Utility of Culturing Marginal Bone in Patients Undergoing Lower Limb Amputation for Infection.

Guidelines suggest culturing clinically uninfected bone at the margin after surgical resection for osteomyelitis, but little published evidence supports this procedure. To investigate whether culturing marginal bone after completing resection of infected bone affected antibiotic use or further surgical intervention, we collected data on sequential patients undergoing amputation for a foot infection at our tertiary care hospital between January 2014 and May 2015. We recorded patient age, sex, presence of diabetes mellitus, level of amputation, whether marginal bone was sent for culture, microbiology of any marginal bone specimens, type and duration of antibiotic therapy, and any further surgical resection. Among 132 patients, the mean age was 71.9 years, 103 (78.0%) were male, and 79 (59.8%) had diabetes. Treating surgeons sent marginal bone in 58 (43.9%) of these patients, 50 (86.2%) of which were culture positive. Patients with a positive bone culture were significantly more likely to undergo further surgical intervention (20.0% vs 6.1%, p = .047). For patients with diabetes, compared with those without, surgeons did not send marginal bone for culture more often (46% vs 42%, p = .72), nor did they undertake further surgical interventions more frequently (13.4% vs 10.1%, p = .89). Our results suggest that the clinicians used the marginal bone culture findings to make clinical decisions but do not clarify if there is a benefit to performing this procedure. Although patients whose proximal bone specimens were culture positive were more likely to undergo a surgical intervention, the reasons for, and benefit of, this additional surgery were unclear.

Induction prednisone dosing for childhood nephrotic syndrome: how low should we go?

BACKGROUND: Historically, children with nephrotic syndrome (NS) across British Columbia (BC), Canada have been cared for without formal standardization of induction prednisone dosing. We hypothesized that local historical practice variation in induction dosing was wide and that children treated with lower doses had worse relapsing outcomes. METHODS: This retrospective cohort study included 92 NS patients from BC Children's Hospital (1990-2010). We excluded secondary causes of NS, age < 1 year at diagnosis, steroid resistance, and incomplete induction due to early relapse. We explored cumulative induction dose and defined dosing quartiles. Relapsing outcomes above and below each quartile threshold were compared including total relapses in 2 years, time to first relapse, and proportions developing frequently relapsing NS (FRNS) or starting a steroid-sparing agent (SSA). RESULTS: Cumulative prednisone was widely distributed with approximated median, 1st, and 3rd quartile doses of 2500, 2000, and 3000 mg/m2 respectively. Doses ≤ 2000 mg/m2 showed significantly higher relapses (4.2 vs 2.7), shorter time to first relapse (61 vs 175 days), and higher SSA use (36 vs 14%) compared to higher doses. Doses ≤ 2500 mg/m2 also showed significantly more relapses (3.9 vs 2.2), quicker first relapse (79 vs 208 days), and higher FRNS (37 vs 17%) and SSA use (28 vs 11%). Relapsing outcomes lacked statistical difference in ≤ 3000 vs > 3000 mg/m2 doses. CONCLUSIONS: Results strongly justify our development of a standardized, province-wide NS clinical pathway to reduce practice variation and minimize under-treatment. The lowest induction prednisone dosing threshold to minimize future relapsing risks is likely between 2000 and 2500 mg/m2. Further prospective studies are warranted.

Indications for kidney biopsy in idiopathic childhood nephrotic syndrome.

