Final answer:
The nurse should assess for ataxia and visual disturbances, which are potential symptoms of phenytoin toxicity at a level of 28 mcg/mL.
Step-by-step explanation:
If a patient has been taking phenytoin (Dilantin) and has a Dilantin level of 28 mcg/mL, which is considered to be a toxic level, the nurse should assess the patient for symptoms of phenytoin toxicity. These symptoms may include ataxia and visual disturbances, which align with option (a) from the choices provided. Phenytoin toxicity can also lead to other symptoms such as nystagmus, dizziness, confusion, and slurred speech, so these should also be monitored closely. Gingival hyperplasia and infection (b), decreased urine output and skin rash (c), jaundice and hirsutism (d) are less directly related to an elevated phenytoin level.