Variability of predialytic, intradialytic, and postdialytic blood pressures in the course of a week: a study of Dutch and US maintenance hemodialysis patients

BACKGROUND

Patients with thrice-weekly hemodialysis have higher predialysis weights and ultrafiltration rates at the first compared with subsequent dialysis sessions of the week. We hypothesized that these variations in weight and ultrafiltration rate are associated with a systematic difference in blood pressure.

STUDY DESIGN

Observational study.

SETTING & PARTICIPANTS

During 3 months, we prospectively collected hemodynamic data for 4,007 hemodialysis sessions involving 124 Dutch patients. A similar analysis was performed with 789 US patients, comprising 6,060 hemodialysis sessions.

FACTOR

First versus subsequent hemodialysis sessions of the week.

OUTCOMES

Blood pressure.

MEASUREMENTS

Blood pressure, weight, and ultrafiltration rate were analyzed separately for the first, second, and third dialysis sessions of the week. Comparisons were made with linear mixed models.

RESULTS

In Dutch patients, predialysis weight and ultrafiltration rate were significantly greater at the first compared with subsequent hemodialysis sessions of the week (P < 0.001). Predialysis systolic and diastolic blood pressures were higher at the first than at subsequent sessions of the week (P < 0.001). Predialysis blood pressure differences persisted throughout the session: systolic and diastolic blood pressures were on average 5.0 and 2.5 mm Hg higher during the first compared to the third session of the week. Postdialysis blood pressures followed a similar pattern (P < 0.001). Blood pressure differences between the first and subsequent days of the week persisted after adjustment for possible confounders. Results in the US cohort were materially identical despite differences in patient characteristics and treatment practice between the 2 cohorts.

LIMITATIONS

Dry weight was not assessed by objective methods.

CONCLUSIONS

Blood pressure of patients on a thrice-weekly dialysis schedule varies systematically over the week. Predialysis blood pressure is highest at the first hemodialysis session of the week, most likely due to greater interdialytic weight gain. Intra- and postdialytic blood pressures also are highest at the first session of the week despite higher ultrafiltration rates.

Improving the delivery of coordinated and individualized care

Pharmatech comprises systems for the automated use and coordination of clinical information, medical devices, care paths, and pharmacologic agents into specific prescription and care-delivery processes tailored to meet individual patient needs. In ESRD, future suites of applications to run on hemodialysis, peritoneal dialysis machines, external computers and devices both in-center and in the home setting offer the potential to further automate billing and inventory, improve documentation, reduce medical errors, and decrease costs. On a clinical basis, these systems will aid nurses, physician assistants, nurse practitioners, and physicians in performing and overseeing a wide range of clinical activities that constitute 21st-century medicine. Future innovations may allow Pharmatech systems to learn by achieving defined outcomes. These developments offer the potential to provide customized ESRD care by integrating standard practices with individual patient characteristics and patient-specific needs. The development of Pharmatech represents one of the next advances in healthcare technology and will become an important component in the delivery of 21st-century medicine. Adoption of information technology (IT) has been prioritized by the federal government, and is a key component of US healthcare policy. The United States Agency for Healthcare Research and Quality is currently funding the development and implementation of a wide array of health IT applications. This extensive funding combined with rapid technologic advances will continue to drive Pharmatech development and the widespread implementation of medical IT in the coming decade.

Effects of citrate acid concentrate (citrasate®) on heparin N requirements and hemodialysis adequacy: a multicenter, prospective noninferiority trial

BACKGROUND

Citrasate®, citric acid dialysate (CD), contains 2.4 mEq of citric acid (citrate), instead of acetic acid (acetate) as in standard bicarbonate dialysate. Previous studies suggest CD may improve dialysis adequacy and decrease heparin requirements, presumably due to nonsystemic anticoagulant effects in the dialyzer.

METHODS

We prospectively evaluated 277 hemodialysis patients in eight outpatient facilities to determine if CD with reduced heparin N (HN) would maintain dialyzer clearance. Subjects progressed through four study periods [baseline (B): bicarbonate dialysate + 100% HN; period 1 (P1): CD + 100% HN; period 2 (P2): CD + 80% HN; period 3 (P3): CD + 66.7% HN]. The predefined primary endpoint was noninferiority (margin -8%) of the percent change in mean dialyzer conductivity clearance between baseline and P2.

RESULTS

Subjects were 57.4% male, 41.7% white, 54.3% black, and 44.4% diabetic; mean age was 59 ± 14.4 years; mean time on dialysis was 1,498 ± 1,165 days; 65.7% had arteriovenous fistula, 19.9% arteriovenous graft, 14.4% catheters, and 27.8% used antiplatelet agents. Mean dialyzer clearance increased 0.9% (P1), 1.0% (P2), and 0.9% (P3) with CD despite heparin reduction. SpKt/V remained stable (B: 1.54 ± 0.29; P1: 1.54 ± 0.28; P2: 1.55 ± 0.27; P3: 1.54 ± 0.26). There was no significant difference in dialyzer/dialysis line thrombosis, post-HD time to hemostasis, percent of subjects with adverse events (AEs), or study-related AEs.

CONCLUSIONS

CD was safe, effective, and met all study endpoints. Dialyzer clearance increased approximately 1% with CD despite 20-33% heparin reduction. Over 92% of P3 subjects demonstrated noninferiority of dialyzer clearance with CD and 33% HN reduction. There was no significant difference in dialyzer clotting, bleeding, or adverse events.

