Acute drop in blood pressure while undergoing dialysis has long vexed many kidney patients. Side effects associated with this situation over the long term ranges from stroke to seizures to heart damage to death.

Over 485,000 Americans are being treated for kidney failure, also called End Stage Renal Disease (ESRD). Of these, more than 341,000 are dialysis patients

A recent study by researchers at the Stanford University School of Medicine and University of Utah reports an increased risk of blood clotting at the point where the patient's blood vessels are connect to the dialysis machine known as the point of vascular access. The new study is published in the Journal of American Society of Nephrology.

"Our analysis shows another adverse consequence associated with a fall in blood pressure during dialysis for patients," said Tara Chang, MD, a Stanford nephrologist and lead author of the study. "Vascular access is their lifeline. It's required for dialysis and without dialysis, they'll die."

Dialysis a life extending medical procedure for patients who have temporarily or permanently lost kidney function due to renal (kidney) failure, involves sitting in a chair twice a week to daily connected to an artificial kidney machine. Unwanted waste in the blood flows into the dialysate a solution containing electrolytes and water that passes through the artificial kidney membrane to remove excess fluids and waste from the blood. The clean blood is then returned to the body. Removing the harmful waste and fluids helps control blood pressure, pH balance, and plasma volume.

Vascular access points are very important during dialysis. On common access point is the fistula (AV fistula) a place where one of the arteries connects to the veins. The tubes linking the body to the dialysis machine are connected at this access point.

Clotting is one of the primary complications of an access point and can lead to its closure.

"These access points don't last forever," said Chang, a postdoctoral scholar. "Many patients go through multiple access points moving from the right to left arm, or into the legs if necessary after repeated failures in the arms. When a patient runs out of access points, it becomes an emergency situation. Anything you can do to extend the life of the access point is important."

The researchers found that patients who had the most frequent episodes of low blood pressure during dialysis were two times more likely to have a clotted fistula than patients with the fewest episodes.

About $2 billion a year is spent on vascular access in dialysis patients in the United States. Low blood pressure during dialysis occurs in about 25 percent of dialysis sessions.

"Physicians already try to avoid low blood pressure during dialysis through various means," Chang said. "This is just one more good reason to continue these efforts.

"There is so much we don't know about blood pressure in people on dialysis," she added. "We need future blood pressure management studies to look at not only mortality and hospitalization, but also consider vascular access survival as another important endpoint to study."

Published in the Journal of American Society of Nephrology.