Can anyone cite references to prove or disprove that static venous pressure monitoring is a good indicator of future access thrombosis? We measured dynamic venous pressures for three months and were unable to see any correlation between dynamic VP and clotting and/or stenosis. Do you need special equipment ( as briefly mentioned in DOQI ) Has anyone had experience with this as relevant to clinical practice? Thanks!

Yes, static pressures do work.

Dr. Tony Besarab will be presenting all current access monitoring ideas at the ASN pre-course "Expanding Our Procedural Domain: Vascular Access, Catheters and Ultrasonography" Nov 3-4, 1999.

Are you or your Nephrologist going to attend the ASN? If so please visit the Medisystems booth and see the new easy to use disposable for reading static pressures. A copy of the Medisystems new video for Access Management: The Graft (and the fistula video) will be a free item at the booth. The video details graft assessment and monitoring techniques.

I will be happy to ask Dr. Besarab for a list of refernces on static press and post them. At the time of the DOQI Guideline final draft the quick and easy way to do static pressures was not completed.

Deborah

[This message has been edited by Deborah Brouwer (edited 07-27-2000).]

We started monitoring static venous pressures a few months ago. The results
seem to correlate to the results of the Doppler flow studies we had done. This
seems to be a more accurate and earlier
predictor of complications than our previous
method, which was observing for elevated
venous pressures at the beginning of dialysis at 200 pump speed.

ASN 1999 Abstract A1038
http://www.abstracts-on-line.com/scripts/abstracts/asn/ASN.cfm/90875313

The Value of Static Venous Pressure Measurement in Predicting Hemodialysis Vascular Access Thrombosis

Dember LM, et al. Boston Univ School of Med and Boston Va Medical Center.

"In conclusion, SVPM is not a useful predictor of access thrombosis..."

[A1026] Access Flow (QA) as a Predictor of Access Dysfunction. A. Besarab, T. Lubkowski, T. Lim, S. Frinak. Henry Ford Hospital, Detroit, MI.

Access flow is an important predictor of access patency in observational cross sectional non-intervention studies. Risk for graft thrombosis increases as QA decreases to less than 600-800 mL/min. Routine static pressure monitoring also detects accesses at risk for thrombosis. We sought to determine the QA associated with the need for intervention or the occurrence of thrombosis in patients with recently constructed but mature upper arm accesses. The need for intervention in these was driven by sequential measurements of intra-access static arterial and venous segment pressures (ASAIO J 1997;43:M539).
We measured access flow rate (Transonic� ultrasound dilution method) at 3-12 week intervals over a period of 4-12 months in 158 new accesses. Initial QA was measured within 2-4 weeks of first cannulation. Change in flow (DQA) was calculated as the difference in QA/observation interval in months. Table below summaries the results (mean � SEM).
Access Type n QA Initial QA Last Observation DQA
Event (ml/min) (ml/min) (months) (ml/mo)
Graft
No Event 55 1023�40 905�41 7.0�0.2 - 22� 3
PTA/Rev 36 748�35 481�25 4.9�0.1 - 58� 5
Thrombosis 21 632�34 428�58 3.8�0.1 - 60�11
AVF
No Event 35 1003�78 976�79 7.3�0.3 - 6 � 5
PTA/Rev 9 533�35 336�30 5.3�0.2 -27 � 8
Thrombosis 2 251�71 223�83 0.9�0.2 -26 � 6
Event-free survival was greater in AVF than G by Kaplan-Meier analysis. The frequency of access dysfunction in grafts (57 of 112) was significantly greater than in AVF (11 of 46), c2 = 12.6, p <0.005. Logistic regression showed that both the absolute QA as well as DQA were significant determinants of the odds ratio for requiring intervention in both G and AVF. Both variables were key predictors of thrombosis in grafts.
We conclude that QA as well as DQA are determinants of the likelihood of thrombosis and both parameters are needed to optimize management. Initial QA is an important determinant of the event free period.

Poster Session: Dialysis Vascular Access I (9:30 AM-5:00 PM)

