A patient has had recent mechanical heart valve surgery and is receiving anticoagulant therapy. While monitoring the patient™s laboratory work, the nurse interprets that the patient™s international normalized ratio (INR) level of 3 indicates that:

Correct Answer: B

Rationale: An international normalized ratio (INR) level of 3 indicates that the patient's warfarin dose is within the therapeutic range for anticoagulation. In patients with mechanical heart valves, the target INR range is usually higher (around 2.5 to 3.5) to prevent thrombus formation on the prosthetic valve. An INR of 3 demonstrates that the anticoagulant effect of warfarin is at an appropriate level to reduce the risk of blood clots while minimizing the risk of bleeding complications. If the INR level was subtherapeutic (below the target range), it would indicate that the patient is not receiving enough warfarin to achieve the desired anticoagulant effect.

Correct Answer: C

Rationale: Thrombolytic drugs are used to dissolve blood clots (thrombi) that are causing blockages in blood vessels, such as the coronary arteries in the case of acute myocardial infarction (heart attack). By breaking down the clot, these drugs help to restore blood flow to the affected area, reducing damage to the heart muscle and improving the patient's prognosis. Thrombolytic therapy is time-sensitive and is most effective when administered soon after the onset of a heart attack to minimize the extent of heart muscle damage.

Correct Answer: A

Rationale: When taking digoxin, low levels of potassium can cause an increased risk of digoxin toxicity. This is because digoxin and potassium compete for binding sites on the sodium-potassium pump in cardiac cells. Low potassium levels can lead to enhanced binding of digoxin to these pumps, resulting in increased concentrations of digoxin within the cells and potential toxicity. Therefore, it is important to monitor potassium levels regularly while taking digoxin to prevent complications.

Correct Answer: D

Rationale: Packed red blood cells (PRBCs) always require cross-matching with the recipient to prevent a transfusion reaction. Cross-matching is crucial for PRBCs because they contain red blood cells with antigens on their surface that may react with antibodies in the recipient's plasma, potentially causing a transfusion reaction. Cross-matching involves testing the compatibility of donor red blood cells with the recipient's plasma to ensure a safe transfusion. Other blood products like granulocytes, platelets, and plasma do not contain red blood cells and, therefore, do not require cross-matching.

Correct Answer: C

Rationale: Lithium is primarily used to stabilize mood and prevent manic episodes in individuals with bipolar disorder. It is a mood-stabilizing medication that helps to lessen the severity and frequency of manic episodes. Lithium is not used to lower blood glucose, slow the heart rate, or heal ulcers. It is important to follow the prescribed dosage and have regular monitoring of lithium levels in the blood to ensure its effectiveness and prevent toxicity.