Thomas and Zoe Quaid were born in 2007. The Quaids were elated. But that joy turned to outrage when a drug mix-up at Cedars-Sinai Medical Center in Los Angeles caused the twins to be given a massive overdose of the blood thinner Heparin.
In a "60 Minutes" interview with correspondent Steve Croft in 2008, Dennis said, "It was the scariest, most frightening day, I think, either of us have ever been through."
The newborns were supposed to get a pediatric blood thinner named Hep-lock. Instead, they were given two doses of Heparin, the adult version, that's 1,000 times stronger.
On "60 Minutes," Dennis said, "The nurse didn't bother to look at the dosage on the bottle. It was 10 units that our kids were supposed to get. They got 10,000. What it did was it turned their blood to the consistency of water."
After undergoing extensive medical tests, both children now show no signs of permanent damage.
Quaid said on "The Early Show" Monday his nearly 2-and-a-half year-olds are doing well. "I can hardly keep up with them," he said.
The error, however, has left an impact on him. Since the incident, he's become the celebrity face of patient advocacy.
He told "Early Show" co-anchor Harry Smith, "(Health care mistakes) happen too often in hospitals all over this country."
He added that "health care harm," if hospital-acquired infection is counted, is the third-leading cause of death in the U.S. "The amazing part about it is, it's preventable."
Since the incident with the twins, the Quaids have founded The Quaid Foundation to raise awareness and address the problem of preventable human medical errors. Quaid has testified to Congress on behalf of patients' rights, and Monday, he was to speak at the National Press Club to address the problem of dangerous medical mistakes.
Quaid is also producing a documentary on the subject called "Chasing Zero: Winning the War on Healthcare Harm." It will air on the Discovery Channel on April 24.
The Centers for Disease Control and Prevention reports an estimated 99,000 deaths every year are due to preventable medical errors.
Dr. Charles Denham, chairman of Texas Medical Institute of Technology (TMIT), is one of the experts Quaid met while researching medical errors.
He said on "The Early Show" honest errors can happen. "We don't have bad people. We have bad systems," he said. "And we just haven't caught up with our support systems to the complexity of care that we deliver. So, human error happens all the time, but they're spread over thousands of hospitals. And without these support systems, human error ... can happen."
What what can you do to lower the risk of medical error? Click on the video below for Denham's tips for hospital stays.
Watch CBS News Videos Online