Effect of differing blood lines on delivered blood flow during hemodialysis.

Unlabelled: BACKGROUND The influence of differing blood tubing sets on delivered dialyzer blood flow (Q B ) was studied using ReadySet (RS; Medisystem Inc, Seattle, WA) and CombiSet (CS; Fresenius, Walnut Creek, CA).

Methods: In vitro, we measured Q B and pre-pump arterial pressures (P A; in millimeters of mercury) during 4 hours at a prescribed blood pump flow (Q P ) of 450 mL/min, using a glycerin-water mixture for RS and CS blood tubing sets (n = 10 each). We then performed 3 clinical studies to determine the difference between Q P and Q B as a function of P A for both tubing types and any effects of tubing type on delivered Kt/V in patients.

Effects of systemic hemodynamics on flow within vascular accesses used for hemodialysis.

Absolute value of access flow (QA) and change in flow (deltaQA) over time are major determinants of access patency. However, QA may change in response to variation in systemic hemodynamics among dialysis sessions. We examined the effect of mean arterial pressure (MAP), cardiac output (CO), and segmental resistances (R) on QA.

Simplified measurement of intra-access pressure.

The measurement of intra-access pressure (P[IA]) normalized by mean arterial BP (MAP) helps detect venous outlet stenosis and correlates with access blood flow. However, general use of P(IA)/MAP is limited by time and special equipment costs. Bernoulli's equation relates differences between P(IA) (recorded by an external transducer as PT) and the venous drip chamber pressure, PDC; at zero flow, the difference in height (deltaH) between the measuring sites and fluid density determines the pressure deltaPH = P(IA) - P(DC) Therefore, P(DC) and PT measurements were correlated at six different dialysis units, each using one of three different dialysis delivery systems machines.

Detection of access strictures and outlet stenoses in vascular accesses. Which test is best?

The location of stenoses within an access may influence the diagnostic value of access monitoring tests. Whereas decreasing access flow (QACC) should occur with both venous outlet stenoses and strictures within the body of the access, normalized intra-access venous pressure (vPIA/MAP) depends on location of the venous needle relative to the lesion. The authors determined the value of vPIA/MAP and direct measurement of percent access recirculation (AR) and QACC in detecting venous outlet stenoses and strictures.

Detecting vascular access dysfunction.

Access flow (QACC) is a major determinant of patency. Access recirculation (AR > 2%), normalized venous intra-access pressure (vPIA/MAP), and QACC are used to detect access dysfunction. We compared these three measures of access function (ultrasound dilution to measure AR and QACC).