Association between troponin level and medium-term mortality in 20 000 hospital patients

INTRODUCTION

Cardiac troponin (cTn) concentrations above the manufacturer recommended upper limit of normal (ULN) are frequently seen in hospital patients without a clinical presentation consistent with type 1 myocardial infarction, and the significance of this is uncertain. The aim of this study was to assess the relationship between medium-term mortality and cTn concentration in a large consecutive hospital population, regardless of whether there was a clinical indication for performing the test.

METHOD

This prospective observational study included 20 000 consecutive in-hospital and outpatient patients who had a blood test for any reason at a large teaching hospital, and in whom a hs-cTnI assay was measured, regardless of the original clinical indication. Mortality was obtained via NHS Digital.

RESULTS

A total of 20 000 patients were included in the analysis and 18 282 of these (91.4%) did not have a clinical indication for cardiac troponin I (cTnI) testing. Overall, 2825 (14.1%) patients died at a median of 809 days. The mortality was significantly higher if the cTnI concentration was above the ULN (45.3% vs 12.3% p<0.001 log rank). Multivariable Cox analysis demonstrated that the log10 cTnI concentration was independently associated with mortality (HR 1.76 (95% CI 1.65 to 1.88)). Landmark analysis, excluding deaths within 30 days, showed the relationship between cTnI concentration and mortality persisted.

CONCLUSION

In a large, unselected hospital population, in 91.4% of whom there was no clinical indication for testing, cTnI concentration was independently associated with medium-term cardiovascular and non-cardiovascular mortality in the statistical model tested.

Imputation and missing indicators for handling missing data in the development and deployment of clinical prediction models: A simulation study

Background: In clinical prediction modelling, missing data can occur at any stage of the model pipeline; development, validation or deployment. Multiple imputation is often recommended yet challenging to apply at deployment; for example, the outcome cannot be in the imputation model, as recommended under multiple imputation. Regression imputation uses a fitted model to impute the predicted value of missing predictors from observed data, and could offer a pragmatic alternative at deployment. Moreover, the use of missing indicators has been proposed to handle informative missingness, but it is currently unknown how well this method performs in the context of clinical prediction models. Methods: We simulated data under various missing data mechanisms to compare the predictive performance of clinical prediction models developed using both imputation methods. We consider deployment scenarios where missing data is permitted or prohibited, imputation models that use or omit the outcome, and clinical prediction models that include or omit missing indicators. We assume that the missingness mechanism remains constant across the model pipeline. We also apply the proposed strategies to critical care data. Results: With complete data available at deployment, our findings were in line with existing recommendations; that the outcome should be used to impute development data when using multiple imputation and omitted under regression imputation. When missingness is allowed at deployment, omitting the outcome from the imputation model at the development was preferred. Missing indicators improved model performance in many cases but can be harmful under outcome-dependent missingness. Conclusion: We provide evidence that commonly taught principles of handling missing data via multiple imputation may not apply to clinical prediction models, particularly when data can be missing at deployment. We observed comparable predictive performance under multiple imputation and regression imputation. The performance of the missing data handling method must be evaluated on a study-by-study basis, and the most appropriate strategy for handling missing data at development should consider whether missing data are allowed at deployment. Some guidance is provided.

Clinical Frailty Scale as a predictor of adverse outcomes following aortic valve replacement: a systematic review and meta-analysis

OBJECTIVES

Assessment of frailty prior to aortic valve intervention is recommended in European and North American valvular heart disease guidelines. However, there is a lack of consensus on how it is best measured. The Clinical Frailty Scale (CFS) is a well-validated measure of frailty that is relatively quick to calculate. This meta-analysis sought to examine whether the CFS predicts mortality and morbidity following either transcatheter aortic valve implantation (TAVI) or surgical aortic valve replacement (SAVR).

METHODS

Nine electronic databases were searched systematically for data on clinical outcomes post-TAVI/SAVR, where patients had undergone preoperative frailty assessment using the CFS. The primary endpoint was 12-month mortality. TAVI and SAVR data were assessed and reported separately. For each individual study, the incidence of adverse outcomes was extracted according to a CFS score of 5-9 (ie, frail) versus 1-4 (ie, non-frail), with meta-analysis performed using a random effects model.

RESULTS

Of 2612 records screened, nine were included in the review (five TAVI, three SAVR and one which included both interventions). Among 4923 TAVI patients, meta-analysis showed 12-month mortality rates of 19.1% for the frail cohort versus 9.8% for the non-frail cohort (RR 2.53 (1.63 to 3.95), p<0.001, I2=83%). For the smaller cohort of SAVR patients (n=454), mortality rates were 20.3% versus 3.9% for the frail and non-frail cohorts, respectively (RR 5.08 (2.31 to 11.15), p<0.001, I2=5%).

CONCLUSIONS

Frailty, as determined by the CFS, was associated with an increased mortality risk in the 12 months following either TAVI or SAVR. These data would support its use in the preoperative assessment of elderly patients undergoing aortic valve interventions.

Use of a device-based remote management heart failure care pathway is associated with reduced hospitalization and improved patient outcomes: TriageHF Plus real-world evaluation

Background

Heart failure (HF) is a leading cause of hospital admission. However, prompt identification of worsening HF using implantable device data and proactive intervention may reduce hospitalizations.

The validated TriageHF algorithm in enabled ICD/CRT devices uses sensor data to risk stratify patients for HF hospitalization in the next 30 days. TriageHF Plus is a novel device-based HF care pathway (DHFP) that uses “high” risk status as the trigger for remote intervention (see Figure 1 for pathway overview). Outcomes after DHFP implementation in a clinical setting have not been examined.

