Acute renal failure after non-cardiac operations

Patients undergoing major, non-cardiac surgery have a one percent risk of developing kidney failure, and those who do have kidney damage are at increased risk of death within a month after their operation.

An article in the December issue of the journal Anesthesiology helps to clarify the rate of acute renal failure after major surgery in patients with previously normal kidney function. "More importantly, we have been able to identify which patients are at highest risk for this complication," comments Dr. Sachin Kheterpal of the University of Michigan Medical School, Ann Arbor.

Dr. Kheterpal and colleagues examined changes in kidney function in more than 15,000 patients undergoing major surgery, other than heart surgery, between 2003 and 2006. Before their operation, patients underwent tests confirming that their kidney function was normal or demonstrated no history of kidney problems. The study defined acute renal failure as about a 40 percent drop in kidney function.

Overall, acute renal failure developed in 121 patients—a rate of 0.8 percent. In fourteen patients (0.1 percent), kidney failure was serious enough to require dialysis.

After adjustment for all risks together, there were seven independent risk factors for acute renal failure:

• Obesity (body mass index over 30)
• Older age (over 59)
• Chronic lung disease due to smoking (also called chronic obstructive pulmonary disease)
• Peripheral vascular disease (also often related to smoking)
• Liver disease (often related to excessive alcohol use)
• Emergency surgery and certain "high-risk" surgical procedures
• Use of certain drugs during surgery, including diuretics

The more risk factors that were present, the higher the risk of kidney failure. For patients with three or more risk factors, the risk of acute renal failure was over four percent.

Patients with acute renal failure were at increased risk of death. Fifteen percent of patients who developed kidney failure died within 30 days after surgery, compared to less than three percent for those without kidney failure who had similar preoperative diseases.

Acute renal failure is a known risk for patients undergoing heart surgery, but few studies have examined the rate of kidney damage after other types of surgery. Even less is known about the risk for patients who have normal kidney function before surgery, who have been assumed to be at low risk.

"Our research is the first large study to demonstrate that approximately one percent of patients with normal preoperative renal function experience acute renal failure after non-cardiac operations," Dr. Kheterpal concludes. "We have also been able to demonstrate that the development of acute renal failure after general surgery is associated with a marked increase in mortality, independent of the patient's underlying diseases."

Future studies will help to clarify the causes of acute renal failure in specific groups of patients, according to an accompanying editorial by Dr. Pamela C. Nagle of Wake Forest University. Dr. Nagle concludes, "Kheterpal and colleagues should be congratulated for carefully using their institution's large databases and reporting potential risk factors that will hopefully lead to further investigations and, someday in the future, improvements that may decrease this major perioperative complication."