Final answer:
The priority assessment when administering IV fluids is blood pressure, as it is a key indicator of volume status and cardiovascular health, and changes can signal serious conditions like circulatory shock.
Step-by-step explanation:
When a nurse is administering IV fluids to a client and monitoring for adverse effects, the priority assessment should be blood pressure. Monitoring blood pressure is crucial because it can reflect changes in the volume status and cardiovascular response, potentially indicating hypovolemia or fluid overload. Hypovolemia can lead to circulatory shock, characterized by a rapid heart rate and low blood pressure, necessitating prompt intervention. Therefore, while respiratory rate, skin temperature, and urinary output are important, the regulation of blood pressure is typically the primary concern when initiating IV therapy.