Purpose

To evaluate the impact of TriageHF Plus clinical pathway on hospitalisation rates.

Methods

A prospective, multi-center evaluation comparing monthly hospitalization rates for patients enrolled in a DHFP with a concurrent standard of care (SoC) cohort and characterizing staffing resources necessary to implement the DHFP. The DHFP cohort received telephonic assessment and guideline-directed clinical care upon transition to high-risk status. Propensity scores (PS) were applied to DHFP and SoC cohorts to allow unbiased comparison. A negative binomial model was fitted to the monthly number of all-cause hospitalizations with treatment group (DHFP vs. SoC) as a covariate, using PS as weights.

Results

Between 09/11/2019 and 06/24/2021, 758 patients were included in the study (443 DHFP, 315 SoC). Proportion CRT 76%/ 89% and LVEF <50% 78%/ 66% for DHFP/ SoC, respectively.

196 high risk transmissions prompted telephone assessment, with successful contact in 182; of which, 79 (43%) identified an explanatory acute medical issue. A secondary intervention was undertaken in 44/79 (56%). High risk transmissions took on average 19 minutes per clinical assessment (initial telephone triage and 30 day follow up). The rate of hospitalizations was 58% lower in the DHFP group, compared with SoC, after PS adjustment (IRR 0.42, 95% CI: 0.23, 0.76, p=0.004), see Figure 2. Sensitivity analyses showed Covid-19 had little effect on results.

Conclusions

This is the first prospective, real-world evaluation of a device-based HF care pathway to report a reduction in hospitalizations and does so with minimal staffing time. Integrated into existing HF services, device-based remote monitoring of HF patients can improve outcomes.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Medtronic

Long-term cardiovascular risk prediction in the emergency department: a mixed-methods study protocol

INTRODUCTION

Cardiovascular disease (CVD) remains one of the leading causes of preventable death in Europe, therefore any opportunity to intervene and improve care should be maximised. Known CVD risk factors are routinely collected in the emergency department (ED), yet they are often not acted on. If the risk factors have prognostic value and a pathway can be created, then this would provide more holistic care for patients and reduce health system inefficiency.

METHODS AND ANALYSIS

In this mixed-methods study, we will use quantitative methods to investigate the prognostic characteristics of routinely collected data for long-term CVD outcomes, and qualitative methods to investigate how to use and implement this knowledge. The quantitative arm will use a database of approximately 21 000 chest pain patient episodes with a mean follow-up of 7.3 years. We will use Cox regression to evaluate the prognostic characteristics of routinely collected ED data for long-term CVD outcomes. We will also use a series of semi-structured interviews to co-design a prototype care pathway with stakeholders via thematic analysis. To enable the development of prototypes, themes will be structured into a logic model consisting of situation, inputs, outputs and mechanism.

ETHICS AND DISSEMINATION

This work has been approved by Research Ethics Committee (Wales REC7) and the Human Research Authority under reference 19/WA/0312 and 19/WA/0311. It has also been approved by the Confidentiality Advisory Group reference 19/CAG/0209. Dissent recorded in the NHS' opt-out scheme will be applied to the dataset by NHS Digital. This work will be disseminated through peer-review publication, conference presentation and a public dissemination strategy.

TRIAL REGISTRATION NUMBER

ISRCTN41008456.

PROTOCOL VERSION

V.1.0-7 June 2021.

The Association Between Socioeconomic Status, Sex, Race / Ethnicity and In-Hospital Mortality Among Patients Hospitalized for Heart Failure

BACKGROUND

The association between socioeconomic status (SES), sex, race / ethnicity and outcomes during hospitalization for heart failure (HF) has not previously been investigated.

METHODS AND RESULTS

We analyzed HF hospitalizations in the United States National Inpatient Sample between 2015 and 2017. Using a hierarchical, multivariable Poisson regression model to adjust for hospital- and patient-level factors, we assessed the association between SES, sex, and race / ethnicity and all-cause in-hospital mortality. We estimated the direct costs (USD) across SES groups. Among 4,287,478 HF hospitalizations, 40.8% were in high SES, 48.7% in female, and 70.0% in White patients. Relative to these comparators, low SES (homelessness or lowest quartile of median neighborhood income) (relative risk [RR] 1.02, 95% confidence interval [CI] 1.00-1.05) and male sex (RR 1.09, 95% CI 1.07-1.11) were associated with increased risk, whereas Black (RR 0.79, 95% CI 0.76-0.81) and Hispanic (RR 0.90, 95% CI 0.86-0.93) race / ethnicity were associated with a decreased risk of in-hospital mortality (5.1% of all hospitalizations). There were significant interactions between race / ethnicity and both, SES (P < .01) and sex (P = .04), such that racial/ethnic differences in outcome were more pronounced in low SES groups and in male patients. The median direct cost of admission was lower in low vs high SES groups ($9324.60 vs $10,940.40), female vs male patients ($9866.60 vs $10,217.10), and Black vs White patients ($9077.20 vs $10,019.80). The median costs increased with SES in all demographic groups primarily related to greater procedural utilization.

CONCLUSIONS

SES, sex, and race / ethnicity were independently associated with in-hospital mortality during HF hospitalization, highlighting possible care disparities. Racial/ethnic differences in outcome were more pronounced in low SES groups and in male patients.

Racial differences in management and outcomes of acute myocardial infarction during COVID-19 pandemic

OBJECTIVE

There are concerns that healthcare and outcomes of black, Asian and minority ethnic (BAME) communities are disproportionately impacted by the COVID-19 pandemic. We investigated admission rates, treatment and mortality of BAME with acute myocardial infarction (AMI) during COVID-19.

