Abstract

ROCA-TEY, Ramón et al. Study of arteriovenous fistula function by the temperature gradient method using the Twister^™ device. Nefrología (Madr.) [online]. 2012, vol.32, n.2, pp.172-179. ISSN 1989-2284.

Introduction. Periodic blood flow (Q_A) measurement is the preferred way for arteriovenous fistula (AVF) surveillance in chronic hemodialysis (HD) patients. Objectives. 1) Assess the efficacy of the temperature gradient method (TGM) on the Q_A determinations using the Twister^™ device and to compare the functional results with the Delta-H method. 2) Evaluate the effect of blood pressure on the AVF function. Patients and method. We measured the Q_A non invasively in 30 AVF (24 radial and 6 brachial; mean duration 53.4 ± 78.5 months) during HD in 30 stable patients (mean age 59.9 ± 14.1 years, males 60 %, females 40 %; mean time on HD 37.4 ± 40.6 months, diabetic nephropathy 20 %) by the TGM, described and validated by Wijnen et al (Kidney Int 2007;72:736). The Q_A was calculated from the temperature values obtained by means of the blood temperature monitor (BTM), integrated into the Fresenius Medical Care 4008-S machine, at normal and reverse configurations of the HD blood lines, with no need for a thermal bolus. The Twister^™ device was used for reversing the blood lines without the need to disconnect them from the AVF lines nor to stop the blood pump. The Q_A was measured within the first hour of two consecutive HD sessions (the values were averaged). The mean arterial pressure MAP (diastolic pressure + 1/3 pulse pressure) was calculated simultaneous with the Q_A. In addition, the AVF blood flow was also determined during the same week in all patients by the Delta-H method using the Crit-Line III Monitor (ABF-mode, HemaMetrics, USA) during HD (manually switching lines). Results. The mean Q_A was 1132.5 ± 515.4 ml/min (range, 446-2233 ml/min). The mean coefficient of variation for duplicate Q_A measurements was 6.8 ± 4.7 %; the MAP was not different when the reproducibility tests were performed (96.1 ± 13.7 versus 96.6 ±12.8 mmHg, p = .72). No significant difference was found when comparing the mean Q_A between diabetic (n = 6, 966.4 ± 340.7 ml/min) and nondiabetic (n = 24, 1174.4 ± 548.3 ml/min) patients (p = .39). The mean Q_A was similar for patients with mean MAP < 100 mmHg (n = 18, 1101.0 ± 552.7 ml/min) and for patients with mean MAP >_ 100 mmHg (n = 12, 1180.4 ± 473.3 ml/min) (p = .69). No correlation was found between the mean Q_A and: age (r = 0.09, p = .62), time on HD (r = 0.06, p = .76), MAP (r = - 0.21, p = .27), Kt/V index (r = 0.12, p = .51), distance between needles (r = - 0.17, p = .37) and AVF duration (r = - 0.01, p = .96). The mean time required to measure Q_A with the TGM using the Twister^™ device (5.9 ± 1.9 min) was significantly shorter compared with the Delta-H technique (26.8 ± 1.9 min) or with the TGM (n = 35, 8.9 ± 3.5 min, manually reversing lines) reported by Wijnen et al (Kidney Int 2007;72:736).) (for both comparisons, p < .001). The mean Q_A obtained by the TGM was not different when compared to mean ABF determined by the Delta-H method (1138.4 ± 502.3 ml/min) (p=.83). The calculated values of AVF blood flow obtained by TGM were highly correlated with those determined by the Delta-H technique (r = 0.963, p < .001). Conclusions. 1) The TGM is a valuable and reproducible indicator of Q_A during HD. 2) The Twister^™ device is useful to reduce the time for Q_A measurement by the TGM. 3) The AVF blood flow values obtained by the TGM and the Delta-H technique correlated highly with each other. 4) It has been shown the lack of relationship between the AVF function and the patient's blood pressure.

Keywords : Arteriovenous fistula; Vascular access blood flow monitoring; Temperature gradient method; Twister^TM device; Delta-H method; Blood pressure.

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