Aaron Chang couldn’t stop pondering a question after his rotation through cardiac surgery: What can be done to prevent patients undergoing heart procedures from developing kidney injuries?

Studies show that 15 percent of cardiac surgeries result in acute kidney injury (AKI), a sudden episode that leaves kidneys damaged or failing, partly because the organs don’t receive enough oxygen. Doctors can prevent AKI by optimizing blood pressure and blood flow during cardiopulmonary bypass, but calculating a healthy blood pressure and flow for each individual patient is tricky business.

“In cardiac surgery, doctors rely on generalized guidelines to set parameters such as blood pressure,” says Chang, a 2015 master’s graduate from the Center for Bioengineering Innovation and Design. “If these guidelines don’t fit the individual, the patient’s kidneys essentially hold their breath for the one to three hours in which they are on cardiopulmonary bypass.”

Though injury occurs during surgery, detection of AKI occurs 24 to 48 hours later. Patients who sustain a stage 1 kidney injury, the least severe of the three stages before kidney failure, become twice as likely to die within five years.

Chang founded Renalert, a startup in Johns Hopkins Technology Ventures’ (JHTV) FastForward 1812 innovation hub, to develop a real-time urine monitoring device for the prevention of acute kidney injury. The device sits beneath operating tables and monitors patient urine, precisely measuring volume, while correlating these values with other vital signs to estimate renal perfusion.

Building off research by clinical collaborators in the Department of Anesthesia and Critical Care Medicine, Renalert’s pilot study at The Johns Hopkins Hospital showed promising results in intraoperatively estimating which surgery patients would eventually develop kidney injury.

In addition to the Wallace H. Coulter Foundation, TEDCO’s Maryland Innovation Initiative and a Johns Hopkins School of Medicine Dean’s Faculty Innovation Award, JHTV has supported Chang’s startup journey.

Such support has accelerated Renalert’s development of technologies, and Chang hopes the innovation he produces can lead to products that reduce kidney injuries during other high-risk procedures.