Influence of Antibiotic Exposure Intensity on the Risk of Clostridioides difficile Infection

BACKGROUND

Antibiotics are a strong risk factor for Clostridioides difficile infection (CDI), and CDI incidence is often measured as an important outcome metric for antimicrobial stewardship interventions aiming to reduce antibiotic use. However, risk of CDI from antibiotics varies by agent and dependent on the intensity (i.e., spectrum and duration) of antibiotic therapy. Thus, the impact of stewardship interventions on CDI incidence is variable, and understanding this risk requires a more granular measure of intensity of therapy than traditionally used measures like days of therapy (DOT).

METHODS

We performed a retrospective cohort study to measure the independent association between intensity of antibiotic therapy, as measured by the antibiotic spectrum index (ASI), and hospital-associated CDI (HA-CDI) at a large academic medical center between January 2018 and March 2020. We constructed a marginal Poisson regression model to generate adjusted relative risks for a unit increase in ASI per antibiotic day.

RESULTS

We included 35,457 inpatient encounters in our cohort. Sixty-eight percent of patients received at least one antibiotic. We identified 128 HA-CDI cases, which corresponds to an incidence rate of 4.1 cases per 10,000 patient-days. After adjusting for known confounders, each additional unit increase in ASI per antibiotic day is associated with 1.09 times the risk of HA-CDI (Relative Risk = 1.09, 95% Confidence Interval: 1.06 to 1.13).

CONCLUSIONS

ASI was strongly associated with HA-CDI and could be a useful tool in evaluating the impact of antibiotic stewardship on HA-CDI rates, providing more granular information than the more commonly used days of therapy.

Use of electronic health record data to identify hospital-associated Clostridioides difficile infections: a validation study

Background

Clinical research focused on the burden and impact of Clostridioides difficile infection (CDI) often relies upon accurate identification of cases using existing health record data. Use of diagnosis codes alone can lead to misclassification of cases. Our goal was to develop and validate a multi-component algorithm to identify hospital-associated CDI (HA-CDI) cases using electronic health record (EHR) data.

Methods

We performed a validation study using a random sample of adult inpatients at a large academic hospital setting in Portland, Oregon from January 2018 to March 2020. We excluded patients with CDI on admission and those with short lengths of stay (< 4 days). We tested a multi-component algorithm to identify HA-CDI; case patients were required to have received an inpatient course of metronidazole, oral vancomycin, or fidaxomicin and have at least one of the following: a positive C. difficile laboratory test or the International Classification of Diseases, Tenth Revision (ICD-10) code for non-recurrent CDI. For a random sample of 80 algorithm-identified HA-CDI cases and 80 non-cases, we performed manual EHR review to identify gold standard of HA-CDI diagnosis. We then calculated overall percent accuracy, sensitivity, specificity, and positive and negative predictive value for the algorithm overall and for the individual components.

Results

Our case definition algorithm identified HA-CDI cases with 94% accuracy (95% Confidence Interval (CI): 88% to 97%). We achieved 100% sensitivity (94% to 100%), 89% specificity (81% to 95%), 88% positive predictive value (78% to 94%), and 100% negative predictive value (95% to 100%). Requiring a positive C. difficile test as our gold standard further improved diagnostic performance (97% accuracy [93% to 99%], 93% PPV [85% to 98%]).

Conclusions

Our algorithm accurately detected true HA-CDI cases from EHR data in our patient population. A multi-component algorithm performs better than any isolated component. Requiring a positive laboratory test for C. difficile strengthens diagnostic performance even further. Accurate detection could have important implications for CDI tracking and research.

225. Evaluating Appropriateness of Antibiotic Prescribing in Pediatric Inpatients

Background

Antibiotic appropriateness is the gold standard for informing antimicrobial stewardship efforts to optimize prescribing. The objectives of this study were to evaluate appropriateness of antibiotics for resistant gram-positive infections in pediatric inpatients and identify factors associated with inappropriate prescribing.

Methods

We included pediatric inpatients between July 2017 and July 2018 where an antibiotic typically used for resistant Gram-positive infections (per NHSN) was administered. We developed an algorithm based on laboratory data and diagnosis codes to categorize each antibiotic day of therapy as appropriate, inappropriate, or indeterminate. If indeterminate, we reviewed charts to assess appropriateness. We calculated total, appropriate, and inappropriate days of therapy (DOT) overall and per patient-day. We evaluated clinical characteristics and indications as potential predictors of inappropriate DOT using Chi-squared or Kruskal-Wallis tests.

Results

Among 591 included encounters, we assessed 708 total antibiotic courses. The algorithm allowed for classification of 422 encounters (71%) and the remaining 171 encounters (29%) were classified using manual record review. The most frequent antibiotics were vancomycin (68%) and clindamycin (29%). Patients received a median of 3 days of gram-positive agent therapy per visit, or 5 per every 10 patient-days. Most common indications for gram-positive therapy were surgical prophylaxis (28% of encounters) and empiric therapy (10%) (Figure 1). Of the 1,754 total days of therapy assessed, 94.8% were ruled appropriate. Thirty-one (4.4%) courses were classified as at least partially inappropriate among 27 unique encounters (4.6%). There was a median of 2 inappropriate days among those with any inappropriate therapy. The reason for inappropriate rulings for empiric or prophylaxis indications was most often “longer than necessary duration,” which was the case for 16 of 21 (76%) occurrences.

Figure 1. Appropriate and Inappropriate Days of Therapy (DOT) by Indication and Antibiotic

Conclusion

Inappropriate antibiotic use for Gram-positive infections was low in our patient population for the agents studied. We identified limiting the duration for patients receiving prophylactic or empiric therapy as a potential stewardship intervention target.

Disclosures

All Authors: No reported disclosures

Antibiotic prescribing without documented indication in ambulatory care clinics: national cross sectional study

OBJECTIVES

To identify the frequency with which antibiotics are prescribed in the absence of a documented indication in the ambulatory care setting, to quantify the potential effect on assessments of appropriateness of antibiotics, and to understand patient, provider, and visit level characteristics associated with antibiotic prescribing without a documented indication.

DESIGN

Cross sectional study.

SETTING

2015 National Ambulatory Medical Care Survey.

PARTICIPANTS

28 332 sample visits representing 990.9 million ambulatory care visits nationwide.

MAIN OUTCOME MEASURES

Overall antibiotic prescribing and whether each antibiotic prescription was accompanied by appropriate, inappropriate, or no documented indication as identified through ICD-9-CM (international classification of diseases, 9th revision, clinical modification) codes. Survey weighted multivariable logistic regression was used to evaluate potential risk factors for receipt of an antibiotic prescription without a documented indication.

RESULTS

Antibiotics were prescribed during 13.2% (95% confidence interval 11.6% to 13.7%) of the estimated 990.8 million ambulatory care visits in 2015. According to the criteria, 57% (52% to 62%) of the 130.5 million prescriptions were for appropriate indications, 25% (21% to 29%) were inappropriate, and 18% (15% to 22%) had no documented indication. This corresponds to an estimated 24 million prescriptions without a documented indication. Being an adult male, spending more time with the provider, and seeing a non-primary care specialist were significantly positively associated with antibiotic prescribing without an indication. Sulfonamides and urinary anti-infective agents were the antibiotic classes most likely to be prescribed without documentation.

CONCLUSIONS

This nationally representative study of ambulatory visits identified a large number of prescriptions for antibiotics without a documented indication. Antibiotic prescribing in the absence of a documented indication may severely bias national estimates of appropriate antibiotic use in this setting. This study identified a wide range of factors associated with antibiotic prescribing without a documented indication, which may be useful in directing initiatives aimed at supporting better documentation.

Predicting Carbapenem-Resistant Enterobacteriaceae Carriage at the Time of Admission Using a Statewide Hospital Discharge Database

BACKGROUND

Timely identification of patients likely to harbor carbapenem-resistant Enterobacteriaceae (CRE) can help health care facilities provide effective infection control and treatment. We evaluated whether a model utilizing prior health care information from a state hospital discharge database could predict a patient's probability of CRE colonization at the time of hospital admission.

