By Dr. Linda Francisco
It is well known that the mortality rate of patients undergoing maintenance hemodialysis remains unacceptably high. An extremely high morbidity and a relatively low quality of life has also been observed in the chronic hemodialysis patient. The institution of more intensive dialysis regimens appears to improve morbidity and, possibly, mortality among this patient population, although studies are still badly needed for the evaluation of mortality improvement. Compared to conventional regimens, hemodialysis associated with longer duration and/or higher frequency correlates with enhanced outcomes as defined by improved laboratory and decreased usage of erythropoiten, with improved Kt/V values. With this in mind, nocturnal hemodialysis was introduced as a more desirable alternative to conventional dialysis. It was thought that nocturnal dialysis could provide superior dialysis based on dose, duration, and frequency. It also takes advantage of the rather unproductive time during the nightly sleep.
In-center hemodialysis is generally performed 3 nights per week for 8-10 hours depending on the center availability. The dialysate composition is a sodium bath of 140 mEq/L, a potassium bath of 2 mEq/L, a bicarbonate bath of 28-35 mEq/L, with a calcium concentration of 2.5-4.0 mEq/L. A higher dialysate calcium is prescribed for patients with high ultrafiltration volumes. The blood flow rate is generally 200300 cc/min, depending on clearances, and the dialysate flow rate is anywhere from 100 cc/min to 800 cc/min.
In-center nocturnal hemodialysis would tend to favor the higher end of blood and dialysate flows since the actual time per week on dialysis is 3 nights per week. The typical ultrafiltration volume is 1-2 liters, with a range of 1-7 liters per dialysis treatment. Any dialyzer membrane can be used, including smaller surface area dialyzers, but most centers use high-flux dialyzers. In addition, nocturnal hemodialysis can be performed with any hemodialysis machine and existing machines can be modified for the requirements of the longer dialysis treatment. Dialyzer reuse can be used and the usual technique of reuse is applied. Anticoagulation is also used and it accounts for approximately 1,000 U of heparin per hour of dialysis.
Vascular access for nocturnal dialysis is the same as it is for any hemodialysis. Central venous catheters can be used, although these are considered less popular, especially with the fistula-first initiative. Preferably, arteriovenous fistulas are used. Arteriovenous grafts have also been successful in nocturnal dialysis.
Nocturnal hemodialysis is usually associated with marked benefits including improved solute clearance and quality of life. Patients will declare their improvement of quality of life almost uniformly. There is also noted to be much better blood pressure control and a reduction of medication requirements for control of hypertension. Urea and phosphorus clearances have been increased with nocturnal hemodialysis. Better hemoglobin values with less erythropoiten usage have also been reported. Some have suggested an enhanced survival, however, this requires further analysis. At present, there are no published randomized trials of nocturnal hemodialysis. As a result, some investigators feel that studies comparing nocturnal hemodialysis to conventional hemodialysis should be performed to better understand the benefits of nocturnal hemodialysis.
In summary, nocturnal hemodialysis done in-center offers another modality of care for the patient with end-stage renal disease and should be available to patients. Further studies are required to evaluate the benefits and indications for its usage.
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Dr. Francisco is a DaVita nephrologist in Wichita, Kansas, currently prescribing nocturnal dialysis for some of her patients.
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