New Dialysis Modality Daily OL-HDF

CVVHD A DIAGRAM AUTHOR UNKNOWN.

A study published in the november issue of Nephrology Dialysis and Transplantation has reported that growth retardation in pediatric dialysis patients (the propensity for children to not achieve normal height) can be improved by a type of dialysis known as daily on line hemodiafiltration (DOLHDF).

OLDHDF is a treatment modality that combines two types of treatment into one. Standard dialysis which utilizes diffusion of solutes from within the blood stream across a dialysis membrane and into the dialysate is combined with toxin removal via a process call ultrafiltration. Many dialysis patients will already by familiar with the process of ultrafiltration, sometimes painfully so as lots of ultrafiltration is associated with cramping on dialysis.

Ultrafiltration is the process of filtering water from the patients blood stream via creation of a negative pressure gradient down which water will naturally flow. The process of ultrafiltration is not purely removal of water however as whatever is dissolved in the water is dragged along with it across the dialysis membrane and out of the blood. The size of the pores in the dialyser determines what stays behind and what is lost. This type of ultrafiltration present in the daily treatment of many patients on dialysis is not particularly effective at clearing toxins from the blood and is primarily used for volume control in the treatment of fluid overload.

By improving the efficiency of the process by adding an additional solution into the dialyser along with the blood more toxins are forced across the dialyser membrane and pure dialysis with ultrafiltration becomes hemodiafiltration. The additional solution added to the dialyser has to be as sterile as IV fluid which has traditionally kept this modality confined to the ICU. But new methods have recently become available that allows for the generation of the replacement solution as needed in a sterile manner. This process has served to reduce the cost of the modality and has allowed studies such as the one outlined hear to be possible.

The efficiencies of dialysis via this modality is superb and when combined with daily dosing may be responsible for the good outcomes outlined in the abstract below.



BACKGROUND:

In children, growth can be used as a measurable parameter of adequate nutrition and dialysis dose. Despite daily administration of recombinant human growth hormone (rhGH), growth retardation remains a frequent problem in children on chronic dialysis. Therefore, we performed an observational prospective non-randomized study of children on in-centre daily on line haemodiafiltration (D-OL-HDF) dialysis with the aim of promoting growth. Patients and methods. Mean age at the start of the study was 8 years and 3 months, and all children had been receiving rhGH treatment for >12 months before enrolment. Mean follow-up time on D-OL-HDF was 20.5 +/- 8 months (range, 11-39 months). Renal residual function was either <3 mL/min/1.73 m(2) or anuric. Vascular access was a fistula (13/15) or a central venous catheter (2/15). Dialysis was delivered daily, six days a week in 3 hourly sessions (18 h/week), in a predilution OL-HDF mode, allowing a high convective volume (18 to 27 L/m(2) body surface area per session), Kt/V(urea) on line measured at least 1.4 per session. RESULTS: Mean growth velocity increased from 3.8 +/- 1.1 cm/year at inclusion to 14.3 +/- 3.8 cm/year during the first year of D-OL-HDF, resulting in a change in height standard deviation score (SDS) over the follow-up period from -1.5 +/- 0.3 SDS to +0.2 +/- 1.1 SDS. Increase in body mass was also noted without impaired control of blood pressure. Time-average deviation for urea (TAD(urea)) was low at 2.5 +/- 0.4 as was TAD(bicarbonate) due to the normal pre and post dialysis bicarbonate levels, respectively, 23.6 +/- 0.5 mmol/L and 26.6 +/- 0.5 mmol/L. The absence of any dietary restrictions permitted a mean protein diet intake (PDI) of 2.5 +/- 0.2 g/kg/day (PDI measured from a 3-day diet survey), contrasting with a mean normalized protein nitrogen appearance (nPNA) of 1.53 +/- 0.12 g/kg/day (nPNA calculated from urea dialytic kinetic). A low C-reactive protein was noted in 13/15 children, and mean beta(2) microglobulin was low, 15.3 +/- 0.3.3 mg/L.

CONCLUSIONS:

Daily OL-HDF promotes catch-up growth in children despite being on chronic dialysis. This catch-up growth if continued, should allow the children to reach their mid-parental target height in the future. It could be speculated that the improved response to rhGH is the result of several combined factors conducting to less malnutrition and to less cachexia.