METHODS

Using multisource national healthcare records, patients hospitalised with AMI in England during 1 February-27 May 2020 were included in the COVID-19 group, whereas patients admitted during the same period in the previous three consecutive years were included in a pre-COVID-19 group. Multilevel hierarchical regression analyses were used to quantify the changes in-hospital and 7-day mortality in BAME compared with whites.

RESULTS

Of 73 746 patients, higher proportions of BAME patients (16.7% vs 10.1%) were hospitalised with AMI during the COVID-19 period compared with pre-COVID-19. BAME patients admitted during the COVID-19 period were younger, male and likely to present with ST-elevation acute myocardial infarction. COVID-19 BAME group admitted with non-ST-elevation acute myocardial infarction less frequently received coronary angiography (86.1% vs 90.0%, p<0.001) and had a longer median delay to reperfusion (4.1 hours vs 3.7 hours, p<0.001) compared with whites. BAME had higher in-hospital (OR 1.68, 95% CI 1.27 to 2.28) and 7-day mortality (OR 1.81 95% CI 1.31 to 2.19) during COVID-19 compared with pre-COVID-19 period.

CONCLUSION

In this multisource linked cohort study, compared with whites, BAME patients had proportionally higher hospitalisation rates with AMI, less frequently received guidelines indicated care and had higher early mortality during COVID-19 period compared with pre-COVID-19 period. There is a need to develop clinical pathways to achieve equity in the management of these vulnerable populations.

Effectiveness of a quality improvement collaborative in reducing time to surgery for patients requiring emergency cholecystectomy

Background

Acute gallstone disease is a high‐volume emergency general surgery presentation with wide variations in the quality of care provided across the UK. This controlled cohort evaluation assessed whether participation in a quality improvement collaborative approach reduced time to surgery for patients with acute gallstone disease to fewer than 8 days from presentation, in line with national guidance.

Methods

Patients admitted to hospital with acute biliary conditions in England and Wales between 1 April 2014 and 31 December 2017 were identified from Hospital Episode Statistics data. Time series of quarterly activity were produced for the Cholecystectomy Quality Improvement Collaborative (Chole‐QuIC) and all other acute National Health Service hospitals (control group). A negative binomial regression model was used to compare the proportion of patients having surgery within 8 days in the baseline and intervention periods.

Results

Of 13 sites invited to join Chole‐QuIC, 12 participated throughout the collaborative, which ran from October 2016 to January 2018. Of 7944 admissions, 1160 patients had a cholecystectomy within 8 days of admission, a significant improvement (P < 0·050) from baseline performance. This represented a relative change of 1·56 (95 per cent c.i. 1·38 to 1·75), compared with 1·08 for the control group. At the individual site level, eight of the 12 Chole‐QuIC sites showed a significant improvement (P < 0·050), with four sites increasing their 8‐day surgery rate to over 20 per cent of all emergency admissions, well above the mean of 15·3 per cent for control hospitals.

Conclusion

A surgeon‐led quality improvement collaborative approach improved care for patients requiring emergency cholecystectomy.

Readmission and processes of care across weekend and weekday hospitalisation for acute myocardial infarction, heart failure or stroke: an observational study of the National Readmission Database

OBJECTIVES

Variation in hospital resource allocations across weekdays and weekends have led to studies of the 'weekend effect' for ST elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), heart failure (HF) and stroke. However, few studies have explored the 'weekend effect' on unplanned readmission. We aimed to investigate 30-day unplanned readmissions and processes of care across weekend and weekday hospitalisations for STEMI, NSTEMI, HF and stroke.

DESIGN

We grouped hospitalisations for STEMI, NSTEMI, HF or stroke into weekday or weekend admissions. Multivariable adjusted ORs for binary outcomes across weekend versus weekday (reference) groups were estimated using logistic regression.

SETTING

We included all non-elective hospitalisations for STEMI, NSTEMI, HF or stroke, which were recorded in the US Nationwide Readmissions Database between 2010 and 2014.

PARTICIPANTS

The analysis sample included 659 906 hospitalisations for STEMI, 1 420 600 hospitalisations for NSTEMI, 3 027 699 hospitalisations for HF, and 2 574 168 hospitalisations for stroke.

MAIN OUTCOME MEASURES

The primary outcome was unplanned 30-day readmission. As secondary outcomes, we considered length of stay and the following processes of care: coronary angiography, primary percutaneous coronary intervention, coronary artery bypass graft, thrombolysis, brain scan/imaging, thrombectomy, echocardiography and cardiac resynchronisation therapy/implantable cardioverter-defibrillator.

RESULTS

Unplanned 30-day readmission rates were 11.0%, 15.1%, 23.0% and 10.9% for STEMI, NSTEMI, HF and stroke, respectively. Weekend hospitalisations for HF were associated with a statistically significant but modest increase in 30-day readmissions (OR of 1.045, 95% CI 1.033 to 1.058). Weekend hospitalisation for STEMI, NSTEMI or stroke was not associated with increased risk of 30-day readmission.

CONCLUSION

There was no clinically meaningful evidence against the supposition that weekend and weekday hospitalisations have the same 30-day unplanned readmissions. Thirty-day readmission rates were high, especially for HF, which has implications for service provision. Strategies to reduce readmission rates should be explored, regardless of day of hospitalisation.

How unmeasured confounding in a competing risks setting can affect treatment effect estimates in observational studies

Background

Analysis of competing risks is commonly achieved through a cause specific or a subdistribution framework using Cox or Fine & Gray models, respectively. The estimation of treatment effects in observational data is prone to unmeasured confounding which causes bias. There has been limited research into such biases in a competing risks framework.

