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NDT Advance Access originally published online on August 18, 2006
Nephrology Dialysis Transplantation 2006 21(12):3514-3519; doi:10.1093/ndt/gfl424
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© The Author [2006]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Impact of a quality improvement programme based on vascular access flow monitoring on costs, access occlusion and access failure

Edwin Wijnen1, Nils Planken2, Xavier Keuter2, Jeroen P. Kooman1, Jan H. M. Tordoir2, Michiel W. de Haan3, Karel M. L. Leunissen1 and Frank van der Sande1

1Department of Internal Medicine and Nephrology, 2Department of Surgery and 3Department of Radiology, University Hospital Maastricht, Maastricht, The Netherlands

Correspondence and offprint requests to: F. M. van der Sande, MD, PhD, Internist-nephrologist, Department of Internal Medicine and Nephrology, University Hospital Maastricht, P. Debyelaan 25, 6202AZ Maastricht, Maastricht, The Netherlands. Email: fvs{at}groupwise.azm.nl



   Abstract
Top
 Abstract
Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
Background. Vascular access thrombosis is a substantial source of morbidity in chronic haemodialysis patients. Periodical access flow measurements can predict the presence of vascular access stenosis and provide an opportunity for early intervention to prevent subsequent vascular access thrombosis. By this system of quality improvement, vascular access-related costs might be reduced. The aim of this study was to analyse the cost impact of a quality improvement programme based on periodic access flow measurements.

Methods. The number and costs of vascular access interventions (summary of angiography, percutaneous transluminal angioplasty, catheter placement, hospitalization days and costs for surgery) in the period 2001–2003 (quality improvement period; QIP, 218.6 patient-years observed) were retrospectively compared with a reference period (RP, 1996–1998, 214.4 patient-years observed) during which no access flow was measured. All access flow measurements were done on a regular base and interventions were performed according to the Kidney Disease Outcome Quality Initiative.

Results. Surgical thrombectomy procedures were significantly less during the QIP (0.25 ± 0.57 events/patient-year) compared with RP (0.63 ± 1.06 events/patient-year; P = 0.000), whereas access loss was not significantly different. During the QIP, 205 radiological interventions were performed (0.88 ± 1.16 events/patient-year), and in the RP around 48 (0.33 ± 0.65 events/patient-year; P = 0.000). Access-related costs tended to be lower during the QIP compared with the RP. The cost reduction appeared to be limited to patients with arteriovenous graft (AVG), in which access-related costs were significantly lower during the QIP ({euro}2360.95 ± 2838.17 patient-year) compared with the RP ({euro}4003.96 ± 3810.92 patient-year; P = 0.012), but not in patients with arteriovenous fistula (AVF).

Conclusion. A quality improvement programme based on periodical access flow measurement reduced the number of acute vascular access failures due to thrombotic events and also significantly reduced health care costs in patients with AVG, but not in patients with AVF. The quality improvement programme had no effect on access survival.



   Introduction
Top
 Abstract
 Introduction
Patients and methods
 Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
Nowadays, more than 300 000 patients in the United States and similar patient numbers in Europe, are being kept alive by chronic intermittent dialysis treatment. It has been estimated that this number will increase dramatically in the forthcoming years. The increase in number of elderly dialysis patients with additional cardiovascular comorbidities and diabetes mellitus makes the creation and maintenance of functioning vascular access more difficult and cumbersome. Vascular access problems place a large burden on care facilities, manpower and costs. In Europe alone, ~60 000 new accesses and >24 000 access replacements per year are performed. In addition, it has been estimated that an autogenous arteriovenous fistula (AVF) needs 0.2–0.4 revisions/year and an arteriovenous graft (AVG) about 0.8–1.2 revisions/year for maintenance [1–4], counting for another 70 000 interventions/year. The vascular access-related costs are substantial due to vascular access complications. The Kidney Disease Outcome Quality Initiative (K/DOQI) clinical practice guidelines for vascular access (Update 2000) recommend monitoring of vascular access by periodical flow measurements [5]. Little is known about the economic effects of maintenance of vascular access. Recently, in a prospective study, the cost analysis of vascular access among incident haemodialysis patients during the first year of dialysis was determined [6]. However, this study did not take into account the effect of a vascular access surveillance programme on saving costs. Monthly monitoring of access flow may be of importance in preventing access clotting.