Vascular Access Monitoring Improves Outcomes

Vascular access monitoring can identify patients at increased risk of future access thrombosis. When coupled with a program of elective stenosis correction, access thrombosis rates decline approximately 50-75%. This results in arteriovenous (AV) fistula thrombosis rates of 0.1-0.2/patient year (vs. 0.2-0.4 at baseline) and AV graft thrombosis rates <0.5/patient year (vs. 0.8-1.2 thromboses/patient year at baseline). Evaluating the long-term impact on access survival remains problematic. There are no large-scale randomized trials and existing studies exhibit marked differences in target populations, clinical protocols and outcome definitions. Differences in payment systems also significantly influence the efficacy of monitoring and intervention programs. Despite these challenges, the current data support the K/DOQI recommendations that all patients undergo a program of regular access monitoring preferably by access flow measurement coupled with prompt imaging and elective stenosis correction for low flow accesses.

Focused vascular access education to reduce the use of chronic tunneled hemodialysis catheters: results of a network quality improvement initiative

Tunneled hemodialysis catheters (TDCs) carry the highest mortality risk for chronic hemodialysis patients of any access modality. Recent data have emphasized that mortality risk decreases when these devices are discontinued. Herein, we present the results of a gap-reduction assisted catheter elimination strategy that Network 7 employed as its quality improvement initiative to reduce the use of TDCs. Hemodialysis facilities with high catheter rates (>90 days) were identified. Interventions included focused vascular access education, monthly follow-up and site visits to assist the facility catheter reduction program. The "goal" of interventions was defined as the gap-reduction of 50% from the baseline catheter rate to the Network mean plus sustainability of catheter reduction for at least 3 consecutive months. Fifteen facilities (n = 891) were identified with high catheter rates (31.5 +/- 5.3%) in May 2006. Interventions resulted in a catheter reduction to 12.2 +/- 8.5% in May 2007 (p = 0.0001). Five of the 15 facilities (n = 280) achieved the goal (preintervention = 31.7 +/- 5.3%, postintervention = 8.7 +/- 2.8%, p = 0.001). In May 2007, eight additional facilities (n = 438) with high catheter rates (31.7 +/- 7.8%) were added to the 10 that failed to achieve the goal previously. Interventions employed in these 18 facilities (n = 1,049) resulted in catheter reduction in all (preintervention = 31.5 +/- 5.5%, postintervention = 16.2 +/- 5%, p = 0.01). Five of these 18 met the goal (preintervention = 32 +/- 8%, postintervention = 5.9 +/- 4.3%). Overall, all 23 facilities (n = 1,329) demonstrated catheter reduction postintervention (preintervention = 31.6 +/- 6%, postintervention = 13.9 +/- 6%, p = 0.001), and 10/23 (43%) met the project goal (preintervention = 31.9 +/- 6%, postintervention = 7.3 +/- 4%, p = 0.002). Medical director's involvement had a positive impact in achieving the goal (p = 0.003). The presence or absence of a vascular access coordinator did not affect catheter reduction. The results of this analysis reveals that an organized approach implemented by an ESRD Network can have a significant impact in reducing catheter use.

Vascular access: the past, present and future

Over the past 40 years, improvements in vascular access management have enhanced patient outcomes and decreased an epidemic of access failure. Arteriovenous fistulae are again the access of choice and new percutaneous therapies and outpatient access centers have revolutionized the therapeutic approach to access failure. Evidence-based guidelines, supported by national and international outcome data have helped rationalize vascular access care. Current challenges and, in particular, the increased use of catheters with resultant increases in patient morbidity and mortality must be rapidly addressed to protect patients and decrease the unacceptably high rates of catheter-related infection. Future technologies will continue to improve vascular access management. Our ability to utilize these new approaches to benefit patients will depend on appropriate application, continued development of standardized delivery systems utilizing outcome measures and payment systems that support and incent outcome improvement.

Facility hemodialysis vascular access use and mortality in countries participating in DOPPS: an instrumental variable analysis

BACKGROUND

Previously, the Dialysis Outcomes and Practice Patterns Study (DOPPS) has shown large international variations in vascular access practice. Greater mortality risks have been seen for hemodialysis (HD) patients dialyzing with a catheter or graft versus a native arteriovenous fistula (AVF). To further understand the relationship between vascular access practice and outcomes, we have applied practice-based analyses (using an instrumental variable approach) to decrease the treatment-by-indication bias of prior patient-level analyses.

STUDY DESIGN

A prospective observational study of HD practices.

SETTING & PARTICIPANTS

Data collected from 1996 to 2004 from 28,196 HD patients from more than 300 dialysis units participating in the DOPPS in 12 countries.

PREDICTOR OR FACTOR

Patient-level or case-mix-adjusted facility-level vascular access use. OUTCOMES/MEASUREMENTS: Mortality and hospitalization risks.

RESULTS

After adjusting for demographics, comorbid conditions, and laboratory values, greater mortality risk was seen for patients using a catheter (relative risk, 1.32; 95% confidence interval, 1.22 to 1.42; P < 0.001) or graft (relative risk, 1.15; 95% confidence interval, 1.06 to 1.25; P < 0.001) versus an AVF. Every 20% greater case-mix-adjusted catheter use within a facility was associated with 20% greater mortality risk (versus facility AVF use, P < 0.001); and every 20% greater facility graft use was associated with 9% greater mortality risk (P < 0.001). Greater facility catheter and graft use were both associated with greater all-cause and infection-related hospitalization. Catheter and graft use were greater in the United States than in Japan and many European countries. More than half the 36% to 43% greater case-mix-adjusted mortality risk for HD patients in the United States versus the 5 European countries from the DOPPS I and II was attributable to differences in vascular access practice, even after adjusting for other HD practices. Vascular access practice differences accounted for nearly 30% of the greater US mortality compared with Japan.

LIMITATIONS

Possible existence of unmeasured facility- and patient-level confounders that could impact the relationship of vascular access use with outcomes.

