Durham, N.C. — Patients exposed to surgical instruments washed in hydraulic fluid at two Duke University Health System hospitals suffered no more subsequent health problems than people in general, according to a report issued Thursday.

Tainted surgical instruments were used on about 3,650 patients at Duke University Raleigh Hospital and Durham Regional Hospital in late 2004. A contractor drained used elevator hydraulic fluid into empty barrels that were labeled as detergent, and the fluid was later used to wash surgical instruments.

Duke Health officials have maintained that the hydraulic fluid would have no impact because the instruments were sterilized after being washed. But outraged patients – some of whom had complained of health problems following their surgeries – demanded that the hospital system monitor their health in case they developed problems.

PharmaLink-FHI, a Durham-based private health research firm hired by Duke Health, reported in a new study that almost 90 percent of the exposed patients had no major clinical problems in the past two years. Another 8.6 percent had been hospitalized since their exposure, while 2.5 percent reported an infection and 1.8 percent had died.

The average time between exposure and subsequent hospitalization was more than six months, according to the report. Likewise, patients who developed infections did so several months after exposure, the report stated, concluding that no correlation could be made between the two events.

"When compared with expected medical outcome rates, the PharmaLink-FHI registry did not identify any rates that were increased above those expected of a general or similar patient population," the report stated.