The hypothesis of the present study was that implementation of a quality improvement programme with periodical access flow measurement, may reduce vascular access-related health care costs.

The aim of the present study was, therefore, first to analyse the cost impact of a quality improvement programme and secondly to study the effect of such a programme on the incidence of thrombotic vascular events and access loss.



   Patients and methods
Top
 Abstract
 Introduction
 Patients and methods
Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
Study protocol
Retrospectively, two patient cohorts were formed; the reference period (RP) (1996–1998) and the quality improvement period (QIP) (2001–2003). The gap (1999–2000) between the RP and the QIP was the period in which the Transonic HD01® (Transonic Systems Inc., Ithaca, NY) was acquired and introduced. This interval was chosen because the K/DOQI Update 2000 on vascular access recommends an organized monitoring approach of vascular access flow [5].

The incidence of pre-emptive intervention and vascular access failure due to thrombotic occlusive events within both periods, was registered to determine the effect of access flow-based radiological intervention on vascular access maintenance costs.

During both periods, it was a standard procedure to perform a surgical thrombectomy of an occluded vascular access, in AVG as well as in AVF. For surgical thrombectomy, patients were hospitalized for 3 days. Not all occluded vascular access sites were suitable for revision. Patients with access loss were given a central vein catheter to overcome the period in which a new vascular access site was created and suitable for cannulation. During both periods, RP and QIP, the same highly experienced vascular access surgeon was responsible for surgical thrombectomy and new access site creation.

The vascular access surveillance programme during the RP was based on non-standardized vascular access surveillance tools, consisting of frequent palpation before access cannulation, incidental auscultation before haemodialysis treatment and registering of arterial and venous pressure findings during haemodialysis treatment. Based on abnormal findings (increased arterial and/or venous pressure, a change in thrill or palpation, and/or high frequent sounds on auscultation) the preferred action was angiography and, in case of a stenotic lesion, followed by percutaneous transluminal angioplasty (PTA). During the QIP, the vascular access surveillance was based on monthly AVG and three monthly AVF vascular access flow measurement, using the Transonic HD01® access flow monitor. In case of low-vascular access flow or a substantial flow decline according to K/DOQI Update 2000 on clinical practice guidelines for vascular access [5], the preferred treatment was also angiography combined with PTA.

Measurements were performed by a group of dialysis nurses during the first hour of dialysis. Although this takes a maximum period of 15 min per measurement, no extra staff was needed to perform these measurements.

Patients
All local incident haemodialysis patients with a vascular access, AVF and AVG, were included. During the RP, 214.4 patient-years were observed (total number of patients: 119); whereas in the QIP, 218.6 patient-years were observed (total number of patients: 117). Patient characteristics are described in Table 1.


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  		Table 1. Patient characteristics

 
Cost calculation
Cost data were delivered by the hospitals' financial administration and were based upon costs for the different interventions and procedures in December 2002. These cost data were uniformly used for both periods in order to make a comparison possible. Cost calculation is based on local hospital costs of imaging, interventions and, when surgical procedure was needed, hospitalization. Amounts are reported in EURO ({euro}) (Table 2). The following procedures were taken into account: angiography, angiography combined with PTA, central vein catheter placement, surgical thrombectomy, new vascular access site creation, devaluation costs for Transonic HD01® and access flow measurement-related labour costs. Procedure costs are the actual effective costs consisting of personnel, equipment, material and overhead costs. Hospitalization costs are also effective costs based on an average hospitalization day on the surgical unit. For the cost calculation regarding hospitalization, the primary reason for admission had to be access failure. If an access failed during a hospitalization period during which patients were admitted for other complications (e.g. pneumonia), only the costs directly related to access failure were included in the calculations.


