New research findings suggest that higher high-density lipoprotein (HDL) concentrations may be protective against acute kidney injury (AKI) after cardiac surgery. The studies were published in the Journal of the American Heart Association

Dr. Loren E. Smith and colleagues from Vanderbilt University Medical Center in Nashville note AKI occurs in up to 30% of patients after heart surgery. Cardiac-surgery morbidity and mortality have declined over the past 10 years, they add, but AKI incidence has remained the same.

Given the anti-inflammatory and anti-oxidant properties of HDLs and their importance in endothelial function, Dr. Smith and her team hypothesized that patients with higher levels of HDL cholesterol would be at lower risk of AKI after cardiac surgery.

They looked at data from a 391-patient randomized controlled trial of atorvastatin to reduce AKI after heart surgery. Preoperative HDL cholesterol levels were independently and negatively associated with postoperative changes in serum creatinine, the researchers found.

Each 10 mg/dL increase in HDL was associated with a 0.05 mg/dL lower postoperative serum creatinine change from baseline. Median HDL was 21% lower in the patients with stage 2 or stage 3 AKI (28.5 mg/dL) compared to those with stage 1 AKI or no kidney injury (36 mg/dL, P=0.04).

Patients on statins long-term showed the strongest association between higher HDL cholesterol level and lower AKI risk, while perioperative treatment with atorvastatin and increasing statin dose further strengthened the relationship.

“We have been working hard to identify novel modifiable risk factors for acute kidney injury after cardiac surgery,” Dr. Smith said. The ultimate goal is to identify new pharmacological interventions that could be used during the perioperative period to decrease patients’ risk of postoperative AKI.

In this study researchers found that statins potentiate the association between a higher preoperative HDL cholesterol concentration and a lower risk of AKI after cardiac surgery.

The findings do not mean patients should be given perioperative statins to prevent AKI, she added, noting that three randomized clinical trials found no benefit from this approach.

She and her colleagues wrote, “Because perioperative statin treatment has non-HDL-mediated detrimental renal effects that outweigh any beneficial effects on HDL function, other pharmacologic agents with the potential for improving HDL function are needed.”

The next step, Dr. Smith said, will be to understand the biological mechanism underlying the association. “We’re looking at HDL function in cardiac surgery patients, including its antioxidant and anti-inflammatory functions and its ability to accept cholesterol in association with the risk of postoperative acute kidney injury.”