Ed Rivers, a third-year medical student, was alone in the hospital emergency room one night.  It was unusually quiet in the ER, so the residents were getting some much-needed sleep.  A patient, Ms. B., was brought in showing signs of serious dehydration.  Ed tried to give her water but she vomited.  Feeling that he must try something else and not wanting to wake the residents, he administered 1 liter (L) of sterile distilled water intravenously (IV).  

The questions that follow are aimed at determining the consequences of Ed’s action. Assume for simplicity that red blood cells (RBC) contain only solutes to which the RBC membrane is impermeable. The osmolarity of the RBC, the concentration of solute particles, is 300 mOsm/L.

Predict the direction of change (Increase, Decrease, No Change) you would expect Ed’s infusion to have produced on and explain the reasoning for your answer –

a)     (2 points) Ms. B’s plasma osmolarity after the infusion ___________________________.

b)    (2 points) Ms. B’s RBC volume after the infusion equilibrates with blood ____________________.

(In both cases be sure to explain your answer).

Ms. B. got much worse after Ed’s treatment so the head resident was called in.  She drew blood from the patient and centrifuged it.  The denser RBC‘s were forced to the bottom of the tube.  The supernatant plasma was PINK!

a)     (2 points) Why was the patient’s plasma pink?

b)    (2 points) After seeing the supernatant the Head Resident gave the patient “glucose”. Why would this help?