Final answer:
The nurse is likely dealing with a case of sensory deprivation due to the patient's isolated condition, rather than sundowning, a stimulating environment, or fluid and electrolyte imbalance.
Step-by-step explanation:
The medical-surgical nurse would recognize that the changes in the patient's mental status experiencing visual hallucinations and following only simple directions could be related to sensory deprivation. Being in isolation, especially someone who is 80 years old, can significantly reduce stimulation from the environment and lead to confusion and hallucinatory experiences. Hospitals implement isolation precautions, like with Methicillin-resistant Staphylococcus aureus (MRSA), to prevent the spread of this antibiotic-resistant bacterium. Patients with MRSA, especially the elderly who are often more susceptible due to weakened immune systems and comorbidities, may experience a range of symptoms from the infection itself, including confusion if it leads to a systemic response such as sepsis.
It is less likely that the patient's mental status changes are due to a fluid and electrolyte imbalance without supporting clinical data. While a stimulating environment can definitely affect mental status, in this case, the patient's isolation would lead to the opposite problem - sensory deprivation. 'Sundowning' typically refers to increased confusion and agitation during the late afternoon or evening and could be a possibility, but sensory deprivation is more consistent with the provided scenario of an alert and oriented individual placed in isolation.