A nurse is obtaining vital signs from a 2-month-old infant. The infant's heart rate is 190/min and his temperature is 40° C (104° F). The father asks the nurse why the infant's heart is beating so fast. Which of the following responses by the nurse is appropriate?

When caring for a child with acute appendicitis, the nurse should anticipate an elevated white blood cell count (WBC) in the laboratory values. A high WBC count is a common finding in acute appendicitis, as it indicates an inflammatory response and infection in the body. The body's immune system responds to the inflammation caused by the infected appendix, leading to an increase in WBCs to fight off the infection.
The other options are not necessarily specific to acute appendicitis:
A. RBC 4.2 million/mm³: The red blood cell count (RBC) measures the number of red blood cells in the bloodstream. This value may be within the normal range, but it is not the primary marker for diagnosing or monitoring acute appendicitis.
B. Lymphocytes 3,000/mm3: Lymphocytes are a type of white blood cell involved in the body's immune response. While changes in lymphocyte levels can occur during inflammation, it is not the primary marker for diagnosing or monitoring acute appendicitis.
C. Neutrophils 3.000/mm³: Neutrophils are a type of white blood cell that increases in response to infection and inflammation. However, the absolute neutrophil count is not as relevant as the overall WBC count in determining the presence and severity of acute appendicitis.

D. A client's blood pressure changes from 112/60 mm Hg to 90/54 mm Hg when standing.
A significant drop in blood pressure when changing positions from lying to standing may indicate orthostatic hypotension, which can be a sign of dehydration, blood loss, or other underlying medical issues. This can be a cause for concern, especially if the client is an adolescent, as it may lead to decreased perfusion of vital organs and may require immediate medical attention.

The other options are as follows:
A. A client who has a burn injury to an estimated 5% of his leg and is crying - While it's essential to assess and address the client's pain and comfort, this finding does not indicate an immediate need for medical attention. Pain management and wound care can be addressed based on the severity of the burn and the client's pain level.
B. A client who has an ankle fracture reports a pain level increase from 3 to 5 after initial ambulation - This finding is concerning, and the nurse should notify the provider to reassess pain management and evaluate for potential complications related to the fracture. However, it may not require immediate medical attention unless there are signs of severe pain or complications.
C. A client who is 1 day postoperative and has a temperature of 37.5° C (99.5° F) - A slight increase in temperature in the immediate postoperative period may not be unusual and can be attributed to the normal inflammatory response after surgery. The nurse should continue monitoring the client's temperature and report any further changes or additional signs of infection or complications to the provider.
Overall, while all findings should be addressed and managed appropriately, the significant drop in blood pressure (option D) should be reported immediately due to the potential implications for the client's overall health and well-being.