Kidney Failure and Open Heart Surgery
Open heart surgery to repair heart valves or to bypass blocked blood vessels is one of the most common major surgeries that adults may face. In general, the surgery is safe and effective. Infrequently, however, problems arise.
One of the most serious complications after open heart surgery is kidney failure, known in this context as acute renal failure or ARF. Acute renal failure that is serious enough to require temporary dialysis occurs in 1-2% of patients after open heart surgery.
This rate may seem relatively low but, unfortunately, the mortality rate in those who develop ARF is 60-70 times higher than in those who do not develop it. Because of this very high mortality rate associated with ARF after open heart surgery, our researchers continue active investigations of the factors that lead to renal failure and how we can overcome them.
To get a clearer picture of the problem, we studied 22,589 patients who had open heart surgery at Cleveland Clinic between March 1993 and April 2000. About 3% developed significant reductions in their kidney function; the overall rate of kidney failure severe enough to need dialysis was 1.8%. Importantly, the mortality rate among those who developed severe kidney failure was 61% as compared to an overall mortality rate of 2.2%.
Our researchers examined about 20 different factors that could be associated with an increased risk of ARF after open heart surgery. Chief among these are the type of heart surgery and the patient's level of kidney function on entering surgery. The level of kidney function, or GFR for glomerular filtration rate, is estimated from a blood test known as the serum creatinine. The normal level is about 1.0 mg/dl; the higher the serum creatinine, the worse the level of kidney function.
As shown in the figure, the frequency of moderate and severe ARF after open heart surgery was clearly higher for those patients who had more complicated surgery, such as a combined bypass and valve repair.
A new finding from the study is that acute renal failure occurred more frequently in women than in men. As shown in the second figure, ARF after open heart surgery occurs more frequently in patients who enter surgery with reduced kidney function as detected by increased serum creatinine values. This is to be expected. At each level of kidney function except the worst, kidney failure occurred more often in women than in men. The overall risk ratio for women over men was 1.6, indicating an increased risk of about 60%.
Research continues with further analysis of many other risk factors that are involved. The goal is to evaluate the relative contribution of each factor so that physicians can more accurately assess the risk and discuss it with their patients. More importantly, we are eager to identify and test agents and treatment strategies that might reduce the occurrence of ARF, especially in the higher risk groups. You can read more about this research in the following two articles by Dr. Charuhas V. Thakar and his colleagues.
ARF after open-heart surgery: Influence of gender and race. American Journal of Kidney Disease 2003, Volume 41, pages 742-751
Renal dysfunction and serious infections after open-heart surgery.Kidney International 2003, volume 64, pages 239-246.