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  		Table 2. Relevant costs

 
Access flow measurements by dilution technique
The access flow measurement technique involves reversing the access lines during dialysis and using the ultrasound dilution methodology, as introduced by Krivitski [7] to measure the resulting fraction of recirculated blood (R) entering the dialyser. If the extra corporeal pump speed (Qb) is known, then access flow (Qa) can be calculated from the following formula: Qa = Qb x ((1 – R)/R)

Dialysis strategy
In the QIP as well as in the RP, patients were treated with bicarbonate haemodialysis with low-flux polysulfone membranes (F8HPS, Fresenius®, Bad Homburg or Polyflux 8L, Gambro®, Lund, Sweden). Sodium concentration of the dialysate was 138 or 140 mmol/l, calcium concentration was 1.5 mmol/l and temperature of the dialysate was 35.5, 36 or 36.5°C. Ultrapure dialysate was used.

Statistical analysis
Differences between QIP and RP were analysed using Poisson or chi-square tests and Mann–Whitney U-tests, where appropriate (SPSS-pc version 12.01). All values are expressed as mean ± SD and range is added for costs. P-value <0.05 was considered significant.



   Results
Top
 Abstract
 Introduction
 Patients and methods
 Results
Discussion
 Conclusions
 Acknowledgements
 References
 
Interventions
Qa screening was performed in all patients during the QIP, with a total of 1652 measurements (7.56 events/patient-year).

During the RP, a total of 77 (0.53 ± 1.25 events/patient-year) angiographic procedures without additional PTA were performed compared with 57 (0.28 ± 0.55 events/patient-year, P = 0.047) in the QIP. Angiography with additional PTA was performed 48 times (0.33 ± 0.65 events/patient-year) in the RP and 205 times (0.88 ± 1.16 events/patient-year; P = 0.000) in the QIP.

The number of vascular access thrombectomies (both AVF and AVG) was higher during RP; 108 (0.63 ± 1.06 events/patient-year) compared with 60 (0.25 ± 0.57 events/patient-year; P = 0.000) during QIP (Figure 1).


Figure 1
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  		Fig. 1. Vascular access-related interventions during the RP and the QIP. RP, reference period; QIP, quality improvement period; PTA, percutaneous transluminal angioplasty.

 
Subgroup analysis yielded 0.21 ± 0.40 AVF thrombotic occlusive events/patient-year in the RP compared with 0.09 ± 0.29 in the QIP, P = 0.022, and 1.14 ± 1.36 AVG thrombotic occlusive events/patient-year in the RP compared with 0.45 ± 0.74 in the QIP, P = 0.000.

Costs
Table 3 summarizes all costs for both the RP and the QIP population. Tables 4 and 5 summarize all costs per period for AVG and AVF, respectively. Vascular access-related costs tended to be lower during the QIP compared with RP for the overall groups. The total costs per patient-year decreased from {euro}2,289.16 ± 3153.68 in the RP to {euro}1538.40 ± 2279.90 in the QIP, which is a relative downtrend of 32.5%, P = NS. However, when distinguishing between patients with AVF and AVG, in patients with AVG a highly significant cost reduction was observed (costs patient-year RP {euro}4003.96 ± 3810.92, costs patient-year QIP {euro}2360.95 ± 2838.17; P = 0.01), but not in patients with AVF.


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  		Table 3. Summary of intervention costs by period

 

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  		Table 4. Summary of intervention costs for AVG by period

 

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  		Table 5. Summary of intervention costs for AVF by period

 
Access loss
A total of 17 access losses were reported during the RP (0.07 ± 0.21 events/patient-year), compared with 17 in the QIP (0.07 ± 0.19 events/patient-year; P = NS) Patients with access loss received a central catheter until a new vascular access site was created, 0.08 ± 0.21 (RP) and 0.08 ± 0.19 (QIP) events/patient-year, respectively, P = NS. Average access survival time until access loss was 888 ± 748 days in the RP (n = 17) compared with 807 ± 499 days in the QIP (n = 17), P = NS.