BACKGROUND: Most cases of childhood nephrotic syndrome (NS) are due to minimal change disease (MCD), while a minority of children have focal segmental glomerulosclerosis (FSGS) and an unfavorable clinical course, requiring a kidney biopsy to confirm diagnosis. We hypothesized that clinical characteristics at diagnosis and initial response to corticosteroid treatment accurately predict FSGS and can be used to guide consistent practice in the indications for kidney biopsy. METHODS: This was a case control study (1990-2012). Inclusion criteria included age 1-17 years, meeting the diagnostic criteria for NS, and having biopsy-proven FSGS or MCD. Clinical characteristics at diagnosis included age, kidney function [estimated glomerular filtration rate (eGFR)], hypertension, hematuria, nephritis (reduced eGFR, hematuria, hypertension), and response to steroids. RESULTS: From a total of 169 children who underwent kidney biopsy for NS we included 65 children with MCD and 22 with FSGS for analysis. There were no significant between-group differences in age, sex, or eGFR at the time of diagnosis. The FSGS group had a higher proportion of hypertension (40 vs. 15%; p = 0.02), hematuria (80 vs. 47%; p = 0.01), and nephritis (22 vs. 2%; p = 0.004) and was more likely to be steroid resistant after 6 weeks of treatment than the MCD group (67 vs. 19%; p < 0.001). As predictors of FSGS, hematuria had a high sensitivity of 0.80 [95% confidence interval (CI) 0.56-0.93] and low specificity of 0.53 (95% CI 0.39-0.66), nephritis had a low sensitivity of 0.22 (95% CI 0.07-0.48) and high specificity of 0.98 (95% CI 0.88-0.99), and steroid resistance had a low sensitivity of 0.67 (95% CI 0.43-0.85) and high specificity of 0.81 (95% CI 0.68-0.90). The combination of steroid resistance after 6 weeks of therapy and/or nephritis at diagnosis yielded the optimal sensitivity and specificity at 0.80 (95% CI 0.56-0.93) and 0.75 (95% CI 0.60-0.86), respectively, confirmed by the highest receiver operator characteristic area under the curve of 0.77. CONCLUSION: Steroid resistance after 6 weeks of therapy and/or nephritis at initial presentation is an accurate predictor of FSGS in children with NS and will be used as the indication for kidney biopsy in our newly developed clinical pathway. This approach will maximize the yield of diagnostic FSGS biopsies while minimizing the number of unnecessary MCD biopsies.

A simple technique to prevent torsion and other obstructions of autogenous vein conduits.

During a bypass or a transposed fistula, there is a risk of twisting or torsion of the vein within the tunnel, which may not be easily apparent when incomplete. When valvulotomes are used some nonobstructing leaflets or flaps may remain. These mechanical problems may go undetected at the time and may cause hemodynamic changes, act as a nucleus for thrombosis, or obstruction postoperatively. These may result in early graft failure. A simple technique to prevent and treat twisting and other obstructions in autogenous venous conduits is described. Use of this method has helped the authors to avoid acute obstructions in vein bypasses and transposed dialysis access fistulas.

In-Vivo Validation of a Novel Robotic Platform for Endovascular Intervention.

OBJECTIVE: In-vivo validation on animal setting of a pneumatically propelled robot for endovascular intervention, to determine safety and clinical advantage of robotic cannulations compared to manual operation. METHODS: Robotic assistance and image-guided intervention are increasingly used for improving endovascular procedures with enhanced navigation dexterity and accuracy. However, most platforms developed in the past decade still present inherent limitations in terms of altered clinical workflow, counterintuitive human-robot interaction, and a lack of versatility. We have created a versatile, highly integrated platform for robot-assisted endovascular intervention aimed at addressing such limitations, and here we demonstrate its clinical usability through in-vivo animal trials. A detailed in-vivo study on four porcine models conducted with our robotic platform is reported, involving cannulation and balloon angioplasty of five target arteries. RESULTS: The trials showed a 100% success rate, and post-mortem histopathological assessment demonstrated a reduction in the incidence and severity of vessel trauma with robotic navigation versus manual manipulation. CONCLUSION: In-vivo experiments demonstrated that the applicability of our robotic system within the context of this study was well tolerated, with good feasibility, and low risk profile. Comparable results were observed with robotics and manual cannulation, with clinical outcome potentially in favor of robotics. SIGNIFICANCE: This study showed that the proposed robotic platform can potentially improve the execution of endovascular procedures, paving the way for clinical translation.

A small-molecule screen in C. elegans yields a new calcium channel antagonist.

