Intradialytic hypotension associated with increased incidence of haemodialysis vascular access thrombosis
Jul 30, 2011 - 7:42:44 PM
A sudden drop in blood pressure while undergoing dialysis (intradialytic hypotension) is a long standing problem in haemodialysis patients. Side effects associated with this situation over the long term range from stroke to seizure to heart damage to death. Patients also suffer in the short term with gastrointestinal, muscular and neurologic symptoms.
A study led by researchers at the Stanford University School of Medicine reports an increased risk of thrombus(clot) formation in the vascular access which is used for haemodialysis as a consequence of intradialytic hypotension. Researchers from the University of Utah also contributed to the study, which is to be published online July 29 in the Journal of the 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."
As the kidneys fail, their ability to eliminate the excess fluid and toxins from the body decreases. The function of the kidneys deteriorates to the point at which an alternate form of elimination needs to be provided in the form of hemodialysis or peritoneal dialysis. Hemodialysis involves cleaning out the blood by passing the blood through a dialysis machine. This is ideally done for four-hour sessions, thrice weekly. The blood vessels of the patient are attached to the dialysis machine through a vascular access.
One of the most common forms of vascular access is a fistula, which is created surgically from the patient's own blood vessels. The tubes used to take blood to and from the body to the dialysis machine are connected to the body 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 study was based on results from the Hemodialysis study, known as HEMO — a National Institutes of Health-sponsored randomized clinical trial that collected data from 1,846 patients on hemodialysis from 1995 to 2000. In the present study, researchers analyzed data from a subset of 1426 HEMO study subjects to determine whether more frequent intradialytic hypotension and lower predialysis systolic BP were associated with higher rates of vascular access thrombosis. 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."
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