CONCLUSIONS

Facility-based analyses diminish treatment-by-indication bias and suggest that less catheter and graft use improves patient survival.

Vascular access 2007

Over the past decades, vascular access management has undergone profound changes resulting in marked improvements in patient care. AV fistulae remain the access of choice and continue to represent the majority of accesses in most countries. Access monitoring is more widely available and new percutaneous therapies have revolutionized the therapeutic approach to access failure. Outpatient access centers providing both percutaneous and surgical therapies have decreased the need for vascular access related hospitalization. These advances have been supported by the development and promulgation of standardized evidence-based guidelines. These guidelines supported by national and international outcome data have helped rationalize vascular access care. Despite these advances many challenges remain. Catheter use has increased on a worldwide basis, with resultant increases in catheter related infections and complications including sepsis, endocarditis and paravertebral abscess. The availability and use of standardized chronic kidney disease care including early access placement in preparation for dialysis initiation remains underutilized in most settings. Payment system and structural barriers often provide disincentives for the efficient outpatient application of available technologies and there are a few available large prospective trials to help guide therapies. As we look to the future, it is anticipated that a wide range of new technologies will continue to improve vascular access management. Enhancing our delivery systems, combined with he thoughtful application of these technologies including new biologics, materials, interventional techniques and cellular technologies offer the promise of continued improvements in patients vascular access care over the coming decade.

Predicting hospitalization and mortality in end-stage renal disease (ESRD) patients using an Index of Coexisting Disease (ICED)-based risk stratification model

We evaluated the use of an additive Index of Coexisting Diseases (ICED)-based stratification schema to determine subsequent hospitalization and mortality in a hemodialysis population. Patients from five commercial health plans were stratified into low-, medium-, and high-risk groups and followed for up to 1 year. Patients were reassessed and restratified at 90-day intervals and censored when disease management ceased. Outcome measures collected through selfreports and health plan records were captured in an active database. Survival to first hospitalization/ mortality was compared by Kaplan Meier curves, survivor function differences by the Wilcoxon test, and group comparisons by ANOVA and chi square. Population characteristics included mean age of 63.0, 57.7% male, and 58.8% diabetic. Mortality was 13.0% per patient year (standardized mortality ratio 0.43) and the hospitalization rate was 0.59 per patient year (standardized hospitalization ratio 0.24). Survival curves demonstrated differences in mortality and hospitalization between the patients in different initial risk categories (p < 0.01). Mean hospitalizations were 0.81 +/- 1.53 per patient year (high risk), 0.45 +/- 0.99 (medium risk), and 0.15 +/- 0.51 for the low-risk group (p < 0.001). Stratification was dynamic; 47.3% decreased and 4.7% increased risk level between the first and second assessment. These changes were associated with survival differences for initial low (p = 0.06) or medium patients (p < 0.01), and hospital-free survival for initial medium (p = 0.08) or high patients (p < 0.05). In conclusion, this ICED-based stratification schema predicted mortality and hospitalization for hemodialysis patients participating in our disease management program.

Increasing AV Fistulae and Decreasing Dialysis Catheters: Two Aspects of Improving Patient Outcomes

Maximizing arteriovenous (AV) fistula prevalence and minimizing catheter use have become the dominant issues in hemodialysis vascular access management and offer the promise of improved patient outcomes with decreased overall expenditures. Recent efforts have increased AV fistula prevalence in the US to 42.9% with regional rates as high as 59.5% and with complementary declines in AV grafts. This should decrease access procedures but may not fully realize the potential reductions in mortality and cost possible if combined with catheter reduction. Successful catheter reduction requires similar approaches to those utilized in the Fistula First Program. Educating patients, the use of clearly defined protocols and updating payment systems to include chronic kidney disease care are crucial to continued progress. Expansion of the Fistula First Program to include a focus on decreasing catheter prevalence and complications should be considered as a requirement in the push toward the breakthrough targets of 66% AV fistula prevalence.

Disease Management Improves End-Stage Renal Disease Outcomes

BACKGROUND/AIMS

Renal disease management organizations have reported achieving significant decreases in mortality and hospitalization in conjunction with cost savings, improved patient satisfaction and quality of life. Disease management organizations strive to fill existing gaps in care delivery through the standardized use of risk assessment, predictive modeling, evidence-based guidelines, and process and outcomes measurement. Patient self-management education and the provision of individual nurse care managers are also key program components.

METHODS

As we more fully measure clinical outcomes and total healthcare costs, including payments from all insurance and government entities, pharmacy costs and out of pocket expenditures, the full implications of disease management can be better defined.

RESULTS

The results of this analysis will have a profound influence on United States healthcare policy.

CONCLUSION

At present current data suggest that the promise of disease management, improved care at reduced cost, can and is being realized in end-stage renal disease.

Dedicated outpatient vascular access center decreases hospitalization and missed outpatient dialysis treatments

Dedicated outpatient vascular access centers (VAC) specializing in percutaneous interventions (angiography, thrombectomy, angioplasty and catheter placement) provide outpatient therapy that can obviate the need for hospitalization. This paper reports the impact of one VAC staffed by interventional nephrologists on vascular access-related hospitalization and missed outpatient dialysis treatments. We performed a retrospective analysis of vascular access-related hospitalized days and missed vascular access-related outpatient dialysis treatments from 1995 to 2002 in 21 Phoenix Arizona Facilities (5928 cumulative patients) and 1275 cumulative Fresenius Medical Care North America (FMCNA) facilities (289,454 cumulative patients) to evaluate the impact of the introduction of a VAC in Phoenix. Vascular access-related hospitalized days/patient year and missed dialysis treatments/patient year declined from 1997 to 2002 across all access types. The decline was greater in Phoenix and coincided with the creation of a VAC in 1998. By 2002, there were 0.57 fewer hospitalized days/patient year and 0.29 fewer missed treatments/patient year than in the national sample (P<0.01). In 2002, the relative risk for vascular access hospitalized days was 0.38 (95% confidence interval (CI) 0.27-0.5) (P<0.01) and for vascular access-related missed outpatient dialysis treatments was 0.34 (95% CI 0.24-0.49) (P<0.01) in Phoenix vs FMCNA after adjustment for age, gender, diabetic status duration of dialysis and access type. VAC development was associated with a significant decrease in vascular access-related hospitalization and missed outpatient dialysis treatments. Further studies are necessary to demonstrate this effect in other communities.

