Correct Answer: B

Rationale: The correct answer is B: Tissue oxygen needs. Polycythemia occurs in response to chronic hypoxia, leading the body to increase red blood cell production to enhance oxygen delivery. In tetralogy of Fallot, a congenital heart defect that results in reduced oxygen levels in the blood, the body compensates by producing more red blood cells. Choice A is incorrect as low tissue oxygen needs would not trigger polycythemia. Choice C, diminished iron levels, is not the cause of polycythemia in this case. Choice D, hypertrophic cardiac muscle, is unrelated to the pathophysiology of polycythemia in tetralogy of Fallot.

Correct Answer: B

Rationale: The correct preoperative intervention for a child with appendicitis scheduled for surgery is maintaining strict NPO (nothing by mouth) status. This is crucial to reduce the risk of aspiration during anesthesia induction and prevent potential complications during surgery. Administering antibiotics may be a part of the treatment plan but is not a preoperative intervention. Encouraging fluid intake is contraindicated preoperatively to avoid delays in surgery and complications related to anesthesia. Monitoring for signs of infection is important postoperatively to assess for any complications that may arise due to the surgical procedure.

Correct Answer: C

Rationale: Low-set ears with lobe creases are often associated with genetic disorders, such as Down syndrome, and can indicate underlying chromosomal abnormalities. This physical characteristic is a common feature seen in various genetic syndromes. The other choices, including feeding problems, weight and height measurements, and motor skills, are not typically specific indicators of genetic disorders in the absence of other associated features.

Correct Answer: C

Rationale: When a dysrhythmia is suspected, an important nursing responsibility is to count the apical pulse for 1 full minute and then compare this rate with the radial pulse rate. This method helps in identifying dysrhythmias as it allows for a direct comparison of the heart's rhythm at two different pulse points. Ordering an immediate electrocardiogram (Choice A) may be necessary but should not be the first step. Counting the radial pulse multiple times (Choice B) is not as accurate as comparing rates directly. Having someone else take the radial pulse simultaneously (Choice D) may introduce errors and inconsistencies in the measurement.

Correct Answer: D

Rationale: The correct preoperative intervention for a child with appendicitis scheduled for surgery is to monitor for signs of infection. This is crucial to ensure that any potential infections are promptly identified and managed before surgery. Administering antibiotics, maintaining strict NPO status, and encouraging fluid intake are important interventions in various clinical situations but are not the priority in this scenario. Administering antibiotics may be part of the treatment plan but is typically prescribed by a physician. Maintaining NPO status is important to prevent complications related to anesthesia but may not directly address the specific needs of a child with appendicitis. Encouraging fluid intake is generally beneficial for hydration but may not be the primary concern before surgery for appendicitis.