Methods

We designed simulations to examine bias in the estimated treatment effect under Cox and Fine & Gray models with unmeasured confounding present. We varied the strength of the unmeasured confounding (i.e. the unmeasured variable’s effect on the probability of treatment and both outcome events) in different scenarios.

Results

In both the Cox and Fine & Gray models, correlation between the unmeasured confounder and the probability of treatment created biases in the same direction (upward/downward) as the effect of the unmeasured confounder on the event-of-interest. The association between correlation and bias is reversed if the unmeasured confounder affects the competing event. These effects are reversed for the bias on the treatment effect of the competing event and are amplified when there are uneven treatment arms.

Conclusion

The effect of unmeasured confounding on an event-of-interest or a competing event should not be overlooked in observational studies as strong correlations can lead to bias in treatment effect estimates and therefore cause inaccurate results to lead to false conclusions. This is true for cause specific perspective, but moreso for a subdistribution perspective. This can have ramifications if real-world treatment decisions rely on conclusions from these biased results. Graphical visualisation to aid in understanding the systems involved and potential confounders/events leading to sensitivity analyses that assumes unmeasured confounders exists should be performed to assess the robustness of results.

Electronic supplementary material

The online version of this article (10.1186/s12874-019-0808-7) contains supplementary material, which is available to authorized users.

Temporal trends in relative survival following percutaneous coronary intervention

OBJECTIVE

Percutaneous coronary intervention (PCI) has seen substantial shifts in patient selection in recent years that have increased baseline patient mortality risk. It is unclear to what extent observed changes in mortality are attributable to background mortality risk or the indication and selection for PCI itself. PCI-attributable mortality can be estimated using relative survival, which adjusts observed mortality by that seen in a matched control population. We report relative survival ratios and compare these across different time periods.

METHODS

National Health Service PCI activity in England and Wales from 2007 to 2014 is considered using data from the British Cardiovascular Intervention Society PCI Registry. Background mortality is as reported in Office for National Statistics life tables. Relative survival ratios up to 1 year are estimated, matching on patient age, sex and procedure date. Estimates are stratified by indication for PCI, sex and procedure date.

RESULTS

549 305 procedures were studied after exclusions for missing age, sex, indication and mortality status. Comparing from 2007 to 2008 to 2013-2014, differences in crude survival at 1 year were consistently lower in later years across all strata. For relative survival, these differences remained but were smaller, suggesting poorer survival in later years is partly due to demographic characteristics. Relative survival was higher in older patients.

CONCLUSIONS

Changes in patient demographics account for some but not all of the crude survival changes seen during the study period. Relative survival is an under-used methodology in interventional settings like PCI and should be considered wherever survival is compared between populations with different demographic characteristics, such as between countries or time periods.

Discharge against medical advice after hospitalisation for acute myocardial infarction

Background

Discharge against medical advice (AMA) occurs infrequently but is associated with poor outcomes. There are limited descriptions of discharges AMA in national cohorts of patients with acute myocardial infarction (AMI). This study aims to evaluate discharge AMA in AMI and how it affects readmissions.

Methods

We conducted a cohort study of patients with AMI in USA in the Nationwide Readmission Database who were admitted between the years 2010 and 2014. Descriptive statistics were presented for variables according to discharge home or AMA. The primary end point was all-cause 30-day unplanned readmissions and their causes.

Results

2663 019 patients were admitted with AMI of which 10.3% (n=162 070) of 1569 325 patients had an unplanned readmission within 30 days. The crude rate of discharge AMA remained stable between 2010 and 2014 at 1.5%. Discharge AMA was an independent predictor of unplanned all-cause readmissions (OR 2.27 95% CI 2.14 to 2.40); patients who discharged AMA had >twofold increased crude rate of readmission for AMI (30.4% vs 13.4%) and higher crude rate of admissions for neuropsychiatric reasons (3.2% vs 1.3%). After adjustment, discharge AMA was associated with increased odds of readmissions for AMI (OR 3.65 95% CI 3.31 to 4.03, p<0.001). We estimate that there are 1420 excess cases of AMI among patients who discharged AMA.

Conclusions

Discharge AMA occurs in 1.5% of the population with AMI and these patients are at higher risk of early readmissions for re-infarction. Interventions should be developed to reduce discharge AMA in high-risk groups and initiate interventions to avoid adverse outcomes and readmission.

Localized Epidermal Drug Delivery Induced by Supramolecular Solvent Structuring

The preferential localization of drug molecules in the epidermis of human skin is considered advantageous for a number of agents, but achieving such a delivery profile can be problematic. The aim of the present study was to assess if the manipulation of solvent supramolecular structuring in the skin could be used to promote drug residence in the epidermal tissue. Skin deposition studies showed that a 175-fold increase in the epidermal loading of a model drug diclofenac (138.65 ± 11.67 μg·cm(-2)), compared to a control (0.81 ± 0.13 μg·cm(-2)), could be achieved by colocalizing the drug with a high concentration of propylene glycol (PG) in the tissue. For such a system at 1 h postdose application, the PG flux into the skin was 9.3 mg·cm(2)·h(-1) and the PG-water ratio in the epidermis was 76:24 (v/v). At this solvent ratio infrared spectroscopy indicated that PG rich supramolecular structures, which displayed a relatively strong physical affinity for the drug, were formed. Encouraging the production of the PG-rich supermolecular structures in the epidermis by applying diclofenac to the skin using a high PG loading dose (240 μg·cm(-2)) produced an epidermal-transdermal drug distribution of 6.8:1. However, generating water-rich solvent supermolecular structures in the epidermis by applying diclofenac using a low PG loading dose (2.2 μg·cm(-2)) led to a loss of preferential epidermal localization of diclofenac in the tissue (0.7:1 epidermal-transdermal drug distribution). This change in diclofenac skin deposition profile in response to PG variations and the accompanying FTIR data supported the notion that supramolecular solvent structures could control drug accumulation in the human epidermis.

