What should be the nurse's first action when an infusion pump indicates an obstruction after opening the roller clamp on IV tubing?

When an infusion pump indicates an obstruction, the nurse's first action should be to reposition the client's arm. This step is crucial because an obstruction may occur if the client's arm is in a position that kinks or compresses the IV tubing. By repositioning the arm, the nurse can often relieve any physical obstruction that might be restricting the flow of fluid.

This action is appropriate as it addresses a potential mechanical issue immediately, allowing for the flow to resume without further intervention. Additionally, it ensures that the client is comfortable and that the IV site remains functional. If repositioning the arm doesn't alleviate the obstruction, the nurse can then consider other actions such as checking for a blood return or assessing the IV site further, but the priority should be to mitigate any kinked tubing caused by the client's position.