Sierra Health Services Inc., Las Vegas, is reviewing the investment options in its $68 million 401(k) plan, said Joan Backman, benefits manager. Plan officials may add a new bond fund that is more heavily weighted in government than corporate securities. Also, they are monitoring a midcap value equity fund for performance, Ms. Backman said. She would not name the funds. The review will be finished in early November, she said. The plan has 13 investment options. Prudential is bundled provider; Arnerich, Massena is assisting.