A D.C. Superior Court jury has awarded $250,000 to a 35-year-old Falls Church nurse, who charged that her dentist improperly injected her with an anesthetic that caused her to have convulsions and to become unconscious at his Northwest office.

The jury took less than an hour after the seven-day trial to make the award in a dental malpractice suit brought by Elizabeth A. Bourke against Sidney M. Fogelman, whose offic is at 1776 Massachusetts Ave. NW.

Bourke's attorneys, Richard Cassell and William J. Skinner, successfully argued that during a Jan. 26, 1976, appointment, Fogelman had been negligent when he injected a local anesthetic directly into Bourke's bloodstream.

After the injection, the attorneys argued, the dentist then administered another anesthetic, nitrous oxide, a gas. The combination of the two accelerated Bourke's heartbeat but slowed the flow of oxygen to her brain, causing her to become unconscious, it was explained. Neither anesthetic is designed to render a person unconscious, the court was told.

She was revived, but after the doctor administered the gas a second time, she collapsed again, Cassell said. After she was revived the second time, she was taken to a hospital by ambulance.

Bourke contended that although she had suffered no permanent physical injuries from the incident, she had suffered psychologically. She said she was still afraid of dentists and injections.

Fogelamn's attorney, Francis L. Casey, argued that the dentist had done nothing wrong and in fact, had acted in accordance with accepted industry standards.

Casey also argued that the fainting was caused by a hereditary heart condition that Bourke has and was not caused by an injection. He also said that Fogelman had administered the nitrous oxide only once. Casey said he would ask for a new trial.