Potentially life-threatening medication errors involving children are vastly underreported in hospitals, according to new research from Canadian scientists.
Drug doses for adults are typically standardised, but doctors usually derive paediatric doses on a patient-by-patient basis determined by body weight. And while physicians are technically considered to be scientists, they're not always mathematicians, so calculating the correct formula leaves room for a stumble.
Children require very small doses
Ironically, children are more vulnerable than adults to large dosing errors because the amount of medication they require is so small. Serious math errors can still leave doses that seem plausible but are in reality much too high.
"You really need a teeny-weeny dose - often, it's so small you're talking about parts of a milligram," said Dr Gideon Koren, a University of Toronto paediatrician who helped conduct the research. "It becomes much more likely that people will make an error."
Potentially life-threatening doses
Koren and his colleagues at the Hospital for Sick Children in Toronto published their findings in a letter in the April 11 issue of the New England Journal of Medicine.
The group looked at errors involving doses of drugs that were at least 10 times higher or 10 times lower than recommended.
Between April 1 and November1, 2000, the hospital reported 20 such cases, the researchers said. Of those, 15 were discovered before the drugs were administered, but five did make it to the patient. Doctors were to blame for 18 of the 20 mistakes.
The 20 cases involved 19 different drugs, including a variety of antibiotics, morphine, and the blood thinner heparin. But most weren't among the most commonly prescribed medications at the hospital.
"This is not a random phenomenon, but something about these drugs caused these errors," Koren said. That something is their potency: Their required units are so low that it's easy to confuse conversions and decimal places.
Indeed, six, or roughly a third, were potent enough to have posed a risk of death; nine could have caused potentially fatal poisoning; and one might have led to mild toxicity.
The researchers then compared reports of large dose errors from the emergency room with those found on audits of medical charts. The result: one immediate ER report for every 13 000 patients, compared with a rate of one in 766 discovered later on charts - a 17-fold difference.
Rely less on human calculation
Koren said the solution is, at least in part, to rely less on humans and more on computers to figure out proper doses for children. Since conducting their study his hospital has implemented such a system, which asks doctors for body weight and spits out the correct amount of drug they should be administering. Many hospitals in the United States have similar systems in place.
"I'm not at all surprised" that charts contain more errors than are reported, said Michael Cohen, president of the Institute for Safe Medication Practices in the USA. "It takes a lot to report an error, and it has to be out of altruism. The only reward they have is to know the information is being used."
Douglas Scheckelhoff, of the American Society of Health-System Pharmacists, said it's "fairly well known" that chart reviews and other intensive checks turn up dosing errors more than voluntary reporting mechanisms.
One non-digital way to reduce the problem, Scheckelhoff said, would be to have a hospital pharmacist review each drug order before it's filled, and make the pharmacist available for questions once the medication is given. Unfortunately, he added, this generally isn't possible in an emergency room setting, where speed is key.
Technology makes process easier
Monica Buck, an expert in paediatric drugs at the University of Virginia, said computers that process prescriptions have "helped tremendously" in reducing drug errors in hospitals. Software makes a doctor's scrawl irrelevant, catches out-of-line prescriptions, and reduces the risk of a botched decimal point.
Before the Internet dosing errors were even more problematic, Buck said, because doctors had trouble getting information about drugs that wasn't on package labelling. In fact, even into the early 1990s, three-quarters of drug labels contained nothing about how the product worked in children, she said. Medical libraries housed reports of small studies on the effects of medication in young patients. Before the advent of the Web, only doctors and hospitals with the most resources had ready access to these papers. Now, the information is a few keystrokes away.