Disease Management Improves ESRD Outcomes

Renal disease management organizations have reported achieving significant decreases in mortality and hospitalization in conjunction with cost savings, improved patient satisfaction and quality of life. Disease management organizations strive to fill existing gaps in care delivery through the standardized use of risk assessment, predictive modeling, evidence based guidelines and process and outcomes measurement. Patient self-management education and the provision of individual nurse care managers are also key program components. As we more fully measure clinical outcomes and total health-care costs including payments from all insurance and government entities, pharmacy costs and out-of-pocket expenditures, the full implications of disease management can be better defined. The results of this analysis will have a profound influence on United States healthcare policy. At present, current data suggests that the promise of disease management, improved care at reduced cost, can and is being realized in ESRD.

Improving vascular access outcomes: a systems approach to eliminating structural barriers

Maximizing AV fistula creation, regular access monitoring, prompt outpatient interventions and minimizing catheter use are well-accepted approaches for vascular access management. Systemic barriers impede the application of these strategies. A misaligned reimbursement system coupled with educational deficits and a lack of accountability has contributed to the institutionalization of substandard vascular access care. The hallmark of performance management is to create systems in which incentives are aligned to produce desired behaviors. Realigning reimbursement through a combination of pre-ESRD funding, enhancements to the composite rate to reward outcomes and cover vascular access monitoring and updated reimbursement for outpatient vascular access procedures would improve care and decrease unnecessary hospitalizations. This should be coupled with clearly defined outcome standards and accountability incorporated into hospital accreditation and credentialing. Capitation may provide alternative solutions. A two-phased approach including reimbursement reform while exploring capitation represents a prudent course with the best likelihood of success.

The role of color flow Doppler ultrasound in dialysis access

Color flow Doppler provides accurate imaging and access flow volume measurement of the hemodialysis vascular access. It can readily identify subsets of patients at high risk for future thrombosis. It is noninvasive, mobile, and allows convenient clinical evaluation at the dialysis facility. In Europe, Doppler ultrasound has become the standard of care for evaluation of arteriovenous (AV) fistula dysfunction and is essential in the preoperative evaluation for access placement. It also can diagnose the arterial inflow disease that has become more prevalent in our aging, diabetic, end-stage renal disease (ESRD) population. Access management programs based on Doppler ultrasound have been highly successful and have produced outcome data as good or better than provided with other techniques. In light of its proven clinical efficacy, reimbursement and regulatory agencies should allow its appropriate inclusion into integrated access management programs. In conclusion, Doppler ultrasound should be included as a part of an integrated vascular access management program. This is supported by clinical outcome data and direct comparisons with other modalities.

Systemic barriers to improving vascular access outcomes

Vascular access dysfunction is the most frequent cause of hospitalization for end-stage renal disease (ESRD) patients. Our system of vascular access care and industry standards developed for historic reasons have resulted in a haphazard approach to access management. The Dialysis Outcome Quality Initiative has provided a road map for improving vascular access management. However, despite widespread acceptance, these recommendations are not routinely followed. This is largely the result of inertia coupled with systemic barriers to improving access outcomes. These barriers include lack of funded pre-ESRD care and preoperative imaging, lack of reimbursement for access monitoring, unavailable surgical and interventional suites, erosion of the real value of the composite rate, bundling of additional new services without rate adjustment, poor accountability of surgeons and hospitals, and a reimbursement system that rewards procedures and, in particular, graft and catheter placement. Currently, Center for Medicare and Medicaid Services is reevaluating the composite rate and its included bundle of services. To provide the best access care with the fewest complications while insuring multidisciplinary involvement and accountability, a realistic appraisal and realignment of incentives must be developed to insure improvement of access care in the United States.

Frequency of anti-heparin-platelet factor 4 antibodies in hemodialysis patients and correlation with recurrent vascular access thrombosis

Heparin-induced thrombocytopenia (HIT), characterized by the formation of antibodies to a complex of platelet factor 4 (PF4) and heparin, is a well-recognized risk factor for thromboembolic complications. The frequency of antibody development varies among patient populations. Hemodialysis patients have repeated heparin exposure and should be at risk of developing HIT. This might, contribute to the development of vascular access thrombosis. We prospectively evaluated 88 hemodialysis patients for the presence of anti-PF4/heparin antibodies. Eighteen patients (20%) had a prior history of 1 or more prior access thrombosis. One patient (1.14%), without a history of graft thrombosis, tested positive for anti-PF4/heparin antibodies. In our study, the presence of anti-PF4/heparin antibodies was rare and was not increased in patients with a history of vascular access thrombosis.

