V. Hemodialysis Dose Troubleshooting


Inadequate Delivery of Hemodialysis (Opinion)

If the delivered Kt/V falls below 1.2, or the URR declines to <65%, on a single determination, at least one of the following actions should be performed:

1. Investigate potential errors in the delivery of the prescribed hemodialysis dose (see Table I-5);

2. Empirically increase the prescribed dose of hemodialysis; and/or

3. Suspend use of the reprocessed hollow fiber hemodialyzer.

The impact of these corrective interventions should be followed by performing more frequent measurements of Kt/V or URR.

Rationale Every effort should be made to ensure that patients receive adequate hemodialysis at each treatment (see Guideline 4: Minimum Delivered Dose of Hemodialysis). Whenever the delivered dose of dialysis falls below the minimum acceptable level (Kt/V = 1.2 or URR = 65%), a systematic investigation should be initiated promptly to identify why the delivered dose has declined to that level. The HD Adequacy Work Group developed an algorithm (see Table I-5) that can be used to identify the causes of inadequate delivery of hemodialysis and to implement corrective actions. The algorithm is based on the following assumptions:

1. It is unrealistic to expect dialysis care teams to immediately identify and correct problems that result in inadequate hemodialysis. Some delay in identifying a problem typically will occur. For example, with routine blood sampling, there is usually a delay of several days to 1 week between blood sampling and the delivery of the lab report that signals a problem. Over that interval, up to three hemodialysis treatments will have occurred. There will be additional delays as the potential causes of the problem are investigated. A prompt corrective response will minimize inadequate treatments.

2. More frequent measurements of Kt/V or URR will assist in identifying the problem(s), the underlying cause(s), and the necessary corrective action(s).

3. Hemodialysis units and clinicians should strive to categorize failures and to identify specific causes, eg, procedural errors by staff, equipment problems, deficient reprocessing techniques/systems, patient nonadherence, etc.

4. Increasing the prescribed hemodialysis dose until appropriate minimum targets are reached will improve patient outcomes.

5. Inadequate performance of reprocessed dialyzers may be associated with reductions in the delivered dose of hemodialysis.72,204-206,209

6. Prudent clinical judgment requires that use of a potentially inadequate hemodialyzer be suspended until the specific etiology of the insufficiency of delivered dose can be identified. If other factor(s) explaining the deficiency are identified, the dialyzer can be returned to use.

Table I-5. Error Analysis for Deficiencies in Delivered Kt/V or URR

Because of the complexity and technological nature of the hemodialysis procedure, deviations from the prescription may occur. It is important to evaluate potential technical problems that may result in significant deviation(s) between the prescribed and delivered dose. For this reason, a clinical algorithm has been developed to assist in the elucidation of potential technical problems. The algorithm has been organized such that the initial assessments focus on elements of the dialysis treatment that can be evaluated immediately using available information and without additional costs. A second level of assessments includes techniques or investigations which may be invasive, require more time, or incur costs to the dialysis center and/or patient (see Appendices E and F).

When investigating potential technical problems, it is useful to remember that there are four primary treatment variables that determine the actual delivered Kt/V. These include the clearance of hemodialyzer, treatment duration, and the flows of blood and dialysate. Any of these elements may vary for a given hemodialysis treatment. Therefore, small deviations in delivered Kt/V are common and should be evaluated within the constraints of time. Significant underdelivery of the hemodialysis prescription by >20% should initiate attempts to determine the cause(s). Errors that contribute to an apparent delivery of hemodialysis that is significantly greater than prescribed should also be investigated. Since the response of many dialysis care teams is to actively decrease the dose of hemodialysis by prescribing less hemodialysis, erroneous reports of overdelivery of this sort are potentially dangerous.

Error analysis algorithm

Initial Assessments Elements of hemodialysis treatment* to evaluate/correct immediately. These elements can be assessed noninvasively, using available data, and/or without incurring cost.

Clearance (K) less than assumed. Elements of the hemodialysis procedure affecting clearance include: dialyzer permeability (KoA), effective dialyzer surface area, blood flow, and dialysate flow.

