Lasting Fixes
Heart surgery has come a long way. Not far enough, says this Cincinnati Children's doctor.
Dr. Krawczeski is director of Cardiac Intensive Care at Cincinnati Children’s and associate professor in the Department of Pediatrics at the University of Cincinnati College of Medicine.
As recently as a few decades ago, correcting a child’s heart defect was considered extraordinary. Today, the ability to fix even the most complex heart problems is pretty much taken for granted, with survival rates climbing upwards of 95 percent.
For Cincinnati Children’s Catherine Dent Krawczeski, MD, that’s not good enough.
“As we have more children who are long-term survivors of heart disease,” says Dr. Krawczeski, “it’s important to improve outcomes in all the organs, not just the heart – and not just for the short term.”
Dr. Krawczeski, director of Cardiac Intensive Care, is involved in two studies of interventions before and after cardiac surgery that could significantly improve those outcomes.
One study looks at whether a simple substance called citrulline - an amino acid that occurs naturally in the body and helps keep blood vessels relaxed - could prevent dangerous pulmonary hypertension after heart surgery.
Another study uses a groundbreaking test developed by a Cincinnati Children’s nephrologist to detect potential kidney problems within just two hours of heart surgery.
Simple Substance, Big Punch
Cincinnati Children’s is one of nearly a dozen pediatric centers that will collaborate in the citrulline study.
Normally, the body produces citrulline on its own. But during the stress of heart surgery and cardiopulmonary bypass, some children stop producing it and develop high blood pressure in their lungs, which increases their recovery time and their chance of dying after surgery.
Currently, these children are treated with inhaled nitric oxide, which relieves the high blood pressure but presents other problems. “Nitric oxide potentially increases the length of stay, the time on a ventilator, and the overall recovery time,” says Dr. Krawczeski.
Citrulline, she points out, has the potential to prevent the high blood pressure in the lungs by helping the body make its own nitric oxide, with none of the problems. Dr. Krawczeski and her colleagues are so optimistic about citrulline, they hope it will eliminate the need for inhaled nitric oxide altogether.
“Not all children have complications from high blood pressure in their lungs after heart surgery,” she says, “but all of them could receive this as a preventive. It’s short-term; it’s given intravenously during the surgery and for the first several hours after. It’s not a long-term medicine that they go home on.“ Most importantly, it’s a natural substance derived from watermelon and does not seem to have significant side effects.
The citrulline study began at Vanderbilt University nearly three years ago. Cincinnati Children’s was the first to join the study. Dr. Krawczeski expects to enroll some 50 to 60 children a year who need surgery for ventricular septal defects, atrioventricular canal defects, transposition of the great arteries or who require a Fontan procedure.
Preventing Kidney Injury
The other study Dr. Krawczeski is participating in tests for biomarkers that identify acute kidney injury after heart surgery. Cardiopulmonary bypass, which is necessary to repair many heart defects, puts children at risk for kidney injury.
Before, doctors had to wait 48 to 72 hours to see if there was an increase in kidney waste products in the blood, such as creatinine, indicating kidney injury. By that time, treatment to reverse or halt the injury is not successful. Now, a simple test developed by Cincinnati Children’s nephrologist Prasad Devarajan, MD, PhD, tells within two hours of surgery whether children are experiencing kidney problems (see sidebar).
By identifying kidney injury early, Dr. Krawczeski points out, “there is potential to reverse or halt the injury. Ultimately our goal is to test substances that can prevent or reverse the injury to the kidneys. The discovery of these biomarkers is a key step toward achieving that goal. In the meantime, we can prevent further injury to the kidney by adjusting our care of the child after surgery – such as avoiding medications that are risky for the kidneys, making sure the children don’t get dehydrated, and optimizing their blood pressure.”
Benefits That Last – to Adulthood
Early detection has immediate and long-term benefits, says Dr. Krawczeski. First, it prevents or lessens complications for kids dealing with heart problems. More important, she points to studies that show even mild insults to the kidneys over timeb can have a snowballing effect, with serious consequences down the road.
“Many of these kids require multiple operations, so they’re exposed to the bypass machine multiple times. That has a cumulative effect. And long-term, what does that do to their kidney function?” she says. “Adult studies show that people with just mild worsening in their kidney function after heart surgery have a significantly higher chance of dying after surgery.” To further investigate the impact of kidney injury after heart surgery, Drs. Krawczeski and Devarajan are participating in a long-term study that will follow children for five years after
heart surgery. This study will not only look at their long term kidney function, but will also evaluate their quality of life and overall well-being.
The bottom line for physicians and researchers today, says Dr. Krawczeski, is that successful treatment means something much different than it used to.
“It was once considered a victory just for a patient to survive. That’s no longer enough,” she says. “The goal is to give these kids normal life expectancy, normal quality of life, normal brain and kidney function – not just to have them survive the operation.”
