Adverse events stemming from contrast injection have emerged as a patient safety issue. As radiology departments replace manifold contrast injectors with automated models, they are establishing protocols to lessen the incidence of contrast-associated adverse events and improve the bottom line.
The risks associated with contrast are well-documented, and among the major notable concerns is contrast-induced nephropathy (CIN). CIN is an "extremely low risk" for patients with normal renal function, according to the American College of Radiology (ACR), but for older patients—and those with diabetes or other conditions—the potential for harm is greater.
Most physicians agree on two methods for reducing risk. "Limiting the dye-load and adequate hydration are the only two things that have been consistently shown to reduce the risk of developing contrast-induced nephropathy," says Jason T. Call, MD, Winchester Cardiology & Vascular Medicine, in Winchester, Va.
Call's opinion is backed by various studies assessing the relationship between contrast and adverse events. Contrast volume was shown to be a key risk factor for contrast-induced acute kidney injury (CI-AKI) for patients undergoing percutaneous coronary intervention (PCI), Jeremiah R. Brown, PhD, MS, of Dartmouth Institute for Health Policy & Clinical Practice, Dartmouth Medical School, and section of cardiology at Dartmouth Hitchcock Medical Center, and colleagues found.
The incremental use of contrast beyond the maximum allowable contrast dose (MACD)—defined as 5 ml x body weight [kg]/baseline serum creatinine—is associated with greater risk of adverse events. In their analysis of nearly 10,000 patients prospectively enrolled from 2000 to 2008, the researchers found that 20 percent of patient procedures exceeded the MACD.
"Patients exceeding the MACD threshold were more likely to be in shock, have two or three vessel disease and left main stenosis, and more stents," Brown wrote. "Patients receiving contrast volumes in excess of the MACD were more likely to have CI-AKI, new onset of dialysis dependent renal failure, cardiac events, bleeding complications, receive transfusions and have a longer length of stay after PCI. Importantly, their mortality rates also were higher during PCI admissions."
Certain patient characteristics indicate greater risk for contrast-induced nephropathy, Call notes. Baseline kidney function and diabetes are the two top variables, he says. If a patient has one, risk for CIN may increase to 3 to 5 percent, however if he or she has both variables, the risk that the kidneys will be transiently harmed rises to 10 to 15 percent.
The ACR notes additional patient risk factors—allergies, asthma, cardiac status, as well as anxiety—and it recommends three primary considerations for physicians: the assessment of patient risk versus potential benefit of the study, imaging alternatives that would provide the same or comparable information and assurance of a valid clinical indication for each contrast medium administration.
Providers should weigh risks against benefits, says Hani Abujudeh, MD, MBA, department of radiology at Massachusetts General Hospital in Boston. In some situations, the benefits outweigh the risks associated with the administration of contrast. However, if an alternative diagnostic method can produce the desired information in a high-risk patient, it may provide a better alternative.
Nevertheless, the potential for kidney damage may be a small price to pay for life-saving information. "If contrast administration results in a diagnosis of a life-threatening condition, then it outweighs the risk of contrast nephropathy," Abujudeh says.
Hospitals are increasingly adopting automated injectors, which have been shown to reduce the use of contrast and diminish cost. However, in a recent meta-analysis, Brown and colleagues recommended further research on the association between reduced contrast volume and the risk of CIN.
In their meta-analysis of six studies, the researchers found that the use of automated contrast injection significantly reduced the volume of contrast delivered to a patient, but there was a lack of evidence regarding the risk of CIN.
"Only one trial reported on the patient outcomes of acute kidney injury. There's a lack of evidence—especially from trials where patients had been randomized through an automated injector or not—on acute kidney injury. Since CI-AKI has been established