Correct Answer: C

Rationale: When administering lithium, it is crucial to watch for the side effect of angioedema. Angioedema is a potential adverse reaction associated with lithium therapy, characterized by rapid swelling beneath the skin, often around the eyes and lips. Monitoring for this side effect is essential to promptly address and manage any signs of angioedema that may occur during lithium treatment.

Correct Answer: A

Rationale: The nurse should check the client's vital signs first because nausea and weakness can be signs of digoxin toxicity. Vital signs can provide immediate information on the client's condition and help guide further interventions.

Correct Answer: B

Rationale: Furosemide is a loop diuretic that can lead to hypokalemia (low potassium levels) due to increased excretion of potassium in the urine. To counteract this effect and maintain electrolyte balance, the client should be advised to increase their intake of potassium-rich foods. This instruction helps prevent potential complications associated with low potassium levels.

Correct Answer: C

Rationale: Lithium is primarily used to stabilize mood, especially in conditions like bipolar disorder. It helps in reducing the frequency and severity of manic episodes, making it an essential medication for mood stabilization.

Correct Answer: A

Rationale: Caffeine can increase the risk of theophylline toxicity as it competes for the same metabolic pathways, so clients should avoid consuming caffeine while on theophylline to prevent adverse effects.