METHODS

We performed a case-control study using the Illinois hospital discharge database. From a 2014-2015 patient cohort, we defined cases as index adult patient hospital encounters with a positive CRE culture collected within the first 3 days of hospitalization, as reported to the Illinois XDRO registry; controls were all patient admissions from the same hospital and month. We split the data into training (~60%) and validation (~40%) sets and developed a logistic regression model to estimate coefficients for predictors of interest.

RESULTS

We identified 486 index cases and 340 005 controls. Independent risk factors for CRE at the time of admission were age, number of short-term acute care hospital (STACH) hospitalizations in the prior 365 days, mean STACH length of stay, number of long-term acute care hospital (LTACH) hospitalizations in the prior 365 days, mean LTACH length of stay, current admission to LTACH, and prior hospital admission with an infection diagnosis code. When applying the model to the validation data set, the area under the receiver operating characteristic curve was 0.84.

CONCLUSIONS

A prediction model utilizing prior health care exposure information could discriminate patients who were likely to harbor CRE at the time of hospital admission.

Regional Spread of an Outbreak of Carbapenem-Resistant Enterobacteriaceae Through an Ego Network of Healthcare Facilities

Background

In 2013, New Delhi metallo-β-lactamase (NDM)-producing Escherichia coli, a type of carbapenem-resistant Enterobacteriaceae uncommon in the United States, was identified in a tertiary care hospital (hospital A) in northeastern Illinois. The outbreak was traced to a contaminated duodenoscope. Patient-sharing patterns can be described through social network analysis and ego networks, which could be used to identify hospitals most likely to accept patients from a hospital with an outbreak.

Methods

Using Illinois' hospital discharge data and the Illinois extensively drug-resistant organism (XDRO) registry, we constructed an ego network around hospital A. We identified which facilities NDM outbreak patients subsequently visited and whether the facilities reported NDM cases.

Results

Of the 31 outbreak cases entered into the XDRO registry who visited hospital A, 19 (61%) were subsequently admitted to 13 other hospitals during the following 12 months. Of the 13 hospitals, the majority (n = 9; 69%) were in our defined ego network, and 5 of those 9 hospitals consequently reported at least 1 additional NDM case. Ego network facilities were more likely to identify cases compared to a geographically defined group of facilities (9/22 vs 10/66; P = .01); only 1 reported case fell outside of the ego network.

Conclusions

The outbreak hospital's ego network accurately predicted which hospitals the outbreak patients would visit. Many of these hospitals reported additional NDM cases. Prior knowledge of this ego network could have efficiently focused public health resources on these high-risk facilities.

Prescribing Associated with High-Risk Opioid Exposures Among Non-cancer Chronic Users of Opioid Analgesics: a Social Network Analysis

BACKGROUND

The continued rise in fatalities from opioid analgesics despite a steady decline in the number of individual prescriptions directing ≥ 90 morphine milligram equivalents (MME)/day may be explained by patient exposures to redundant prescriptions from multiple prescribers.

OBJECTIVES

We evaluated prescribers' specialty and social network characteristics associated with high-risk opioid exposures resulting from single-prescriber high-daily dose prescriptions or multi-prescriber discoordination.

DESIGN

Retrospective cohort study.

PARTICIPANTS

A cohort of prescribers with opioid analgesic prescription claims for non-cancer chronic opioid users in an Illinois Medicaid managed care program in 2015-2016.

MAIN MEASURES

Per prescriber rates of single-prescriber high-daily-dose prescriptions or multi-prescriber discoordination.

KEY RESULTS

For 2280 beneficiaries, 36,798 opioid prescription claims were submitted by 3532 prescribers. Compared to 3% of prescriptions (involving 6% of prescribers and 7% of beneficiaries) that directed ≥ 90 MME/day, discoordination accounted for a greater share of high-risk exposures-13% of prescriptions (involving 23% of prescribers and 24% of beneficiaries). The following specialties were at highest risk of discoordinated prescribing compared to internal medicine: dental (incident rate ratio (95% confidence interval) 5.9 (4.6, 7.5)), emergency medicine (4.7 (3.8, 5.8)), and surgical subspecialties (4.2 (3.0, 5.8)). Social network analysis identified 2 small interconnected prescriber communities of high-volume pain management specialists, and 3 sparsely connected groups of predominantly low-volume primary care or emergency medicine clinicians. Using multivariate models, we found that the sparsely connected sociometric positions were a risk factor for high-risk exposures.

CONCLUSION

Low-volume prescribers in the social network's periphery were at greater risk of intended or discoordinated prescribing than interconnected high-volume prescribers. Interventions addressing discoordination among low-volume opioid prescribers in non-integrated practices should be a priority. Demands for enhanced functionality and integration of Prescription Drug Monitoring Programs or referrals to specialized multidisciplinary pain management centers are potential policy implications.

2058. Patient Satisfaction Not Impacted by Antibiotic Prescribing for Viral Upper Respiratory Infections

Background

Treating viral upper respiratory infections (URI) with antibiotics is a major contributor to the rise of antimicrobial resistance. Major drivers of unnecessary prescribing are a patient’s expectation to receive an antibiotic for acute illness and the physician’s desire to provide satisfactory care. Our objective was to determine whether receiving an antibiotic prescription for a URI is associated with increased patient satisfaction.

Methods

We identified emergency department (ED) and ambulatory visit (AC) visits with an acute URI diagnosis code between September 2015 and May 2016 that had an associated patient satisfaction survey. The survey queried patients’ overall satisfaction (“Overall rating of care received during your visit”) using a Likert-type scale ranging from 1 (Very Poor) to 5 (Very Good). We assessed survey responses among patients receiving and not receiving antibiotics using the Wilcoxon rank-sum test. Results from ED and AC visits were compared separately.

Results

We collected survey responses from 282 ED patients and 1306 AC patients with acute URI. Compared with non-recipients, ED respondents receiving an antibiotic were more likely to be female (67% vs. 55%) and on Medicare (28% vs. 21%); AC respondents receiving a prescription were more likely to be female (68% vs. 61%) and have private insurance (63% vs. 53%). Overall satisfaction was very high (Median = 5, IQR 4–5 for both groups). Median responses did not differ by antibiotic prescription status in either group (rank-sum P = 0.4 and 0.8 for ED and AC respectively). When dichotomizing the overall satisfaction score, more patients receiving an antibiotic reported satisfaction of good to very good than those not receiving an antibiotic (84% vs. 76%; Pearson’s Χ²P = 0.1) among ED patients, but not AC patients (95% vs. 94%; P = 0.5).

Conclusion

Patient satisfaction with their visit was not strongly associated with antibiotic receipt among ED and AC patients with URI in our study. This finding suggests that providers may limit the spread of antibiotic resistance by ceasing to unnecessarily prescribe antibiotics without jeopardizing patient satisfaction. Given low response rates to visit satisfaction surveys, further work is needed to verify the validity of this study and evaluate its generalizability.

Disclosures

All authors: No reported disclosures.

2167. Predicting Carbapenem-Resistant Enterobacteriaceae (CRE) Carriage on Admission using Updated Statewide Hospital Discharge Data

Background

We previously built a patient-level prediction model to assess an individual’s risk of Carbapenem-resistant Enterobacteriaceae (CRE) carriage upon hospital admission based on the following factors: past hospital visits (short- and long-term acute care (STACHs and LTACHs)), endoscopic procedures, infection-related diagnosis codes, and patient age and sex. Our model discriminated CRE cases relatively well (c-statistic = 0.86). In the hopes of operationalizing our results, we evaluated the distribution of predicted probabilities on an updated dataset using existing model parameters.

Methods

We used Illinois Hospital discharge data (CYs 2015–2016) with ICD-10 diagnosis and procedure codes to establish baseline exposure history (2015) and to generate predicted probabilities (2016). We calculated the number of hospital visits and the average number of hospital days in the past year (STACH and LTACH). We identified infection-related diagnosis codes using prior knowledge, and included procedure codes for endoscopic retrograde cholangiopancreatography (ERCP). We then used the model parameters from our previous work to generate predicted probabilities corresponding to each hospital visit.

