A clinical staff worker at the First Hill hospital made the discovery this week and the medical center notified patients Friday.
Swedish spokesman Clay Holtzman said the risk of infection is extremely low because three steps out of the four step process were done properly.
The equipment wasn’t doused in the sterilization fluid between uses.
That is the fourth step of the four-part sterilization procedure.
The errors occurred between September 19th and December 10th.