1. Assess fistula integrity to determine if there may be recirculation.

• Perform hydraulic compression test during next dialysis.

• Review A/V needle placement, proximity, and orientation with patient care staff and patient.

• Verify graft flow configuration.

2. Review written documentation of hemodialysis treatment when Kt/V or URR was measured.

• Review hemodialyzer reuse log to evaluate total cell volume (TCV).

• Review maintenance log for machine to check last calibration date and results.

• Review hemodialysis log to compare prescribed versus actual parameters, including:

a. Recorded blood flow rate (Qb)

b. Dialysate flow rate (Qd)

c. Type of hemodialyzer

d. Extracorporeal pressures compared to previous sessions with prescribed Qb

–Were prepump arterial pressures 200 mmHg?

–Were prepump arterial or venous pressures close to upper limit per dialysis unit policy?

• Review dialysis log for clinical events, eg, hypotension, muscle cramps or chest pain that may have resulted in a change in treatment parameters (blood flow).

Effective hemodialysis treatment time (Td) less than prescribed. Hemodialysis treatment time is the total time at the prescribed blood and dialysate flow rates with the prescribed dialyzer, or is the dialysis time determined to provide an equivalent Kt/V at the prevailing blood and dialysate flow rates for a particular hemodialyzer.

1. Review written documentation of total duration of the dialysis treatment for determination of any of the following:

• Patient arrived late for hemodialysis treatment

• Facility/staff late starting dialysis without compensatory extension of time

• Patient requested early termination of hemodialysis treatment

• Clinical events (eg, hypotension, muscle cramps, chest pain, etc) that may have caused premature discontinuation or interruption of hemodialysis

• Hemodialyzer blood leak

• Needle problems or need for recannulation of angioaccess

• Extracorporeal pressures close to alarm limits

Errors in blood sampling or processing for BUN Concentration.

Predialysis BUN sample concentration is low.

• Check with patient care provider about whether needles were saline-filled or if blood sample was drawn after initiation of dialysis.

• Consider asking lab to rerun sample.

Postdialysis BUN sample concentration is high.

• Review with patient care staff whether the postdialysis blood sample was drawn at end of dialysis or after reinfusion of blood.

Secondary Assessments Evaluation of these elements of hemodialysis treatment requires further investigation. These investigations may be invasive, require more staff time or equipment maintenance, and/or are cost generating.

Clearance (K) less than assumed.

1. If hydraulic compression test is positive, perform measurement of recirculation in fistula using slow flow/stop pump sampling technique.51

2. Determine if dialyzer clearance is overestimated by reviewing urea kinetic modeling results on other patients using same dialyzer model and same prescribed Kt/V.

3. Review dialyzer clotting. May warrant review of anticoagulation protocol.

4. Determine if blood pump calibration was inaccurate by reviewing kinetic modeling results on other patients using same equipment.

5. Review hemodialysis log for extracorporeal pressures (particularly prepump arterial pressure) for values 200 mmHg.

6. For delivery systems with computers, review the total liters of blood processed.

7. Empirically recalibrate blood pump and dialysate flow rate.

Effective hemodialysis treatment time (Td) less than prescribed.

1. Review patient arrival time in unit and transportation needs.

2. Evaluate repetitive early termination with patient and patient care staff.

3. Review understanding of treatment components with patient and patient care staff.

Errors in sampling or processing for BUN concentration.

Postdialysis BUN sample concentration is low (Kt/V is significantly greater than prescribed).

• Review sampling procedure with patient care staff with focus on the following areas:

a. Using slow flow/stop pump sampling technique for postdialysis BUN sampling to avoid recirculation contamination

b. Avoiding sample dilution from saline reinfusion before sampling

c. Preventing sampling from venous instead of arterial bloodline

Repeat predialysis and postdialysis BUN sampling to determine Kt/V or URR.

* The hemodialysis care team should note that list is not all-inclusive. However, the elements provided are the most common sources of error.






© 2001 National Kidney Foundation, Inc

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