Final answer:
After observing urine flow in the tubing during catheter insertion, the nurse should inflate the catheter balloon with 5 ml of sterile water.
Step-by-step explanation:
When inserting an indwelling urinary catheter into a client and urine flow is observed in the tubing, the nurse should next inflate the balloon with 5 ml of sterile water. This step comes after ensuring the catheter is correctly placed, indicated by the presence of urine, and before it is secured in place. Inflating the balloon with sterile water helps to anchor the catheter within the bladder.
Proper technique and aseptic procedures should be followed to prevent infection and ensure patient safety. Monitoring client comfort and asking them to breathe deeply may also be beneficial throughout the catheterization process to enhance relaxation, but the immediate next step after observing urine flow is to inflate the balloon.