Preventing Worsening Kidney Function in Patients Receiving Peritoneal Dialysis

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The summary below is from the full report titled "Effects of an Angiotensin-Converting Enzyme Inhibitor on Residual Renal Function in Patients Receiving Peritoneal Dialysis. A Randomized, Controlled Study." It is in the 15 July 2003 issue of Annals of Internal Medicine (volume 139, pages 105-112). The authors are P.K.-T. Li, K.-M. Chow, T.Y.-H. Wong, C.-B. Leung, and C.-C. Szeto.

What is the problem and what is known about it so far?

Kidneys filter out waste products and water from the blood. When kidneys fail to function properly, dialysis can clean waste products artificially. There are two forms of dialysis: a kidney machine that filters the blood (hemodialysis) and an exchange process that uses the lining of the inside of the abdomen as a filter (peritoneal dialysis). In peritoneal dialysis, a cleansing liquid drains from a bag into the abdomen through a tube. Over several hours, waste products and water pass through the lining of the abdomen into the liquid. The waste-filled liquid is then drained from the abdomen. The exchange process is repeated several times each week.

Many patients who receive dialysis still have some kidney function and some urine production. These patients need less frequent dialysis, may feel healthier, and may live longer than dialysis patients without any kidney function. Several drugs (called angiotensin-converting enzyme [ACE] inhibitors) help prevent kidney failure in people with early kidney disease who do not yet need dialysis. Whether these drugs can prevent worsening kidney failure in patients who need dialysis but have some remaining kidney function is not known.

Why did the researchers do this particular study?

To see whether an ACE inhibitor, ramipril, prevents worsening kidney function in patients who need dialysis but have some kidney function.

Who was studied?

60 adults treated with peritoneal dialysis at one university teaching hospital.

How was the study done?

Patients were randomly assigned to receive either ramipril or usual care without ramipril. Because dummy pills (placebo) were not used, patients and doctors knew who received ramipril. The researchers measured urine amounts and kidney function (glomerular filtration rate) at the beginning of the study and every 3 months thereafter for 1 year. Then, they compared differences in these outcomes between groups. They also asked patients who received ramipril about side effects and did blood tests to see whether ramipril increased potassium levels to dangerous levels (hyperkalemia).

What did the researchers find?

Both groups had worsening kidney function over time, but ramipril reduced the decline in kidney function. Also, fewer patients given ramipril stopped producing urine. The benefits of ramipril were not apparent until 1 year; some patients had worsening kidney function with ramipril within the first 9 months of treatment. Five of the 30 patients given ramipril had to stop taking the drug because of dizziness or cough. None had to stop as a result of hyperkalemia.

What were the limitations of the study?

First, the trial did not use a placebo comparison group and only involved patients from one university teaching hospital. Second, the findings shouldn't be generalized to patients receiving hemodialysis. Third, the trial was too small to detect potentially important differences in health care use and survival between groups.

What are the implications of the study?

An ACE inhibitor, ramipril, is a promising intervention for patients receiving peritoneal dialysis who have some remaining renal function. Whether it improves clinical outcomes and decreases health care use and costs should be tested in much larger studies involving multiple sites.