Controlling granule size through breakage in a novel reverse-phase wet granulation process: the effect of impeller speed and binder liquid viscosity

The feasibility of a novel reverse-phase wet granulation process has been established previously highlighting several potential advantages over the conventional wet granulation process and making recommendations for further development of the approach. The feasibility study showed that in the reverse-phase process granule formation proceeds via a controlled breakage mechanism. Consequently, the aim of the present study was to investigate the effect of impeller speeds and binder liquid viscosity on the size distribution and intragranular porosity of granules using this novel process. Impeller tip speed was found to have different effects on the granules produced by a conventional as opposed to a reverse-phase granulation process. For the conventional process, an increase in impeller speed from 1.57 to 3.14 ms(-1) had minimal effect on granule size distribution. However, a further increase in impeller tip speed to 3.93 and 4.71 ms(-1) resulted in a decrease in intragranular porosity and a corresponding increase in mean granule size. In contrast when the reverse-phase process was used, an increase in impeller speed from 1.57 to 4.71 ms(-1) resulted in increased granule breakage and a decrease in the mean granule size. This was postulated to be due to the fact that the granulation process begins with fully saturated pores. Under these conditions further consolidation of granules at increased impeller tip speeds is limited and rebound or breakage occurs. Based on these results and analysis of the modified capillary number the conventional process appears to be driven by viscous forces whereas the reverse-phase process appears to be driven by capillary forces. Additionally, in the reverse-phase process a critical impeller speed, represented by the equilibrium between centrifugal and gravitational forces, appears to represent the point above which breakage of large wet agglomerates and mechanical dispersion of binder liquid take place. In contrast the conventional process appears to be difficult to control due to variations in granule consolidation, which depends upon experimental variables. Such variations meant increased impeller tip speed both decreased and increased granule size. The reverse-phase process appears to offer simple control over granule porosity and size through manipulation of the impeller speed and further evaluation of the approach is warranted.

Bile Salt- and Lysophosphatidylcholine-induced Membrane Damage in Human Erythrocytes

The interaction of bile salts and lysophosphatidylcholine (LPC) with membranes has implications both in understanding the aetiology of a number of gastrointestinal disorders, including gastritis, gastric ulcers and colonic cancer, and in enhancing drug absorption by various epithelia. The membrane toxicity of nine bile salts (the sodium (S) salts of chenodeoxycholate (CDC), deoxycholate (DC) and cholate (C) and their glycine (G) and taurine (T) conjugates) and LPC was determined using erythrocyte haemolysis as a model parameter. Washed human erythrocytes were incubated for 15–60 min at 20°C with media buffered at pH 8, 7 and 6. Bile salt toxicity was shown to be a function of type, concentration, pH and contact time with the membrane. At pH 7 toxicity decreased in the order LPC &gt; unconjugated dihydroxy salts (SDC and SCDC) &gt; conjugated deoxycholates (SGDC and STDC) &gt; conjugated chenodeoxycholates (SGCDC and STCDC) &gt; unconjugated trihydroxy salt (SC) &gt; conjugated trihydroxy salts (SGC and STC). Incubation with equimolar combinations of bile salts (SDC + SCDC; STCDC + SGDC; SDC + STDC) indicated that the resultant damage was an additive function of the damage induced by the individual bile salts.

Further characterization of a bacteriocin produced by Lactobacillus paracasei HL32

AIMS

Purification, identification and partial characterization of bacteriocin produced by Lactobacillus paracasei HL32. It has been shown to have activity against Porphyromonas sp.

METHODS AND RESULTS

The purification of bacteriocin consisting of gel exclusion followed by anion exchange chromatography produced a single band upon an electrophoresis gel with a molecular weight corresponding to 56 kDa. The isolated protein contained 171 amino acids and the first 151 were sequenced. The bacteriocin contained a high percentage of cationic amino acids near the N-terminus, hydrophobic amino acids in the central region (Leu, Ile, Val, Phe, Trp and Gly) and hydrophilic residues (Ser, Asn and Gln) at the C-terminus. This structure did not match with that of previously reported bacteriocins. The antimicrobial activity of the bacteriocin was determined against some pathogens and normal microbiota (P. gingivalis, P. intermedia, T. forsythensis, S. salivarius and S. sanguinis) found in saliva and crevicular fluid. The bacteriocin was found to inhibit P. gingivalis at the minimum bactericidal concentration (MBC) of 0.14 mmol l(-1), but was found not to inhibit the other oral micro-organisms. The bacteriocin was found from transmission electron microscopy studies to cause pore formation in the cytoplasmic membranes of P. gingivalis at the pole and induce potassium efflux. Bacteriocin concentrations of two to four times of MBC were shown to induce haemolysis. The bacteriocin was heat-stable, surviving at 110 degrees C under pressure and possessed activity over a pH range of 6.8-8.5. Only a small reduction of activity was found to occur after incubation in biological fluids (saliva and crevicular fluid).

CONCLUSIONS

A novel bacteriocin has been identified that has selective activity against Porphyromonas sp. associated with periodontal disease.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings of this work gained the knowledge of specific antibacterial activity of bacteriocin against Porphyromonas gingivalis.

Influence of alcohol on the release of tramadol from 24-h controlled-release formulations during in vitro dissolution experiments

Recent warnings by regulatory bodies and a product recall by the FDA have generated much interest in the area of dose dumping from controlled-release opioid analgesic formulations when coingested with alcohol. It was the aim of this study to address this issue and in doing so, gain understanding on how alcohol-induced effects may be avoided. In this study, tramadol release from Ultram ER tablets and T-long capsules was significantly increased in the presence of ethanol. Conversely, a decrease in the rate of tramadol release was seen from Tridural extended-release tablets in the presence of alcohol.

