About half of all surgeries involve some kind of medication error or unintended drug side effects, if a new study done at one of America’s most prestigious academic medical centers is any indication.

The rate, calculated by researchers from the anesthesiology department at Massachusetts General Hospital who observed 277 procedures there, is startlingly high compared with those in the few earlier studies. Those studies relied mostly on self-reported data from clinicians, rather than directly watching operations, and found errors to be exceedingly rare.

“There is a substantial potential for medication-related harm and a number of opportunities to improve safety,” according to the new study, published today in the journal Anesthesiology. More than one-third of the observed errors led to some kind of harm to the patient.

Attention has been focused on reducing medical errors since 1999. That’s when the Institute of Medicine identified them as a leading cause of death, killing at least 44,000 Americans a year — more than car crashes or breast cancer. Since then, hospitals have attempted to improve safety during surgery with simple checklists to avoid lapses like operating on the wrong side of the body. They’ve also switched to electronic prescribing systems that can warn doctors of potential medication errors.

…Mistakes at the intersection of medication and surgery “have really not been studied in any systematic way,” said Karen Nanji, an anesthesiologist at Mass General and lead author of the new study.

Drugs delivered during an operation don’t have the same safeguards that other medication orders do. In most parts of a hospital, prescriptions are typically double-checked by pharmacists and nurses before they reach the patient. Operating wards are riskier.

“In the operating room things happen very rapidly, and patients’ conditions change quickly, so we don’t have time to go through that whole process, which can take hours,” Nanji said.

While all the errors observed in the study had the potential to cause harm, only three were considered life-threatening, and no patients died because of the mistakes, Nanji said. In some cases, the harm lay in a change in vital signs or an elevated risk of infection…

The research may begin to draw attention to drug mistakes in the surgical suite. “It’s like a black box,” said Helen Haskell, a patient safety advocate and founder of Mothers Against Medical Error, whose son died because of a medication error after a routine surgery. Patients under anesthesia may not be aware that an error is made, especially if there is no lasting consequence.

Realize this study was done at one of the best general hospitals in the country. I shudder to think what the percentages might be some other places in the United States. Imagine what the numbers may be in a hospital where patient rights, modern standards, aren’t the rule.