Final answer:
A phenytoin level of 35 mg/dL is significantly higher than the therapeutic range, and the most likely symptom associated with this level of toxicity is ataxia, a neurological condition affecting coordination and balance.
Step-by-step explanation:
The expected symptom for a client with a phenytoin level of 35 mg/dL would most likely be ataxia. Phenytoin is a medication used primarily for the control of seizures and has a therapeutic range usually between 10 to 20 mg/dL. A level of 35 mg/dL indicates significant overdose or toxicity, which can lead to neurological symptoms such as nystagmus, ataxia, slurred speech, and encephalopathy.
Potassium deficit, neglect syndrome, and tetraplegia are not directly associated with phenytoin levels or toxicity. Therefore, ataxia appears to be the most appropriate answer from the given options as it is a common sign of phenytoin toxicity. It is important to closely monitor levels of phenytoin and avoid overdose, as the side effects can be severe.