Results

Our study year (2016) included 1,229,158 visits by 816,500 unique adult patients. Sixty-two percent of patients had no inpatient visits in the previous year. Among those with a prior hospitalization, the median STACH length of stay was 4 days (IQR: 2–6). Three thousand five hundred and sixty-six patients (0.4%) had previous LTACH exposure upon admission, with a median length of stay of 25 days (IQR: 13–40). Thirty-two percent of hospital visits had an infection-related diagnosis code, and 0.5% had an ERCP procedure code. Of the more than 1.2 million visits, our model predicted 10,614 visits associated with a CRE risk of over 1%, 946 visits of over 10%, and 96 visits by 63 unique patients with over a 50% risk. On average, highest risk patients were exposed to (median) 15 (7–97) STACH, 104 LTACH (37–174) days; 83% had infection codes.

Conclusion

Using a large, de-identified statewide dataset, we were able to identify a small number of extremely high-risk individuals. Selective screening of these individuals upon admission could prove to be a valuable way to identify CRE-colonized patients in order to take proper precautions.

Disclosures

All authors: No reported disclosures.

Aprotinin Reduces Blood Loss after Cardiopulmonary Bypass by Direct Inhibition of Plasmin

The effectiveness and mechanism of aprotinin reduced bleeding after cardiopulmonary bypass surgery was studied in a double blind randomised study of 106 patients undergoing valve replacement surgery. Aprotinin therapy was associated with significant reduction in perioperative bleeding and postoperative blood transfusion requirements. Although initially tissue plasminogen activator (t-PA) activity was lower in the aprotinin than placebo group, as surgery proceeded this difference was reversed due to less plasminogen activator inhibitor-1 release in the aprotinin group. This indicates that aprotinin-mediated suppression of fibrinolysis as demonstrated by reduced D-dimer concentration was not related to t-PA. Furthermore, similar perioperative reduction of plasminogen levels in aprotinin and placebo groups indicated a similar degree of conversion of plasminogen to plasmin. However, less plasmin bound with alpha 2-antiplasmin in the plasma in the aprotinin group as it was already complexed with aprotinin where it remained protected from the natural inhibitor on the intact fibrin surface. The reduced fibrinolytic activity of the aprotinin group was thus brought about by the complexing of aprotinin with the plasmin which was bound to the fibrin surface.

The Dependence of the International Sensitivity Index on the Coagulometer Used to Perform the Prothrombin Time

This study was designed to detect any effect that different types of coagulation instrument may have on the International Sensitivity Index (ISI) of a thromboplastin.

Manufacturers of commercial thromboplastins now calibrate their reagents against the World Health Organization international reference preparation to assign them an IST. This enables the prothrombin time (PT) estimated with that reagent to be expressed as an International Normalised Ratio (INR).

One batch of Thromborel S was calibrated against the Australasian Reference Thromboplastin (ART). The Thromborel S was used on three photo-optical instruments, the Automated Coagulation Laboratory (ACL) (Instrumentation Laboratory), the Cobas Fibro (Roche), and the Coag-a-Pet (General Diagnostics). PTs using ART were performed manually using the reference method.

The ISIs calibrated in our laboratory when the ACL and Cobas Fibro were used were not significantly different at the 95% level, being 1.102 ± 0.018 and 1.134 ± 0.022 respectively. The ISI with the Coag-a-Pet of 1.223 ± 0.023 was significantly different to that of the ACL and the Cobas Fibro at the 95% level.

The flowcharts for a computer program to perform the necessary calculations are provided. The program allows for the entry and editing of data from the calibration procedure, and provides a mean normal PT and normal range, the ISI and 95% confidence limits of the calibration, and a chart for the conversion of the test PTs to INRs.

The authors have made available an IBM compatible program for the calibration of thromboplastins.

Assessing the Ability of Hospital Diagnosis Codes to Detect Inpatient Exposure to Antibacterial Agents

OBJECTIVE Because antibacterial history is difficult to obtain, especially when the exposure occurred at an outside hospital, we assessed whether infection-related diagnostic billing codes, which are more readily available through hospital discharge databases, could infer prior antibacterial receipt. DESIGN Retrospective cohort study. PARTICIPANTS This study included 121,916 hospitalizations representing 78,094 patients across the 3 hospitals. METHODS We obtained hospital inpatient data from 3 Chicago-area hospitals. Encounters were categorized as "infection" if at least 1 International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) code indicated a bacterial infection. From medication administration records, we categorized antibacterial agents and calculated total therapy days using Centers for Disease Control and Prevention (CDC) definitions. We evaluated bivariate associations between infection encounters and 3 categories of antibacterial exposure: any, broad spectrum, or surgical prophylaxis. We constructed multivariable models to evaluate adjusted risk ratios for antibacterial receipt. RESULTS Of the 121,916 inpatient encounters (78,094 patients) across the 3 hospitals, 24% had an associated infection code, 47% received an antibacterial, and 13% received a broad-spectrum antibacterial. Infection-related ICD-9-CM codes were associated with a 2-fold increase in antibacterial administration compared to those lacking such codes (RR, 2.29; 95% confidence interval [CI], 2.27-2.31) and a 5-fold increased risk for broad-spectrum antibacterial administration (RR, 5.52; 95% CI, 5.37-5.67). Encounters with infection codes had 3 times the number of antibacterial days. CONCLUSIONS Infection diagnostic billing codes are strong surrogate markers for prior antibacterial exposure, especially to broad-spectrum antibacterial agents; such an association can be used to enhance early identification of patients at risk of multidrug-resistant organism (MDRO) carriage at the time of admission. Infect Control Hosp Epidemiol 2018;39:377-382.

Spread of Carbapenem-Resistant Enterobacteriaceae Among Illinois Healthcare Facilities: The Role of Patient Sharing

BACKGROUND

Carbapenem-resistant Enterobacteriaceae (CRE) spread regionally throughout healthcare facilities through patient transfer and cause difficult-to-treat infections. We developed a state-wide patient-sharing matrix and applied social network analyses to determine whether greater connectedness (centrality) to other healthcare facilities and greater patient sharing with long-term acute care hospitals (LTACHs) predicted higher facility CRE rates.

METHODS

We combined CRE case information from the Illinois extensively drug-resistant organism registry with measures of centrality calculated from a state-wide hospital discharge dataset to predict facility-level CRE rates, adjusting for hospital size and geographic characteristics.

RESULTS

Higher CRE rates were observed among facilities with greater patient sharing, as measured by degree centrality. Each additional hospital connection (unit of degree) conferred a 6% increase in CRE rate in rural facilities (relative risk [RR] = 1.056; 95% confidence interval [CI], 1.030-1.082) and a 3% increase among Chicagoland and non-Chicago urban facilities (RR = 1.027; 95% CI, 1.002-1.052 and RR = 1.025; 95% CI, 1.002-1.048, respectively). Sharing 4 or more patients with LTACHs was associated with higher CRE rates, but this association may have been due to chance (RR = 2.08; 95% CI, .85-5.08; P = .11).

CONCLUSIONS

Hospitals with greater connectedness to other hospitals in a statewide patient-sharing network had higher CRE burden. Centrality had a greater effect on CRE rates in rural counties, which do not have LTACHs. Social network analysis likely identifies hospitals at higher risk of CRE exposure, enabling focused clinical and public health interventions.

Heparin monitoring during cardiac surgery. Part 1: validation of whole-blood heparin concentration and activated clotting time

There is limited published data on the agreement between techniques for monitoring heparin levels. The aim of this study was to validate the Hepcon/HMS, with particular focus on the agreement with laboratory anti-Xa assay. The performances of two ACT instruments - Hemochron and HemoTec - were also evaluated, including an assessment for interchangeability. Blood samples from 42 adult cardiopulmonary bypass (CPB) patients were analysed for activated clotting time (ACT), whole-blood heparin concentration (Hepcon/HMS) and anti-factor Xa (anti-Xa) plasma heparin concentration. Agreement between measures was determined using the method of Bland and Altman. Simple analysis of agreement between the Hepcon and anti-Xa heparin revealed the Hepcon has a mean bias of -0.46 U/mL, with the limits of agreement ±1.12 U/mL. The comparison between ACT instruments indicated a mean difference of -96 seconds for the HemoTec, with limits of ±265 seconds. The Hepcon/HMS instrument displayed satisfactory agreement with anti-Xa plasma heparin concentration, as the expected variation would not be expected to cause problems in the clinical setting. Agreement between the two measurements of ACT may be satisfactory, provided each is assigned a different target value.

