at 1-year and overall follow-up, time to presentation (≤ 24 h vs. > 24 h) remained the only significant variable (p = 0.017 & p = 0.02, respectively). CONCLUSION: Oesophageal perforation remains a condition with high mortality. The paradigm shift in our tertiary unit suggests the more liberal use of CT to establish an earlier diagnosis and a higher rate of oesophageal stenting as a primary management option for iatrogenic perforations. Time to diagnosis and management continues to be the most critical variable in the overall outcome.

Influence of muscle loading on early-stage bone fracture healing.

Designing weight-bearing exercises for patients with lower-limb bone fractures is challenging and requires a systematic approach that accounts for patient-specific loading conditions. However, 'trial-and-error' approaches are commonplace in clinical settings due to the lack of a fundamental understanding of the effect of weight-bearing exercises on the bone healing process. Whilst computational modelling has the potential to assist clinicians in designing effective patient-specific weight-bearing exercises, current models do not explicitly account for the effects of muscle loading, which could play an important role in mediating the mechanical microenvironment of a fracture site. We combined a fracture healing model involving a tibial fracture stabilised with a locking compression plate (LCP) with a detailed musculoskeletal model of the lower limb to determine interfragmentary strains in the vicinity of the fracture site during both full weight-bearing (100% body weight) and partial weight-bearing (50% body weight) standing. We found that muscle loading significantly altered model predictions of interfragmentary strains. For a fractured bone with a standard LCP configuration (bone-plate distance = 2 mm, working length = 30 mm) subject to full weight-bearing, the predicted strains at the near and far cortices were 23% and 11% higher when muscle loading was included compared to the case when muscle loading was omitted. The knee and ankle muscles accounted for 38% of the contact force exerted at the knee joint during quiet standing and contributed significantly to the strains calculated at the fracture site. Thus, models of bone fracture healing ought to account explicitly for the effects of muscle loading. Furthermore, the study indicated that LCP configuration parameters play a crucial role in influencing the fracture site microenvironment. The results highlighted the dominance of working length over bone-plate distance in controlling the flexibility of fracture sites stabilised with LCP devices.

The effects of mechanical instability on PDGF mediated inflammatory response at early stage of fracture healing under diabetic condition.

BACKGROUND AND OBJECTIVE: Mechanical stability plays an important role in fracture healing process. Excessive interfragmentary movement will continuously damage the tissue and newly formed capillaries at the fracture site, which leads to overproduction of platelet-derived growth factor (PDGF) that attracts more macrophages into fracture callus, ultimately persistent and enhanced inflammatory response happens. For diabetic condition, the impact of mechanical instability of fracture site on inflammatory response could be further compliciated and the relevant research in this field is relatively limited. METHODS: Building on previous experimental studies, this study presents a numerical model consisting of a system of reactive-transport equations representing the transport as well as interactions of different cells and cytokines within the fracture callus. The model is initially validated by available experimental data, and then implemented to investigate the role of mechanical stability of fracture site in inflammatory response during early stage of healing. It is assumed that there is an increased release of PDGF due to the rupture of blood vessels resulting from mechanical instability, which leads to increased production of inflammatory cytokines (i.e., TNF-α). The bone healing process under three different conditions were investigated, i.e., mechanically stable condition with normal inflammatory response (Control, Case 1), mechanically unstable condition with normal inflammatory response (Case 2) and mechanically unstable condition with diabetes (Case 3). RESULTS: Mechanical instability can promote the macrophage infiltration and thus induce an enhanced and prolonged inflammatory response, which could impede the MSCs proliferation during the early fracture healing stage (e.g., compared with the control condition, the MSCs concentration in unstable fracture with normal inflammatory response can be reduced by 3.2% and 5.2% on day 2 and day 10 post-fracture, respectively). Under diabetic condition, the mechanical instability of fracture site could lead to a significant increase of TNF-α concentration in fracture callus (Case 3) in comparison to control (Case 1) (e.g., three-fold increase in TNF-α concentration compared to control). In addition, the results show that the mechanical instability affects the cell differentiation and proliferation in fracture callus in a spatially dependent manner, e.g., for diabetic fracture patients, the mechanical instability could potentially decrease the concentration of MSCs, osteoblasts and chondrocytes by around 39%, 30% and 29% in cortical callus, respectively, in comparison to control. CONCLUSION: The mechanical instability together with diabetic condition can significantly affect the natural resolution of inflammation during early stage of healing by turning acute inflammation into chronic inflammation which is characterized by a continuously upregulated TNF-α pathway.