Small-molecule inhibitors of protein function are powerful tools for biological analysis and can lead to the development of new drugs. However, a major bottleneck in generating useful small-molecule tools is target identification. Here we show that Caenorhabditis elegans can provide a platform for both the discovery of new bioactive compounds and target identification. We screened 14,100 small molecules for bioactivity in wild-type worms and identified 308 compounds that induce a variety of phenotypes. One compound that we named nemadipine-A induces marked defects in morphology and egg-laying. Nemadipine-A resembles a class of widely prescribed anti-hypertension drugs called the 1,4-dihydropyridines (DHPs) that antagonize the alpha1-subunit of L-type calcium channels. Through a genetic suppressor screen, we identified egl-19 as the sole candidate target of nemadipine-A, a conclusion that is supported by several additional lines of evidence. egl-19 encodes the only L-type calcium channel alpha1-subunit in the C. elegans genome. We show that nemadipine-A can also antagonize vertebrate L-type calcium channels, demonstrating that worms and vertebrates share the orthologous protein target. Conversely, FDA-approved DHPs fail to elicit robust phenotypes, making nemadipine-A a unique tool to screen for genetic interactions with this important class of drugs. Finally, we demonstrate the utility of nemadipine-A by using it to reveal redundancy among three calcium channels in the egg-laying circuit. Our study demonstrates that C. elegans enables rapid identification of new small-molecule tools and their targets.

A genetic screen for dihydropyridine (DHP)-resistant worms reveals new residues required for DHP-blockage of mammalian calcium channels.

Dihydropyridines (DHPs) are L-type calcium channel (Ca(v)1) blockers prescribed to treat several diseases including hypertension. Ca(v)1 channels normally exist in three states: a resting closed state, an open state that is triggered by membrane depolarization, followed by a non-conducting inactivated state that is triggered by the influx of calcium ions, and a rapid change in voltage. DHP binding is thought to alter the conformation of the channel, possibly by engaging a mechanism similar to voltage dependent inactivation, and locking a calcium ion in the pore, thereby blocking channel conductance. As a Ca(v)1 channel crystal structure is lacking, the current model of DHP action has largely been achieved by investigating the role of candidate Ca(v)1 residues in mediating DHP-sensitivity. To better understand DHP-block and identify additional Ca(v)1 residues important for DHP-sensitivity, we screened 440,000 randomly mutated Caenorhabditis elegans genomes for worms resistant to DHP-induced growth defects. We identified 30 missense mutations in the worm Ca(v)1 pore-forming (alpha(1)) subunit, including eleven in conserved residues known to be necessary for DHP-binding. The remaining polymorphisms are in eight conserved residues not previously associated with DHP-sensitivity. Intriguingly, all of the worm mutants that we analyzed phenotypically exhibited increased channel activity. We also created orthologous mutations in the rat alpha(1C) subunit and examined the DHP-block of current through the mutant channels in culture. Six of the seven mutant channels examined either decreased the DHP-sensitivity of the channel and/or exhibited significant residual current at DHP concentrations sufficient to block wild-type channels. Our results further support the idea that DHP-block is intimately associated with voltage dependent inactivation and underscores the utility of C. elegans as a screening tool to identify residues important for DHP interaction with mammalian Ca(v)1 channels.

An MR-Safe Endovascular Robotic Platform: Design, Control, and Ex-Vivo Evaluation.

OBJECTIVE: Cardiovascular diseases are the most common cause of global death. Endovascular interventions, in combination with advanced imaging technologies, are promising approaches for minimally invasive diagnosis and therapy. More recently, teleoperated robotic platforms target improved manipulation accuracy, stabilisation of instruments in the vasculature, and reduction of patient recovery times. However, benefits of recent platforms are undermined by a lack of haptics and residual patient exposure to ionising radiation. The purpose of this research was to design, implement, and evaluate a novel endovascular robotic platform, which accommodates emerging non-ionising magnetic resonance imaging (MRI). METHODS: We proposed a pneumatically actuated MR-safe teleoperation platform to manipulate endovascular instrumentation remotely and to provide operators with haptic feedback for endovascular tasks. The platform task performance was evaluated in an ex vivo cannulation study with clinical experts ( N = 7) under fluoroscopic guidance and haptic assistance on abdominal and thoracic phantoms. RESULTS: The study demonstrated that the robotic dexterity involving pneumatic actuation concepts enabled successful remote cannulation of different vascular anatomies with success rates of 90%-100%. Compared to manual cannulation, slightly lower interaction forces between instrumentation and phantoms were measured for specific tasks. The maximum robotic interaction forces did not exceed 3N. CONCLUSION: This research demonstrates a promising versatile robotic technology for remote manipulation of endovascular instrumentation in MR environments. SIGNIFICANCE: The results pave the way for clinical translation with device deployment to endovascular interventions using non-ionising real-time 3D MR guidance.

