Heart and lung failure finally claimed the life of a 2-year-old boy who survived 90 minutes under the waters of a cold river last month. Doctors at Scenic General Hospital in Modesto said Allen Lee Smith had suffered considerable brain damage due to lack of oxygen after he fell into the Stanislaus River on Oct. 9. He had been under water for about 90 minutes when rescuers found him, and it took doctors two hours to restore heartbeat and respiration. A week later at UC Davis Medical Center in Sacramento, however, doctors confirmed major brain damage and attending physicians said the child had gone through several days of progressive weight loss, erratic heart rate and high temperature before he died peacefully in his sleep. His parents, Dennis and Lynn Smith, had decided against using an artificial respirator.