Functional vascular access evaluation after elective intervention for stenosis

Abstract

Purpose

To evaluate the functional effects of preventive vascular access (VA) intervention through periodic blood flow (Q_A) measurements during hemodialysis (HD) by the delta-H method.

Methods

We prospectively monitored the blood flow rate (Q_A) of 100 VA (arteriovenous fistula (AVF) 81% or AV graft (AVG) 19%; mean VA duration 24.6 ± 42.3 months) during HD in 89 end-stage renal disease patients (mean age 62.7 ± 13.6 yrs; mean time on HD 30.9 ± 43.9 months; 18% with diabetes) over a 3-yr period. Q_A was measured at least every 4 months by the delta-H method (Yarar (6)) using the Crit Line III Monitor (overall mean Q_A 1247.6 ± 519.7 ml/min). The mean arterial pressure (MAP) and Kt/V index were measured simultaneously with Q_A. Thirty-eight VA (38%) met the positive evaluation criteria (absolute Q_A <700 ml/min 50%, Q_A decreased >20% from baseline 50%). Most cases with positive evaluation underwent angiography (36/38, 95%) and had stenosis ≥50% (34/36, 94%). Of VA with significant stenosis, 17 (17/34, 50%) VA (AVF 76.5%, AVG 23.5%; mean VA duration 12.5 ± 22.4 months, mean percentage of VA stenosis 75.8%) in 15 patients (mean age 68.4 ± 9.8 yrs; mean time on HD 14.2 ± 18.2 months; 33.3% with diabetes) underwent corrective intervention by angioplasty, 35.3% (6/17), and revision surgery, 64.7% (11/17).

Results

Short-term results: Elective intervention was successful in 88% of treated VA (15/17). Mean Q_A increased from 563.8 ± 115.4 ml/min just before intervention (Q_A pre) to 975.7 ± 351.8 ml/min just after intervention (Q_A post) (mean ΔQ_A = 411.8 ± 290.1 ml/min) (p < 0.001). We found a significant difference between the overall mean Q_A before (689.6 ± 227.0 ml/min) vs after intervention (965.9 ± 396.8 ml/min) (p = 0.011). No difference was found when the highest recorded mean Q_A before intervention (877.7 ± 415.4 ml/min) and mean Q_A post were compared (p = 0.25). Mean MAP did not change after intervention (91.5 ± 12.5 vs 92.7 ± 14.2 mmHg, p = 0.46). Mean Kt/V index improved from 1.44 ± 0.24 just before intervention to 1.49 ± 0.23 just after intervention without any change in dialyzer type or HD duration (p = 0.025). Mean ΔQ_A was similar for diabetic patients vs non-diabetic patients (p = 0.34), for younger patients (age < 65 yrs) vs older patients (age ≥65 yrs) (p = 0.64) and for AVF vs AVG (p = 0.39). We found a positive correlation between mean ΔQ_A and mean Q_A post (r = 0.95, p < 0.001) or between mean ΔQ_A and overall mean Q_A after intervention (r = 0.77, p < 0.001).

Long-term results

Prevalence of VA thrombosis during the follow-up period (354.4 ± 293.1 days): 17.6% (3/17). Five (29.4%) treated VA showed restenosis and two of them (40%) underwent reintervention by surgery. Mean restenosis period and mean decrease in Q_A were 232.6 ± 74.1 days and 2.8 ± 0.6 ml/min/day, respectively. No significant correlation was found between mean ΔQ_A or Q_A pre and mean restenosis period or decrease in Q_A (p = ns).

Conclusions

1) Monitoring Q_A by the delta-H method is useful in assessing the hemodynamic response to elective VA intervention. 2) Mean Q_A post was similar to the highest recorded mean Q_A before intervention. 3) Mean ΔQ_A was related to mean Q_A post and overall mean Q_A after intervention. 4) The HD effectiveness (Kt/V index) improved after intervention.