Vegetative buffers for fan emissions from poultry farms: 1. temperature and foliar nitrogen

This study sought to evaluate the potential of trees planted around commercial poultry farms to trap ammonia (NH(3)), the gas of greatest environmental concern to the poultry industry. Four plant species (Norway spruce, Spike hybrid poplar, Streamco willow, and hybrid willow) were planted on eight commercial farms from 2003 to 2004. Because temperature (T) can be a stressor for trees, T was monitored in 2005 with data loggers among the trees in front of the exhaust fans (11.4 to 17.7 m) and at a control distance away from the fans (48 m) during all four seasons in Pennsylvania. Norway spruce (Picea abies) foliage samples were taken in August 2005 from one turkey and two layer farms for dry matter (DM) and nitrogen (N) analysis. The two layer farms had both Norway spruce and Spike hybrid poplar (Populus deltoides x Populus nigra) plantings sampled as well allowing comparisons of species and the effect of plant location near the fans versus a control distance away. Proximity to the fans had a clear effect on spruce foliar N with greater concentrations downwind of the fans than at control distances (3.03 vs. 1.88%; P < or = 0.0005). Plant location was again a significant factor for foliar N of both poplar and spruce on the two farms with both species showing greater N adjacent to the fans compared to the controls (3.75 vs. 2.32%; P < or = 0.0001). Pooled foliar DM of both plants was also greater among those near the fans (56.17, fan vs. 44.67%, control; P < or = 0.005). Species differences were also significant showing the potential of poplar to retain greater foliar N than spruce (3.52 vs. 2.55%; P < or = 0.001) with less DM (46.00 vs. 54.83%; P < or = 0.05) in a vegetative buffer setting. The results indicated plants were not stressed by the T near exhaust fans with mean seasonal T (13.04 vs. 13.03 degrees C, respectively) not significantly different from controls. This suggested poultry house exhaust air among the trees near the fans would not result in dormancy stressors on the plants compared to controls away from the fans.

Vegetative buffers for fan emissions from poultry farms: 2. ammonia, dust and foliar nitrogen

This study evaluated the potential of trees planted around commercial poultry farms to trap ammonia (NH(3)) and dust or particulate matter (PM). Norway spruce, Spike hybrid poplar, hybrid willow, and Streamco purpleosier willow were planted on five commercial farms from 2003 to 2004. Plant foliage was sampled in front of the exhaust fans and at a control distance away from the fans on one turkey, two laying hen, and two broiler chicken farms between June and July 2006. Samples were analyzed for dry matter (DM), nitrogen (N), and PM content. In addition, NH(3) concentrations were measured downwind of the exhaust fans among the trees and at a control distance using NH(3) passive dosi-tubes. Foliage samples were taken and analyzed separately based on plant species. The two layer farms had both spruce and poplar plantings whereas the two broiler farms had hybrid willow and Streamco willow plantings which allowed sampling and species comparisons with the effect of plant location (control vs. fan). The results showed that NH(3) concentration h(- 1) was reduced by distance from housing fans (P < or = 0.0001), especially between 0 m (12.01 ppm), 11.4 m (2.59 ppm), 15 m (2.03 ppm), and 30 m (0.31 ppm). Foliar N of plants near the fans was greater than those sampled away from the fans for poplar (3.87 vs. 2.56%; P < or = 0.0005) and hybrid willow (3.41 vs. 3.02%; P < or = 0.05). The trends for foliar N in spruce (1.91 vs. 1.77%; P = 0.26) and Streamco willow (3.85 vs. 3.33; P = 0.07) were not significant. Pooling results of the four plant species indicated greater N concentration from foliage sampled near the fans than of that away from the fans (3.27 vs. 2.67%; P < or = 0.0001). Foliar DM concentration was not affected by plant location, and when pooled the foliar DM of the four plant species near the fans was 51.3% in comparison with 48.5% at a control distance. There was a significant effect of plant location on foliar N and DM on the two layer farms with greater N and DM adjacent to fans than at a control distance (2.95 vs. 2.15% N and 45.4 vs. 38.2% DM, respectively). There were also significant plant species effects on foliar N and DM with poplar retaining greater N (3.22 vs. 1.88%) and DM (43.7 vs. 39.9%) than spruce. The interaction of location by species (P < or = 0.005) indicated that poplar was more responsive in terms of foliar N, but less responsive for DM than spruce. The effect of location and species on foliar N and DM were not clear among the two willow species on the broiler farms. Plant location had no effect on plant foliar PM weight, but plant species significantly influenced the ability of the plant foliage to trap PM with spruce and hybrid willow showing greater potential than poplar and Streamco willow for PM(2.5)(0.0054, 0.0054, 0.0005, and 0.0016 mg cm(- 2); P < or = 0.05) and total PM (0.0309, 0.0102, 0.0038, and 0.0046 mg cm(- 2), respectively; P < or = 0.001). Spruce trapped more dust compared to the other three species (hybrid willow, poplar, and Streamco willow) for PM(10) (0.0248 vs. 0.0036 mg cm(- 2); P < or = 0.0001) and PM(> 10) (0.0033 vs. 0.0003 mg cm(- 2); P = 0.052). This study indicates that poplar, hybrid willow, and Streamco willow are appropriate species to absorb poultry house aerial NH(3)-N, whereas spruce and hybrid willow are effective traps for dust and its associated odors.

