In one case, doctors removed a patient's healthy thyroid after a laboratory mix-up led to an incorrect cancer diagnosis.
In another, a neurosurgeon halted a procedure after making an incision on the wrong side of the patient's head.
In yet another, a surgeon inserted a needle into a patient's right knee before realizing that the operation was planned for the other leg.
Those surgical misadventures are examples of the 175 errors made by hospitals and surgery centers in Pennsylvania, according to a report released Tuesday from the state's Patient Safety Authority. The survey, the first of its kind, covered the 21/2 years that ended Dec. 31.
Though rare, "wrong-site" surgeries are among the most sensational medical errors because they are so clearly avoidable. But the problems persist despite more than a decade of national efforts to stop them.
The safety authority also reported 253 close calls, incidents where errors were spotted before patients were hurt.
"Every other day in Pennsylvania we have a report of a wrong-site surgery being caught either before or after the start of the operation," said Stan Smullens, vice chair of the safety authority.
In 83 reported cases, the procedure was completed before the mistake was detected.
A third of the hospitals in Pennsylvania reported a wrong-site surgery or near-miss, the safety authority said. During the period under study, a 300-bed hospital would, on average, have one such mishap each year. Eighteen hospitals in the state had two or more wrong-site surgeries in a single year, the safety authority reported.
The report examined four surgical errors: the wrong side, the wrong body part, the wrong procedure, and the wrong patient. Nearly a third of the errors and near-misses occurred on legs, a quarter on the head and neck region, and a fifth around the groin.
Established in 2003, the safety authority collects and analyzes reports on medical mistakes and near-misses. The goal is to identify and recommend changes to improve safety. The agency does not release hospital-specific data on errors.
National estimates of the wrong-site surgeries range from one in 10,000 operations to one in 113,000.
"There is no appropriate rate but zero," said Bill Marella, director of the safety authority's computerized reporting system. "The benchmark to use here is a prolonged period with no incidents."
Nonetheless, thousands of patients across the country experience these avoidable medical mistakes at enormous cost, both human and financial.
Because Pennsylvania is one of only a handful of states to require reports of such errors, it is impossible to determine whether the state's hospitals are better or worse than those in other parts of the country.
Eliminating medical mistakes is a key component of Gov. Rendell's broad plan to expand insurance coverage and reduce health-care costs.
If Rendell's proposals are enacted, the state will stop paying for the care involving hospital-acquired infections, wrong-site surgeries, and other avoidable errors, said Rosemarie B. Greco, director of the Governor's Office of Health Care Reform.
The state's effort to improve the quality and safety of medical care has won national recognition.
"Pennsylvania is a leader in public accountability for health-care outcomes," said David B. Nash, chairman of the department of health policy at Jefferson Medical College in Philadelphia. "We only improve that which we measure."
For example, Pennsylvania is the only state that requires hospitals to report near-misses. Learning from those incidents is key to preventing more serious errors, said Smullens, of the safety authority.
"We want to get more proactive," Smullens said. "We need to look at hospitals that are doing well and put what they are doing out there for others to learn from."
That can be accomplished by looking at the near-misses and how problems were caught before getting to patients.
The report highlights some methods to prevent such problems, including pauses at multiple points before surgery; medical record verification by the surgeon and nurses; improved communication and teamwork among caregivers; greater patient involvement; and marking of the surgical site.
The National Quality Forum classifies wrong-site surgeries as serious misadventures that should never occur in medicine - so-called never events.
Most hospitals and surgery centers have systems in place - required pauses or "time-outs" - to review patient information before starting an operation.
But that doesn't always work.
Safety experts say that protocols and policies are not enough to prevent errors.
"If that is all you do, then you will fail," said Doron Schneider, associate director of patient safety at Abington Memorial Hospital.
Schneider said every hospital must infuse itself with a "culture of safety" that stretches from administrators and trustees to doctors, nurses and medical technicians.
Moreover, hospitals need to take a page from the nuclear power industry and the space program, building safety systems with multiple redundancies.
"We want to become a high reliability industry," Schneider said, "but health care is behind in this area and is just trying to play catch-up."