Search

The reaction CH3C(O)O2+HO2 → CH3C(O)OOH+O2 (Reaction R5a), CH3C(O)OH + O3 (Reaction R5b), CH3 + CO2 + OH + O2 (Reaction R5c) was studied in a series of experiments conducted at 1000 mbar and (293±2) K in the HIRAC simulation chamber. For 5 the first time, products, (CH3C(O)OOH, CH3C(O)OH, O3 and OH) from all three branching pathways of the reaction have been detected directly and simultaneously. Measurements of radical precursors (CH3OH, CH3CHO), HO2 and some secondary products HCHO and HCOOH further constrained the system. Fitting a comprehensive model to the experimental data, obtained over a range of conditions, determined the 10 branching ratios α(R5a) = 0.37±0.10, α(R5b) = 0.12±0.04 and α(R5c) = 0.51±0.12 (errors at 2σ level). Improved measurement/model agreement was achieved using k(R5) = (2.4±0.4)×10-11 cm³ molecule-1 s-1, which is within the large uncertainty of the current IUPAC and JPL recommended rate coefficients for the title reaction. The rate coefficient and branching ratios are in good agreement with a recent study performed by Groß 15 et al. (2014b); taken together, these two studies show that the rate of OH regeneration through Reaction (R5) is more rapid than previously thought. GEOS-Chem has been used to assess the implications of the revised rate coefficients and branching ratios; the modelling shows an enhancement of up to 5% in OH concentrations in tropical rainforest areas and increases of up to 10% at altitudes of 6-8 km above the equator, 20 compared to calculations based on the IUPAC recommended rate coefficient and yield. The enhanced rate of acetylperoxy consumption significantly reduces PAN in remote regions (up to 30 %) with commensurate reductions in background NOx. [ABSTRACT FROM AUTHOR]

The calibration of field instruments used to measure concentrations of OH and HO2 worldwide has traditionally relied on a single method utilising the photolysis of water vapour in air in a flow tube at atmospheric pressure. Here the calibration of two FAGE (fluorescence assay by gaseous expansion) apparatuses designed for HOx (OH and HO2) measurements have been investigated as a function of external pressure using two different laser systems. The conventional method of generating known concentrations of HOx from H2O vapour photolysis in a turbulent flow tube impinging just outside the FAGE sample inlet has been used to study instrument sensitivity as a function of internal fluorescence cell pressure (1.8-3.8 mbar). An increase in the calibration constants COH and CHO2 with pressure was observed, and an empirical linear regression of the data was used to describe the trends, with ΔCOH =(17±11)% and ΔCHO2 =(31.6±4.4)% increase per millibar air (uncertainties quoted to 2σ). Presented here are the first direct measurements of the FAGE calibration constants as a function of external pressure (440–1000 mbar) in a controlled environment using the University of Leeds HIRAC chamber (Highly Instrumented Reactor for Atmospheric Chemistry). Two methods were used: the temporal decay of hydrocarbons for calibration of OH, and the kinetics of the second-order recombination of HO2 for HO2 calibrations. Over comparable conditions for the FAGE cell, the two alternative methods are in good agreement with the conventional method, with the average ratio of calibration factors (conventional : alternative) across the entire pressure range, COH(conv)/COH(alt) =1.19±0.26 and CHO2(conv)/CHO2(alt) =0.96±0.18 (2σ). These alternative calibration methods currently have comparable systematic uncertainties to the conventional method: ~28% and ~41% for the alternative OH and HO2 calibration methods respectively compared to 35% for the H2O vapour photolysis method; ways in which these can be reduced in the future are discussed. The good agreement between the very different methods of calibration leads to increased confidence in HOx field measurements and particularly in aircraft-based HOx measurements, where there are substantial variations in external pressure, and assumptions are made regarding loss rates on inlets as a function of pressure. [ABSTRACT FROM AUTHOR]