Validation of a reverse-phase high performance liquid chromatographic method for concurrent assay of a weak base (salmeterol xinafoate) and a pharmacologically active steroid (fluticasone propionate)

The analysis of weakly basic drugs such as salmeterol xinafoate (SX) by reverse-phase liquid chromatography remains a problem, particularly when present in combination with other drugs such as steroids and weak acids. This study describes the validation of an assay for a weakly basic drug, salmeterol (SB), its weakly acidic counter-ion, 1-hydroxy-2-naphthoic acid (XA), and the neutral glucocorticoid, fluticasone propionate (FP) using a second-generation silica stationary phase (Inertsil ODS-2). The assay utilized an Inertsil ODS-2 base-deactivated 250 mm x 4.6mm, 5 microm HPLC column, with 75:25 methanol:0.6% aqueous ammonium acetate as the mobile phase. Under these near neutral conditions, SB demonstrated a good peak shape (tailing factor=1.21+/-0.02, n=85). The method provided a short analysis time: XA, t(R)=2.96 min; SB, t(R)=5.23 min and FP, t(R)=7.01 min. The assay displayed good sensitivity for both XA (LOD for SX=0.22 microgmL(-1)) and SB (LOD for SX=0.26 microgmL(-1)). The limit of detection for FP was 0.19 microgmL(-1). Neither of the drugs was found to interfere in the determination of the other and the assay accuracy (% recovery) was high (the recoveries were: 99.58+/-1.85% for XA, 99.49+/-1.88% for SB and 100.24+/-1.28% for FP). The assay reproducibility was determined with a mean coefficient of variance for the five calibration concentrations of XA=0.71+/-0.18%; SB=1.11+/-0.64% and FP=0.92+/-0.14%. Analysis of a pressurized metered dose inhaler formulation demonstrated recovery of the analytes that are within pharmacopoeial limits. It was shown that RP-HPLC was suitable for the high throughput analysis of the combination of SX and FP.

High-pressure aerosol suspensions—A novel laser diffraction particle sizing system for hydrofluoroalkane pressurised metered dose inhalers

In this study, a novel laser diffraction particle size analysis dispersion system, capable of sizing particles in situ within suspension hydrofluoroalkane (HFA) pressurised metered dose inhalers (pMDIs), was developed and tested. The technique was compared to four indirect particle sizing methods commonly used to determine the size of particles suspended in HFA pMDIs. The median volume diameter obtained using laser diffraction of both the salbutamol sulphate and fluticasone propionate suspended either in 2H, 3H-decafluoropentane or perfluoropentane (employed as surrogate propellants) was over one-order of magnitude larger than the particle sizes of the drugs suspended in HFA 134a. In contrast, the "in-flight" particle size using the Sympatec inhaler 2000 laser diffraction equipment undersized the particles, predicting higher delivery efficacy compared to the other sizing methods. However, the size of particles suspended in HFAs derived using the novel pressurised dispersion system, showed a linear correlation with the impaction results, r2=0.8894 (n=10). The novel pressure cell sizing technique proved to be simple to use, has the ability to be automated and was accurate, suggesting it could be an essential tool in the development of new suspension-based pMDI formulations.

Determination of polyvinylpyrrolidone using high-performance liquid chromatography

Polyvinylpyrrolidone (PVP) is a versatile polymer with innate surface activity. It is very difficult to accurately assay due to its wide molecular weight range and amphiphilic nature. This study evaluated a reversed-phase HPLC method to separate and quantify PVP K15. The assay used a Hicrome C18 150 mm x 3 microm HPLC column in combination with an 80/20 propanol-1-ol: deionised water, 0.01% TFA mobile phase, which resolved the polymer as a single peak, tR = 10.69+/-0.17 min (n=120) at 243 nm. The column's performance was constant throughout the study, N (theoretical plates) = 1729+/-22 and the peak symmetry remained good (As ranged from 0.74 to 0.92, n=10 over the calibration range). The developed assay proved to be accurate, sensitive and capable of recovering PVP K15 from pharmaceutical formulations. The limits of quantification and detection were calculated statistically as 2.40 and 0.72 mg ml(-1), respectively. Assay reproducibility assessed at five concentrations gave an average coefficient of variance <3.5% and the accuracy of the analytical method was 102.62+/-2.04%. The recovery of PVP K15 from directly compressed tablets and Refresh eye drops was 98.02+/-2.73 and 108.35+/-6.52%, respectively.

Stereoselective release behaviors of imprinted bead matrices

In this work, the stereoselective release behaviors of "low"-swelling molecularly imprinted polymer (MIP) bead matrices in pressed-coat tablet type were studied. Either R-propranolol selective MIP or S-propranolol selective MIP was combined with excipients and racemic propranolol and fabricated into the matrix. Subsequently, the release of different propranolol enantiomers from the matrices was examined. Also, the microscopic structure of the hydrated "low"-swelling MIP matrix was determined using a cryogenic scanning electron microscope in order to compare with that of the hydrated "high"-swelling MIP matrix. In vitro release profiles of the "low"-swelling matrices showed a difference in the release of enantiomers, in that the non-template isomer was released faster than the template isomer. However, in the last phase of dissolution this difference reduced and later reversed, resulting at last in the type of specificity being similar to that obtained previously with "high"-swelling MIP matrices. In summary, MIP beads can be fashioned into matrices and incorporated into different formulations to regulate the resultant stereoselectivity. From the behaviors of stereoselective release observed in MIP matrices, we can conclude that the enantioselective-controlled delivery mechanism of MIPs via formulations depends on the relative affinity of the enantiomer for the template sites, as well as the nature of the polymer, such as hydrophobicity and swellability.

