Patients who check in to the nation's hospitals have new protections against one of the most devastating and preventable medical errors -- surgery on the wrong body part. Rules imposed July 1 by the agency that accredits most of the nation's hospitals, as well as some surgery centers, will require specific actions designed to prevent wrong-site surgery.

Regulations issued by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) require that doctors "sign their site" -- writing "yes" or their initials on the operative site with a surgical pen after conferring with a patient just before surgery.

The new rules also require that the medical team take a "timeout" in the operating room to verify the identity of the patient, confirm the procedure to be performed and ensure that all necessary equipment is present.

Hospitals whose staffs fail to comply with the new procedures could face the loss of their accreditation, an action that would imperil their funding. The new rules are an effort to stem an alarming increase in the number of reports of operations conducted on the wrong body part, the wrong procedure or even the wrong patient.

Every year since 1995, JCAHO officials say, they have seen a rise in voluntary, confidential reports of such mistakes, which experts believe are significantly underreported. Determining the precise number is impossible because there is no mandatory national reporting system for medical errors, although a few states, including Florida, require that cases be reported to state officials.

In 1998, 16 wrong-site cases were reported to JCAHO, compared with 75 last year. Cases included the removal of the wrong breast and a noncancerous kidney, a biopsy on the wrong side of the brain and surgery on the wrong patient.

While wrong-site surgery constitutes only a fraction of the estimated 98,000 medical errors that kill hospitalized patients annually or of the approximately 60 million surgeries performed in the United States, medical experts say it is indefensible because it is so easy to prevent.

"This is not quite Dick and Jane, but it's pretty close," JCAHO president Dennis S. O'Leary has said, noting that many wrong-site errors are the result of "very simple stuff" -- such as whether the X-rays were placed on the view box correctly or whether anyone made sure the right patient was on the operating table.

Three months ago doctors at a Sarasota, Fla., hospital performed a cardiac catheterization on the wrong patient after failing to verify the patient's identity, according to officials at the Florida Agency for Healthcare Administration. The case was one of 23 wrong-site errors reported to the state as required by law in the first three months of 2004, according to the agency's Web site.

In 2001 neurosurgeons at a Brooklyn, N.Y., hospital operated on the wrong side of the brain of a 41-year-old man because they were working from a CT scan that was reversed.

"This kind of mistake should never happen," said Russell Massaro, JCAHO's executive vice president for accreditation operations. While human error is inevitable, the solution is to design a system "with redundancies and double-checks," Massaro said.

To monitor compliance with the new rules, commission inspectors will audit charts at random and talk with patients and staff at hospitals JCAHO accredits, Massaro said. In addition, hospitals that report a wrong-site error to the commission will be required to devise a corrective plan and demonstrate that it works.

By requiring all doctors to follow basic standard procedures prior to starting surgery, the commission has borrowed a long-standing requirement from commercial aviation, which orders pilots to follow a prescribed checklist prior to takeoff. Such standardization is alien in medicine, where physician autonomy is prized.

"We decided that an airline approach was necessary, where we all do the same thing in the same way and in the same sequence," Massaro said, adding that many doctors practice at multiple hospitals that have different procedures. "No matter what airline you get on, you hear the same set of instructions."

While some hospitals have required that doctors mark the body part that is to be treated before surgery, there has been no uniformity in the procedures. Some surgeons marked the site with an "x" or put an adhesive sticky note on it, while others put an "x" over the site that they intended to avoid or simply wrote "no" on it.

Under the new rules, none of these actions is permissible. Because an "x" can be interpreted to mean either the wrong site or the correct one, only the operative site is to be signed, preferably with the doctor's initials. And the new rules explicitly bar the use of adhesive notes alone.

Site signing is required for procedures involving a left-right distinction such as kidneys or eyes, and multiple structures such as fingers, and in spinal surgery.

The rules also require that the doctor performing the procedure talk to the patient and agree on what is to be done. A nurse must then verify the patient's identity using both a name and birth date. Finally the entire surgical team must take a "timeout" in the operating room, making sure that all agree on the patient's identity, the operation to be performed and whether all necessary equipment is present and functioning.

These rules may be suspended in an emergency situation where "obviously you do what you need to for the patient," Massaro said.

The new regulations, which were endorsed by 49 major medical groups, faced no serious opposition, according to Massaro, who said that during the comment period before the rules were adopted some doctors and institutions questioned whether the changes were necessary.

S. Terry Canale, former president of the American Academy of Orthopaedic Surgeons, said that he has detected a softening in the opposition he encountered in 1997 when, under his leadership, the academy launched a "Sign Your Site" campaign aimed at its members. Studies have found that orthopedists have the greatest chance of performing wrong-site surgery because they operate on limbs.

"All these famous prima donna orthopedic surgeons said, 'I don't have time to talk to a patient before surgery' or 'I've never make a mistake, why should I do this?' " recalled Canale, who practices in Memphis.

"But I think surgeons have become a bit more realistic and more tolerant in the past four or five years about the problem of medical errors, and realize they better pay attention to this," he said.

"They're beginning to buy into the aviation model a little," Canale added. "Just don't tell them how to do the operation."