Final answer:
The height at which an IV bag must be placed to overcome a venous pressure of 18 mm Hg is 0.24 m above the entry point into the vein.
Step-by-step explanation:
When determining the appropriate height at which to place an IV bag above the entry point into a vein for fluid administration, we must consider the pressure needed to facilitate fluid entry. Given that the blood pressure in the vein is 18 mm Hg above atmospheric pressure, and the density of the fluid being administered is 1.00 g/ml, the corresponding height can be calculated using the formula for pressure due to a fluid column, P = hρg, where P is the pressure, h is the height of the fluid column, ρ is the density of the fluid, and g is the acceleration due to gravity. Converting the required blood pressure from mm Hg to Pascals (1 mm Hg = 133 Pa), and solving for h, results in a necessary height of 0.24 m for the surface of the saline solution in the IV bag to exert enough pressure to overcome the venous pressure and just enter the vein. For safety and practicality, IV bags are often placed higher than this minimum height.