Antibodies to prothrombin, factor V, and beta2-glycoprotein I and vascular access thrombosis

We studied 88 hemodialysis patients for the presence of antibodies to human factor II (hFII), bovine factor V (bFV), and human beta2-glycoprotein 1 (beta2GPI). Forty-one patients had elevated anti-hFII antibodies, 17 had elevated anti-bFV antibodies, and 9 had elevated anti-beta2GPI antibodies. Fifty-two patients had elevated antibodies to one or more protein. Patients with PTFE grafts had elevated antibodies most frequently (21 [75%] vs. 20 fistulas [45%; p = 0.016 compared with PTFE] and 11 tunneled catheters [68.8%]). Twelve of 13 patients (92.3%) with PTFE grafts and thrombosis had elevated antibody levels, compared with 9 of 15 without thrombosis (60%; p = 0.049). The number of thromboses and mean thrombosis rates were significantly higher in PTFE patients with antibodies (1.24 vs. 0.14 thromboses, p < 0.01; 42.67 vs. 6.44 thromboses/100 patient years, p < 0.05). When analyzed individually, thrombotic complications occurred more frequently in patients with PTFE grafts and elevated anti-bFV antibodies (p = 0.016), but did not correlate with anti-hFII or anti-beta2GPI antibodies. Thrombotic complications did not correlate with elevated antibody levels in patients with AV fistulas or cuffed catheters. In conclusion, hemodialysis patients with PTFE grafts frequently have elevated antibodies to FII, FV, and beta2GPI, and the presence of elevated antibody levels to one or more of these proteins is associated with an increased thrombotic risk. Further studies are necessary to determine whether limiting exposure to bovine thrombin preparations will decrease the incidence of these antibodies and PTFE graft thrombosis.

Increasing AV fistulas: revisiting a time-tested solution

Despite having the lowest complication rate of all hemodialysis accesses, the prevalence of autologous arteriovenous (AV) fistulas has declined to 28% in the United States. The reasons for this decline include high early AV fistula failure rates, long maturation times, the frequent need for emergent dialysis, unavailable or poor pre-ESRD programs and planning, patient resistance to the realities of impending ESRD, and financial disincentives to AV fistula placement. Despite these barriers, programs throughout the country have demonstrated the ability to increase AV fistula prevalence to more than 50%. The strategies employed have included increased reliance on upper arm brachiocephalic and transposed basilic vein fistulas, the use of preoperative imaging to identify the best sites for fistula creation, and aggressive attempts at salvage of nonmaturing fistulas. Other groups have systematically and successfully replaced failed grafts with upper arm brachiocephalic or bracheobasilic fistulas. These experiences clearly show that exceeding the National Kidney Foundation Dialysis Outcomes Quality Initiative (NKF-DOQI) goal of more than 50% fistula placement is achievable in the United States. Declining numbers of AV fistulas are the result of a combination of factors, including changes in our patient population and learned practice patterns coupled with a failure of our delivery system to provide education, timely referral, and incentives for fistula placement. Increasing AV fistula prevalence in the United States is achievable and will improve patient outcomes and decrease the costs of ESRD.

Antibodies to topical bovine thrombin correlate with access thrombosis

Bovine thrombin is often used topically to promote hemostasis during vascular surgery, including dialysis-access placement. Patients frequently develop antibodies to bovine thrombin preparations, and some may develop antiphospholipid antibodies. We evaluated 88 hemodialysis patients for the presence of antibodies to topical bovine thrombin to determine if elevated antibody levels correlated with vascular access thrombosis. Twenty-seven patients (30.7%) had elevated antibody levels to topical bovine thrombin. More patients with elevated antibody levels had prior vascular access thrombosis than patients with normal antibody levels (13 of 27 versus 5 of 61 patients; P < 0.001). This difference was almost entirely the result of greater levels of thrombosis in patients with polytetrafluoroethylene (PTFE) grafts and elevated antibody levels. In these patients, 11 of 13 patients (84.6%) with elevated antibody levels had a previous thrombosis compared with 2 of 15 patients (13. 3%) with normal antibody levels (P < 0.001). Patients with elevated antibody levels and PTFE grafts also had more prior thromboses (1.92 +/- 1.60 versus 0.133 +/- 0.35 thromboses; P < 0.01) and a greater thrombosis rate (66.89 +/- 63.71 versus 4.65 +/- 12.05 thromboses/100 patient-years; P < 0.01) than patients with normal antibody levels. There were no differences in the frequency of myocardial infarction, coronary artery bypass, access age, presence of diabetes mellitus, platelet counts, anticardiolipin antibody, albumin, lactate dehydrogenase, or C-reactive protein levels. In conclusion, patients with PTFE grafts and elevated antibody levels to topical bovine thrombin had significantly more vascular access thrombosis.

Intervention based on monthly monitoring decreases hemodialysis access thrombosis

We randomized 103 patients (68 arteriovenous [AV] fistulas, 35 polytetrafluoroethylene [PTFE] grafts; mean follow-up 197 days) to monthly measurement of access flow (QAT), monthly measurement of static venous pressure (VPS), or no monthly monitoring (control patients) to determine whether access thrombosis would decrease. Patients with access flow <750 cc/min or with static venous pressure > or =0.5 were referred for angiography and angioplasty of stenotic lesions > or =50%. Six of sixty-two (9.7%) of monthly monitored patients (MM) developed access thrombosis vs. 9 of 41 (22%) of control patients (p<0.05). Fewer MM patients developed thrombosis in AV fistulas (2.4% [2 of 42] vs. 15.4% [4 of 26] control patients; p<0.05). Monthly monitored patients had fewer thrombotic episodes than control patients (19 vs. 125 per 100 patient-years; p<0.01). Thrombosis rates were lowest in patients receiving monthly access flow measurement (5.9 [QAT] vs. 30.3 per 100 patient-years [VPS]; p<0.05). In conclusion, intervention based on monthly access flow measurement or static venous pressure decreased hemodialysis access thrombosis. Measurement of access flow tended to result in lower thrombosis rates than after static venous pressure. We believe that monthly access flow measurement will ensure the lowest incidence of thrombosis and decrease the cost of access maintenance.

