Medical mistakes account for between 18 and 45 cents of every health care dollar spent in the U.S., and a medical error or adverse effect occurs in one out of every three hospital admissions, researchers say.

According to studies published in the journal Health Affairs, the single most expensive cause of harm is infection after surgery, with more than 252,000 infections costing $3.36 billion reported in 2008, while pressure ulcers (bedsores) are the most common preventable event, with with nearly 375,000 cases in 2008 costing $3.27 billion.