Nitric oxide reduces kidney injury following cardiopulmonary bypass
Nitric oxide administration during and after multiple-valve heart surgery significantly reduced patients’ chances of developing acute and chronic kidney problems, according to a randomized trial published in the American Journal of Respiratory and Critical Care Medicine.
The study included 244 Chinese adults—127 who received nitrogen gas (control group) and 117 who were randomized to nitric oxide. All patients required cardiopulmonary bypass for at least 90 minutes.
"Previous studies showed that prolonged cardiopulmonary bypass causes disruption of circulating red blood cells and the release of hemoglobin, which can cause acute kidney injury, leading to kidney failure and the need for long-term hemodialysis," lead author Lorenzo Berra, MD, medical director of respiratory care at Massachusetts General Hospital in Boston and assistant professor at Harvard Medical School, said in a press release. "We tested whether administration of nitric oxide, a gas normally produced by cells in the lining of blood vessels, might render hemoglobin 'inert,' thereby decreasing the risk of both acute and chronic kidney injury."
Patients in the intervention group received 80 parts per million of nitric oxide during the procedure and for 24 hours afterward. Half of them developed post-surgery acute kidney injury, compared to 64 percent of patients in the control group.
Those inhaling nitric oxide were also less likely to have stage 3 chronic kidney disease than people in the placebo arm at both three months (21 percent versus 33 percent) and one year (18 percent versus 31 percent). According to the authors, this is the first drug that has been demonstrated to reduce kidney injury after prolonged cardiopulmonary bypass.
“Other than preventing vasoconstriction due to (oxyhemoglobin), [nitric oxide] might have improved pulmonary perfusion in this study by its well-described selective pulmonary vasodilator properties, which might have increased cardiac output especially in patients with (pulmonary arterial hypertension),” the researchers wrote.
Berra and colleagues acknowledged the findings may not be generalizable to all patients. Their subjects were all Chinese and younger than typical heart patients—48 years old on average—because most of the valve issues were caused by rheumatic fever. North American and European patients are more likely to have valve dysfunction as a result of degenerative heart disease, so that population would likely be older and have more comorbidities.
"We believe that the older patients with an increased number of cardiovascular risk factors, including obesity, hypertension and diabetes, may derive even greater benefit from nitric oxide administration during and after heart surgery,” said Berra, who plans to lead a study at Massachusetts General Hospital to see whether the benefits translate to other patients.
The study was also limited by its inability to detect mortality differences and lack of a cost-effectiveness analysis, which is noteworthy considering nitric oxide gas is expensive and not usually available in China.
Daniel joined TriMed’s Chicago editorial team in 2017 as a Cardiovascular Business writer. He previously worked as a writer for daily newspapers in North Dakota and Indiana.