Which finding indicates a therapeutic effect of IV mannitol in a client with increased ICP?

The therapeutic effect of IV mannitol in a client with increased intracranial pressure (ICP) is primarily indicated by increased urine output. Mannitol is an osmotic diuretic that draws fluid from the extracellular space, including the brain, into the vascular compartment, which helps to reduce cerebral edema and subsequently lower ICP. As this fluid is excreted through the kidneys, a significant increase in urine output is often observed. This indication not only reflects the action of mannitol in reducing swelling and pressure in the brain but also serves as a measure of its efficacy.

While reduced headache severity and improved level of consciousness can also be desired outcomes of treatment in increased ICP, they are more subjective and may not provide a direct measurement of the therapeutic effect of mannitol. Increased heart rate could occur due to various factors, including fluid shifts or stress responses, but does not specifically indicate the effectiveness of mannitol in managing ICP. Therefore, the most definitive indicator of mannitol's therapeutic effect is the increased urine output.