Final answer:
The successful administration of 1 L of 0.9% sodium chloride in a postoperative patient with a fluid volume deficit is typically indicated by an increased urine output due to normalized blood volume and improved kidney perfusion.
Step-by-step explanation:
The question pertains to identifying the indication that the administration of 1 L of 0.9% sodium chloride to a postoperative patient with fluid volume deficit was successful. Increased urine output is an expected outcome of administering isotonic saline because the saline solution can correct the fluid deficit, leading to normalization of the blood volume. As a result, there is increased kidney perfusion and subsequently increased urine output. Furthermore, this fluid replacement should stabilize vital signs and improve blood pressure, not decrease it. Weight gain could indicate that fluid is being retained rather than appropriately excreted, and an elevated heart rate could be a sign of ongoing dehydration or other complications.