Presentation Date: Friday, November 5, 1999, Time: 9:30AM, Room: Halls B and C

[A1038] The Value of Static Venous Pressure Measurement in Predicting Hemodialysis Vascular Access Thrombosis. Laura M. Dember, Erika F. Holmberg, James S. Kaufman. Boston Univ School of Medicine and Boston VA Medical Center, Boston, MA.While a static venous pressure to systolic blood pressure ratio (SVPR) of >0.4 has been shown to be sensitive and specific for venous outflow stenosis, it is not known how well it predicts subsequent access thrombosis. We obtained monthly SVPR in all patients (pts) with a functioning upper extremity arteriovenous graft in 2 hemodialysis units (N=141) during an 11 month period. Pts were excluded from analysis because of follow-up <3 months (N=26), access surgery for infection or pseudoaneurysm (N=7), or participation in an ongoing randomized controlled trial requiring access angiography for SVPR>0.4 (N=13). None of the remaining 95 pts had diagnostic or therapeutic intervention unless access thrombosis occurred. Thirty-nine of the 95 pts (41%) had one or more thrombotic events during follow-up (clotters). SVPR>0.4 occurred in 74% of clotters during the month prior to thrombosis and mean time from SVPR>0.4 to thrombosis was 2.9 months. There was no time-dependent change in SVPR in pts without thrombosis (non-clotters), and among non-clotters with SVPR>0.4, the SVPR elevation persisted for at least 3 months in 52%. The predictive value of SVPR for thrombosis shown below was determined using SVPR just prior to thrombosis for clotters and SVPR 3 months prior to last measurement for non-clotters. SVPR >0.2 >0.3 >0.4 >0.5 >0.6 >0.7 >0.8
Sensitivity (%) 95 82 74 51 36 15 5
Specificity (%) 4 13 34 63 84 91 98
Pos Pred Value (%) 41 40 44 49 61 55 67
Neg Pred Value (%) 50 50 66 65 65 61 60
No SVPR threshhold had acceptable predictive value for thrombosis. Venous stenosis>50% was found in 92% of pts in the randomized controlled trial who underwent angiography for SVPR>0.4.In conclusion, SVPR is not a useful predictor of access thrombosis. The poor test characteristics we observed were not due to inadequate follow-up in non-clotters, absence of stenosis in pts with elevated SVPR, or lack of persistence of SVPR elevation.Free Communication Session: Vascular Access Monitoring (4:00 PM-6:30 PM)Presentation Date: Friday, November 5, 1999, Time: 4:00PM, Room: C124

A1024] A Simpler Method for Measuring Intra-Access Pressure in Vascular Accesses. A. Besarab, T. Lubkowski, S. Frinak. Henry Ford Hospital, Detroit, MI.

An on-going vascular access monitoring program (access pressure or access flow over time) is mandated by HCFA's translation of several NKF-DOQI guidelines into Clinical Performance Measures. We have shown that intra-access pressure can be measured from the drip-chamber transducer at zero blood pump flow by correcting for the difference in height (offset) between the drip chamber and the dialysis needle (JASN1998;9:284). Measurements from both the arterial (AS) and venous segments (VS) increase the detection of hemodynamically significant access lesions (ASAIO J 1997;43:M539).
The multiple steps that assure accuracy also make the procedure �user unfriendly� and have limited wider acceptance of the above technique. A simple device consisting of a sterile fistula needle equipped with a preattached sterile hydrophobic luer connector when connected to an aneroid manometer permits direct measurement of access pressures at the time of access cannulation (Access Alert�, Medisystems). In 19 patients with PTFE grafts, we compared this technique (AA) with our standard method using the Fresinius H Dialysis Delivery System and correcting for the offset and zero-calibration error. Absolute pressures (mm Hg) and pressure ratios (absolute/mean BP) are tabulated below; all results mean � SEM.
Standard Access Alert
Mean BP 107�4 109�5
(Range) (77-148) (79-151)
AS pressure / AS ratio 55 � 5 / 0.52 � 0.04 55 � 5 / 0.52 � 0.04
(Range) (20-94 / 0.18-0.78) (23-107 / 0.21-0.81)
VS pressure / VS ratio 41 � 5 / 0.38 � 0.03 45 � 5 / 0.41 � 0.03
Range (17-89 / 0.15-0.67) (19-98 /0.16-0.66)
There were no statistically significant differences between the two methods in absolute pressure or normalized pressure ratios. The correlation between the two methods in determining the AS and VS pressure ratios was high (R2 = 0.84 for AS, R2 = 0.68 for VS) over a wide range of values with a difference of more than 0.10 units in less than 20% of measurements. All 5 grafts with stenosis were detected by the AA technique.
We conclude that the AccessAlert technique is a user friendly and accurate monitoring method for detecting access grafts stenosis.

Poster Session: Dialysis Vascular Access II (9:00 AM-4:30 PM)