Accuracy of the surveillance tools used in the RP and QIP for AVF and AVG
In the QIP, PTA was executed in 71.9% of all AVF angiographic procedures, compared with 81.9% of all AVG angiographic procedures. In the RP, PTA was executed in 39.5% of all AVF angiographic procedures, compared with 37.8% of all AVG angiographic procedures.

During QIP, 0.85 angiographic procedures per patient-year were performed in AVF compared with 1.57 in AVG. During RP, 0.37 angiographic procedures per patient-year were performed in AVF compared with 0.83 in AVG.



   Discussion
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
Conclusions
 Acknowledgements
 References
 
Implementation of a quality improvement programme based on regular access flow measurement (QIP) resulted in a decline in thrombotic occlusive events, and surgical interventions, and an increase in radiological interventions compared with conventional vascular access surveillance tools (RP). The reduction in vascular access-related costs appeared to be primarily limited to patients with AVG. The quality improvement programme had no effect on access survival.

Effects of the QIP on access-related morbidity
Implementation of the decline limits in Qa for immediate radiological intervention (K/DOQI Update 2000 on vascular access) resulted in a reduction in thrombotic occlusive event rate during the QIP compared with the RP, where access surveillance was based on more conventional surveillance tools. The lower thrombotic occlusive event rate after implementation of an access flow-based vascular surveillance programme was observed both in patients with AVG and in patients with AVF, in agreement with earlier literature [1–4]. In our study, the reduction in occlusive event rate appeared to be the highest in patients with AVG. As is well known, AVFs have a longer life span and need fewer interventions compared with AVGs as mentioned previously. This is reflected in the number of angiographic procedures, which was lower in patients having AVF compared with patients having AVG.

In agreement with earlier studies [8–10], a quality improvement programme based on access flow monitoring did not result in a reduction in access survival.

Effects of the QIP on costs
Cost-effectiveness of an access flow-based surveillance programme has only been examined once before to our knowledge. McCarley et al. [11] analysed three phases of access thrombosis monitoring and treatment. Phase 1 consisted of haemodialysis treatment without access monitoring, phase 2 was a period of dynamic venous pressure monitoring and phase 3, a period of vascular access blood flow monitoring according to K/DOQI Update 2000 on clinical practice guidelines for vascular access [5]. The authors calculated an overall cost-cutting benefit during phase 3 of 49% compared with phase 1 and 54% compared with phase 2. The phase 3 period, however, was only 10 months.

In the overall group, access-related costs tended to decline during the QIP. However, when distinguishing between AVF and AVG, the cost reduction appeared to be limited in AVG, in which a highly significant reduction in costs was observed, which did not hold true in AVF. Two explanations might be provided for this difference. First, in 81.9% of angiographic procedures in AVG, concomitant PTA was performed compared with 71.9% in AVF. Thus, more unnecessary procedures may have been performed in the AVF group. Moreover, the reduction in access thrombosis during the QIP appeared to be higher for AVG (60.5%) compared with AVF (57.1%).

Several issues concerning our cost analysis deserve consideration
Theoretically, in the case of equal occlusive events, the use of percutaneous thrombectomy would probably be less expensive because it can be performed in an out-patient setting. Green et al. [12], however, performed a meta-analysis comparing surgical thrombectomy with percutaneous thrombectomy in AVG, which included seven studies. They concluded that the overall results of this meta-analysis showed a clear superiority of surgery over percutaneous thrombectomy.

In the case of out-patient surgery, the cost analysis presumably would have been different because hospitalization costs would be irrelevant. However, we feel that, at least in our hospital, out-patient surgery in the case of thrombotic occlusive events are generally not feasible, not only due to logistic reasons but also due to the need of monitoring the patients until the time of surgery and the moment of actual dialysis treatment.

