Final answer:
Mannitol can cause hyperkalemia by reducing the reabsorption of potassium in the kidneys, resulting in increased blood potassium levels. The underlying mechanism involves the osmotic effect of mannitol on the tubular fluid, which affects the regulation of potassium balance in the body.
Step-by-step explanation:
Mannitol, an osmotic diuretic, can cause hyperkalemia by increasing the concentration of potassium in the blood. When mannitol is administered, it cannot be reabsorbed by the renal tubules and remains in the tubular fluid. This increase in osmolarity of the tubular fluid causes water to be drawn out of the cells into the tubular fluid, resulting in diuresis. However, the increased flow of tubular fluid also washes out potassium ions, leading to hyperkalemia.
The underlying mechanism is related to the regulation of potassium balance in the body. Normally, the kidneys reabsorb most of the filtered potassium back into the blood, maintaining a low concentration of potassium in the urine. However, with high osmolarity of the tubular fluid due to mannitol, the reabsorption of potassium is reduced, leading to a higher concentration of potassium in the urine and eventually in the blood.