In past studies, doctors rarely self-reported medication errors during surgery. But a new study out of Massachusetts General Hospital, based on researcher observations during 277 procedures in the anesthesiology department, arrived at a far different conclusion: that about half of all surgeries involve a medication error or "adverse" drug event, Bloomberg reports.

Coming in Anesthesiology, the study also noted that surgeries lasting more than six hours were found to result in more errors than shorter operations. What's behind the high rate of surgery drug errors? Seems it's the hectic nature of OR procedures, which give doctors less time to make checks and balances—unlike drugs administered at other times that get double-checked before the patient takes them.

"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," says anesthesiologist Karen Nanji, one of the study's lead authors.

But while the numbers appear high, only three of the errors seemed potentially fatal, and no one died because of them; mistakes that were made sometimes simply resulted in a higher risk of infection or a change in one's vitals, according to a press release.

And hospitals are trying to cut down on these slip-ups by using operating checklists and e-medication systems that can provide warning if the wrong medicine or dosage is prescribed.

"Patients don't need to go into surgery thinking that they're going to have lasting permanent harm every second operation," says Nanji. (Why do doctors mess up in the OR, anyway?)

This article originally appeared on Newser: Errors With Meds Happen in Half of All Surgeries

More From Newser