Filamentation in low pressure conditions.

Filamentation is favorable for many long-range outdoor laser applications, some of which require propagation to or at high altitudes. Understanding how the filamentation process and filament properties are impacted by the low pressure conditions present at high altitudes is essential in designing effective applications. The scaling of filament preconditions with pressure is considered. An increase in critical power and decrease in transition numerical aperture (NA) is predicted to occur with a drop in pressure, indicating that nonlinear pulse propagation and filamentation at high altitudes requires higher energy and a longer assisted focal length than sea level filamentation. A summary of pressure-scaled filament properties is also presented. New simulations demonstrate filamentation at pressures as low as 0.0035 atm (38.5 km altitude) is possible.

Review article: A comprehensive review of unusual causes of acute limb compartment syndrome.

Acute limb compartment syndrome (ALCS) is a surgical emergency that can have serious consequences unless promptly diagnosed and treated, which is particularly challenging when there is an unusual cause. This is a comprehensive review of reported causes of ALCS. From 1068 included articles, we found 299 discrete causes of ALCS including toxins, infections, endocrine pathology, haematological emergencies, malignancy and iatrogenic ALCS. Familiarity with this wide range of ALCS causes may assist in early diagnosis of this limb-threatening condition.

Demographic factors associated with length of stay in hospital and histological diagnosis in adults undergoing appendicectomy.

Objectives: Appendicectomy remains of the most common emergency operations in the United Kingdom. The exact etiologies of appendicitis remain unclear with only potential causes suggested in the literature. Social deprivation and ethnicity have both been demonstrated to influence outcomes following many operations. There are currently no studies evaluating their roles with regards to severity and outcomes following appendicectomy. Material and Methods: Demographic data were retrieved from health records for adult patients who underwent appendicectomy between 2010-2016 within a single NHS trust. To measure social deprivation, Indices of Multiple Deprivation (IMD) rankings were used. Histology reports were reviewed and diagnosis classified into predefined categories: non-inflamed appendix, uncomplicated appendicitis, complicated appendicitis and gangrenous appendicitis. Results: Three thousand four hundred and forty-four patients were identified. Mean age was 37.8 years (range 73 years). Using a generalized linear model, South Asian ethnicity specifically was found to be independently predictive of increased length of stay following appendicectomy (p <0.001). Amongst South Asian patients, social deprivation was found to be further predictive of longer hospital stay (p= 0.005). Deprivation was found to be a predictor of complicated appendicitis but not of gangrenous appendicitis (p= 0.01). Male gender and age were also independent predictors of positive histology for appendicitis (p <0.001 and p= 0.021 respectively). Conclusion: This study is the first to report an independent association between South Asian ethnicity and increased length of stay for patients undergoing appendicectomy in a single NHS trust. The associations reported in this study may be a result of differences in the pathophysiology of acute appendicitis or represent inequalities in healthcare provision across ethnic and socioeconomic groups.

Setting up a surgical complex gallstone service in a non-HPB unit.

