Study Finds Delaying Surgery After PCI Prevents Kidney Injury

Reed Miller

January 28, 2010

January 28, 2010 (Fort Lauderdale, Florida) Patients undergoing cardiac surgery subsequent to a coronary intervention during the same hospital admission have a much higher risk of acute kidney injury than patients who are discharged after the PCI and come back later for their surgery, an observational study in Maine shows [1].

The results of the single-center study were presented by Dr Robert Scott Kramer (Maine Medical Center, Portland) here at the Society for Thoracic Surgeons (STS) 2010 Annual Meeting on January 27. They suggest that "there may be an opportunity to decrease the incidence of acute kidney injury by moving a subset of urgent patients with surgery that may be safely delayed from the urgent to the nonurgent category," Kramer said. "Keeping in mind that acute kidney injury is predictive of short- and long-term mortality following cardiac surgery, this analysis generates the hypothesis that, when it is safe, moving the surgical admission to a subsequent admission is potentially renal-protective, not only in elective patients but also in patients with no recent MI and in those without unstable angina, regardless of the type of surgery, congestive heart failure, or left-main disease."

"We're going to advocate for separate admission" of PCI-plus-surgery patients for whom the indication for surgery is not immediately life-threatening, Kramer said.

Of the 722 adult cardiac surgical patients enrolled in the study, 43% had acute kidney injury, according to the Acute Kidney Injury Network definition of injury--an increase in creatinine of at least 50% or 0.3 mg/dL over baseline. A subset of 347 patients had a heart catheterization procedure followed by surgery during the same hospital admission. Univariable and multivariable logistic regression was used to adjust for significant baseline covariates, including vascular disease, atrial fibrillation, and concomitant procedure. Other covariates, including baseline creatinine, were found to be not significant.

The incidence of acute kidney injury was 48% in the patients who had catheterization and surgery during the same cardiac admission and 38% in the patients who had cardiac catheterization during a previous admission (p=0.009). The adjusted risk ratio of kidney injury was 1.44 (95% CI, 1.06 to 1.96). Logistic regression analysis shows that acute kidney injury is equally likely to develop in patients treated for valve problems, coronary artery disease, or both.

Why Wait? Why Not?

Kramer pointed out that his group's study could not establish a minimum time to wait between PCI and surgery because there was so much variability in the wait times in the study, with an average time between PCI and surgery of 40 days. However, he cited previous studies of the relation between high doses of contrast medium in PCI and kidney injury, which suggest that the minimum wait time should be somewhere from one to five days following a high-contrast PCI.

Commenting on the study at the STS conference, Dr John Conte (Johns Hopkins University, Baltimore, MD) suggested that to better define which indications for surgery post-PCI ought to be considered urgent and which can wait, further studies should look at the factors that led the patient and physician to elect to do both procedures during the same hospital admission or not. "This study brought forth a complex and often vexing issue faced by your brethren in this Society on a daily basis: When is the best time to operate on our patients? There are many medical and nonmedical issues that go into the decision-making process," he pointed out. "We must balance the medical issues with competing interests, which often include the convenience of the patients and their families, referring physician pressures, administrative pressures to keep our operating rooms full and the balance sheet in the black, and our own pressures to keep our lifestyles acceptable and make efficient use of our time. Often doing the right thing is neither easy nor apparent."

Given the well-established long-term mortality risk associated with kidney injury and the financial costs associated with treating kidney injury, Conte suggested that further research examine the costs of performing PCI and surgery in separate admissions and the benefit of reducing the risk of kidney injury. Kramer responded: "We haven't done a cost analysis, but outcomes are certainly one way to measure costs as far as value is concerned."


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