Access flow, venous saturation, and digital pressures in hemodialysis.

BACKGROUND

A hemodialysis arteriovenous fistula (AVF) requires surgical modification in patients with cardiac overload or dialysis access-associated steal syndrome (DASS). Creation of an artificial stenosis (banding) within the AVF may be used, but this technique lacks the guidance of objective parameters. The aim of this pilot study was to identify indicators that reflect AVF flow in dialysis patients with either access-related cardiac overload (CO) or DASS requiring corrective surgery.

METHODS

Patients underwent serial measurements of subclavian venous saturation (Sat(ven)), access flow (Flow(us)), and index digital pressures (P(dig)) during a corrective banding procedure.

RESULTS

Data were obtained in 14 individuals (9 men; mean age, 53 +/- 6 years) during 16 studies (CO, n = 8; DASS, n = 8). Before surgery, correlations between preoperative flow, Sat(ven) and P(dig) were not significant. Stepwise banding of the AVF altered Sat(ven) in both groups from a mean of 91% +/- 1% (open AVF) to 84% +/- 2% (closed AVF, P < .001). The CO patients demonstrated a larger drop (-13%) compared with the DASS patients (-4%). Values of P(dig) increased from 68 +/- 9 to 90 +/- 9 mm Hg (P < .001), and both groups demonstrated a similar +23 mm Hg increase. In concert, the digital brachial index also significantly improved in all patients from 0.60% +/- 0.09% to 0.74% +/- 0.10%. Linearity was present between alterations in Flow(us) and Sat(ven) in all patients, but mostly in the CO patients (r(2) = 0.96).

CONCLUSIONS

Stepwise banding of hemodialysis fistulas leads to dose-dependent decreases in flow and ipsilateral subclavian venous saturation combined with augmented digital pressures in patients with cardiac overload and dialysis associated steal syndrome. Intraoperative measurements of venous saturation and digital pressures may have the potential of guiding surgical correction in these patients.