Albumin is a protein that remains In the bloodstream, so would be a good tool to measure blood (plasma) volume, but it already is present to some extent. Suppose the albumin content of a patient’s blood Is measured to be 4.5g/dl. If you administer an IV with 10g/l albumin you might expect a rise In blood albumin to happen quickly, since the entire blood volume is pumped each minute (on average). Also, albumin is not normally excreted In urine so would be expected to remain in the blood vessel compartment. Now let’s suppose after 30 minutes you draw and measure the patient’s blood and find 4.7g/dl. What was that patient’s plasma volume? ” Aha”, you say, ” what was 10g/L has added 0.2 g/dl, and that’s 1/50^th” as concentrated therefore our patient holds SOL of plasma!” Would you be right? Hmmm, let’s think about this another way. Say you have a cup of beads but you don’t know how many there are. If you added 10 red beads and mixed well, then drew a sample of 10 beads at random, you might find 2 of the red beads you added. This would predict the total number of beads to be 5 times what you added (but. you might need to subtract the 10 you added from this to be accurate). Now calculate the patient’s blood volume based on the added albumin you found: One last consideration is that not all of the blood volume (or the sample of blood you withdrew) is plasma. You have to account for the hematocrit. Assuming a “normal hematocrit of 45%, what is the volume of plasma alone? If you subtracted the plasma volume from total fluid volume of the body, would what’s left represent the intracellular fluid volume? Why or why not?