BREA — 18 y/o Ma S/P TC 8 mo. ago.

Medical personnel can read that sentence, but most of us don't have a clue to its meaning. It describes an 18-year-old man who was in a traffic accident eight months ago.

The abbreviations are standard argot for a medical chart. But they befuddle most lawyers and insurance claims representatives who deal with medical malpractice, personal injury and medical products liability cases.

In the past, lawyers and insurance companies have hired doctors to read the charts and testify as experts--at a cost of $300 to $500 an hour. Today, nurses are marketing themselves as legal nurse consultants with some success at the much lower hourly rate of $75 to $150.

Karen McLachlan, president of the 45-member Orange County chapter of the American Assn. of Legal Nurse Consultants, wears a beeper just about everywhere she goes. It went off twice during a recent Friday breakfast.

McLachlan believes she is the busiest independent legal nurse consultant in Orange County, with 30 clients. "There are a couple in L.A. who are busier," said McLachlan, who serves Orange County clients from her home office in Long Beach. She moved there recently after living in Anaheim.

Her job consists of reading charts and summarizing the history of medical care for lawyers. She also attends jury selections as an adviser, sits in on depositions and researches the likely cost of care for an injured patient throughout his or her lifetime.

What McLachlan likes best, though, is sifting through the charts. Recently, she investigated a case of a 2-year-old girl who is severely retarded because of alleged medical mishandling. Lawyers believed the baby was damaged during delivery. But McLachlan discovered that the delivery was fine and that negligent postpartum nursing care probably caused the child's brain damage.

"The attorneys could have wasted their time going after the obstetrician," said McLachlan, who still works one day a week as a nurse at St. Mary's Hospital in Long Beach. "It's like being a detective. You want to find the missing link that caused the problem."

She said she has some misgivings about criticizing the work of other nurses. But she reminds herself that her role is as a patient advocate.

The profession of legal nurse is about five years old and grew most rapidly in Arizona because state law there requires a nurse's review of cases charging negligence by a nurse. Many Arizona law firms employ nurse consultants on staff. The year-old national association is based in Phoenix.