Heparin monitoring during cardiac surgery. Part 2: calculating the overestimation of heparin by the activated clotting time

Activated clotting time (ACT) values were converted to heparin concentration, enabling an assessment of the accuracy of the ACT and a quantification of the prolongation imposed by bypass. Blood samples were obtained from 42 adult cardiopulmonary bypass (CPB) patients before and during bypass surgery. Samples were analysed for ACT (HemoTec ACT) and anti-factor Xa (anti-Xa) plasma heparin concentration. The mean heparin concentration calculated before bypass was an accurate reflection of plasma heparin; however, calculated values rose to around 170% of anti-Xa values upon connection to bypass. By adjusting for this rise, for 95% of cases the calculated heparin concentration would vary between 0.60 and 1.65 times anti-Xa values. Without accounting for artificial prolongation or individual sensitivities, the ACT may give values between 0.8 and 3.0 times that indicated by the anti-Xa assay. When both individual heparin sensitivities and the effects of bypass are considered, the ACT may provide a more suitable indication of heparin levels; however, typical use may overestimate heparin up to threefold.

Investigation of factors relating to neuropsychological change following cardiac surgery

Background. An analysis of neuropsychological impairment following cardiopulmonary bypass was performed in 55 patients undergoing elective coronary artery bypass grafting. Methods. Neurocognitive function was measured preoperatively using the MicroCog: Assessment of Cognitive Functioning computer-based testing tool. Testing was repeated in the postoperative period immediately prior to discharge from hospital. Analysis of significant score decline was performed using the standardised regression-based technique. A patient was classified as overall impaired when ≥20% of test scores were significantly impaired. The proposed marker of neurological damage S-100β was also used. Prothrombin Fragment 1+2 (F1+2) was measured as a marker of thrombin development to test the hypothesis that excessive haemostatic activation may lead to thromboembolic damage to the brain. Results and Conclusions. 32.7% of patients were classified as significantly impaired. No relationship was detected between F1+2 and any neuropsychological test score; however, the study was limited due to small sample size. F1+2 levels were higher in patients undergoing prolonged bypass times. Neuropsychological decline was significantly correlated with patient age, suggesting a degree of caution is warranted when operating on an elderly cohort. An unexpected relationship was detected between higher heparin concentrations and increased risk of neuropsychological impairment; however, this requires re-evaluation. Perfusion (2007) 22, 27—33.

Insights into nitrogen allocation and recycling from nitrogen elemental analysis and 15N isotope labelling in 14 genotypes of willow

Minimizing nitrogen (N) fertilization inputs during cultivation is essential for sustainable production of bioenergy and biofuels. The biomass crop willow (Salix spp.) is considered to have low N fertilizer requirements due to efficient recycling of nutrients during the perennial cycle. To investigate how successfully different willow genotypes assimilate and allocate N during growth, and remobilize and consequently recycle N before the onset of winter dormancy, N allocation and N remobilization (to and between different organs) were examined in 14 genotypes of a genetic family using elemental analysis and (15)N as a label. Cuttings were established in pots in April and sampled in June, August and at onset of senescence in October. Biomass yield of the trees correlated well with yields recorded in the field. Genotype-specific variation was observed for all traits measured and general trends spanning these sampling points were identified when trees were grouped by biomass yield. Nitrogen reserves in the cutting fuelled the entirety of the canopy establishment, yet earlier cessation of this dependency was linked to higher biomass yields. The stem was found to be the major N reserve by autumn, which constitutes a major source of N loss at harvest, typically every 2-3 years. These data contribute to understanding N remobilization in short rotation coppice willow and to the identification of traits that could potentially be selected for in breeding programmes to further improve the sustainability of biomass production.

Reaction wood - a key cause of variation in cell wall recalcitrance in willow

BACKGROUND

The recalcitrance of lignocellulosic cell wall biomass to deconstruction varies greatly in angiosperms, yet the source of this variation remains unclear. Here, in eight genotypes of short rotation coppice willow (Salix sp.) variability of the reaction wood (RW) response and the impact of this variation on cell wall recalcitrance to enzymatic saccharification was considered.

RESULTS

A pot trial was designed to test if the 'RW response' varies between willow genotypes and contributes to the differences observed in cell wall recalcitrance to enzymatic saccharification in field-grown trees. Biomass composition was measured via wet chemistry and used with glucose release yields from enzymatic saccharification to determine cell wall recalcitrance. The levels of glucose release found for pot-grown control trees showed no significant correlation with glucose release from mature field-grown trees. However, when a RW phenotype was induced in pot-grown trees, glucose release was strongly correlated with that for mature field-grown trees. Field studies revealed a 5-fold increase in glucose release from a genotype grown at a site exposed to high wind speeds (a potentially high RW inducing environment) when compared with the same genotype grown at a more sheltered site.

CONCLUSIONS

Our findings provide evidence for a new concept concerning variation in the recalcitrance to enzymatic hydrolysis of the stem biomass of different, field-grown willow genotypes (and potentially other angiosperms). Specifically, that genotypic differences in the ability to produce a response to RW inducing conditions (a 'RW response') indicate that this RW response is a primary determinant of the variation observed in cell wall glucan accessibility. The identification of the importance of this RW response trait in willows, is likely to be valuable in selective breeding strategies in willow (and other angiosperm) biofuel crops and, with further work to dissect the nature of RW variation, could provide novel targets for genetic modification for improved biofuel feedstocks.

Investigation of tension wood formation and 2,6-dichlorbenzonitrile application in short rotation coppice willow composition and enzymatic saccharification

BACKGROUND

Short rotation coppice willow is a potential lignocellulosic feedstock in the United Kingdom and elsewhere; however, research on optimising willow specifically for bioethanol production has started developing only recently. We have used the feedstock Salix viminalis × Salix schwerinii cultivar 'Olof' in a three-month pot experiment with the aim of modifying cell wall composition and structure within the stem to the benefit of bioethanol production. Trees were treated for 26 or 43 days with tension wood induction and/or with an application of the cellulose synthesis inhibitor 2,6-dichlorobenzonitrile that is specific to secondary cell walls. Reaction wood (tension and opposite wood) was isolated from material that had received the 43-day tension wood induction treatment.

RESULTS

Glucan content, lignin content and enzymatically released glucose were assayed. All measured parameters were altered without loss of total stem biomass yield, indicating that enzymatic saccharification yield can be enhanced by both alterations to cell wall structure and alterations to absolute contents of either glucan or lignin.

CONCLUSIONS

Final glucose yields can be improved by the induction of tension wood without a detrimental impact on biomass yield. The increase in glucan accessibility to cell wall degrading enzymes could help contribute to reducing the energy and environmental impacts of the lignocellulosic bioethanol production process.

Abstract 4664: The effect of neoadjuvant androgen deprivation therapy on long-term outcome after radical prostatectomy

Neoadjuvant androgen deprivation therapy (NADT) was championed for men treated with radical prostatectomy (RP) for high risk prostate cancer (CaP) in the early 1990s. Although NADT improved neither surgical margin positivity nor progression-free survival, it continues to be part of some clinical trials. The effect of NADT on long term outcome was evaluated using modern aggressiveness and failure criteria among 720 patients treated with RP at Roswell Park Cancer Institute between 1993 and 2005. Among RP patients, 125 received NADT. NCCN pre-surgery risk categories were low in 36 (29%), intermediate in 54 (43%), and high or very high in 35 (28%). Clinical and pathological aggressiveness indicators included clinical Gleason sum, clinical tumor stage (2002 TNM), highest preoperative PSA, pathological Gleason sum, pathological tumor stage (2002 TNM) and surgical margin status. Ten post-RP recurrence definitions were considered: 1) at least 1 detectable PSA, 2) at least 2 detectable PSAs, 3) PSA&gt;0.2 ng/ml, 4) PSA&gt;0.4 ng/ml, 5) at least 1 post RP treatment (chemotherapy, hormone, radiation), 6) PSA doubling time &lt;9 months, 7) NCCN definition of failure, 8) AUA definition of failure, 9) development of metastatic CaP, 10) death from CaP. In bivariate analysis, men treated with NADT were 105% (p&lt;0.0001) more likely to fail using the AUA definition, 202% (p=0.004) more likely to develop metastatic CaP, and 673% (p=0.001) more likely to die of CaP. The increased risk of recurrence persisted for NADT in multivariate analysis, despite control for all clinical and pathological parameters; the table shows data for clinical and pathological parameters that have been associated with RP failure. Analysis of hazards regression for AUA failure across NCCN risk category demonstrated that NADT was detrimental for men treated with RP, regardless of any level of risk.

Manual and automated systems in the analysis of images from prostate tissue microarray cores

OBJECTIVE

To compare manual and automated image analysis systems in morphologic analysis of nuclei from benign prostate, high-grade prostatic intraepithelial neoplasia (HGPIN) and prostate cancer (CaP). Morphologic features derived using automated image analysis systems may be more objective and reproducible than manual systems, which require humans to segment nuclei from histologic images.

STUDY DESIGN

Images of hematoxylin-eosin-stained sections of prostate tissue microarray were analyzed independently using the automated and manual systems. Mean optical density (MOD), nuclear area (NA), and nuclear roundness factor (NRF) were the morphologic features studied. The ability to differentiate between tissue types using morphologic features derived from an automated and a manual system was compared.

RESULTS

Nuclei from 17 benign prostate hyperplasia (BPH), 4 HGPIN, and 8 aggressive CaP were analyzed. The manual system distinguished better between BPH and HGPIN (p < 0.0001), whereas the automated system distinguished better between BPH and CaP (p = 0.01) in multivariate models. The manual system distinguished better BPH and HGPIN using NA (p < 0.0001) and MOD (p < 0.0001), whereas the automated system distinguished better BPH and CaP using MOD (p < 0.0001) and NRF (p = 0.004).

CONCLUSION

The minimal human effort required for automated image analysis makes it superior to the manual system.

Variability in visual segmentation of digitized prostate tissue microarray cores

OBJECTIVE

To examine bias associated with human-interactive semi-automated systems key components with machine vision used in quantitative histometry.

STUDY DESIGN

A standard image set of 20 images was created using 5 nuclei sampled from hematoxylin-eosin-stained sections of benign tissue within a prostate tissue microarray that were rotated through the cardinal directions. Four trained technicians performed segmentation of these images at the start, then at the end, of 3 daily sessions, creating a total analytic set of 480 observations. Measurements of nuclear area (NA), nuclear roundness factor (NRF), and mean optical density (MOD) were compared by segmenter, time, and rotational orientation.

RESULTS

NA varied significantly among sessions (p < 0.0009) and session variance differed within segmenter (p < 0.0001). NRF was significant among segmenters (p < 0.001) and sessions (p < 0.0001), and in session (p < 0.0001) and intra-session differences (p = 0.026). Differences in MOD varied among sessions (p < 0.0001) and within sessions (p < 0.049).

CONCLUSION

Imaging systems remain vulnerable to statistical inter-segmenter variation, in spite of extensive efforts to eliminate variation among individual segmenters. As statistical significance often guides decision-making in morphometric analysis, statistically significant effects potentially produce bias. Current practices and quality assurance methods require review to eliminate individual operator effects in semiautomated machine systems.

Are compatible solutes compatible with biological treatment of saline wastewater? Batch and continuous studies using submerged anaerobic membrane bioreactors (SAMBRs)

This study investigated fundamental mechanisms that anaerobic biomass employ to cope with salinity, and applied these findings to a continuous SAMBR. When anaerobic biomass was exposed to 20 and 40 g NaCl/L for 96 h, the main solute generated de novo by biomass was trehalose. When we separately introduced trehalose, N-acetyl-β-lysine and potassium into a batch culture a slight decrease in sodium inhibition was observed. In contrast, the addition of 0.1 mM and 1 mM of glycine betaine dramatically improved the adaptation of anaerobic biomass to 35 g NaCl/L, and it continued to enhance the adaptation of biomass to the salt for the next three batch feedings without further addition. No shift in archaeal microbial diversity was found when anaerobic biomass was exposed in batch mode to 35 g NaCl/L for 360 h, and no changes were found when glycine betaine was added. The dominant species identified under these conditions were Methanosarcina mazeii and Methanosaeta sp. The addition of 5 mM glycine betaine to a continuous SAMBR at 12 h hydraulic retention time (HRT), and operation in batch mode for 2 days can significantly enhance saline (35 g NaCl/L) synthetic sewage degradation. In addition, the injection of 1 mM of glycine betaine into a SAMBR for five subsequent days also significantly enhanced dissolved organic carbon (DOC) removal from sewage under these conditions. The main compatible solutes generated by anaerobic biomass after 44 days exposure to 35 g NaCl/L in a SAMBR were N-acetyl-β-lysine and glycine betaine. Finally, the addition of 1 mM glycine betaine to the medium was beneficial for anaerobic biomass in batch mode at 20 °C under saline and non saline conditions.

Pre-operative platelet-bound CD40 ligand is probably associated with peri-operative cardiac events in hip and knee arthroplasty

BACKGROUND

Peri-operative cardiac events are common and associated with significant morbidity. A predictive biomarker would assist in pre-operative risk stratification of surgical patients. This study explored the utility of pre-operative measurements of platelet-bound CD40 ligand and other biomarkers for predicting peri-operative cardiac events in total hip or knee arthroplasty.

METHODS

Blood samples were collected from 62 patients prior to surgery and tested for the biomarkers platelet CD40 ligand, platelet factor V/Va, platelet P-selectin, high-sensitivity C-reactive protein, B-type natriuretic peptide and soluble CD40 ligand. The Revised Cardiac Risk Index was also calculated. Patients were then followed up prospectively and screened for peri-operative cardiac events by means of ECG, serial troponin I, a cardiologist's review and an interview at 6 weeks post operation.

RESULTS

Six of 62 (9.7%) patients had a cardiac event. Patients who experienced a cardiac event had higher pre-operative platelet CD40 ligand levels as measured by flow cytometry [median 0.55% vs. 0.29% (P = 0.02)]. In this sized sample, platelet CD40L was the only biomarker independently associated with cardiac events (P = 0.02), the area under the receiver-operator characteristic curve being 0.79.

CONCLUSION

In a study of this number of patients, of the six biomarkers tested, only platelet CD40 ligand was found to have a probable association with peri-operative cardiac events in hip and knee arthroplasty.

Performance of a three-stage membrane bioprocess treating the organic fraction of municipal solid waste and evolution of its archaeal and bacterial ecology

A novel three-stage bioprocess achieved 75% volatile solids (VS) removal at an organic loading rate (OLR) of 4g VSL(-1)day, a solids retention time (SRT) of 66days, a hydraulic retention time (HRT) of 20days, at a temperature of 35 degrees C. The bioprocess consisted of an anaerobic hydrolytic reactor (HR) where the solids and liquid fractions of the Organic Fraction of the Municipal Solid Waste (OFMSW) were separated with a mesh. The leachate was pumped to a Submerged Anaerobic Membrane Bioreactor (SAMBR) and the treated permeate was polished in an Aerobic Membrane Bioreactor (AMBR). Denaturing Gradient Gel Electrophoresis (DGGE) and DNA sequencing analyses indicated that the increase in methane content in the HR caused by the excess sludge recycle from the SAMBR was associated with an increase in the number of hydrogenotrophic species, mainly Methanobrevibacter sp., Methanobacterium formicicum and Methanosarcina sp. At 20 degrees C VS removal dropped to 50% in the HR and some DGGE bands disappeared when compared to 35 degrees C samples, while some bands such as the one corresponding to Ruminococcus flavefaciens were reduced in intensity. The species associated with the COD-polishing properties of the AMBR correspond to the genera Pseudomonas, Hyphomonas and Hyphomicrobiaceae. These results highlight the positive effect of recycling the excess sludge from the SAMBR to re-inoculate the HR with hydrogenotrophic species.

