NKF K/DOQI GUIDELINES 2000
 
 
GUIDELINES FOR HEMODIALYSIS ADEQUACY

VI. Maximizing Patient Adherence to the Hemodialysis Prescription

GUIDELINE 15

Optimizing Patient Comfort and Adherence (Opinion)

Without compromising the delivered dose of hemodialysis, efforts should be undertaken to modify the hemodialysis prescription to prevent the occurrence of intradialytic symptoms that adversely affect patient comfort and adherence.

Rationale Based on clinical experience, the HD Adequacy Work Group recognizes that a major barrier to providing adequate hemodialysis is patient nonadherence. Patients may confound attempts to provide an otherwise adequate treatment by missing hemodialysis sessions, arriving late for treatments, temporarily interrupting the treatment, or leaving the hemodialysis session prematurely.32,53,54,77,78,113,211 The reasons for patient nonadherence can be varied. Hence, an assessment by the dialysis care team should be undertaken to determine the cause(s); interventions should be planned and executed accordingly. The Work Group was impressed by the number of patients reported to have discontinued hemodialysis treatments prematurely because of complications occurring during the treatment. In a large observational study of this problem, 55% of the premature terminations were because of medical reasons.77 Within this category, 70% were because of cramps, 48% were a consequence of feeling sick, and 15% were secondary to symptomatic hypotension. Intradialytic hypotension and/or cramps thus can adversely affect the delivered dose of hemodialysis.

Because of physical discomfort associated with hemodialysis treatments, many patients miss sessions more often and/or terminate their dialysis sessions prematurely.77,114,193 Hemodialysis adequacy is further compromised by the response that is taken when these adverse symptoms occur. Many hemodialysis healthcare teams respond to hypotensive or cramping patients by decreasing the blood flow and ultrafiltration rate. In this situation, the patient may receive less than the prescribed hemodialysis dose and not meet the ultrafiltration goal. Lastly, protracted hypotension during a hemodialysis session may exaggerate urea rebound.178 Therefore, if possible, repeated symptomatic hypotension and cramps should be avoided.

Some members of the Work Group were especially concerned about the clinical practice of routinely and deliberately provoking hypotension to operationally define a patients estimated dry weight (EDW).*

The literature does not support the notion that hypotension is a reasonable clinical indicator of the achievement of EDW. Based on invasive measures of intravascular volume, such as right heart catheterization with or without pulmonary capillary wedge measurements, patients who are hypotensive during hemodialysis may be intravascularly euvolemic, hypovolemic, or hypervolemic.212-215 This finding is not surprising in view of the contradictory literature describing the association between intravascular volume, intradialytic hypotension and/or cramps, and the volume of fluid removed.216-221

The Work Group was unable to find a practical clinical measure of EDW. Typically, the degree of volume expansion is defined historically. It is based on the increase of the patient’s weight above the value at discharge from the previous hemodialysis session. However, this assumes that the previous discharge weight was appropriate. For many patients, this assumption is incorrect.216 For example, the historical EDW may change because of unappreciated alterations in the patient’s nutritional status. Alternatively, the historical dry weight may have been erroneous but well tolerated.213,215

In view of the difficulty in establishing a value for EDW, and considering the deleterious consequences of hypotension and cramps on the delivery of hemodialysis, the Work Group suggests that clinicians modify the dialysis prescription for patients whose hemodialysis treatments are frequently complicated by intradialytic hypotension and cramps (as suggested in Guideline 16: Strategies to Minimize Hypotensive Symptoms).

RECOMMENDATIONS FOR RESEARCH

The Work Group suggests that efforts be undertaken to develop accurate, but practical methods of measuring intravascular volume during hemodialysis and of relating these changes to blood pressure measurements.

GUIDELINE 16

Strategies to Minimize Hypotensive Symptoms (Evidence)

Without compromising the delivered dose of hemodialysis, efforts should be undertaken to minimize intradialytic symptoms that compromise the delivery of adequate hemodialysis, such as hypotension and cramps. These efforts may include one or more of the following:

1. Avoid excessive ultrafiltration.

2. Slow the ultrafiltration rate.

3. Perform isolated ultrafiltration.

4. Increase the dialysate sodium concentration.

5. Switch from acetate to bicarbonate-buffered dialysate.

6. Reduce the dialysate temperature.

7. Administer midodrine predialysis.

8. Correction of anemia to the range recommended by NKF-K/DOQI Anemia Guidelines.

9. Administer supplemental oxygen.

Rationale Clinicians have an obligation to minimize discomfort associated with hemodialysis treatments without compromising the efficacy of the treatment. Symptomatic hypotension and cramps during hemodialysis are well-documented causes of patient discomfort as well as of early termination of dialysis therapy.77,114 Therefore, efforts should be made to minimize the occurrence of hypotension and cramps by modification of the hemodialysis prescription. The HD Adequacy Work Group reviewed several relatively simple strategies that can be implemented in most hemodialysis units to attenuate these intradialytic complications.