Assessment of hemodialysis access performance by color-flow Doppler ultrasound

Hemodialysis access failure is a major cause of morbidity for patients with end stage renal disease with costs in excess of $743 million annually. Color-flow doppler ultrasound is the only mobile noninvasive technique that provides direct visual imaging of the access and measurement of access flow. Doppler ultrasound can identify patients at increased risk of future thrombosis and allow preventive intervention. Prospective trials show that ultrasound-based access management programs can decrease thrombosis rates, prolong access longevity, and decrease the cost of hemodialysis access management. It should be included as part of a coordinated program of hemodialysis management.

A novel approach to the detection of classical swine fever virus by RT-PCR with a fluorogenic probe (TaqMan)

Detection of classical swine fever virus (CSFV) and its discrimination from other pestiviruses can be achieved by virus isolation (VI) in cell cultures, antigen detection, or molecular analysis. To simplify the latter, a 5'-nuclease assay (TaqMan) was developed for the rapid and specific detection of CSFV with the minimum of downstream PCR processing. A pair of 5'-non-coding region, panpestivirus-specific PCR primers were assessed in a one-step reverse transcription-PCR with each of 36 diverse pestiviruses. The PCR products were subsequently reamplified, in conjunction with a CSFV-specific fluorogenic probe, in a nested-PCR with a second set of panpestivirus PCR primers. During nested PCR, when the target of interest was present, the CSFV probe annealed to the amplicon between the forward and reverse primers and was subsequently cleaved via the 5'-3' nucleolytic activity of the DNA polymerase resulting in the release of the fluorescent reporter dye. Each PCR tube was then placed directly into a luminescence spectrometer to monitor for any increase in fluorescence due to cleavage of the probe. This assay detected representatives of all genetic sub-groups of CSFV, but gave negative results for other pestiviruses. A preliminary assessment showed that the method could be used to detect CSFV RNA extracted from infected pig blood with a sensitivity greater than that of VI.

Identifying a new reality: zero vascular access recirculation using ultrasound dilution

Access recirculation measurements by blood urea nitrogen (BUN) sampling methods have come under recent criticism regarding their reliability especially at low levels of recirculation. New methods have shown that the majority of patients have much less recirculation than previously suspected. However, some of these methods are prone to the same factors that limit BUN measurement accuracy. A new method, ultrasound dilution, was studied that avoids these problems and supports a new clinical reality--zero access recirculation. Information on the relationship of recirculation to access flow was also obtained which supports the assumption that patients with adequate vascular access flows have no recirculation.

State-of-the-Art Review : Treatment of Hemodialysis Access Failure: A Role for Thrombolysis

Thrombosis of hemodialysis accesses remains a major source of morbidity, hospitalization, and expense for patients with end-stage renal disease. Treatment of hemodialysis accesses includes strategies to prevent ac cess failure and methods for treating acute thromboses. Such techniques as Doppler ultrasonography, venous pressure monitoring during dialysis, measurement of ra tios of venous to systemic pressures, and measurement of recirculation have been used to predict accesses at risk of thrombosis. Elective interventions, including surgical re visions and angioplasties, have been shown to lessen the thrombosis rate in both polytetrafluoroethylene (PTFE) grafts and arterio-venous fistulas. Elective revision has also improved long-term patency of both grafts and fistu las when compared with repairing the accesses only after thrombosis. Despite these attempts, acute thrombosis of hemodialysis accesses remains a common complication for patients with end-stage renal disease. Historically, surgical thrombectomy has been the gold standard for treatment of acute hemodialysis access failure. Over the past 10 years, thrombolytic therapy has gained an in creasing role in the treatment of acutely thrombosed PTFE grafts. Thrombolysis has had at least comparable results to surgical thrombectomy in the best centers, with similar complication rates. Thrombolytic therapy is also significantly less expensive than surgical thrombectomy. In summary, we believe that hemodialysis access treat ment should encompass a comprehensive program, in cluding access surveillance to select accesses at risk of failure. Elective intervention should be performed in an attempt to prevent thrombosis and increase long-term ac cess patency. When thrombosis does occur, pharmaco mechanical thrombolysis is the preferable first interven tion for acutely occluded PTFE hemodialysis accesses.

Prolongation of hemodialysis access survival with elective revision

153 hemodialysis accesses (56 fistulas and 97 PTFE grafts) were followed from placement to see if elective intervention prolonged access survival. The mean follow-up was 772 days (minimum 14 days, maximum 2755 days). Patients who expired, were transplanted or transferred were excluded. The groups of fistulas and grafts were subdivided into those whose first intervention was an episode of clotting versus those whose first intervention was an elective revision (either surgical repair or angioplasty of an area of stenosis within the access or run-off). These groups were compared to see whether electively revising an access prior to clotting would change the ultimate longevity of the access when compared to repairing the access after clotting. PTFE grafts with an initial elective intervention had an improved survival compared to grafts that clotted first (1023 days vs 689 days, p = 0.01). The electively revised grafts had fewer subsequent clotting episodes (1.1 clots per patient year vs 3.6, p = 0.02) and fewer interventions (1.8 interventions per patient year vs 3.7, p = 0.06). In fistulas, an initial elective revision increased access longevity when compared to repair after the fistula clotted (999 days vs 358 days, p = 0.005). Clotting episodes were decreased in those electively revised (0.5 clots per patient year vs 4.8, p = 0.014). Total interventions per patient year were also lower in those electively revised (1.2 vs 5.3, p = 0.028). In conclusion, elective correction of abnormalities in PTFE grafts and in AV fistulas prolongs access life when compared to repair after an initial episode of clotting. Elective revision also decreased the subsequent number of clotting episodes per patient year and the total number of interventions (revisions and declottings) per patient year in both grafts and fistulas.

