Final answer:
The effectiveness of Osmitrol (mannitol) for a client with increased intracranial pressure is best indicated by an increased urinary output. Mannitol is an osmotic diuretic that draws fluid from the brain to decrease swelling and consequently ICP. This process leads to increased urine production, reflecting the drug's activity.
Step-by-step explanation:
The direct effectiveness of Osmitrol (mannitol) for a client with increased intracranial pressure (ICP) would be indicated by increased urinary output. Mannitol is an osmotic diuretic that promotes water loss through osmosis. When administered, it draws fluid from the brain tissue, which reduces swelling, thereby decreasing intracranial pressure. As mannitol is not reabsorbed by the renal tubules, it leads to increase in urine production, effectively reducing the amount of fluid in the body and the brain.
Mannitol's mode of action contrasts with loop diuretics, which inhibit the reabsorption of Na* and Cl- ions in the loop of Henle thereby also increasing urination as a side effect. However, this mechanism is specific to its indication and should not be confused with drugs that treat other conditions like hypertension or hypotension.
Therefore, the correct finding that indicates the direct effectiveness of mannitol in reducing increased intracranial pressure is increased urinary output, as opposed to changes in pulse rate, blood pressure, or pupil size.