The calibration of field instruments used to measure concentrations of OH and HO2 worldwide have traditionally relied on a single method utilising the photolysis of water vapour in air in a flow tube at atmospheric pressure. Here the calibration of two FAGE (Fluorescence Assay by Gaseous Expansion) apparatuses designed for HOx (OH and HO2) measurements have been investigated as a function of external pressure and temperature, using two different laser systems. The conventional method of generating known concentrations of HOx from H2O vapour photolysis in a turbulent flowtube impinging just outside the FAGE sample inlet has been used to study instrument sensitivity as a function of internal fluorescence cell pressure (1.8-3.8mbar). An increase in the calibration constants COH and CHO2 with pressure was observed and an empirical linear regression of the data was used to describe the trends, with ΔCOH = (17±11)% and ΔCHO2 = (31.6±4.4)% increase per mbar air (uncertainties quoted to 2. Presented here are the first direct measurements of the FAGE calibration constants as a function of external pressure (440-1000mbar) in a controlled environment using the University of Leeds HIRAC chamber (Highly Instrumented Reactor for Atmospheric Chemistry). Two methods were used: the temporal decay of hydrocarbons for calibration of OH, and the kinetics of the second-order recombination of HO2 for HO2 calibrations. Over comparable conditions for the FAGE cell, the two alternative methods are in good agreement with the conventional method, with the average ratio of calibration factors (conventional : alternative) across the entire pressure range COH(conv)/COH(alt) = 1.19±0.26 and CHO2(conv) /CHO2(alt) = 0.96±0.18 (2). These alternative calibration methods currently have comparable systematic uncertainties than the conventional method: ~28% and ~41% for the alternative OH and HO2 calibration methods respectively compared to 35% for the H2O vapour photolysis method; ways in which these can be reduced in the future are discussed. The good agreement between the very different methods of calibration leads to increased confidence in HOx field measurements and particularly in aircraft based HOx measurements, where there are substantial variations in external pressure, and assumptions are made regarding loss rates on inlets as a function of pressure. [ABSTRACT FROM AUTHOR]

Objectives: Traditionally, patients have to wait until assessed by a physician for opioid analgesia to be administered, which contributes to delays to analgesia. Western Hospital developed a protocol enabling nurses to initiate opioid analgesia prior to medical assessment for selected conditions. The aim of this study was to determine the impact of this protocol on time to first opioid dose in patients presenting to the emergency department (ED) with renal or biliary colic.Methods: This was an explicit medical record review of all adult patients with an ED discharge diagnosis of renal or biliary colic presenting to a metropolitan teaching hospital ED. Patients were identified via the ED data management system. Data collected included demographics, condition, triage category, time of presentation, whether analgesia was nurse-initiated or not, and interval from arrival to first opioid analgesic dose. The narcotic drug register for the relevant period was also searched to cross-check whether opiates were doctor- or nurse-initiated.Results: There were 58 presentations in the nurse-initiated opioid analgesia group and 99 in the non-nurse-initiated analgesia group. Groups were reasonably well matched for gender, triage category and time of presentation, but there was a higher proportion of biliary colic in the non-nurse-initiated analgesia group. Median time to first analgesic dose was 31 minutes in the nurse-initiated group and 57 minutes in the non-nurse-initiated analgesia group (effect size, 26 minutes; 95% confidence interval 16-36 min; p < 0.0001]. There were no major adverse events in either group.Conclusion: A nurse-initiated opioid analgesia protocol reduces delays to opioid analgesia for patients with renal and biliary colic. [ABSTRACT FROM AUTHOR]

End-stage kidney disease is associated with reduced exercise capacity, muscle atrophy, and impaired muscle function. While these may be improved with exercise, single modalities of exercise do not traditionally elicit improvements across all required physiological domains. Blood flow-restricted exercise may improve all of these physiological domains with low intensities traditionally considered insufficient for these adaptions. Investigation of this technique appeals, but is yet to be evaluated, in patients undergoing dialysis. With the use of a progressive crossover design, 10 satellite patients undergoing hemodialysis underwent three exercise conditions over 2 wk: two bouts (10 min) of unrestricted cycling during two consecutive hemodialysis sessions ( condition 1 ), two bouts of cycling with blood flow restriction while off hemodialysis on 2 separate days ( condition 2 ), and two bouts of cycling with blood flow restriction during two hemodialysis sessions ( condition 3 ). Outcomes included hemodynamic responses (heart rate and blood pressure) throughout all sessions, participant-perceived exertion and discomfort on a Borg scale, and evaluation of ultrafiltration rates and dialysis adequacy (Kt/V) obtained post hoc. Hemodynamic responses were consistent regardless of condition. Significant increases in heart rate, systolic blood pressure, and mean arterial blood pressure ( P < 0.05) were observed postexercise followed by a reduction in blood pressures during the 60-min recovery (12, 5, and 11 mmHg for systolic, diastolic, and mean arterial pressures, respectively). Blood pressures returned to predialysis ranges following the recovery period. Blood flow restriction did not affect ultrafiltration achieved or Kt/V. Hemodynamic safety and tolerability of blood flow restriction during aerobic exercise on hemodialysis is comparable to standard aerobic exercise.