The retrospective character of the study design causes some of the study's drawbacks. Although both patient cohorts (RP and QIP) seem to be comparable, the focus on failure was likely to be more intense during the QIP, due to the increased attention for quality improvement. Reasonably, this very focus resulted in better practice-based educated personnel. Moreover, in agreement with the recent trend, in the QIP there are more upper arm fistulas compared with the RP, although the ratio between AVF and AVG was not different.



   Conclusions
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
Acknowledgements
 References
 
A quality improvement programme based on periodical access flow measurement, with additional angiography and intervention, led to a reduction in the number of acute vascular access thrombotic occlusive events. Moreover, the QIP resulted in reduced health care costs in patients with AVG, but not in patients with AVF. However, the quality programme had no effect on access survival.



   Acknowledgements
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 Acknowledgements
References
 
The authors would like to acknowledge the participating radiology personnel, Michael Geelen, Valerie Renette, Alfred Kerkhofs, Peter Hameleers, Rene Senden, Frans Creusen, Ellie Blezer, Jos Jacobs, and especially Magda van Loon and Ger van Meijel who extracted several significant data out of the electronic patient database.

Conflict of interest statement. None declared.

(See related article by Ikizler and Himmelfarb. Trials and trade-offs in haemodialysis vascular access monitoring. Nephrol Dial Transplant 2006; 21: 3362–3363.)



   References
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 Acknowledgements
 References
 

  1. Schwab S, Oliver M, Suhocki P, McCann R. (2001) Hemodialysis arteriovenous access: detection of stenosis and response to treatment by vascular access blood flow. Kidney Int 59:358–362.[CrossRef][Web of Science][Medline]
  2. Valj K. (2002) Prophylactic angioplasty: is it worthwhile? In Gray RJ and Sands JJ (Eds.). Dialysis Access: A Multidisciplinary Approach(Philadelphia, Lippincott Williams & Wilkins) pp. 153–156.
  3. Sands J, Jabyac P, Miranda C, Kapsick B. (1999) Intervention based on monthly monitoring decreases hemodialysis access thrombosis. ASAIO J 45:147–150.[Web of Science][Medline]
  4. Smits JH, Van Der Linden J, Hagen EC, et al. (2001) Graft surveillance: venous pressure, access flow or the combination? Kidney Int 59:1551–1558.[CrossRef][Web of Science][Medline]
  5. NKF-K/DOQI. (2001) Clinical practice guidelines for vascular access: Update 2000. Am J Kidney Dis 37:S137–S181.[Medline]
  6. Manns B, Tonelli M, Yilmaz S, et al. (2005) Establishment and maintenance of vascular access in incident hemodialysis patients: a prospective cost analysis. J Am Soc Nephrol 16:201–209.[Abstract/Free Full Text]
  7. Krivitski NM. (1995) Theory and validation of access flow measurement by dilution technique during haemodialysis. Kidney Int 48:244–250.[Web of Science][Medline]
  8. Paulson WD. (2005) Access monitoring does not really improve outcomes. Blood Purif 23:50–56.[CrossRef][Web of Science][Medline]
  9. Moist LM, Churchill DN, House AA, et al. (2003) Regular monitoring of access flow compared with monitoring of venous pressure fails to improve graft survival. J Am Soc Nephrol 14:2645–2653.[Abstract/Free Full Text]
  10. Dember LM, Holmberg EF, Kaufman JS. (2004) Randomized controlled trial of prophylactic repair of hemodialysis arteriovenous graft stenosis. Kidney Int 66:390–398.[CrossRef][Web of Science][Medline]
  11. McCarley P, Wingard RL, Shyr Y, Pettus W, Hakim R, Ikizler TA. (2001) Vascular access blood flow monitoring reduces access morbidity and costs. Kidney Int 60:1164–1172.[CrossRef][Web of Science][Medline]
  12. Green LD, Lee DS, Kucey DS. (2002) A metaanalysis comparing surgical thrombectomy, mechanical thrombectomy, and pharmacomechanical thrombolysis for thrombosed dialysis grafts. J Vasc Surg 36:939–945.[Web of Science][Medline]
Received for publication: 8.12.05
Accepted in revised form: 20. 6.06


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