Objectives: Complex gallstone disease is associated with a higher risk of complication during laparoscopic cholecystectomy than biliary colic and simple cholecystitis. It is traditionally managed in a hepatopancreaticobiliary (HPB) unit where there is expertise for common bile duct exploration and repair. We developed a mentorship scheme for a busy upper gastro-intestinal (UGI) unit, with support from a specialist HPB unit to treat complex gallstone disease, to reduce the burden on the HPB unit and enable local treatment of patients. Material and Methods: Through the creation of a service level agreement, the specialist HPB unit were commissioned to provide mentorship for two surgeons at a large UGI unit with an interest in providing a complex gallstone service to their local population. Eight sessions of mentored operating were supported, with the provision for additional support if complications occurred. Results: There were 14 patients included in the mentorship phase of the programme from November 2015 to May 2017. Cholecystectomies were performed on patients with previously complex histories, which included: previous cholecystostomy; CBD stones and multiple ERCPs; suspected choledochoduodenal fistula; suspected cholecystoduodenal fistula; suspected Mirrizzi's syndrome; previous significant intra-abdominal operation; and significant medical co-morbidities. There was one post-operative complication requiring a return to theatre, and one minor wound infection associated with the complex gallstone lists. Conclusion: We demonstrated a method to reduce the burden on specialist HPB unit for the operative management of complex gallstone disease and safely implement such a service at large UGI unit with an interest in providing a complex gallstone service.

In-verse reflection: structured creative writing exercises to promote reflective learning in medical students.

Medical educators recognize the value of reflection for medical students and the role creative writing can play in fostering this. However, direct creative writing tasks can be challenging for many students, particularly those with limited experience in the arts and humanities. An alternative strategy is to utilize an indirect approach, engaging students with structured tasks that obliquely encourage reflection. This paper reports one such approach. We refer to this approach as in-verse reflection, playing on both the structure of the writing and its novel approach to reflection. Students were invited to write, in verse-like structures, about their personal and clinical experiences as medical students. Thematic analysis of their creative outputs and reactions identified four principal themes: the challenges of life as a medical student, the emotional demands of the medical course, a sense of connectedness and solidarity with fellow students, and a sense of marginality within the hospital system. Students generally found the tasks highly engaging and conducive to reflection, producing texts representing significant insights into their experiences as medical students. The reported method offers a relatively simple, structured, and guided approach to reflective writing, adding to the repertoire of methods available to educators in the medical humanities.

Sonic anemometer data processing for comparison to optical turbulence theory and simulation.

With appropriate processing techniques, sonic anemometry can provide useful insights into the strength and spectral shape of optical turbulence. Closed form propagation models and simulations require stationary optical turbulence statistics to make a meaningful comparison with experimental results. This work presents a new approach for examining the stationarity of data provided by sonic anemometry and by fitting optical turbulence parameters. Von Kármán, Greenwood-Tarazano, and one minus exponential spectral models are fitted to experimental data. Each model fit is evaluated using information criteria. The Greenwood-Tarazano model is shown to provide the best fit to experimental data. Optical turbulence parameters from the Greenwood-Tarazano model are compared with results from instruments at varying heights above the ground.

Role of TNF-α in early-stage fracture healing under normal and diabetic conditions.

BACKGROUND AND OBJECTIVE: Inflammatory response plays a crucial role in the early stage of fracture healing. Immediately after fracture, the debris and immune cells (e.g., macrophages), recruited into the fracture callus, lead to the secretion of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), which governs the mesenchymal stem cells (MSCs) mediated healing processes. However, it is still unclear how chronic inflammatory diseases (e.g., diabetes) affect the level of TNF-α in fracture callus, ultimately the healing outcomes at the early stage of healing. Therefore, the purpose of this study is to develop a numerical model for investigating TNF-α mediated bone fracture healing. METHODS: A mathematical model consisting of a system of partial differential equations that represent the reactive transport of cells and cytokines in the fracture callus is developed in this study. The model is first calibrated by using available experimental data and then implemented to study the effect of TNF-α on the early stage of fracture healing under normal and diabetic conditions. RESULTS: There is a significant elevation of TNF-α level in facture callus during the first 24 h post-fracture in normal condition, and its influence in the concentration of MSCs and cell differentiation becomes significant three days post-fracture (e.g., the absence of TNF-α signaling could reduce the concentration of MSCs more than 20% in cortical callus). In addition, the excessive secretion of TNF-α induced by diabetes could decrease the concentration of MSCs at the initial stage of healing, particularly reduce the concentration of MSCs in cortical callus by around 25%. CONCLUSION: The model predictions suggested that there should be an optimal concentration of TNF-α in fracture callus, which enhances the early stage of healing, and excessive or insufficient secretion of TNF-α might significantly hinder the healing process.

