CHAPTER 1: Hemodialysis Adequacy in Adults

Recommendations

1. All hemodialysis patients should have regular global assessments of dialysis adequacy. (Grade D, opinion) Assessment of hemodialysis adequacy should include urea clearance, volume control, blood pressure, mineral metabolism, and clinical symptoms. (Grade C)

2. The minimum acceptable target for urea clearance during hemodialysis is a single-pool Kt/V of 1.2 or percent reduction of urea (PRU) of 65% three times per week. (Grade C)

3. Hemodialysis centers should consider offering a range of options, including more frequent or sustained treatment times, for those patients with dialysis inadequacy. (Grade D, opinion)

Background

Urea clearance as assessed by Kt/V or PRU is a surrogate for dialysis dose. Although practice guidelines have traditionally emphasized the role of urea clearance, this parameter is only one component of dialysis adequacy.

The National Cooperative Dialysis Study (NCDS) established that higher dialysis dose resulted in reduced morbidity (1), although the intensity of dialysis in both treatment groups was considerably lower than in current practice. More recently, observational studies have suggested that urea clearance below a single-pool Kt/V of 1.2 or PRU of 65% three times per week is associated with increased mortality (2–6). Although observational data from patients treated with thrice-weekly and quotidian hemodialysis suggest that even higher levels of urea clearance are associated with better clinical outcomes (7–12), a well-designed, randomized study found no benefit of a single-pool Kt/V target of 1.65 compared with 1.25 (13). Although this study cannot exclude a mortality benefit <25%, there is no evidence to support increasing the target Kt/V above currently recommended levels. Since no grade A evidence (apart from the NCDS) indicates that increasing hemodialysis dose will reduce morbidity or mortality, it is possible that reducing the target Kt/V to levels <1.2 might not compromise clinical outcomes. However, in the absence of an adequately powered randomized study to confirm this hypothesis, the Committee continues to recommend a target single-pool Kt/V of >1.2.

Higher levels of urea clearance might be a marker for longer dialysis times, better control of blood pressure (BP) and extracellular fluid volume, or higher clearance of larger molecular weight substances. However, the use of high-flux dialyzers, which remove higher molecular weight toxins more efficiently, does not appear to reduce mortality, making the latter possibility less likely (13). Although the hypothesis that improved volume control will reduce mortality is attractive, it remains untested in hemodialysis patients. Nonetheless, optimal control of extracellular fluid volume and BP are rational goals given the large body of evidence linking these characteristics to better health outcomes. Longer dialysis duration or more frequent dialysis treatments may aid in achieving these clinical objectives.

To ensure that patients are receiving the prescribed urea clearance, the clinician must regularly monitor and measure the dose delivered. Urea clearance should be measured at least every 8 wk. Examples of acceptable techniques for estimating delivered dose are formal single-pool urea kinetics, PRU or urea reduction ratio (URR), and Kt/V natural logarithm formulae.

Of the three suggested techniques, single-pool urea kinetics predicts the dose delivered most accurately. However, the goal of monitoring urea clearance is to ensure that patients receive at least a minimum dose of therapy. Although PRU does not take into account urea removal by ultrafiltration, measurements using this technique will underestimate the dialysis dose, which would not compromise patient care. Similarly, the contribution of residual renal function can be ignored. Because all three parameters correlate with mortality, there is no strong reason to recommend one in particular. Clinicians should consider reproducibility, ease of use, and familiarity when selecting a measure of urea clearance for use in their hemodialysis programs. To facilitate comparisons between units, the index of urea clearance used should be consistent within a hemodialysis program. Methods for measuring urea clearance appear in Appendix A.

Clinicians should recognize that staff and patients may conduct themselves differently on the day when the dose of therapy is being measured. Therefore, clinicians are encouraged to use some additional techniques, which may be less precise but permit the measurement of the dose of hemodialysis delivered on a daily basis (e.g., volume of blood processed, average pump speed, and duration of treatment), and to correlate them with the more formal dosage measurement.

In addition to considering urea clearance and volume status, the clinician must consider many other measures and indicators in assessing a patient’s health and prescribing treatment, including control of extracellular volume and BP, uremic symptoms, quality of life, control of hyperphosphatemia, adequate nutritional status, and treatment of anemia. (See the guidelines on Mineral Metabolism and Management of Blood Pressure in Hemodialysis Patients for details).

Hemodialysis centers should have a continuous quality improvement/patient review system in place that recognizes patients who are receiving suboptimal dialysis adequacy, identifies the cause, and corrects it. This process may be facilitated by the use of multidisciplinary sit-down rounds in addition to regular contact between patients and nephrologists (14).