Background: Many renal programs have targets to increase home dialysis prevalence. Data from a large Canadian home dialysis program were analyzed to determine if home dialysis prevalence accurately reflects program activity and whether prevalence-based assessments adequately reflect the work required for program growth., Methods: Data from home dialysis programs in British Columbia, Canada, were analyzed from 2005 to 2015. Prevalence data were compared to dialysis activity data including intakes and exits to describe program turnover. Using current attrition rates, recruitment rates needed to increase home dialysis prevalence proportions were identified., Results: We analyzed 7,746 patient-years of peritoneal dialysis (PD) and 1,362 patient-years of home hemodialysis (HHD). The proportion of patients on home dialysis increased by 3.34% over the ten years examined, while the number of prevalent home dialysis patients increased 2.65% per year and the number of patients receiving home dialysis at any time in the year increased 4.04% per year. For every 1 patient net home dialysis growth, 13.6 new patients were recruited. Patient turnover included higher rates of transplantation in home dialysis than facility-based HD. Overall, the proportion dialyzing at home increased from 29.3 to 32.6%., Conclusions: There is high patient turnover in home dialysis such that program prevalence is an incomplete marker of total program activity. This turnover includes high rates of transplantation, which is a desirable interaction that affects home dialysis prevalence. The shortcomings of this commonly used metric are important for renal programs to consider, and better understanding of the activities that support home dialysis and the complex trajectories that home dialysis patients follow is needed., (Copyright © 2018 International Society for Peritoneal Dialysis.)

Background: Exercise during haemodialysis improves strength and physical function. However, both patients and clinicians are time poor, and current exercise recommendations add an excessive time burden making exercise a rare addition to standard care. Hypothetically, blood flow restriction exercise performed during haemodialysis can provide greater value for time spent exercising, reducing this time burden while producing similar or greater outcomes. This study will explore the efficacy of blood flow restriction exercise for enhancing strength and physical function among haemodialysis patients., Methods: This is a randomised controlled trial design. A total of 75 participants will be recruited from haemodialysis clinics. Participants will be allocated to a blood flow restriction cycling group, traditional cycling group or usual care control group. Both exercising groups will complete 3 months of cycling exercise, performed intradialytically, three times per week. The blood flow restriction cycling group will complete two 10-min cycling bouts separated by a 20-min rest at a subjective effort of 15 on a 6 to 20 rating scale. This will be done with pressurised cuffs fitted proximally on the active limbs during exercise at 50% of a pre-determined limb occlusion pressure. The traditional cycling group will perform a continuous 20-min bout of exercise at a subjective effort of 12 on the same subjective effort scale. These workloads and volumes are equivalent and allow for comparison of a common blood flow restriction aerobic exercise prescription and a traditional aerobic exercise prescription. The primary outcome measures are lower limb strength, assessed by a three repetition maximum leg extension test, as well as objective measures of physical function: six-minute walk test, 30-s sit to stand, and timed up and go. Secondary outcome measures include thigh muscle cross sectional area, body composition, routine pathology, quality of life, and physical activity engagement., Discussion: This study will determine the efficacy of blood flow restriction exercise among dialysis patients for improving key physiological outcomes that impact independence and quality of life, with reduced burden on patients. This may have broader implications for other clinical populations with similarly declining muscle health and physical function, and those contraindicated to higher intensities of exercise., Trial Registration: Australian and New Zealand Clinical Trial Register: ACTRN12616000121460.

♦ BACKGROUND: Peritoneal dialysis (PD) is challenging for patients with functional limitations, and assisted PD can support these patients, but previous reports of assisted PD have not examined the role of temporary assisted PD and had difficulty identifying adequate comparator cohorts. ♦ METHODS: Peritoneal Dialysis Assist (PDA), a 12-month pilot of long-term and temporary assisted PD was completed in multiple PD centers in British Columbia, Canada. Continuous cycler PD (CCPD) patients were identified for PDA by standardized criteria, and service could be long-term or temporary/respite. The PDA program provided daily assistance with cycler dismantle and setup, but patients remained responsible for cycler connections and treatment decisions. Outcomes were compared against both the general CCPD population and patients who met PDA criteria but were not enrolled (PDA-eligible). ♦ RESULTS: Fifty-three PDA patients had an 88% 1-year death- and transplant-censored technique survival that was similar to the general CCPD cohort (84%) and PDA-eligible cohort (86%). The PDA cohort had lower peritonitis rates (0.18 episodes/patient-year vs 0.22 and 0.36, respectively), but higher hospitalization (55% vs 34% and 35%, respectively). Long-term PDA cost approximately CDN$15,000/year in addition to existing dialysis costs. A total of 8/11 respite PDA patients (73%) returned to self-care PD after a median PDA use of 29 days, which costs $1,250/patient. ♦ CONCLUSIONS: Peritoneal Dialysis Assist provides effective support to functionally-limited CCPD patients and yields acceptable clinical outcomes. The program costs less than transfer to HD or long-term care, which represents cost minimization for failing self-care PD patients. Respite PDA provides effective temporary support; most patients returned to self-care PD and service was cost-effective compared with alternatives of hospitalization or transfer to HD., (Copyright © 2017 International Society for Peritoneal Dialysis.)