The Urban River Syndrome: Achieving Sustainability Against a Backdrop of Accelerating Change.

Human activities have been affecting rivers and other natural systems for millennia. Anthropogenic changes to rivers over the last few centuries led to the accelerating state of decline of coastal and estuarine regions globally. Urban rivers are parts of larger catchment ecosystems, which in turn form parts of wider nested, interconnected systems. Accurate modelling of urban rivers may not be possible because of the complex multisystem interactions operating concurrently and over different spatial and temporal scales. This paper overviews urban river syndrome, the accelerating deterioration of urban river ecology, and outlines growing conservation challenges of river restoration projects. This paper also reviews the river Thames, which is a typical urban river that suffers from growing anthropogenic effects and thus represents all urban rivers of similar type. A particular emphasis is made on ecosystem adaptation, widespread extinctions and the proliferation of non-native species in the urban Thames. This research emphasizes the need for a holistic systems approach to urban river restoration.

Laser-plasma coupling for enhanced ablation of GaAs with combined femtosecond and nanosecond pulses.

The laser-plasma interactions that occur during the ablation of solid materials by a femtosecond filament superimposed with a lower-intensity nanosecond pulse are investigated. Pulses of 50 fs duration with intensities of ∼1014 W/cm2 centered at 800 nm are combined with 8 ns pulses at 1064 nm with ∼1010 W/cm2 intensity with delays of ±40 ns on crystalline GaAs targets in air. For each delay, the volume of material removed by a single femtosecond-nanosecond dual-pulse is compared to the laser-plasma interactions that are captured with ultrafast shadowgraph imaging of the plasma and shockwave generated by each pulse. Sedov-Taylor analysis of the shockwaves provides insight on the coupling of energy from the second pulse to the plasma. These dynamics are corroborated with radiation-hydrodynamics simulations. The interaction of the secondary pulse with the pre-existent plasma is shown to play a critical role in enhancing the material removal.

Publication output of National Health Service Bariatric centres in England.

Obesity has been identified as an independent risk factor for a wide range of health conditions. Therefore, there is a clear need for high quality Bariatric research in order to improve patient selection, outcomes and safety for patients with obesity. We sought to identify and compare the quantitative and qualitative publication output from Bariatric centres in England. We identified 42 National Health Service (NHS) Trusts and 162 surgeons providing Bariatric services in England. A median of 4 (range 1-7) Bariatric surgeons were identified per centre. Eight NHS Trusts (19%) and 75 surgeons (46.3%) had no Bariatric publications during the study period, while 87 surgeons published a total of 432 Bariatric papers. Only 15 surgeons (9%) had ≥10 publications within the study period. However, these surgeons produced >50% of all Bariatric publications. Departments with more than 4 surgeons produced a significantly higher number of Bariatric publications (median 8.5 vs 2, p = 0.01). There is significant variation in research contribution amongst Bariatric centres in England. Academia should be encouraged and promoted across all bariatric services in order to broaden our understanding on Bariatric outcomes by expanding the service and proportional increase in funding. Given that a number of health conditions can afflict individuals living with obesity, bariatric surgery research becomes all the more important.

Stereotactic body radiation therapy (SBRT) in recurrent, persistent or oligometastatic gynecological cancers.

