JACKSON — Batson Children’s Hospital says its pediatric emergency department and trauma unit have tripled in size now that a $5.8 million expansion is complete.

University of Mississippi Medical Center spokeswoman Jennifer Hospodor (HOS-poh-dohr) says the 16,000-square-foot facility was fully open for the first time Thursday, after weeks of moving in.

It replaces a children’s emergency room built in 1982 to handle 15,000 patients a year. The children’s ER at the state’s only Level 1 pediatric emergency and trauma center currently sees 32,000 to 35,000 patients a year.

Work on the expansion began in late 2009.

It has 23 treatment rooms, including several reserved for patient overflow; two designated trauma areas, two waiting areas and separate rooms for family consultation, cast treatments and triage.

The old ER has a small waiting area, one triage room and a jumble of treatment areas scattered throughout its 5,100 square feet, including a hall enclosed with a fabric curtain and a large room divided into four patient areas.

Dr. Magolia Castilla, associate professor and director of pediatric emergency medicine, said operating in such a confined space has been a challenge. She pointed out that not only has the volume of patients steadily increased to twice the size intended for the space but also that the patients are sicker.

“There is a larger critical mass of patients coming through our doors that coincides with the children’s hospital’s expansion of its specialty and subspecialty programs,” she said. “Being in such a small space has required us to be very efficient in everything that we do. We have to think outside of the box sometimes in order to move that volume of patients through such a small space.”

Money for the expansion included $1 million each from the Colonel Harland Sanders and the Selby and Richard McRae foundations, so the emergency department is named for Sanders and the trauma unit for the McRaes.