Transonic, thermodilution, or ionic dialysance to manage vascular access: Which method is best?

Abstract

Regularly monitoring blood flow through a vascular access (Qa) can predict a dysfunction and dramatically reduce the number of thromboses. The aim of our study was to compare two integrated access flow devices, thermodilution (Qa-BTM: BTM(®), Fresenius Medical Care, Bad Homburg, Germany) and ionic dialysance (Qa-ID: OCM(®), Fresenius Medical Care, Bad Homburg, Germany), with the "gold standard" saline dilution (Qa-T: Transonic(®), Systems Inc., Ithaca, NY, USA). Measurements were performed sequentially and were repeated in the first 90 minutes of a single dialysis session in 24 long-term hemodialysis patients with a vascular access. Bland-Altman, linear regression (r(2)), and intraclass correlation coefficients (ICC) assessed reproducibility, correlations, and concordance between the techniques. Average access flow for Qa-T was 1549 (± 844) mL/minute, Qa-BTM was 1530 (± 856) mL/minute (P = NS), and Qa-ID was 1619 (± 1085) mL/minute (P = NS). Respectively, ICC, (r(2)), and bias were 0.99, (0.98), and -19 mL/minute for Qa-BTM, and 0.75, (0.65), and +69 mL/minute for Qa-ID. The limits of agreement were -287 to +250 mL/minute for Qa-BTM and -1647 to +1785 mL/minute for Qa-ID. Reproducibility of thermodilution and ionic dialysance, expressed as relative differences, was not significantly different from saline dilution. Recirculation, measured by saline dilution, was 0% (0-4%), the same as the 0% measured by thermodilution, with correct placement of bloodlines and corrected for cardiopulmonary recirculation. The integrated access flow measurement devices, thermodilution and ionic dialysance, are reasonable alternatives to using saline dilution to measure Qa: Thermodilution showed better precision and correlation. They are reliable, make monitoring of vascular access easier, incur no extra costs, and use no additional consumables.

Does the extracorporeal blood flow affect survival of the arteriovenous vascular access?

“…The reported mean Qa values of over 1110 mL/min at baseline may appear uncharacteristically high for some countries. However, such values are common in Portugal and not uncommon elsewhere . It should be emphasized that high Qa should not be taken as a license to increase Qb indefinitely.…”

“…Comparisons with the saline dilution and ionic dialysance techniques have proven its validity for calculation of Qa . A recent comparison of thermodilution (BTM), saline dilution (Transonic) and ionic dialysance (OCM) methods has demonstrated that the reproducibility of Qa measurements with the BTM does not significantly differ from that with Transonic: the Qa concordance (expressed as ICC, Intraclass Correlation Coefficients), the Qa correlation (r 2 ) and bias were 0.99 (P < 0.001), 0.98 (95% CI: 0.983, 0.995) and −19 ± 108 mL/min, respectively . The BTM also has added advantages, such as lower work load, ease‐of‐performance, and its noninvasive character (i.e., no need for injection of indicators).…”

“…However, such values are common in Portugal 14 and not uncommon elsewhere. 28 It should be emphasized that high Qa should not be taken as a license to increase Qb indefinitely. In fact, the dialysis machines used here do not permit prescription of Qb >600 mL/min as a safety precaution.…”

Vascular Access Management for Haemodialysis: A Value-Based Approach from NephroCare Experience

“…In case of dialysis efficiency reduction due to VA dysfunction, that will be expressed by a Kt/V decline trend over time [35] (better if evaluated with online automated system and in continuous mode [36,37]) and an increasing of serum potassium, phosphate, urea and creatinine levels. Dynamic pressure changes in vascular access either from venous or arterial side are reflecting VA dysfunction and suggesting a stenosis either on the distal vein or the proximal artery and impeding access flow reduction [38].…”

pCO₂ Reveals Arteriovenous Fistula Recirculation in Bicarbonate Hemodialysis (RecirCO₂lation Test)

“…Recently, it has become possible to perform VAR measurements during dialysis using devices that can be integrated directly into the dialysis machine; in fact, many artificial kidneys provide accurate self-assessment of VAR by online monitoring of blood temperature (blood temperature monitoring) [9,10] or by measuring changes in optical density of blood (Crit-Line) [11][12][13] or in blood conductivity (online clearance monitoring) [14][15][16] . All are reliable alternatives [17] to the 'ultrasound velocity dilution technique' (Transonic) based on the Krivitski's method [18,19] ; this latter is an external device that needs to be connected to the dialysis machine and is currently considered the gold standard for VAR evaluation [3] . The main problem of all such 'indicator dilution techniques' is that for the correct evaluation of true VAR, they require exact timing of sampling (Transonic and online clearance monitoring) [14,18] or double evaluation and reversal of blood lines (BTMB) [9,20] .…”