Which action would require follow-up by the supervising nurse after a patient is scheduled to undergo a CT scan with intravenous contrast dye?

The action that would require follow-up by the supervising nurse after a patient is scheduled to undergo a CT scan with intravenous contrast dye is to cancel the CT scan if the patient reports a shellfish allergy. This is correct because individuals with a shellfish allergy may be at a higher risk for allergic reactions to iodinated contrast media used in CT scans. The presence of this allergy should prompt a thorough assessment and possibly an alternate imaging method or pre-medication protocol to prevent any adverse reactions. Therefore, the supervising nurse must address this contraindication to ensure the patient's safety and avoid implementing a procedure that poses an unnecessary risk.

Other actions mentioned, such as encouraging fluids after the scan, confirming consent, and raising side rails during transport, are standard procedural practices that do not inherently indicate a need for immediate follow-up based on specific patient history or allergies related to the CT scan procedure itself. These actions, while important for patient care and safety, do not require the same level of immediate intervention as the direct risk posed by a shellfish allergy in the context of receiving contrast dye.