A patient with known steroid-dependent rheumatoid arthritis (RA) developed an acute symmetrical polyarthropathy of small and medium-sized joints associated with markedly elevated inflammatory markers suggestive of RA flare, on day 4 after deceased-donor renal transplantation. The patient received standard induction immunosuppression with methylprednisolone and basiliximab, and had commenced prednisolone, tacrolimus and mycophenolate mofetil. Serological investigations and joint aspirate to exclude infective causes and crystal arthropathy were unremarkable. High-dose prednisolone (50 mg daily) resulted in partial but unsustained symptomatic improvement. On suspicion of a medication-related adverse event, tacrolimus and mycophenolate mofetil were changed to cyclosporine A and azathioprine on day 16. This was followed by rapid improvement in symptoms and normalization of inflammatory markers. Unexpected sequelae in the early post-transplantation period create diagnostic and management challenges. Medication-related adverse events are not uncommon, and we speculate in this case on the potential for medication-induced immune system dysregulation stimulating disease activity in a chronic autoimmune condition after introduction of new immunosuppressants., (© 2014 Asian Pacific Society of Nephrology.)

Calciprotein particles (CPP) are a novel marker of mineral stress. High levels of CPP are found in patients with calciphylaxis, a condition associated with marked vascular calcification and a poor prognosis. We report substantial reductions in CPP levels in a dialysis patient having combined haemodialysis (HD) and plasma exchange (PEx) prior to an ABO-incompatible kidney transplant. We also report the effects of the same treatments combined with sodium thiosulphate (STS) in a patient newly diagnosed with calciphylaxis. Combining HD with intra-dialytic STS and PEx we achieved a significant reduction in CCP with the least rebound between treatment sessions. After 6 weeks of treatment, the CPP reduction was paralleled by clinical improvement. Measurement of CPP may be an attractive marker for monitoring the effectiveness of calciphylaxis therapy., (© 2013 Asian Pacific Society of Nephrology.)

Aim: Fetuin-A (Fet-A) is an important regulator of extracellular matrix mineralization. Fet-A plays a critical role in the formation and stabilization of high molecular weight colloidal protein-mineral complexes known as calciprotein particles (CPP). The aim of this study was to examine the effects of inflammation, renal function and dialysis modality on serum Fet-A and CPP., Methods: This is an observational study of patients with chronic kidney disease (CKD) and those with chronic inflammatory disease (CID) but normal renal function. Serum CPP were quantified indirectly by analysing the apparent reduction in serum Fet-A concentration (reduction ratio, RR) after high-speed centrifugation., Results: Serum total Fet-A concentrations are reduced in renal disease and in patients with CID. CPP were not detectable in the serum of normal individuals. CPP represent an increasing percentage of total circulating Fet-A concentrations in patients with CID (RR, 13.3 ± 8.5%), as well as in patients with pre-dialysis CKD (12.4 ± 7.3%) and those undergoing peritoneal dialysis (RR, 22.8 ± 6.0%) or haemodialysis (RR, 38.1 ± 12.8%). The highest Fet-A RR were found in patients with calcific uraemic arteriolopathy (CUA) on haemodialysis (73.9 ± 15.6%). Serum total Fet-A concentrations and Fet-A reduction ratios decreased during a single haemodialysis session, by 24% (P < 0.001) and 34% (P < 0.001), respectively., Conclusion: Inflammation appears to be associated with mineral stress even in the absence of renal dysfunction. Patients with CUA on haemodialysis have very high serum Fet-A reduction ratios, suggesting that this measurement may have a prognostic/diagnostic role in this condition., (© 2012 The Authors. Nephrology © 2012 Asian Pacific Society of Nephrology.)