The nurse has been teaching the caregiver about Aricept. The nurse knows teaching has been effective by which of the following statements?

Choice A reason: A BUN of 18 mg/dL is within normal range (7–20 mg/dL) and does not indicate lithium toxicity. Lithium is renally excreted, and normal renal function, as reflected by BUN, suggests adequate clearance. Toxicity arises from sodium imbalances or dehydration, not directly from normal BUN levels, making this unremarkable.

Choice B reason: A fasting blood glucose of 80 mg/dL is normal (70–100 mg/dL) and unrelated to lithium toxicity. Lithium affects sodium and water balance, not glucose metabolism. Toxicity involves neurological symptoms from elevated serum lithium due to impaired renal clearance, not glycemic changes, so this value requires no further assessment.

Choice C reason: A potassium level of 3.6 mEq/L is within normal range (3.5–5.0 mEq/L) and does not indicate lithium toxicity. Lithium primarily affects sodium reabsorption in renal tubules, not potassium. Toxicity symptoms like tremors or confusion stem from sodium imbalances or high lithium levels, not normal potassium levels.

Choice D reason: A sodium level of 128 mEq/L (normal 135–145 mEq/L) indicates hyponatremia, increasing lithium toxicity risk. Lithium is reabsorbed in renal tubules like sodium; low sodium reduces lithium excretion, elevating serum levels, causing neurological symptoms like tremors or seizures. This requires immediate assessment to prevent toxicity.

Choice A reason: Orientation to person but disorientation to place and time occurs in both delirium and dementia. In delirium, acute cerebral dysfunction from causes like infection disrupts attention, while dementia’s gradual hippocampal loss affects memory. This symptom is non-specific, as it does not distinguish the acute onset critical to delirium diagnosis.

Choice B reason: Fragmented, incoherent speech can occur in delirium due to acute brain dysfunction or in advanced dementia from cortical degeneration. It reflects disrupted neural communication but is not specific to delirium’s rapid onset. This symptom alone does not differentiate the conditions, as both involve cognitive processing deficits.

Choice C reason: A history of increasing confusion over years indicates dementia, characterized by progressive neuronal loss, particularly in Alzheimer’s or vascular dementia. Delirium, conversely, has an acute onset due to reversible causes like infection. This chronic history rules out delirium, making this choice incorrect for identifying delirium.

Choice D reason: Being oriented and alert on admission, then developing confusion, indicates delirium’s acute onset, typically from pneumonia-related hypoxia or sepsis disrupting cerebral metabolism. Unlike dementia’s gradual progression, delirium’s rapid cognitive decline, often within days, reflects reversible brain dysfunction, making this the key differentiator in diagnosis.