Updated

While patient safety in US hospitals is improving, "medical mistakes still occur at an alarming rate," according to the sixth annual HealthGrades study of patient safety in American hospitals, released today.

Between 2005 and 2007, medical errors cost Medicare over $6.9 billion and were responsible for more than 92,000 potentially preventable in-hospital deaths among Medicare beneficiaries, report Dr. Rick May and others at HealthGrades, a healthcare ratings organization in Golden, Colorado.

May's group used a Medicare database to evaluate 12 patient safety indicators at nearly 5000 hospitals. The 242 best-performing hospitals were recognized with the HealthGrades 2009 Patient Safety Excellence Award.

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More than 913,000 total "patient safety events" occurred, representing 2.3 percent of the nearly 38 million Medicare hospital admissions.

Patients who suffered one of these mistakes had a one-in-ten chance of dying, the report indicates.

The investigators observed that, on average, Medicare patients treated at award-winning hospitals were 43 percent less likely to experience a medical error compared with those at bottom-ranking hospitals. "This finding of better performance was consistent across all 12 patient safety indicators studied," the authors write.

Errors with the highest occurrence rates were "failure to rescue," defined as death among surgical inpatients with serious treatable complications; bed sores; postoperative respiratory failure; and serious postoperative infections.

"The good news is that there are hospitals that are doing an amazing job when it comes to patient safety," May said in a press release. "Patients need to know that they have a substantially lower risk of experiencing a medical error and therefore a lower risk of death or complications when they are admitted to one of these exceptional top-performing hospitals."

Individual hospital ratings can be viewed for free at www.healthgrades.com.