After analyzing medical malpractice insurance claims that involved 22 hospitals, researchers at Brigham and Women’s Hospital (BWH) have identified risk factors underlying medical errors that involve leaving surgical sponges or instruments inside patients after an operation, a rare but serious complication. Their findings appear in the Jan. 16 edition of the New England Journal of Medicine.

The study found that in the instances when these types of errors do occur, they happen during emergency procedures, or in operations where there is a sudden change in plan. Additionally, the research revealed that the higher a patient’s weight the more statistically likely it is that an object will be inadvertently left behind.

“Often when you hear about these kinds of cases, people assume it is due to negligence,” said Atul Gawande of BWH. “But we found that these errors usually occur despite teams following proper procedures. These errors tend to occur in unpredictable situations, such as emergency operations, that challenge standard protocols.”

Gawande and his colleagues analyzed malpractice claims filed with one particular insurance company between 1985 and 2001. In all, 54 cases were confirmed to involve retained objects. Sixty-nine percent of the cases involved sponges, and 31 percent involved instruments. These cases were then compared to data from patients undergoing the same operations who did not have this complication.

In emergency operations, retained object errors are nine times more likely to happen, the study showed. It was also determined that these errors were four times as likely to happen when the operation involved a change in procedure.

All hospitals follow procedures that mandate an inventory of all tools and sponges be taken before and after a procedure. But Gawande’s research concluded that, while the careful counting of instruments is a valuable safety precaution, in over two-thirds of the cases objects were retained despite proper procedures being followed.

After statistical analysis of the records, Gawande estimated that at least 1,500 errors of this type occur each year in the United States. However, given that over 28.4 million inpatient operations were performed in 1999 alone, such errors happen rarely, the study found. In fact, the current research showed that these types of errors occur in approximately one in every 9,000 to 19,000 surgeries that involve an open cavity.

When it does happen, however, retained objects can bring on serious medical problems, including perforation of the bowel, sepsis, and even death. Only one case studied resulted in a death, however, and the study found that 69 percent of the examined cases resulted in successful reoperations.

“Again, it’s important to note that the urgency inherent to emergency situations may impact the effectiveness of an otherwise well-intentioned inventorying of instruments,” said Gawande. “The way to further reduce these errors from happening is to step up the use of X-rays, CT scans, and other radiographic technologies to ensure that surgical objects are not left behind.”