Hemodialysis vascular assessment by an ultrasound dilution method (transonic) in patients older than 65 years

Arteriovenous Fistula Surveillance Using Tomographic 3D Ultrasound

OBJECTIVE

A well functioning arteriovenous fistula (AVF) is essential for haemodialysis. Despite regular duplex ultrasound (DUS) a significant number of AVFs fail. Tomographic 3D ultrasound (tUS) creates a 3D image of the AVF that can be interpreted by the clinician. DUS, tUS, and fistulograms were compared for the identification and measurement of flow limiting stenosis.

METHODS

Patients with AVF dysfunction on routine Transonic surveillance, defined as (1) > 15% reduction in flow on two consecutive occasions, (2) > 30% reduction in flow on one occasion, (3) flow of < 600 mL/sec, (4) presence of recirculation, underwent DUS. AVF tUS imaging was performed prior to fistulography. All fistulograms were reported by the same consultant radiologist and tUS images by the same vascular scientist blinded to the fistulogram results. Maximum diameter reduction in all stenoses were measured using all three imaging techniques.

RESULTS

In 97 patients with 101 stenoses, the mean (± standard deviation [SD]) severity of stenosis was 63.0 ± 13.9%, 65.0 ± 11.6%, and 64.8 ± 11.7% for the fistulograms, DUS, and tUS respectively. The mean (± SD) time between ultrasound and fistulography imaging was 15.0 ± 14.5 days. Assuming the fistulogram as the "gold standard", Bland-Altman agreement for DUS was -1.9 ± 15.5% (limit of agreement [LOA] -32.2 - 28.4) compared with -1.7 ± 15.4% (LOA -31.9 - 28.4) for tUS. Median (± interquartile range) time to complete the investigation was 09:00 ± 03:19 minutes for DUS and 03:13 ± 01:56 minutes for tUS (p < .001).

CONCLUSION

DUS and tUS were equally accurate at detecting AVF complications but tUS investigation requires less skill and was significantly quicker than DUS.

Analysis of access flow using duplex ultrasonography and the ultrasound dilutional method

BACKGROUND

This study aimed to evaluate the correlation between duplex ultrasonography (DUS) and ultrasound dilution (UD) measurement's results and determine the factors affecting the correlation of the measured values among other clinical factors in patients.

METHODS

This cross-sectional study was conducted from April 2020 to May 2020 and included 60 patients who visited our dialysis centre. The flow of the fistula was measured in the proximal brachial artery using DUS. While dialysis was performed on the same day, the access flow was measured using the UD method. The correlation and agreement between the access flows acquired by each measurement method were analysed. Similarly, the correlation was analysed by classifying the groups based on the predisposing factor, and statistically significant factors were observed through comparison.

RESULTS

Both measurements showed a moderate positive correlation (r = 0.60, p < 0.01). The bias (mean of UD-DUS) between the two measurements was about 230 mL/min. When the measurement site of DUS was near the inflow artery and in the same anatomical section, a strong correlation with the measurement value of UD was observed (brachial based fistula: r = 0.85, radial based fistula: r = 0.87). Similarly, for patients without diabetes and those who regularly underwent access surveillance for the dialysis route, strong correlations were observed between the two measurements (r = 0.79 and r = 0.88).

CONCLUSIONS

Several factors can influence the correlation between UD and DUS. The findings showed a high correlation for DUS measurement sites within the same anatomical section as the inflow artery, patients without diabetes, and patients undergoing periodic surveillance.

Determinants of native arteriovenous fistula blood flow

BACKGROUND

Determinants of native arteriovenous fistula (AVF) placement have been well studied. Little is known on whether these factors impact on subsequent blood flow (Qa) in the mature AVF.

METHODS

Arteriovenous fistula Qa and cardiac index (CI) were determined by ultrasound dilution. Multiple linear regression was used to assess independent predictors of AVF Qa.

RESULTS

Of the 148 patients available for the analysis, 68% were male, with 61% using a radiocephalic AVF. Aetiology of renal disease was: 38% glomerulonephritis (GN), 22% diabetes mellitus (DM), 9% hypertension/ischaemic (HTN) and 31% other. Thirty per cent had coronary artery disease (CAD), 10% cerebrovascular disease and 11% peripheral vascular disease (PVD). Median (iqr) Qa was 1185 mL/min (790-1650) and CI was 3.15 L/min per 1.73 m(2) (2.60-3.93). On univariable analysis, log CI (0.98, P < 0.001), age (-0.1 per 10 years, P = 0.002), access position (upper vs lower 0.26, P = 0.003, PVD (-0.35, P = 0.015), CAD (-0.25, P = 0.008), and primary renal disease (DM vs GN, -0.35, P = 0.003, HTN vs GN, -0.34, P = 0.04) were associated with Qa. On multivariable analysis, CI (0.84, P < 0.001), access position (upper vs lower, 0.17, P = 0.018) and primary renal disease (DM vs GN, -0.26, P = 0.005, and HTN vs GN, -0.26, P = 0.038) remained significant predictors of AVF Qa.

CONCLUSION

Once established, CI, AVF position and primary renal disease (hypertension/ischaemic and diabetes) are the major determinants of AVF Qa while female gender, CAD, PVD and body mass index were not significant determinants of Qa in this cohort.