Presentation Date: Saturday, November 6, 1999, Time: 9:00AM, Room: Halls B and C

[A1025] Effect of Normalizing Hemoglobin (HB) on Intraaccess Pressure, Access Flow, and Access Event Rate. A. Besarab, S. Frinak. Henry Ford Hospital, Detroit, MI.The effect of complete correction of anemia on hemodialysis vascular access (VA) hemodynamics is unknown. Reports on the association of higher HB to increased thrombosis rates are contradictory. To examine for any changes in access flow due to viscosity, we measured intra-access pressure normalized by mean arterial pressure (nPIA) and access flow (QA, mL/min) using Doppler US in HD subjects enrolled into the �Normal versus Anemic Hematocrit� clinical trial (NEJM 1998;339:584). Group A was targeted to a HB of 13-15 g/dL whereas Group B was maintained within an anemic HB range of 9-11 g/dL.VA consisted of 12 graft (G) and 7 autologous vein fistulas (AVF) in group A compared to 15 G and 3 AVF in group B (c2 = 3.6, p > 0.1). Prior access problems had occurred in 13 of 27 G and 1 of 10 AVF (c2 = 6.8, p=0.033 for effect of access type) but there was no difference in prior access events between Group A and B. Access pressure and QA measurements were made at enrollment (baseline) and after 2,4,7,10, & 13 months of the study. Intervention (revision or angioplasty) was performed only for increases in nPIA (absolute value > 0.5 or increase of 0.15 above baseline).Baseline HB was 10.3�0.2 and 10.2�0.3 g/dL in Groups A and B respectively. In group A, target HB of 13.9�0.4 g/dL was achieved by 7 months and maintained thereafter. Two patients in group A were transplanted at 3 and 7 mo. Five access events occurred in each group within the first 13 months of study. In the 25 accesses without events, 110 observations were made during successive 2-4 mo intervals. Table below summarizes temporal changes in nPIA and in QA in these VA having no events. Baseline 4 mo. 7 mo. 10 mo. 13 mo.
nPIA A 0.23�0.03 0.25�0.04 0.23�0.04 0.28�0.04 0.28�0.04
nPIA B 0.36�0.06 0.42�0.06 0.41�0.06 0.42�0.06 0.41�0.07
QA A 894�143 759�115 837�149 819�147 894�179
QA B 1030�130 1013�166 1024�166 1022�246 1057�199
All results mean�sem. Multivariate analysis showed no effect of HB on either parameter. Mean changes in nPIA and QA from baseline were +0.03�0.01 and -33�29 mL/min (n=110). By contrast, in the 10 accesses that sustained a thrombosis or intervention (PTA), nPIA increased by 0.15�0.03 whereas QA decreased by 276�57 mL/min (14 observations).In this study, full correction of anemia did not alter VA hemodynamics nor alter thrombosis or intervention rates of monitored VA. The reported increased risk for thrombosis may be mediated by non-rheologic factors.Poster Session: Dialysis Vascular Access II (9:00 AM-4:30 PM)Presentation Date: Saturday, November 6, 1999, Time: 9:00AM, Room: Halls B and C

[A1111] Vascular Access Monitoring: Comparison of Different Techniques. Kevin S. Stadtlander, Sanford D. Altman. Interventional Radiology, Open Access Vascular Access Center, North Miami Beach, FL.

Each prospective vascular access monitoring technique described in the DOQI clinical practice guidelines has its limitations in terms of accuracy, ease of implementation, and cost. To further evaluate these parameters, we designed a protocol to simultaneously collect three monitoring data points: ultrasound dilution access blood flow (ABF), static venous pressure (SVP), and Doppler ultrasound (US gray scale imaging + access volume flow). We evaluated for consistency, trends, and concordance among these indicators over a 3-month period. Each patient who participated for the entire study had ABF and SVP performed each month. US was performed at month one and again at month three in selected patients. Angiographic imaging for percent stenosis was performed in 39% of patients who had complete monitoring data. Ultrasound imaging served as the "imaging benchmark" in the remaining 61% of the patients. Each monitoring data point was determined to be "normal" or "abnormal" utilizing recognized threshold criteria, as were the 3-month trends for ABF, SVP, and US. A total of 177 ABF and SVP results were obtained in 65 patients. A total of 105 US studies were performed, 65 at month one and 40 at month three. 11 patients exited during the study period, 3 due to thrombosis. In comparing absolute value abnormalities for ABF and SVP, we found 36% (63/177 data points) disagreement, and for 3-month trending 24% (13/54 patients) disagreement. A similar comparison between US and SVP resulted in 49% (52/105 data points) disagreement, and 37% (20/54 patients) trended disagreement. The same comparison between US and ABF resulted in 25% (27/105 data points) disagreement, and 20% (11/54 patients) trended disagreement. We then compared ABF, SVP, and combinations of ABF and SVP, ABF and US, and SVP and US, with our imaging benchmarks for true pathology states. This resulted in sensitivity/specificity of: 83%/87.5% for ABF; 80%/79% for SVP; 86.6%/91.6% for ABF and SVP; 86.6%/100% for ABF and US; and 93.3%/100% for SVP and US. Data pertaining to ease of implementation and cost of utilizing these monitoring combinations will be presented. This study further supports: 1) combining monitoring techniques to improve accuracy, 2) trending of monitoring data, and 3) careful utilization of resources available within the dialysis center to make a monitoring program feasible.

Poster Session: Dialysis Vascular Access II (9:00 AM-4:30 PM)

Presentation Date: Saturday, November 6, 1999, Time: 9:00AM, Room: Halls B and C

Russell,
Have you used static VP's? With the current SVP method there are several key steps that must be done for the SVP to be a correct reading. Were all the proper steps used by the Boston group? I did not get to hear this presentaion at ASN- did you? The above postings are asbtracts from ASN about VA monitoring. Would like to hear about your experince with SVP's or other methods.
Deborah

Doing static venous pressure monitoring just got easier !
Medisystems is launching a new product at the ANNA this year called Access Alert. This device is used to measure static pressures at the patient access. You can monitor both venous and arterial pressures this way.
Trend analysis of static venous pressures can help to identify venous stenosis and trend analysis of static arterial pressures can be used to identify in flow problems or mid-graft stenosis. The technique is easy and quick. It doesn't take more than a minute and it's done at the point of cannulation.
Access Alert is the device Dr. Besarab used in his study written up in the ASN abstracts last fall.

Be sure to come by the Medisystems booth at the ANNA to see Access Alert and other new products.