Although there are no randomized studies demonstrating that nocturnal, daily, or sustained hemodialysis treatments improve clinical outcome compared with standard care (12), multiple observational studies indicate that such treatments may improve surrogate outcomes in select patients at a reasonable cost (7–9,15–20). Recognizing that this evidence base is inconclusive, hemodialysis centers should consider offering a range of options for hemodialysis including more frequent or sustained treatment times, especially for patients in whom standard dialysis appears inadequate. (See the guideline on Frequent and Sustained Hemodialysis). On the other hand, less frequent dialysis may be acceptable for brief periods in patients with greater levels of residual kidney function, or those in whom the primary indication for dialysis is control of extracellular fluid volume rather than solute clearance (i.e., those with renal insufficiency due to severe heart failure).

Recommendations

1. Confirm dialysis inadequacy by assessing procedural issues and vascular access function. (Grade D)

2. Once dialysis inadequacy is confirmed, increase one or more of the following treatment parameters: dialysis time, needle diameter, dialyzer KoA, or dialysis frequency. (Grade D)

Background

When the patient fails to receive the minimum target dose of dialysis or when there is a significant drop in the dose of dialysis being delivered, the clinician should consider procedural issues (prescription, anticoagulation, appropriate measurement of dialysis dose, optimization of needle placement) and inadequate access function Table 1

The following techniques may be used to increase urea clearance and possibly dialysis adequacy:

• blood flow rate (21,22)

• dialyzer KoA (21)

• dialysis time (23)

• dialysis frequency (23)

• dialysate flow (24–26)

• needle size (27)

• ensuring adequate anticoagulation (28)

Consideration could also be given to use of a newer dialytic modality such as more frequent or sustained hemodialysis.

Recommendations

1. A single person or a multi-professional team should be responsible for the quality of the medical care and have the authority to establish universal standards of care for the unit. (Grade D, opinion)

2. Validated clinical protocols or algorithms should be considered to reduce inappropriate variability in quality of dialysis care. (Grade D)

Background

To ensure the quality of medical care for all patients, all those involved in providing care must be accountable. In a multi-professional setting, the combination of a number of different professionals with different priorities dealing with complex situations may lead to variations in standards of practice and care. To ensure that the guidelines are applied uniformly to all patients in the unit, the individual or management team accountable for the quality of medical care must be clearly identified. The multidisciplinary team/dialysis program should evaluate its practice via Continuous Quality Improvement.

Maximizing patient adherence is critical to the long-term success of therapy. An environment that encourages optimal care may include the patient’s primary care physician and appropriate specialists (e.g., gynecologists, endocrinologists) in the patient’s care. There is evidence that an individualized, patient-centered approach improves clinical performance compared with standard care (29).

Nonadherence may be the result of a number of factors (e.g., socioeconomic, educational, emotional) that are beyond the patient’s control and may require specific attention from physicians or allied health personnel. The clinician should provide appropriate information about renal failure and its treatment, and encourage patients to have continuing contact with their primary care physicians. The information provided to patients should account for educational level and language differences.

The increasing number of hemodialysis patients may potentially compromise the ability of clinicians to provide optimal care. Although management of hemodialysis patients is complex and multifactorial, many of the individual components of care (management of metabolic bone disease or anemia, control of extracellular fluid volume) are amenable to protocolization. Although no studies indicate that such protocols improve clinical outcomes, they appear to improve process of care in patients with and without end-stage renal disease (ESRD) (30,31). Protocolization of these facets of care would be expected to free more of clinicians’ time to devote to other aspects that require more individualized attention.

Drawing Samples for Measuring Urea Clearance

1. Predialysis and postdialysis samples must be drawn at the same dialysis session.

2. Draw predialysis blood from the arterial needle before administering any saline or heparin.

3. When central lines are used and if heparin and/or saline is used, withdraw at least 10 cc of blood before drawing the blood sample. The blood withdrawn may then be returned to the patient.

4. The postdialysis [urea] blood sample must not be diluted by either recirculation or saline.

5. For formal urea kinetic modeling, the sample must be drawn before any rebound; therefore, the slow flow/stop pump technique must be used. For other techniques (PRU and log prediction of Kt/V), the blood sample may be taken postdialysis when the possibility of access and cardiopulmonary recirculation is eliminated. To eliminate the possibility of cardiopulmonary recirculation, draw the sample at least 2 to 3 min postdialysis. To facilitate longitudinal comparisons, the sampling technique for the unit should be clearly stated, documented, and consistent from treatment to treatment and between patients.

Background

Because the goal is to ensure at least a minimum standard, a postdialysis sample is preferable and easier to obtain than a stop flow sample. Although the postdialysis sample may be more variable (due to rebound), it will tend to underestimate rather than overestimate delivered dialysis.