Final answer:
The nurse should prioritize reporting vomiting in a toddler with leukemia receiving chemotherapy as it could lead to serious dehydration and complications. While urticaria, fatigue, and anorexia are also concerns, vomiting demands immediate attention to manage the toddler's care effectively.
Step-by-step explanation:
The priority finding that a nurse should report to the provider for a toddler with leukemia receiving their first round of chemotherapy is vomiting. Among the listed side effects, vomiting can be an immediate concern as it may lead to dehydration, electrolyte imbalance, and can affect the absorption of chemotherapy drugs, as well as indicate a potentially severe hypersensitivity or toxic reaction to the medication. Additionally, persistent vomiting in the context of cancer treatment can lead to more serious complications and requires the attention of healthcare providers to manage and possibly adjust treatment.
Urticaria (hives) is also a concern, particularly as it could indicate an allergic reaction, but does not usually take precedence over vomiting, unless the urticaria is part of a systemic allergic reaction. Fatigue and anorexia (loss of appetite) are common and expected side effects of chemotherapy, but are not as immediately life-threatening as uncontrolled vomiting could be.
When assessing blood counts before chemotherapy, an absolute neutrophil count (ANC) of 1900 cells per microliter is considered within a safe range to proceed with chemotherapy. Neutrophils are a type of white blood cell important for fighting infection, and chemotherapy can lower their count, increasing the risk of infections.