Minimizing Blood Flow Interruption During Surgery Lowers Kidney Disease Risk

Interrupting blood flow for more than 20 to 25 minutes during kidney cancer surgery leads to a greater risk for patients developing chronic kidney disease, according to a new study.

Researchers at the Mayo Clinic (Rochester, MD, USA) and the Cleveland Clinic (OH, USA) analyzed the outcomes of 362 patients (median age 62 years) with only one kidney who underwent surgery for renal cortical tumors at the Mayo Clinic and Cleveland Clinic between 1990 and 2008. The surgeons used a technique called warm ischemia, which involves cutting off the blood supply to the kidney with clamps in order to control bleeding and to keep blood from obscuring the surgeon's view of the kidney; the ischemia is warm as the patient's kidneys are maintained at body temperature during the partial nephrectomy.

The researcher reported that the median ischemia time was 21 minutes; each additional minute of warm ischemia was associated with a 5-6% increase in the odds of developing acute renal failure or reduced kidney functioning, and was associated with a 6% increased risk of new onset Stage IV chronic kidney disease during long-term follow-up. The researchers stressed that the study's results do not have implications for patients treated with cold ischemia.

"These results suggest that every minute counts when the renal arteries and veins are clamped,” said lead author urologist R. Houston Thompson, M.D., of the Mayo Clinic. "When planning for the surgery, surgeons should make efforts to minimize ischemia time, especially in situations where a person only has one kidney.”

"Historically, 30 minutes was considered the maximum safe duration of warm ischemia during partial nephrectomy, and other retrospective clinical studies have suggested that warm ischemia for 40 to 55 minutes is safe,” added Dr. Thompson. "However, these studies included patients with two kidneys, which could mask the true effects of ischemia on renal function. Because each additional minute of warm ischemia invites the risk for chronic kidney problems, if longer ischemic times are unavoidable, techniques such as ice slush (cold ischemia) should be considered.”

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