Production, characterization and reactivity of monoclonal antibodies to porcine reproductive and respiratory syndrome virus

This report describes the preparation of six monoclonal antibodies (MAbs) raised against a British isolate of porcine reproductive and respiratory syndrome virus (PRRSV), their characterization in terms of protein specificity and their reactivity with different PRRS viruses from Europe and the USA. Radioimmunoprecipitation and Western blotting studies of MAb reactivity with proteins from cell lysates of infected cells and purified virus revealed that four of the six MAbs (WBE1 and WBE4-6) precipitated a 15 kDa viral protein. Further studies using in vitro translated products of the Lelystad virus genome showed that this protein was the product of ORF7, the putative nucleocapsid protein. The specificity of another MAb, WBE2, was found to be for a 45 kDa protein, determined to be the product of ORF3 and demonstrated to be present in purified virion preparations. The protein specificity of the sixth MAb, WBE3 could not be determined. Thirty-three PRRSV isolates from Europe and the USA were grown in alveolar macrophages and examined by immunoperoxidase staining, using the panel of six MAbs. All European isolates were recognized by the four MAbs specific for the putative nucleocapsid, but the viruses showed different patterns of reactivity with WBE2 and WBE3. Furthermore, these two MAbs stained only a small proportion of the cells infected with certain isolates, suggesting that a single isolate may be antigenically heterogeneous. No MAbs bound to US isolates, indicating a consistent antigenic difference between the putative nucleocapsid of US and European isolates. Detergent extraction of cell lysate antigen abrogated the binding of WBE1-3, suggesting that the epitopes are conformation dependent.

Identification of herd-specific bovine viral diarrhoea virus isolates from infected cattle and sheep

Thirteen pestiviruses isolated from ruminants on four different farms in Sweden were compared antigenically and genetically. On two farms, viruses were isolated from both cattle and sheep, a third farm contained only sheep and a fourth only cattle. Seven viruses were isolated from six different cattle and six viruses were isolated from five different sheep. Epitope conservation between the viruses was studied with a panel of 32 monoclonal antibodies, revealing that all of the isolates were BVDV-like. However, certain epitopes present in isolates from cattle were lost following virus transmission to sheep. In vitro amplification of the 5'-untranslated region of the 13 isolates by the polymerase chain reaction (PCR) and subsequent analyses of amplified products with restriction enzymes also indicated that all 13 isolates belong to the BVDV group of pestiviruses. A fragment of the E2 (gp53) gene of each virus was amplified by PCR and a comparison of the amplified sequence of 188 nucleotides separated the isolates into four groups each of which could be identified with a particular farm of origin. The 13 isolates were thus herd-specific rather than species-specific demonstrating that BVDV is readily transmitted between cattle and sheep.

Classical swine fever: genetic detection and analysis of differences between virus isolates

Two pairs of oligonucleotide primers were designed that specifically amplified regions of the classical swine fever virus genome. These products, corresponding to a 671 bp portion of the genes encoding the E1 and E2 (gp33 and gp55) proteins and a 1090 bp portion of the putative polymerase gene, were amplified from eight virus isolates which had been responsible for a series of classical swine fever outbreaks in Italy involving both domestic pigs and wild boar. For each virus the fragments were partially sequenced to give 475 bp of the E1/E2 glycoprotein and 212 bp of the putative polymerase gene sequences. The data from each set of fragments were compared with one another and with reference strains. This allowed us confidently to assign most of the viruses to one of three subgroups. An analysis of the same viruses with a panel of monoclonal antibodies was much less informative. The subgrouping of the isolates suggested that, in this region of Italy, there had been at least two separate introductions of classical swine fever over a 7 year period and that virus had been transmitted between domestic pigs and wild boar. A consensus nucleotide sequence derived from the glycoprotein fragments of all the viruses examined revealed conservation at the wobble position of some codons.

Border disease virus: delineation by monoclonal antibodies

Many ovine pestiviruses from Britain and a number of atypical porcine isolates are largely unrecognised by monoclonal antibodies (mAbs) specific for reference strains of classical swine fever virus and bovine viral diarrhoea virus (BVDV). Additional mAbs have therefore been produced using some of these "unreactive" pestiviruses. Two of the viruses used were atypical porcine isolates (strains 87/6 and Vosges), whilst another had been isolated from a sheep (59386). Thirty-three mAbs were selected, none of which recognised two reference strains of BVDV, but three of which recognised the Alfort strain of classical swine fever. On the basis of radioimmunoprecipitation they were considered to be directed at one of three different pestivirus proteins (gp 53, gp 48 or p 125). Three virus subgroups were evident when the mAbs were used to type 16 ovine and two atypical porcine pestiviruses. One subgroup contained the Vosges and 59386 viruses and four ovine field isolates. The second subgroup comprised the 87/6 virus, the Moredun and Aveyron reference strains of border disease virus and four further ovine field isolates. Three of four ovine viruses making up the third subgroup had been previously categorised as BVDV-like and were largely unrecognised by the new mAbs. The findings were in agreement with previous attempts to segregate some of the same viruses using partial genomic comparisons or cross-neutralization tests.

