Four patients expecting routine surgeries at Ascension St. Thomas Midtown Hospital in Nashville faced a medical nightmare after staff accidentally gave them the wrong drugs. A drug mix-up reportedly involved patients being given potassium instead of an anesthetic, leading to two people becoming paralyzed and at least one other ending up on a ventilator. Hospital staff realized something was wrong when multiple patients went into cardiac arrest, since too much potassium given too quickly can stop a person's heart. The incident occurred inside the hospital's pharmacy, a detail confirmed by the family of one patient. In a statement, the hospital said they were deeply sorry for the harm caused and had implemented corrective safeguards. CBS News correspondent Nicole Valdes reported from the scene while the Tennessee Bureau of Investigations is looking into the mix-up. There are still unanswered questions regarding the specific safety protocols now in place.