High-dose tirofiban with enoxaparin and inflammatory markers in high-risk percutaneous intervention

AIM

The study assessed the benefit of high bolus dose tirofiban (HD-tirofiban) with enoxaparin compared with HD-tirofiban with unfractionated heparin (UFH). The study examined markers of platelet activation, thrombin generation and inflammation.

MATERIALS AND METHODS

The study is a prospective single centre open-label trial of patients with high-risk acute coronary syndrome treated with percutaneous intervention (PCI) who were randomized to anticoagulation with UFH or enoxaparin with HD-tirofiban (25 microg kg(-1) bolus). This study measured a panel of platelet activation markers, inflammatory biomarkers and thrombus generation between the two groups.

RESULT

Sixty patients undergoing high-risk PCI were enroled in the study. Platelet inhibition as assessed by whole blood aggregometry following HD-tirofiban infusion was similar in both the UFH and enoxaparin groups. CD40 ligand expression on platelets was significantly reduced following PCI with HD-tirofiban and either UFH or enoxaparin. Following PCI, there were significant reductions measured in other markers of platelet activation including PAC-1, P selectin, factor V/Va, platelet-monocyte aggregates and monocyte expression of Mac-1 as determined by analysis of venous blood samples using flow cytometry. Prothrombin fragment 1+2, D-dimer, von Willebrand factor and high sensitive C-reactive protein levels were significantly less post PCI in the enoxaparin group compared with those patients receiving UFH.

CONCLUSION

The combination of HD tirofiban with enoxaparin resulted in an attenuated inflammatory response when compared with that of the combination of HD tirofiban with UFH.

A comparison of anticoagulation with bivalirudin and provisional GPIIb/IIIa inhibition with unfractionated heparin and mandatory GPIIb/IIIa inhibition during percutaneous coronary intervention in relation to platelet activation and the inhibition of coagulation

AIMS

Our study sought to evaluate mechanisms of the current strategies for optimal anticoagulation during percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Thirty-two high risk acute coronary syndrome patients were randomised to bivalirudin and provisional GPIIb/IIIa inhibition (GPIIb/IIIa) or unfractionated heparin (UFH) and mandatory GPIIb/IIIa. Flow cytometric measurements immediately after anticoagulation showed that, unlike UFH, bivalirudin did not activate platelets as indicated by P-selectin expression and fibrinogen binding while decreasing platelet-monocyte aggregates and monocyte expression of tissue factor. UFH released tissue factor pathway inhibitor (TFPI) during and immediately after PCI while bivalirudin (irrespective of GP IIb/IIIa) did not. Lower levels of TFPI with bivalirudin were seen during and immediately after PCI (P<0.01). Thrombin generation as indicated by prothrombin fragment F 1+2 levels was reduced during PCI in the UFH group (P<0.01) but not with bivalirudin. Soluble CD40 ligand is associated with thrombosis and levels were higher in the bivalirudin group irrespective of GPIIb/IIIa at the same stages (P<0.05).

CONCLUSIONS

Bivalirudin has some early advantages on platelet activation when compared to UFH. However, there are significant limitations in its mechanism of action, particularly a lack of release of tissue factor pathway inhibitor.

Pathology processes and emergency department length of stay: the impact of change

OBJECTIVES

To determine whether redesign of pathology processes, including indicators of sample priority, could reduce patient length of stay (LOS) in an emergency department (ED), and assess the long-term impact of two indicators of sample priority on pathology clinical performance indicators for ED samples.

DESIGN, SETTING AND PARTICIPANTS

Two observational studies of de-identified data from standard databases were conducted--a single-site pilot trial of patients attending the ED of one hospital compared with historical controls, and a multisite study of 132,521 full blood count (FBC) requests for patients attending seven EDs that utilised either of two pathology process changes (coloured specimen transport bags alone, or coloured specimen bags plus blood tubes with a priority indicator).

MAIN OUTCOME MEASURES

LOS in the ED was measured for the pilot trial, and collected-to-validated times for FBCs that fulfilled computer algorithm validation rules were measured for the multisite study.

RESULTS

In the pilot trial, the redesigned pathology process resulted in a 29-minute reduction (15.6%) in the median ED LOS for all patients (P < 0.001) compared with historical controls. In the multisite study, use of coloured specimen bags plus blood tubes with a priority indicator resulted in an 8-minute reduction (20.1%) in mean collected-to-validated times for FBC requests compared with FBC requests that used coloured specimen bags alone (P < 0.001).

CONCLUSIONS

Our pilot trial revealed a direct relationship between pathology process design and LOS in the ED, suggesting that redesigned pathology processes can significantly reduce LOS in the ED. Our multisite study showed that collecting samples directly into blood tubes with an incorporated priority indicator reduces pathology test turnaround times. These data suggest that LOS in the ED can be significantly reduced by simple changes to pathology processes, such as collecting samples directly into specimen containers with an incorporated priority indicator.

Test-retest norms and reliable change indices for the MicroCog Battery in a healthy community population over 50 years of age

The increasing availability of computerized test batteries used to assess neuropsychological changes requires the availability of suitable test-retest normative data. Reliable change indices can then be used to evaluate significance of change in an individual's performance on retesting. We tested (N = 40) neurologically normal adults on three occasions (initially, two weeks, and three months) on the MicroCog: Assessment of Cognitive Functioning computerized testing instrument. Normative retest data are presented for two analytic techniques: the Reliable Change Index adjusted for practice and the Standardized Regression-Based technique. At two weeks, the correlation coefficients ranged from .49 to .84, with all scores demonstrating significant practice effects. At 3 months, coefficients ranged from .50 to .83, with all scores except Attention / Mental Control demonstrating significant practice compared to baseline. Regression equations were generated for all scores using age, sex, education level, and score at Time 1 as predictors. For all measures the only significant predictor was the Time 1 score. The reliable change indices and regression equations presented here can be used to determine the significance of change from predicted retest scores in a matched interventional cohort.

Assessment of statistical change criteria used to define significant change in neuropsychological test performance following cardiac surgery

OBJECTIVE

This paper compares four techniques used to assess change in neuropsychological test scores before and after coronary artery bypass graft surgery (CABG), and includes a rationale for the classification of a patient as overall impaired.

METHODS

A total of 55 patients were tested before and after surgery on the MicroCog neuropsychological test battery. A matched control group underwent the same testing regime to generate test-retest reliabilities and practice effects. Two techniques designed to assess statistical change were used: the Reliable Change Index (RCI), modified for practice, and the Standardised Regression-based (SRB) technique. These were compared against two fixed cutoff techniques (standard deviation and 20% change methods).

RESULTS

The incidence of decline across test scores varied markedly depending on which technique was used to describe change. The SRB method identified more patients as declined on most measures. In comparison, the two fixed cutoff techniques displayed relatively reduced sensitivity in the detection of change.

CONCLUSIONS

Overall change in an individual can be described provided the investigators choose a rational cutoff based on likely spread of scores due to chance. A cutoff value of > or =20% of test scores used provided acceptable probability based on the number of tests commonly encountered. Investigators must also choose a test battery that minimises shared variance among test scores.

Platelet–monocyte aggregates predict troponin rise after percutaneous coronary intervention and are inhibited by Abciximab

BACKGROUND

Platelet-monocyte aggregates and other markers of platelet activation were investigated before and after percutaneous coronary intervention (PCI) with abciximab therapy. The study sought to assess the relationship between the level of platelet-monocyte aggregation and increases in cardiac troponin I post coronary intervention.

METHODS

Blood samples were collected from 40 patients before PCI and 10 min after abciximab administration. These were tested for platelet activation markers by flow cytometry. Cardiac troponin I levels were assayed at baseline and at 24 h post PCI.

RESULTS

Compared to healthy controls, patients with coronary artery disease had elevated markers of platelet activation including platelet-monocyte aggregates, P-selectin and PAC-1 (a marker specific for activated glycoprotein IIb/IIIa) prior to PCI. Increased levels of platelet-monocyte aggregates before PCI were associated with increased expression of P-selectin on the platelet surface. Abciximab therapy reduced platelet-monocyte aggregate levels but had no effect on P-selectin expression. The high levels of expression of activated glycoprotein IIb/IIIa (PAC-1) on platelets prior to PCI was reduced with abciximab therapy. Patients with higher levels of platelet-monocyte aggregates prior to PCI were more likely to develop an elevation of cardiac troponin I during the 24 h after PCI.