OBJECTIVE: SBRT is a well-tolerated technique and provides local-regional control in a variety of metastatic and recurrent tumor types. The role of SBRT in extracranial recurrent, persistent, or oligometastatic gynecological tumors is not well-studied. We therefore retrospectively analyzed a sizeable number of patients in this setting. METHODS: We performed a retrospective review of 86 patients with 209 tumors treated at our institution with SBRT for recurrent, persistent, or oligometastatic extracranial gynecological tumors. The median follow-up was 20 months (range 1-91). The median SBRT dose was 24 Gy (range 10-50) delivered in a median of 4 fractions (range 1-6). The Kaplan-Meier curves and log rank tests were used to assess local control (LC) and overall survival (OS). Cox proportional hazards model was used to evaluate for covariates associated with LC and OS. RESULTS: The 1- and 3-year LC were 80% and 68% respectively. The 1- and 3-year OS were 70% and 39%. 32% of the lesions demonstrated complete response, 23% partial response and 20% stable disease. SBRT achieved better local control in smaller tumors. Toxicity was typically mild with grade 1 gastrointestinal toxicity and fatigue being the most common. Only 4.3% of treatments resulted in grade 2 or greater toxicity. There was only one case of grade 3 and no grade 4 or 5 toxicities. CONCLUSIONS: SBRT offers a high rate of local control with low incidence of toxicity, mainly grade 1 GI toxicity and fatigue, and provides effective salvage therapy for oligometastatic extracranial pelvic and extra-pelvic gynecological tumors.

Filament conductivity enhancement through nonlinear beam interaction.

Laser filament applications relying on filament plasma conductivity are limited by their low electron densities and corresponding short lifetimes. Filament plasma formation, an intensity-dependent process, is limited by the clamping of the filament core intensity. Consequently, increasing initial beam energy results in the breakup of the beam into multiple filaments rather than the enhancement of the electron density and conductivity of an individual filament. However, we demonstrate here the augmentation of the filament plasma density up to three times the typical value through the energy exchange between two co-propagating femtosecond beams with total powers between 1.7 and 2.2 Pfil.

Clostridium histolyticum (AA4500) for the Treatment of Adhesive Capsulitis of the Shoulder: A Randomised Double-Blind, Placebo-Controlled Study for the Safety and Efficacy of Collagenase - Single Site Report.

BACKGROUND/HYPOTHESIS: Adhesive capsulitis of the shoulder results in pain and restricted movement of the glenohumeral joint. Hypothesis: There would be a difference in active range of movement in the affected shoulder of patients with adhesive capsulitis after receiving a series of injections of collagenase Clostridium histolyticum (CCH) compared to placebo. METHODS: This study reports the results from a single site that was part of a 321-participant, multicenter, double-blind, prospective parallel-group, randomized controlled clinical trial. Inclusion criteria: over 18 years of age, unilateral idiopathic adhesive capsulitis for >3 months, but <12 months. Exclusion criteria: recent physical therapy, injections, subacromial impingement, calcific tendonitis or glenohumeral joint arthritis in the affected shoulder. Subjects were randomized 3:1 to receive CCH 0.58 mg or placebo under ultrasound guidance. Injections were on days 1, 22, and 43. The primary outcome measure was a functional assessment of active range of movement. RESULTS: Overall, 37 patients were screened, 26 subjects were excluded, and 11 subjects were randomly assigned to the treatment group (n=9) or the control group (n=2). Both control and treatment groups showed improvement in ROM between baseline and day 95. In the treatment group, AROM improved from the baseline of 272.89° (SD 86.25) to 462.11° (SD 96.89) and the control group from 246.00° (SD 5.66) to 451.50° (SD 50.20) at day 95 with no statistical difference between groups p=0.78. Site data were in line with the whole study findings. Treatment-related adverse events at the injection site, including haematoma (bruising) and localised pain and swelling, were common. CONCLUSION: Although the participants showed improvement in function, statistical significance was neither reached in the site nor the overall study cohort. Given the adverse events and the potential risks of the procedure, we would not recommend this drug for the treatment of adhesive capsulitis of the shoulder. LEVEL OF EVIDENCE: 2, cohort from one site of RCT.