Condition category
Urological and Genital Diseases
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status

Plain English Summary

Background and study aims
During haemodialysis (removal of waste from the blood) blood flows out from the patient into the dialyzer. Substances move by diffusion from the blood into the dialysate (one of the two solutions used in dialysis), or vice-versa. Dialysis is not a selective process and substances in the dialysate can equally pass into the patient’s blood if in higher concentration. Haemodialysis patients are at increased risk of hardening (calcification) of soft tissues, especially calcification of blood vessels. This leads to reduced blood supply to the skin and feet and an increased risk of calcium deposits leading to skin ulceration and amputation. Intake of calcium in the form of calcium-containing medications increases the risk of calcification. However, dialysis patients get calcium from the dialysate which can directly pass into their blood. Although the amounts of calcium transferred during a single session may be small, repeating this three times a week, year after year can result in a large amount of calcium infused and so increase the risk of calcification of blood vessels. Unfortunately there is no information on the amount of calcium gained or lost during haemodialysis or a newer dialysis treatment (haemodiafiltration), and no evidence-based guidelines as how to choose a dialysate calcium concentration for patients. We will measure how much calcium has been gained or lost during dialysis, using dialysis fluids containing different amounts of calcium. This study will allow the development of evidence-based guidelines to help doctors decide on what dialysate calcium concentration to use to reduce calcium loading and vascular calcification.

Who can participate?
Patients with long-term kidney disease who are treated by outpatient haemodialysis can participate in this study.

What does the study involve?
One of three different commercially available dialysate calcium concentrations will be chosen. All patients will initially receive their standard dialysis. An electronic recording of the heart (ECG) will be made at the start and end of the dialysis session. After completing the sequence of dialysis sessions, patients would then have two additional dialysis sessions, one each of haemodiafiltration and haemodialysis, using a different calcium concentration. Each session would be one week apart. We will do blood tests both at the start and the end of the dialysis session.

What are the possible benefits and risks of participating?
At the end of the study the information obtained will be given to the patient’s consultant who can then choose the correct calcium concentration in the dialysis fluid. All three dialysis calcium concentrations in dialysis fluid are in routine clinical use and do not pose a health risk. As an additional safety measure we will check your ECG prior to the dialysis treatment, and your blood test at the start and end of the dialysis session.

Where is the study run from?
The study is run from the UCL Centre for Nephrology at the Royal Free Hospital, UK.

When is study starting and how long is it expected to run for?
It starts in October 2013 and depending upon recruitment is expected to last for three years.

Who is funding the study?
The study is funded by the Royal Free Hospital, UK.

Who is the main contact?
Dr Andrew Davenport

Trial website

Contact information



Primary contact

Dr Andrew Davenport


Contact details

UCL Centre for Nephrology
Royal Free Hospital
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number

protocol version 1.1

Study information

Scientific title

Study to investigate calcium balance during haemodiafiltration and high flux haemodialysis


Study hypothesis

Dialysis patients are at increased risk of vascular calcification. We wish to determine whether the mode of dialysis affects calcium influx or loss during a dialysis treatment.

Ethics approval

NRES Committee London - Central; date: 03/04/2013; REC reference:13/LO/0384; IRAS project ID:118378

Study design

Cross over cohort study

Primary study design


Secondary study design

Non randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet




1. ECG
2. Measurement of pre and post dialysis biochemistry including ionised serum calcium and dialysate biochemistries during haemodialysis and haemodiafiltration treatments

Intervention type



Not Applicable

Drug names

Primary outcome measures

To determine whether there is a difference in calcium balance between haemodialysis and haemodiafiltration treatments. Calcium balance will be measured by comparing the amount of calcium delivered in the dialysate and that recovered in the spent dialysate, and the calcium flux (difference between the two) compared to measurements of calcium, and other electrolytes in blood tests at the start and end of calcium and parathyroid hormone concentrations.

Secondary outcome measures

Sodium and other electrolyte balance, changes in blood pressure and fluid removal and ECG changes

Overall trial start date


Overall trial end date


Reason abandoned


Participant inclusion criteria

1. Thrice weekly haemodialysis or haemodiafiltration
2. Ability to provide informed consent
3. Serum total calcium within laboratory normal reference range
4. Reliably functioning vascular access for dialysis

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Unable to provide informed consent
2. Aged 18 to 85 years
3. ECG with prolonged QTc
4. History of life-threatening cardiac arrhythmias
5. Recent myocardial infarction within previous 3 months
6. Admission to hospital for change in vascular access
7. Unlikely to survive 6 months
8. Planned living donor transplant
9. Patients with history of missing dialysis sessions

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

UCL Centre for Nephrology
United Kingdom

Sponsor information


Royal Free Hospital (UK)

Sponsor details

Pond street
United Kingdom

Sponsor type

Hospital/treatment centre



Funder type

Hospital/treatment centre

Funder name

Royal Free Hospital (UK)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Results - basic reporting

Publication summary

Publication citations

Additional files

Editorial Notes