CONCLUSIONS

Increased levels of platelet-monocyte aggregates may predict patients at risk for troponin elevation following PCI and identify those most likely to benefit from abciximab.

Point-of-care testing shows clinically relevant variation in the degree of inhibition of platelets by standard-dose abciximab therapy during percutaneous coronary intervention

Administration of GP IIb/IIIa inhibitors during percutaneous coronary intervention (PCI) has proven clinical benefit, but is administered at a dose allowing for the patients' weight but not other variables. This study of 75 patients evaluated platelet inhibition achieved by standard-dose abciximab therapy during PCI as measured by two point-of-care (POC) instruments, Plateletworks (PW) and whole blood aggregation (WB). Results were related to the decrease of platelet activation produced as well as patients' return of angina within 30 days. Flow cytometric measurement showed abciximab suppressed platelet-monocyte aggregates (P < 0.001) and activated glycoprotein IIb/IIIa (P < 0.001) but not P-selectin. Greater POC-measured inhibition corresponded to less postabciximab expression of platelet-monocyte aggregates (P < 0.01). Patients above the lowest quartile of POC inhibition with PW demonstrated a relative risk of experiencing return of angina within 30 days of 0.48 (0.23-0.99). In conclusion, POC measurements reflect platelet activation suppression, higher PW measurements being associated with a decreased risk of return of angina.

Postoperatively administered aprotinin or epsilon aminocaproic acid after cardiopulmonary bypass has limited benefit

BACKGROUND

Intraoperative antifibrinolytic treatment with aprotinin and epsilon aminocaproic acid (EACA) has been shown to be effective prophylaxis in the reduction of excessive bleeding after cardiopulmonary bypass operations. This study investigated the effectiveness of both drugs when used as a postoperative treatment of patients showing early signs of increased bleeding.

METHODS

In a double-blind, randomized study, 69 patients with chest drainage of 100 mL or more 1 hour after bypass were treated with aprotinin, EACA, or placebo.

RESULTS

In the first 24 hours postoperatively, neither drug significantly reduced chest drainage or blood transfusion requirements compared with placebo. Median (interquartile) cumulative chest drainage volumes for the first 24 hours postoperatively for the aprotinin, EACA, and placebo groups were 525 (340, 750), 575 (450, 762), and 650 (550, 800) mL, respectively. Among the study patients, 4 undergoing valve operation and treated with aprotinin showed a trend toward less bleeding during the first 12 hours postoperatively compared with 5 valve operation patients who received placebo (p = 0.06). Among all patients, the treatment with aprotinin or EACA failed to reduce levels of D-dimer compared with placebo after treatment, indicating that fibrinolysis was not significantly inhibited.

CONCLUSIONS

Aprotinin or EACA administered in the early postoperative period was ineffective in reducing postoperative bleeding with the exception of a small group of patients having valve operations in whom aprotinin treatment may have shown some benefit.

Epsilon-aminocaproic acid promotes the release of alpha2-antiplasmin during and after cardiopulmonary bypass

This double-blind, randomized study compared the mechanisms by which low-dose aprotinin and epsilon-aminocaproic acid (EACA) inhibited fibrinolysis during cardiopulmonary bypass surgery. D-dimer levels during and after bypass were similar, indicating an equivalent inhibition of fibrinolysis. Effects on tissue plasminogen activator release were not associated with the inhibition of fibrinolysis by either drug. Treatment with EACA was associated with a substantial release of endogenous alpha2-antiplasmin, particularly 1 h after bypass. Compared with the aprotinin group, higher levels of the plasmin-alpha2-antiplasmin complex in the EACA group confirmed an increased inhibition of plasmin by alpha2-antiplasmin. In conclusion, it is hypothesized that EACA inhibited fibrinolysis by stimulating the release of the patients' own alpha2-antiplasmin.

Comparison of epsilon aminocaproic acid and low-dose aprotinin in cardiopulmonary bypass: efficiency, safety and cost

BACKGROUND

In this study we compared the clinical efficiency, safety, and economic benefit of low-dose aprotinin with epsilon aminocaproic acid (EACA) in reducing bleeding after cardiopulmonary bypass operation.

METHODS

In a double-blind, randomized study, 100 patients received low-dose aprotinin (2 x 10(6) kallikrein inhibitor units) or EACA (20 g). The surgical procedure was single- or double-valve replacement with or without coronary artery bypass grafts.

RESULTS

Mediastinal chest drainage and transfusion requirements with both therapies were similar. There were no urgent reoperations to secure hemostasis in either group. Similar levels of D-dimer with both therapies indicate a similar inhibition of fibrinolysis. Release of troponin I was less in the low-dose aprotinin group 1 and 4 hours after bypass, although electrocardiographic measurements did not reflect this difference. Levels of S-100beta and neuron-specific enolase were similar with both therapies, confirming that there was no difference in the occurrence of any adverse neurologic events in either group.

CONCLUSIONS

Low-dose aprotinin and EACA showed similar effects on the reduction of intraoperative and postoperative bleeding. The lower cost of EACA with no change in safety outcome suggests it is the preferred treatment.

Remifentanil and controlled hypotension; comparison with nitroprusside or esmolol during tympanoplasty

PURPOSE

To determine whether remifentanil, combined with propofol, could induce controlled hypotension, reduce middle ear blood flow (MEBF) measured by laser-Doppler flowmetry, provide a "dry" operative field, and could be compared with nitroprusside or esmolol combined with alfentanil and propofol.

METHODS

Thirty patients undergoing tympanoplasty and anesthetized with 2.5 mg x kg(-1) propofol iv followed by a constant infusion of 120 microg x kg(-1) x min(-1), were randomly assigned in three groups to receive either 1 microg x kg(-1) remifentanil iv followed by a continuous infusion of 0.25 to 0.50 microg x kg(-1) x min(-1), or nitroprusside iv, or esmolol iv combined for the latter two groups with alfentanil iv.

RESULTS

Controlled hypotension was achieved at the target pressure of 80 mmHg within 107 +/- 16, 69 +/- 4.4, 53.3 +/- 4.4 sec for remifentanil, nitroprusside and esmolol respectively. MEBF decreased by 24 +/- 0.3, 22 +/- 3.3, 37 +/- 3% and preceded the decrease in SABP, within 30 +/- 6.1, 11.2 +/- 3.1, 15 +/- 2.8 sec for remifentanil, nitroprusside and esmolol respectively. Remifentanil, and nitroprusside decreased MEBF autoregulation less than esmolol (0.36 +/- 0.1, 0.19 +/- 0.2, -0.5 +/- 0.2). Controlled hypotension was sustained in all three groups throughout surgery, and the surgical field rating decreased in a range of 80% in all three groups. Nitroprusside decreased pH and increased PaCO2. There were no postoperative complications in any of the groups.

CONCLUSIONS

Remifentanil combined with propofol enabled controlled hypotension, reduced middle ear blood flow and provided good surgical conditions for tympanoplasty with no need for additional use of a potent hypotensive agent.

Economic evaluation of high-dose and low-dose aprotinin therapy during cardiopulmonary bypass

BACKGROUND

Aprotinin therapy is now widely used during cardiac surgery. This study examined the clinical and economic effectiveness of high-dose or low-dose aprotinin in comparison to placebo.

METHODS

In a double blind, randomized study, three groups of 50 patients received high-dose aprotinin costing AUS$614 per patient (AUS$ = Australian dollars), low-dose aprotinin costing AUS$220 per patient or placebo. Resource use influenced by aprotinin therapy was measured.

RESULTS

Both doses were effective in reducing chest drainage and postoperative transfusion requirements, high-dose being more effective than low-dose. Both doses reduced the rate of reoperations for hemostasis. A base case of statistically significant differences associated with the high-dose and low-dose aprotinin showed cost savings of AUS$77 and AUS$348 per patient, respectively. If the demonstrated less significant reductions in operating room and ward stay are included, these savings become AUS$463 and AUS$715, respectively. Alternately, if cross-matches are replaced by group-and-hold and cell savers are not used, the savings per patient would be AUS$196 and AUS$467, respectively.

