• Cardiovascular

    Vascular Access for Hemodialysis – What do we really know?

What do we know, how much do we know, and how reliable is that knowledge? That’s part of the job of what Mayo Clinic calls the science of health care delivery – and the charge of the research center dedicated to that search for hard medical evidence on which to base decisions. This is the story of one group in that center and what it found.

In the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery, there is an interesting research program called “Knowledge Synthesis.” This group – led by M. Hassan Murad, M.D. – collects, appraises and summarizes the available evidence on any particular topic. These evidence summaries help guideline developers, physicians, patients, and other stakeholders make decisions consistent with the best available evidence.

M. Hassan Murad, M.D.
M. Hassan Murad, M.D.

Dr. Murad was the senior author on a recent publication that does just this for providers of hemodialysis and their patients. In 2008, the Society for Vascular Surgery developed guidelines, and at the time, they acknowledged a dearth of evidence. To aid in developing new or updated guidelines, Dr. Murad’s research team conducted a knowledge synthesis project: “Outcomes of vascular access for hemodialysis: A systematic review and meta-analysis.”

Published in July in the Journal of Vascular Surgery, the study includes information gleaned from 200 studies that evaluated 875,269 cases of adults receiving long-term dialysis, and specifically looked at:

  • Patency (how long the vein access stays unobstructed)
  • Mortality
  • Access site infections
  • Maturation of vascular access (enlargement and thickening of the vein wall to allow dialysis)

There are three types of vascular access used for hemodialysis: arteriovenous (AV) fistula, AV graft, or central venous catheter (typically for emergency use only).

The research team found that patency at two years was higher for fistulas than grafts and catheters; although lower in individuals with diabetes, coronary artery disease, older individuals, and in women. Mortality was highest with catheters and lowest with fistulas.

This information may not be significantly different from what was known before, but care decisions can now be made based on a much broader evidence base and with more confidence. In addition, the researchers were able to identify specific patient subgroups that are not as likely to achieve the best results, and therefore may wish to consider other possible options. At a minimum, the available evidence can now be easily accessed by patients and clinicians engaged in shared-decision making surrounding access placement.

“This is one of the key reasons we conduct systematic reviews and knowledge synthesis,” says Dr. Murad. “Patients and providers should be armed with the best information available as they make decisions regarding their health and care delivery options.”

Knowledge synthesis can also inform other researchers as they evaluate a particular research question, he says.

“We look at whether the question has been asked before,” explains Dr. Murad. “If it has, is there sufficient evidence already around a particular topic such that more research would be a waste of resources? Or conversely, is there a gap in current knowledge such that future research will add value?”

Because of Mayo Clinic’s expertise in this area, it has been designated by the Agency for Healthcare Research and Quality (AHRQ) as an Evidence-Based Practice Center. This expands the Knowledge Synthesis mission beyond the walls of Mayo Clinic to nationally generated questions that seek to make health care safer, more accessible, equitable and affordable.

- Elizabeth Zimmermann Young, August 4, 2016