Ultrafiltration changes. Severe recurrent hypotension and cramps should prompt a review of the current EDW. As stated earlier, hypotension cannot be used to define intravascular volume.192,212-215 Therefore, the dialysis care team should reevaluate the current EDW.214,216 A clue that the EDW may be too low is a history of an increased dietary intake accompanied by biochemical signs of improving nutrition (increasing serum albumin and/or creatinine concentration, and/or NPCR) in the presence of hypotension.

Both the ultrafiltration volume and the rate of ultrafiltration greatly affect blood pressure.213,215,216 Patients with excessive weight gain should be encouraged to decrease their fluid intake. Alternatively, if the large fluid intake is a consequence of robust food intake,224 the duration of the hemodialysis treatment should be extended so that the hourly ultrafiltration rate is lower. Lastly, ultrafiltration can be segregated temporally from diffusive clearance by performing sequential ultrafiltration/clearance.225-229 Ultrafiltration alone results in a prompt and appropriate increase in stroke index, cardiac index, pulmonary artery wedge pressure, and mean arterial pressure.225 However, if this strategy is used to attenuate intradialytic hypotension and cramps, the total duration of hemodialysis must be extended so that compensation is made for the time lost for diffusive clearance.

Dialysate modifications. The dialysate solute concentration can also be manipulated to attenuate the likelihood of intradialytic hypotension and cramps. Increasing the dialysate sodium concentration (148 mEq/L), especially early in the dialysis session, followed by a continuous or stepwise decrease later in the treatment ("sodium ramping") is a simple and effective means of ameliorating intradialytic hypotension and cramps.230-235 These interventions may be associated with increased weight gain and variable increase in interdialytic blood pressure.235

Conversion from an acetate-containing dialysate to a bicarbonate-containing dialysate will also minimize hypotension and cramps.215,237-240 In addition to a beneficial effect on blood pressure, the use of bicarbonate results in fewer headaches and less nausea and vomiting.239 Acetate contributes to the occurrence of hypotension by inappropriately decreasing total vascular resistance and increasing venous pooling and myocardial oxygen consumption.237

Reducing the dialysate temperature from 37°C to 34-35°C increases peripheral vasoconstriction and cardiac output, thereby reducing the occurrence of hypotension and accompanying symptoms.241-246 This benefit is achieved secondary to increased sympathetic tone.247 In one study, decreasing the dialysate temperature to 35°C decreased the incidence of symptomatic hypotension from 44% to 34%.248 The benefit was greatest for patients with frequent episodes of hypotension249 and those with baseline mild hypothermia (tymapanic membrane temperature <36°C).249 This intervention is beneficial even in patients who have excessive weight gains.247 Cold dialysis does not compromise urea clearance or increase urea rebound,242,246 but does induce mild to intolerable symptomatic hypothermia in some patients.244,248,249

Alternative strategies. Ingestion of the oral, selective α1-adrenergic agonist, midodrine, has been demonstrated to minimize intradialytic hypotensive events, raise the lowest intradialytic blood pressure, decrease interventions for hypotension, and reduce intradialytic hypotensive symptoms.250-253 When administered within 30 minutes of the initiation of hemodialysis, midodrine raises blood pressure by increasing peripheral vascular resistance (arteriolar vasoconstriction) and enhancing venous return and cardiac output (venular constriction).254 The drug is well tolerated and associated with few side-effects. The hemodynamic benefits of hypothermic dialysis alone or in combination with midodrine, were comparable across interventions.250

Finally, the experience of some members of the Work Group suggests that raising the hemoglobin to 11 g/L and/or administering supplemental inhaled oxygen also reduces the incidence of intradialytic hypotension, especially for patients with cardiovascular or respiratory disease.

Optimizing patient behavior. Patient behavior may also influence the likelihood of intradialytic cramps and hypotension. As stated earlier, appropriately limiting fluid intake is beneficial. In addition, food intake immediately prior to or during hemodialysis causes a decrease in peripheral vascular resistance and hence may result in hypotension.255-257

The Work Group found the literature characterizing the impact of antihypertensive medications on the occurrence of intradialytic hypotension and cramps to be contradictory. Some studies have observed a strong correlation between the use of antihypertensive medications and hypotension,258 but the correlation has not been observed by other investigators.259 This issue should be evaluated individually for problematic patients.

The Work Group emphasizes the need to engage the patient in the process of hemodialysis care, especially regarding the issue of adherence with the hemodialysis prescription. Failure of the hemodialysis care team to properly educate patients about the value of complying with a proper hemodialysis regimen compromises the success of all the aforementioned strategies.

*For the purpose of this guideline, EDW is the target postdialysis weight at which the patient has intravascular euvolemia.

 

 

 

 


© 2001 National Kidney Foundation, Inc

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