In a child with a head injury, what is the best indicator of the effectiveness of intravenous mannitol treatment?

The best indicator of the effectiveness of intravenous mannitol treatment in a child with a head injury is decreased intracranial pressure. Mannitol is an osmotic diuretic that works by drawing fluid out of the brain and into the bloodstream, thereby reducing cerebral edema and lowering intracranial pressure (ICP). Monitoring ICP is critical in managing head injuries, as elevated pressure can lead to further brain injury and complications.

While increased urine output, improved level of consciousness, and decreased edema are important clinical markers, they are secondary indicators in this context. Increased urine output might suggest that the mannitol is effective, but it does not directly measure ICP. An improved level of consciousness may occur as a result of decreased ICP, but it is also influenced by other factors. Decreased edema is a desirable outcome but does not specifically quantify the intra-cranial pressure changes. Therefore, the most direct and relevant measure of the treatment's effectiveness is the decrease in intracranial pressure.