Final answer:
Mannitol is ordered by the physician to promote osmotic diuresis and decrease ICP in a patient with a subdural hematoma. It works by attracting water into the urine, which decreases brain swelling and alleviates symptoms of increased intracranial pressure such as restlessness and pupil dilation.
Step-by-step explanation:
A patient with a subdural hematoma experiences increased intracranial pressure (ICP) due to the accumulation of blood between the brain and the skull. The physician orders mannitol as it works as an osmotic diuretic, which means it helps promote water loss from the body via osmosis. When mannitol is administered, it does not get reabsorbed by the renal tubules; instead, it remains in the nephrons of the kidneys, attracting water from surrounding tissues into the urine through osmotic forces. This increased water excretion leads to a reduction of fluid volume in the brain and thus decreases the ICP. The process of osmotic diuresis helps lower intracranial pressure more effectively than other types of diuretics, which is essential for treating patients with brain swelling or injury.
Osmotic diuretics like mannitol are not metabolized, and their presence in the renal tubule prevents the reabsorption of water, resulting in an increase in urine output and decreased fluid volume in tissues, including the brain. This mechanism is critical for alleviating the symptoms of restlessness and confusion seen in subdural hematoma by countering the cerebral edema and reducing the ICP. It is important to note that this use of mannitol should be carefully monitored due to its potent effects and possible complications.