The patient is exhibiting signs of shock and hemodynamic instability, likely secondary to toxic megacolon, a medical emergency associated with ulcerative colitis. The nurse must first contact the provider for further evaluation of this condition. It may be necessary to prepare the patient for emergency surgery and perform fluid resuscitation, but these are not the initial actions. The patient is already in significant abdominal pain. It is not appropriate to wait and reassess this patient later.