The influence of crowds on consumer health decisions: an online prospective study.

This paper presents an online prospective study investigating whether the strength of social feedback, i.e. the proportion of persons who concur or do not concur with one's own answer to a question, influences the way one answers health-related questions. Two hundred and twenty-seven undergraduate students were recruited to use an online search engine to answer six health-related questions. Subjects recorded their pre- and post-search answers to each question and their level of confidence in these answers. After answering each question post-search, subjects were presented with a summary of post-search answers provided by previous subjects and were asked to answer the question again. There was a statistically significant relationship between the absolute number of others with a different answer (the crowd's opinion volume) and the likelihood of an individual changing an answer (P<.0001). Subjects' likelihood of changing answer increased as the percentage of others with a different answer (the crowd's opinion density) increased (P=0.047). Overall, 98.3% of subjects did not change their answer when it concurred with the majority (i.e. >50%) of subjects. When subjects had a post-search answer that did not concur with the majority, they were 24% more likely to change answer than those with answers that concurred (P<.0001). This study provides empirical evidence that strength of social feedback influences the way healthcare consumers answer health-related questions.

Medium-term outcomes of fenestrated endovascular repair of juxtarenal abdominal aortic aneurysms.

BACKGROUND: Abdominal aortic aneurysms pose a substantial clinical burden, and a significant proportion are not anatomically suitable for open repair or standard endovascular aneurysm repair (EVAR), instead requiring fenestrated EVAR (fEVAR). We sought to compare clinical outcomes and trends over time in patients undergoing fEVAR in Australia. METHODS: We conducted a retrospective analysis of all patients undergoing fEVAR at a tertiary referral centre between 2010 and 2015, including outcomes and complications, both as inpatients and after discharge. RESULTS: Thirty-nine patients underwent fEVAR during the study period, with mean age of 75 years and mean aneurysm size of 61 mm. One hundred and thirty-four target vessels were treated and inhospital mortality was 5% (two patients). There were nine inhospital, eight Type II and one Type III endoleaks. Ten patients suffered acute kidney injury, one of whom required dialysis. Mean follow-up was 14.5 months (range: 0-46.7). Target vessel patency was 99.2% at follow-up. There were six Type II endoleaks at follow-up, and two patients died during the follow-up period (of non-aneurysm-related causes). CONCLUSION: fEVAR is an effective treatment with low morbidity and mortality, and we have demonstrated excellent survival and target vessel patency at a mean follow-up of 14 months. Endoleak rates were low, despite the high complexity of the aneurysms treated.

YouTube as a source of patient information for varicose vein treatment options.

OBJECTIVE: The purpose of this study was to analyze the quality of content and potential sources of bias in videos available on YouTube pertaining to interventional treatment for varicose veins. METHODS: Searches were performed on YouTube to identify videos pertaining to interventional treatment for varicose veins. Videos that met eligibility criteria were analyzed and rated according to predetermined criteria by two independent assessors, with a third independent assessor to resolve any discrepancy. Each video was rated for its informational quality (good, fair, poor) and stance (for, neutral, against, unclear) toward the treatment option discussed. RESULTS: A total of 284 videos were extracted, of which 228 met eligibility criteria and were analyzed. The largest group of videos (47.3%) received a quality rating of fair, meaning that they discussed one or two aspects of a treatment option, such as procedural technique and indications. Among those videos rated poor (25.0%), nearly all videos (98.2%) failed to mention a specific treatment. Most videos (71.1%) were in favor of the treatment discussed without presenting balanced discussion of alternatives. Private companies represented the most frequent source of videos analyzed (73.2%). There was a statistically significant correlation between quality and video source (χ2 = 9.308; df = 2; P = .010), with videos from private companies generally receiving poorer quality ratings than other videos. There was no association between quality and viewing frequency of videos (P = .379). CONCLUSIONS: On the whole, the videos available on YouTube are neither sufficiently comprehensive nor adequately balanced to be recommended as patient education material regarding interventional treatment options for varicose veins.

Pseudoaneurysm of the thoracic aorta following botulinum toxin injection to the esophagus.

Aortic pseudoaneurysms are uncommon and are usually secondary to penetrating trauma. We describe the presentation and management of an elderly woman who suffered a pseudoaneurysm of the descending thoracic aorta several days after receiving botulinum toxin injection to the esophagus. Urgent thoracic endovascular aortic repair was performed, and long-term antibiotic therapy was commenced. Despite a slow initial clinical recovery, she returned to an independent lifestyle, with radiographic resolution of the pseudoaneurysm seen at follow-up. This case illustrates that endovascular aortic repair is a suitable and safe treatment option for this unusual presentation.

Differential sensitivities of CaV1.2 IIS5-S6 mutants to 1,4-dihydropyridine analogs.

1,4-Dihydropyridines (DHPs), L-type calcium channel (Ca(V)1) blockers, are known to interact with Ca(V)1.2 subunits through their binding site located at IIIS5-S6 and IVS6 regions. We recently identified two domain II residues (S666 and A752) critical for nifedipine blockade (Kwok et al., 2008). In this study, we examined the blockade effects of two DHP analogues, nemadipine and nicardipine, on wildtype, M1161A (in IIIS6), S666V (in IIS5) and A752T (in IIS6) mutants of the rat alpha(1C) subunit transiently expressed with beta(2a) and alpha(2)delta in cultured tsA201 cells. We found that the IC(50) ratio of the mutants to the wildtype channel was similar in S666V and M1161A mutants for both drugs, but in A752T it was lower for nemadipine than nicardipine (P<0.05). At saturating drug concentrations, not all the current was completely blocked in the mutants. The residual current recorded in 100 microM nemadipine was approximately 10% of the total current for the A752T channel, which was significantly higher than that in 100 microM nicardipine (approximately 2%). In wildtype, S666V and M1161A, there was no significant difference in residual current between nemadipine and nicardipine, although it was greater in S666V (approximately 15%) and M1161A approximately 30%) as compared to the wildtype channel (<5%). Taken together, our findings suggest that the domain II residues alter the DHP effect in a structure-specific manner and may be involved in a pathway downstream of DHP binding.

High-throughput screening of small molecules for bioactivity and target identification in Caenorhabditis elegans.

This protocol describes a procedure for screening small molecules for bioactivity and a genetic approach to target identification using the nematode Caenorhabditis elegans as a model system. Libraries of small molecules are screened in 24-well plates that contain a solid agar substrate. On top of the agar mixture, one small-molecule species is deposited into each well, along with worm food (E. coli), and two third-stage or fourth-stage larval worms using a COPAS (Complex Object Parametric Analyzer and Sorter) Biosort. Three to five days later the plates are screened for phenotype. Images of the wells are acquired and archived using a HiDI 2100 automated imaging system (Elegenics). Up to 2,400 chemicals can be screened per week. To identify the predicted protein target of a bioactive molecule, wild-type worms are mutagenized using ethylmethanesulfonate (EMS). Progeny are screened for individuals resistant to the molecules effects. The candidate mutant target that confers resistance is then identified. Target identification might take months.

Regulation of chromosome stability by the histone H2A variant Htz1, the Swr1 chromatin remodeling complex, and the histone acetyltransferase NuA4.

NuA4, the only essential histone acetyltransferase complex in Saccharomyces cerevisiae, acetylates the N-terminal tails of histones H4 and H2A. Affinity purification of NuA4 revealed the presence of three previously undescribed subunits, Vid21/Eaf1/Ydr359c, Swc4/Eaf2/Ygr002c, and Eaf7/Ynl136w. Experimental analyses revealed at least two functionally distinct sets of polypeptides in NuA4: (i) Vid21 and Yng2, and (ii) Eaf5 and Eaf7. Vid21 and Yng2 are required for bulk histone H4 acetylation and are functionally linked to the histone H2A variant Htz1 and the Swr1 ATPase complex (SWR-C) that assembles Htz1 into chromatin, whereas Eaf5 and Eaf7 have a different, as yet undefined, role. Mutations in Htz1, the SWR-C, and NuA4 cause defects in chromosome segregation that are consistent with genetic interactions we have observed between the genes encoding these proteins and genes encoding kinetochore components. Because SWR-C-dependent recruitment of Htz1 occurs in both transcribed and centromeric regions, a NuA4/SWR-C/Htz1 pathway may regulate both transcription and centromere function in S. cerevisiae.