ST. JOHN’S, NEWFOUNDLAND—Central venous catheters (CVCs) are associated with the highest mortality risk among hemodialysis (HD) vascular access options, according to a systematic literature review presented at the Canadian Society of Nephrology’s 2012 annual meeting. Arteriovenous grafts confer the second-highest risk for mortality, followed by native arteriovenous fistulas (AVFs).

Although these findings are congruent with clinical practice guidelines—which tout AVFs as the preferred form of vascular access in HD patients—lead investigator Pietro Ravani, MD, told Renal & Urology News that solid evidence to support this recommendation is lacking.

“The surprise is the low level of quality of the available studies and the huge variation of the point estimates from those studies,” said Dr. Ravani, of the Department of Medicine and the Department of Community Health Science at the University of Calgary in Alberta. “Better-quality data are needed, but not from studies with the same design as those already available.”

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Dr. Ravani and colleagues analyzed 59 studies, 68% of which were conducted in North America. The mean ages of the combined 315,960 subjects ranged from 16 to 80 years. Dr. Ravani’s team found that the risk of several bias items (participation, attrition, measurement, confounding and analysis) was generally moderate or high, and that no study was at low risk of bias in all assessed domains.

Compared with patients who had AVFs, those with arteriovenous grafts had a 12% increased mortality risk. Furthermore, compared with arteriovenous grafts, CVCs conferred a 25% higher death risk. The researchers, however, could not account for the marked variability they found, “suggesting the existence of unexplored/unknown confounders that warrant further study,” Dr. Ravani said. Thus, considerable uncertainty exists as to whether these associations can be considered causal, he said.