A 25-year-old client is admitted for a tonsillectomy. She tells the nurse that she has had episodes of muscle cramps, weakness, and unexplained temperature elevation. Many years ago her father died shortly after surgery after developing a high fever. She further tells the nurse that her surgeon is having her take dantrolene sodium (Dantrium) prophylactically prior to her tonsillectomy. Dantrolene sodium is ordered preoperatively to reduce the risk or prevent: