Certified Surgical First Assistant (CSFA) 2026 – 400 Free Practice Questions to Pass the Exam

Mannitol is known to affect renal vascular resistance due to its role as an osmotic diuretic. When mannitol is administered, it increases osmotic pressure in the renal tubules, leading to a higher volume of fluid remaining in the tubular system. This not only promotes diuresis but also induces changes in renal blood flow dynamics.

The introduction of mannitol can also lead to an increase in renal perfusion pressure, which can effectively influence how blood vessels in the kidneys respond to changes in pressure and volume. As a result, mannitol helps to reduce renal vascular resistance through its osmotic effects and its ability to affect the hemodynamics of renal circulation.

In contrast, substances like urea primarily reflect metabolic waste and impact renal function indirectly, ammonia serves as a waste product but does not directly modulate vascular resistance, and creatinine is a byproduct of muscle metabolism typically used as a marker for kidney function but does not influence vascular resistance dynamics in the same way that mannitol does. Therefore, mannitol's specific action in the renal system makes it the substance most directly associated with affecting renal vascular resistance.