CONCLUSIONS

While high-dose aprotinin is clinically more effective than low-dose aprotinin, low-dose therapy demonstrates greater cost savings.

Aprotinin reduces blood loss after cardiopulmonary bypass by direct inhibition of plasmin

The effectiveness and mechanism of aprotinin reduced bleeding after cardiopulmonary bypass surgery was studied in a double blind randomised study of 106 patients undergoing valve replacement surgery. Aprotinin therapy was associated with significant reduction in perioperative bleeding and postoperative blood transfusion requirements. Although initially tissue plasminogen activator (t-PA) activity was lower in the aprotinin than placebo group, as surgery proceeded this difference was reversed due to less plasminogen activator inhibitor-1 release in the aprotinin group. This indicates that aprotinin-mediated suppression of fibrinolysis as demonstrated by reduced D-dimer concentration was not related to t-PA. Furthermore, similar perioperative reduction of plasminogen levels in aprotinin and placebo groups indicated a similar degree of conversion of plasminogen to plasmin. However, less plasmin bound with alpha 2-antiplasmin in the plasma in the aprotinin group as it was already complexed with aprotinin where it remained protected from the natural inhibitor on the intact fibrin surface. The reduced fibrinolytic activity of the aprotinin group was thus brought about by the complexing of aprotinin with the plasmin which was bound to the fibrin surface.

Structural analysis of apolipoprotein A-I: limited proteolysis of methionine-reduced and -oxidized lipid-free and lipid-bound human apo A-I

The domain structures of lipid-free and lipid-bound apolipoprotein A-I (apo A-I) containing reduced and oxidized methionines were analyzed by limited proteolysis. Lipid-free apo A-I is cleaved primarily in the extreme carboxy-terminus and, to a much lesser extent, in the central region of the protein between residues 115 and 136. Oxidation of methionines 112 and 148 to the corresponding sulfoxides in putative amphipathic helices 4 (P99-E120) and 6 (P143-A164), respectively, causes helices 1 (L44-G65), 2 (P66-S87), and 7 (P165-G186) to become susceptible to protease digestion. These results are consistent with a discrete, globular tertiary structure for the lipid-free protein minimally formed from amphipathic helices 1, 2, 4, 6, and 7. In distinct contrast to lipid-free apo A-I, lipid-bound apo A-I is most susceptible to cleavage in the extreme amino-terminus and, to a lesser extent, in both the central and carboxy-terminal regions. The observed cleavage pattern for the reduced lipid-bound protein supports the existence of many of the turns between helices predicted by sequence analysis of the lipid-bound protein. Methionine oxidation of lipid-bound protein results in a decreased protease susceptibility in the extreme amino-terminus and a concomitant increase in protease susceptibility in the central and carboxy-terminal regions. The results from methionine oxidation indicate the oxidation state of the protein is an important determinant in defining the conformation of both lipid-free and lipid-bound apo A-I.

Truncation of the amino terminus of human apolipoprotein A-I substantially alters only the lipid-free conformation

An amino-terminal deletion mutant (residues 1-43) of human apolipoprotein A-I (apo hA-I) has been produced from a bacterial expression system to explore the structural and functional role of these amino acids, encoded by exon 3, in apo hA-I. Lipid binding of apo delta (1-43)A-I and lipid binding of apo hA-I are very similar as assessed by surface activity, lipid association with palmitoyloleoylphosphatidylcholine (POPC) vesicles, and lipid association with plasma lipoproteins. Preliminary kinetic measurements appear to show that the reactivity of lecithin:cholesterol acyltransferase (LCAT) with the mutant is slightly decreased compared to wild-type apo hA-I. Collectively, these results indicate that the N-terminal region is not necessary for lipid binding or activation of LCAT. In contrast, there are significant structural differences between lipid-free apo delta (1-43)A-I and apo hA-I, as judged by denaturant-induced unfolding, binding of the fluorescent probe 1-anilinonaphthalene-8-sulfonate, surface balance measurements, and far- and near-ultraviolet circular dichroic spectroscopy. All spectral and physical measurements indicate apo delta (1-43)A-I has a folded, tertiary structure, although it is significantly less stable than that of apo hA-I. It is concluded that the N-terminal 43 residues are an important structural element of the lipid-free conformational state of apo hA-I, the absence of which induces a fundamentally different fold for the remaining carboxy-terminal residues, compared to those in native apo hA-I.

Preoperative platelet dysfunction increases the benefit of aprotinin in cardiopulmonary bypass

BACKGROUND

This study was designed to determine the benefit of aprotinin therapy in reducing bleeding during and after cardiopulmonary bypass in patients with preoperative platelet dysfunction. Platelet function involvement in the mechanism by which aprotinin acts was also investigated.

METHODS

In a double-blind, randomized study, patients received high-dose aprotinin (n = 54) or placebo (n = 52). Whole blood aggregation was measured preoperatively. Platelet function and activation in both groups were assessed intraoperatively and postoperatively at five times.

RESULTS

Aprotinin significantly reduced perioperative bleeding and postoperative blood transfusion. Placebo-treated patients with reduced preoperative platelet aggregation bled more postoperatively, but aprotinin reduced the bleeding in patients with normal or reduced platelet function to similar levels. Any cardiopulmonary bypass-induced changes in platelet aggregation, platelet activation as measured by P-selectin expression, and von Willebrand factor antigen and function were similar in aprotinin-treated and placebo-treated groups.

CONCLUSIONS

The mechanism by which aprotinin reduced bleeding was independent of any effect on platelet function. However, aprotinin produced a greater reduction in bleeding among patients whose condition was hemostatically compromised by preoperative platelet dysfunction.

Changes in plasminogen activator inhibitor-1 levels in non-small cell lung cancer

Increased urokinase plasminogen activator (uPA) levels are increased in a number of malignancies and have been correlated with decreased disease-free interval and decreased overall survival. We have, therefore, examined components of this plasminogen activating system in patients with Non-Small Cell Lung Cancer (NSCLC). Levels of uPA, urokinase-plasminogen activator receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1) were measured semiquantitatively in paraffin sections of tumours from 147 patients with NSCLC. Immunohistochemically stained sections of tumour were allocated a score for stain intensity and results correlated to: survival; tumour stage(T); nodal stage(N); stage grouping (I to IIIb), survival status and sex. Increased levels of PAI-1 were associated with a decreased survival in squamous cell carcinoma (SCC) X2 = 5.72, p = 0.017 (n = 74). There was a significant positive relationship between PAI-1 levels and N-stage (p = < 0.05), presence of nodal metastases (p = < 0.05), stage grouping (p = < 0.01) and extent of disease (p = < 0.05) in the total group and the SCC subgroup, but not adenocarcinoma. There was a significant positive relationship between PAI-1 levels and T-stage (p = < 0.05) in the total group, and survival status (p = < 0.05) in the SCC subgroup alone. uPA and uPAR levels were not significantly associated with tumour staging or survival. We conclude that increased PAI-1 antigen levels may be associated with a decreased survival in patients with SCC.

A proposed model to monitor heparin therapy using the concentrated thrombin time which allows standardisation of reagents and improved estimation of heparin concentrations

The concentrated thrombin time (CTT), a thrombin time performed with a high concentration of thrombin, was evaluated as an alternative to the activated partial thromboplastin time (APTT) for monitoring of heparin therapy. Forty-nine plasmas from patients receiving unfractionated heparin therapy were tested. It was first demonstrated that CTTs using three commercial reagents could be standardised against CTTs performed with a reference reagent, MRC reagent 66/305. For comparison, APTTs were performed on the plasmas. As a benchmark of the degree of heparinisation, the heparin concentration of the plasmas was determined by chromogenic anti-IIa heparin assays, therapeutic range being 0.2-0.4 units/ml. The optimal relationships of the CTTs and APTT with the heparin concentration were established. These were used to predict the heparin concentrations of the plasmas from the results of the APTT, CTT performed with the reference reagent, and transformed CTT performed with each of the three commercial reagents. In predicting the assayed plasma heparin concentrations, the accuracy of the APTT was only 53%, while the CTT was from 78 to 82%. The CTT can be standardised and, subject to results of clinical trials, could provide an improved method of monitoring heparin therapy.