Children who gave themselves morphine at the touch of a button suffered less pain after major surgery than those who had to call a nurse for shots, a new study says.

The children, ages 5 to 15, reported significantly less pain in the two days after their operations, said researcher Edwin Dodd.He reported preliminary study results recently at the annual meeting of the American Society of Anesthesiologists. Dodd, director of the Jackson Anesthesia Associates Pain Clinic in Jackson, Miss., did the work while a fellow at the Bowman Gray School of Medicine at Wake Forest University.

"Patient-controlled analgesia" has become commonplace for adults in the past five years. A patient who wants a dose of painkiller pushes a button, which makes a pump adminster a small dose through an intravenous line.

To avoid overdoses, the pump puts a minimum amount of time between doses. In Dodd's study, for example, children could get morphine no more frequently than once every six minutes.

Through random selection, half the 20 children in the study were hooked up to a pump, while the others had the standard treatment of calling a nurse for morphine shots. They were asked about the degree of pain they were feeling right after surgery, and in the mornings and afternoons of the following two days.

They indicated their degree of pain on a 10-point scale that featured five faces, ranging from a happy one to a crying one.

As expected, both groups reported the same amount of pain immediately after surgery, Dodd said. But each time they were asked in the next two days, children on the pump averaged significantly less pain than the other children did.

No sign of addiction appeared in children using the pump, Dodd said.