Carotid surgery comes with complications.

More than 500,000 people suffer strokes in the United States each year, but the number would be higher without a procedure in which surgeons clear blockages inside the carotid artery. The surgery facilitates blood flow to the head and is particularly useful for people who don't have symptoms of stroke but who do have dangerously clogged carotid arteries.

The surgery poses a risk of stroke even for these outwardly healthy people, but new research shows that the risk is greater than previously thought. Moreover, for seeing, high-risk patients, another approach altogether may be advisable.

Scouring out the Y-shaped carotid artery in the neck is common surgery in the United States. In 1995, 132,000 people had such a carotid endarterectomy. To assess the risk of stroke associated with the procedure, scientists recently reviewed the cases of 463 asymptomatic patients at 12 medical centers who had the operation between 1987 and 1990.

Shortly after the surgery, 13 patients suffered a stroke or died, apparently because of obstructed blood flow during the operation or because bits of plaque shaken loose from the blood vessel wall during surgery lodged in the brain, says study coauthor Larry B. Goldstein, a neurologist at Duke University Medical Center in Durham, N.C.

This 2.8 percent complication rate, reported in the April Stroke, is nearly double the 1.5 percent rate found in a 1996 report.

The findings may differ because of the surgeons involved, Goldstein says. The earlier report monitored only doctors who had performed at least 12 such operations a year with high success rates. In contrast, Goldstein and his colleagues reviewed operations done by doctors who didn't necessarily have as much experience with the procedure.

The new report may actually understate the risk, says Goldstein. In the earlier report, patients were tracked for 30 days after surgery. Goldstein's team analyzed data on patients only until discharge from the hospital, usually after a few days, yet it found a higher rate of complications.

The researchers also found that women faced a 5.3 percent complication rate, whereas men encountered only a 1.6 percent rate.

Many of the people in direst need of a carotid endarterectomy face the greatest danger from the operation. The risk of complications rises to 10 to 20 percent for patients who are over 80, who have had previous carotid surgery, or whose blood flow to the brain is otherwise restricted, says cardiologist Gary S. Roubin of Lenox Hill Medical Center in New York City. Also boosting the risk are heart disease and blockage that occurs in a part of the carotid artery that is difficult to reach.

For such high-risk patients, Roubin implants a stent--a cylindrical device that props the vessel open while holding back the arterial wall with a fine mesh that prevents bits of plaque from entering the bloodstream. In the April 7 Circulation, Roubin and his colleagues report that, compared to carotid endarterectomies, stents halved the complication rates in most high-risk patients and reduced even further the problems encountered by those who had very large blockages.