In vivo evaluation of novel hyaluronan/chitosan microparticulate delivery systems for the nasal delivery of gentamicin in rabbits

Biodegradable microparticles containing gentamicin were prepared using chitosan hydroglutamate (CH), hyaluronic acid (HA) and a combination of both polymers by a solvent evaporation method. These formulations were administered nasally via an insufflator. Gentamicin was also administered nasally into rabbits as a solution and powder (a physical mixture of gentamicin and lactose), intravenously (IV) and intramuscularly (IM). The resultant serum levels of gentamicin were determined by Fluorescence Polarisation Immunoassay (FPIA). The bioavailability of gentamicin was poor when administered as a nasal solution (1.1%) and dry powder (2.1%) when compared with IV. However, the microparticulate systems composed of CH and HA/CH considerably enhanced the bioavailability of gentamicin (31.4 and 42.9%, respectively,) with HA microparticles inducing a less significant enhancement (23.3%). Previous in vitro dissolution and frog palate studies indicated that these microparticulate formulations were all mucoadhesive and demonstrated prolonged drug release. Such findings were translated into an increase in the bioavailability of gentamicin when compared with a simple nasal solution in vivo. When HA and CH were combined in the HA/CH formulation, the polymers appeared to improve the absorption of incorporated gentamicin synergistically in comparison to the individual polymers, suggesting a promising nasal delivery system.

In vivo and in vitro characterization of novel microparticulates based on hyaluronan and chitosan hydroglutamate

This study examined the application of previously characterized microparticles composed of hyaluronan (HA) and chitosan hydroglutamate (CH) as well as novel microparticles consisting of both polymers (HA/CH) to improve the nasal delivery of a model drug. The rabbit bioavailabilities of gentamicin incorporated in HA, CH, and HA/CH microparticles were increased 23-, 31-, and 42-fold, respectively, compared with the control intranasal solution of gentamicin, indicating that all test microparticles were retained for longer periods on the nasal mucosa of the rabbits as supported by previous in vitro dissolution as well as frog palate mucoadhesion studies, thereby improving drug absorption. The higher bioavailabilities of CH-based formulations (CH and HA/CH) suggest the penetration-enhancing effects of CH may also be partially responsible for the improvement. A model was developed, based on a glass impinger device, to deliver dry powder formulations reproducibly onto the surface of cultured cell monolayers. In vitro permeability and fluorescence microscopy studies on the tight junctions of the 16HBE14o- cell lines further confirmed the ability of CH-based formulations to enhance penetration. Furthermore, the in vitro absorption profile from cell culture studies was consistent with those determined from in vivo studies. The complementary effect from the mucoadhesive nature of HA coupled with the penetration-enhancing effects of CH makes the novel HA/CH formulation a promising nasal delivery system.

In vivo and in vitro characterization of novel microparticulates based on hyaluronan and chitosan hydroglutamate

This study examined the application of previously characterized microparticles composed of hyaluronan (HA) and chitosan hydroglutamate (CH) as well as novel microparticles consisting of both polymers (HA/CH) to improve the nasal delivery of a model drug. The rabbit bioavailabilities of gentamicin incorporated in HA, CH, and HA/CH microparticles were increased 23-, 31-, and 42-fold, respectively, compared with the control intranasal solution of gentamicin, indicating that all test microparticles were retained for longer periods on the nasal mucosa of the rabbits as supported by previous in vitro dissolution as well as frog palate mucoadhesion studies, thereby improving drug absorption. The higher bioavailabilities of CH-based formulations (CH and HA/CH) suggest the penetration-enhancing effects of CH may also be partially responsible for the improvement. A model was developed, based on a glass impinger device, to deliver dry powder formulations reproducibly onto the surface of cultured cell monolayers. In vitro permeability and fluorescence microscopy studies on the tight junctions of the 16HBE14o- cell lines further confirmed the ability of CH-based formulations to enhance penetration. Furthermore, the in vitro absorption profile from cell culture studies was consistent with those determined from in vivo studies. The complementary effect from the mucoadhesive nature of HA coupled with the penetration-enhancing effects of CH makes the novel HA/CH formulation a promising nasal delivery system.

Lactose as a carrier in dry powder formulations: the influence of surface characteristics on drug delivery

The aim of the study was to investigate the interdependence of carrier particle size, surface treatment of the carrier, and inclusion of fines on the drug delivery from dry power inhaler formulations. Two size fractions (< 63 and 63-90 microm) of alpha-lactose monohydrate were subjected to treatment with 95% (v/v) ethanol to introduce small asperities or cavities onto the otherwise smooth surface without substantially changing the particle shape. After blending with albuterol sulfate [ALB; volume median diameter (VMD), 1.9 microm; geometric standard deviation (GSD), 1.5], the solvent-treated lactose produced a fine particle fraction (FPF; < 6.18 microm) and dispersibility of the drug that was significantly (ANOVA p < 0.01) lower than that which resulted from formulations containing untreated lactose of a similar size fraction, after aerosolization at 60 L min(-1) via a Rotahaler. The two size fractions of the treated lactose resulted in similar deposition profiles of ALB. The effects of such surface asperities or cavities of lactose were offset by introducing a small amount (5% w/w) of smaller-sized lactose (5-10 microm) to the powder formulations. The fine lactose increased the FPF and dispersibility of ALB to such a level that all lactose batches, regardless of particle size or whether solvent treated, produced a similar fraction of aerosolized ALB. The inclusion of recrystallized needle lactose (5-15 microm) was superior to micronized lactose in improving the aerosolization of ALB. The findings of this study indicate that the presence and characteristics of the finer fraction of lactose carrier particles dominate over the particle size and surface smoothness of the carrier particles in determining dispersion and deaggregation of drugs from dry powder formulations for inhalation.