Pharmacomechanical thrombolysis with urokinase for treatment of thrombosed hemodialysis access grafts. A comparison with surgical thrombectomy

Seventy-one consecutively occluded polytetrafluoroethylene (PTFE) grafts treated with pharmacomechanical thrombolysis were compared with 75 surgical controls. The patients undergoing thrombomechanical lysis had a comparable rate of successful declotting (91% vs. 90.7%) and no significant difference in patency at 24 and 48 hr, 1 week, and 1 and 6 months. Patients undergoing thrombolysis required less overnight hospitalization (17 vs. 82%) (P < 0.001) and their hospital stays averaged 1.03 days versus 3.43 days in the surgical thrombectomy group (P < 0.0001). Complication rates were similar in both groups. Hospital charges and physician fees were significantly lower in the thrombolysis group, with total charges averaging $6,802 versus $12,740 (P = 0.0018). These cost differences were maintained even when patients with extended stays were excluded. In conclusion, pharmacomechanical thrombolysis provides efficacy and complications comparable to surgical thrombectomy, with the benefits of a decreased rate of hospitalization, decreased total number of days of hospitalization, and significant cost savings. The authors determined that pharmacomechanical thrombolysis is the preferable first intervention for acutely occluded PTFE grafts.

BVD monoclonal antibodies: relationship between viral protein specificity and viral strain specificity

Seventeen monoclonal antibodies raised against bovine viral diarrhoea virus were divided into three groups on the basis of radioimmunoprecipitation results. Seven monoclonal antibodies precipitated a polypeptide of 80kD and defined four domains, all of which showed considerable conservation amongst the 180 pestivirus strains and isolates examined. Nine monoclonal antibodies, including six with virus neutralizing activity, precipitated a 53kD polypeptide and all appeared to be directed towards a single domain of clustered epitopes. Several of these epitopes were present in many ruminant virus strains and isolates, but not in hog cholera viruses. A single monoclonal antibody precipitated a 48kD polypeptide, defining an epitope that was also present on many ruminant viruses, but not hog cholera viruses. Most pestiviruses from cattle and some from sheep shared a number of epitopes located on three different proteins.

Immunocytochemical localization of border disease virus in the spinal cord of fetal and newborn lambs

The peroxidase-antiperoxidase technique was used to determine the cellular localization of Border Disease (BD) virus in cryostat sections of fetal and newborn lamb spinal cord following experimental infection by maternal inoculation in early gestation. Viraemic fetuses and lambs with hypomyelinogenesis showed BD viral antigen in neurons, glia, ependymal cells, vascular endothelial cells and fibrocytes within the dura mater. Double immunolabelling demonstrated co-expression of BD viral antigen and glial fibrillary acidic protein (GFAP) or myelin basic protein (MBP) in both fetal and newborn lamb glia. In fetal lambs there was a pia-associated population of glia in which viral antigen was also co-expressed with GFAP or MBP. The results suggest that BD virus infects myelinating oligodendroglia, astroglia and probably also transitional cells and pluripotential glioblasts. The relationship between infection of specific cell types and hypomyelinogenesis was not resolved but infection of transitional cells and oligodendroglia may affect oligodendroglial function and permit morphologically inapparent perturbations leading to hypomyelinogenesis. A single nonviraemic lamb with a precolostral antibody titre to BD virus and cystic cerebral cavities but no hypomyelinogenesis showed BD viral antigen confined to glia of the spinal cord white matter. This suggests that oligodendroglia may require to be infected before a critical period in their development or factors additional to oligodendroglia infection are necessary for hypomyelinogenesis.

The application of monoclonal antibody panels to characterize pestivirus isolates from ruminants in Great Britain

Monoclonal antibodies were prepared against bovine virus diarrhoea virus and hog cholera virus. They were used to test 101 field isolates of ruminant pestivirus in a simple binding assay using an indirect immunoperoxidase label on fixed cell cultures. The monoclonals were divided into three panels: (1) pestivirus group specific, (2) hog cholera specific, (3) selectively reactive with ruminant pestiviruses. The reaction patterns with panel 3 were analyzed by a computer spreadsheet to determine the percentage match with seven reference patterns. Field viruses could be divided into two main groups. Group A consisted of 73 (87%) of the 84 bovine isolates and three (19%) of the 16 ovine, and was reactive with 40% or more of panel 3. Group B showed only limited reactivity with panel 3 and comprised 13/16 (81%) of the ovine (border disease) isolates together with the remaining 11 (13%) bovine viruses.

Antibody-mediated enhancement of rabies virus infection in a mouse macrophage cell line (P388D1)

The suggestion that antibodies might enhance rabies virus infection of macrophages through opsonization of immune complexes was tested in vitro by adaptation of the rapid fluorescent focus inhibition technique for the examination of a macrophage cell line (P388D1). Some enhancement of rabies virus infection was shown. The relationship between such enhancement with the 'early death' phenomenon and its occurrence in vivo is discussed.

Safety and efficacy of live and inactivated infectious bovine rhinotracheitis vaccines

Two commercial live virus infectious bovine rhinotracheitis (IBR) vaccines for intranasal administration and an inactivated polyvalent calf pneumonia vaccine were compared for safety and efficacy in calves against experimental IBR infections. All three products were clinically safe for use in young calves; a mild, transient, febrile response was induced by one of the live vaccines. Vaccinal virus was recovered for up to 16 days after vaccination from nasal secretions of all calves given live vaccine. Both live vaccines stimulated a serum neutralising antibody response, but the inactivated vaccine failed to elicit any serological response. Following intranasal challenge four months after the first dose of vaccine, all live virus vaccinates remained systemically healthy. A slight nasal discharge and a few rapidly healing ulcers of the nasal mucosa were the only abnormalities observed. Both the group given the inactivated vaccine and the unvaccinated controls developed clinical IBR with pyrexia, ocular and nasal discharges, severe ulceration of the nasal mucosa and tracheitis and tachypnoea to varying degrees of severity. Parenteral administration of dexamethasone six months after challenge induced reactivation of virus shedding followed by a rise in humoral antibody titre irrespective of the original vaccination history.