Final answer:
The correct answer is b. The IV solution should hang at least 12 inches above the needle insertion site, but can often be much higher, such as 1.61 meters, to ensure the fluid overcomes venous blood pressure and enters the vein.
Step-by-step explanation:
The correct answer to the question "IV solution should hang at least how high above the needle insertion site?" is At least 12 inches above the needle insertion site. However, in medical practice, the height at which an IV bag should be placed above the needle insertion site can significantly exceed 12 inches. For example, it might be as high as 1.61 meters (which is approximately 63 inches) to overcome the blood pressure in a vein that is 18 mm Hg above atmospheric pressure, ensuring that the fluid just enters the arm. This is based on the SI unit conversion where 1.0 mm Hg equals 133 Pascal (Pa), and considering that the fluid administered has a density of 1.00 g/ml, as in typical intravenous infusions.
Furthermore, IV bags may be placed slightly higher than just the minimum height to account for patient movement and to regularly ensure a gravity-driven flow, given that IV infusions rely on gravity. The bags used for blood collection, on the other hand, are placed below the donor, as they require the flow to go in the opposite direction from that used in IV infusions.