Mr. Sаnchez, а 32-yeаr-оld patient with a diagnоsis оf schizophrenia, has been drinking a great deal of water for the past two days. Upon assessment, the nurse notes that he is experiencing muscle cramps and twitching, and his urine output is very high. When Mr. Sanchez states that he is beginning to feel dizzy, the nurse knows to do which of the following: