Almost half of the patients flown by helicopter to Maryland trauma centers are released within 24 hours, making some lawmakers wonder whether the state's vaunted Medevac system is overused.

At an Annapolis hearing this morning, legislators plan to question state medical officials about the discharge rates and overall efficiency of the Medevac program. The hearing was prompted in part by a legislative audit last month that was critical of the Maryland State Police's fiscal management and maintenance of the program's aging 12-helicopter fleet.

"The audit report brought up one piece of the helicopter issue," said Del. Dan K. Morhaim, a Baltimore County Democrat and co-chairman of the Joint Committee on Health Care Delivery and Financing. "It also means you should look at the operations in general."

Officials with the state's Medevac system defend the use of the helicopters, saying they save lives.

Earlier this year, Morhaim, a former emergency room physician, asked the Maryland Institute for Emergency Medical Services Systems for statistics on patient discharge rates. MIEMSS is a Baltimore-based state agency that oversees and coordinates the state's emergency medical response network. Among the data it provided to Morhaim:

•35 percent of helicopter-transported patients in fiscal year 2007 were discharged from trauma centers within 12 hours.

•An additional 11.5 percent of those patients were released within 24 hours.

•The average Medevac flight time was 12 minutes.

Morhaim said yesterday that the information "raises questions about triage criteria" used to determine which patients require helicopter transport to a trauma center rather than ground transport to a local emergency room.

Dr. Bryan E. Bledsoe, a University of Nevada School of Medicine professor who has studied medical helicopter operations nationwide, was more blunt in his assessment of Maryland's data, saying that "over 90 percent" of those patients discharged within 24 hours should not have been taken to a trauma center in the first place.

"A 50 percent over-triage rate is way over anything I've ever seen," said Bledsoe.

But Dr. Robert R. Bass, MIEMSS' executive director, said Maryland's statistics were in the same "ballpark" as national trends. He also noted that 15 percent of injured patients in Maryland are taken to a trauma center, about the same rate as in other states.

"We feel that these helicopters contribute to a reduction in mortality from trauma," Bass said. He said he intended to present evidence today that Maryland's Medevac program - begun in 1970 and considered the oldest organized Medevac system in the country - remains among the best in the nation. "It saves lives and works very well ... and should be maintained," Bass said.

The hearing comes amid renewed questions from some lawmakers about the need to invest in a planned $120 million overhaul of the 12-helicopter fleet at a time when anemic tax collections means serious budget cuts are in the offing.

Sen. John C. Astle, an Anne Arundel County Democrat and former helicopter pilot, has said he and others would likely question the wisdom of purchasing new helicopters at a hearing this month.

Legislative auditors found that the state police did not maintain up-to-date maintenance records for its helicopters, keep critical parts in stock or effectively manage parts inventories. A lack of reliable data kept by the police aviation unit also made it impossible for auditors to assess whether the Medevac program transported patients to hospitals within a 60-minute window, a critical time period for emergency medicine.

Asked whether Gov. Martin O'Malley, a Democrat, remained committed to replacing the helicopter fleet by 2012, spokesman Shaun Adamec said, "The best answer is, we certainly hope so."

State police Superintendent Col. Terrence B. Sheridan yesterday said it's not up to the police to determine the appropriateness of Medevac calls. He pointed to the success of the transport service itself, which auditors praised for its "impeccable" safety record.

"When we get a call from a medic on the ground asking for a helicopter ... we're merely responding to what we've been requested to do," Sheridan said. "I firmly believe this is the best system in the country, if not the world."

Morhaim said he will ask Bass to respond to a review of scientific literature conducted at the delegate's request by area public health scholars. The review concluded: "A growing body of literature suggests there is no measurable health benefit associated with air transport for the majority of patients who use" helicopter emergency medical services.

Bass said he would present Morhaim with counter-evidence. "We've got data in Maryland suggesting that those patients taken by air have better outcomes despite having more serious injuries," Bass said.

He said Maryland paramedics use guidelines developed by the American College of Surgeons when deciding whether to summon a helicopter transport. Those guidelines are regularly refined to try to increase the system's efficiency, Bass said.