Ed Rivers, a 3rd year medical student, was alone in the hospitalER one night. It was unusually quiet that night, and the residentwas getting some much needed sleep. A patient, Mrs. X, was broughtin showing signs of serious dehydration. Ed tried to give herewater, but she vomited this back up. Feeling he must try something,and not wanting to wake the resident, Ed administered 1 liter ofsterile distilled water IV. Assume for simplicity that the redblood cells contain only solutes to which the rbc membrane isimpermeable, and that the rbcs and plasma are in osmoticequilibrium when the patient is brought in. The osmolarity of therbc is 300 mOsm/L.
The volume of Mrs.X's plama was 3 liters before Ed administeredthe IV. Assume there was a complete mixing of the administeredwater with her plasma but no mixing with her interstitialfluid.
Calculate Mrs.X's plasma osmolarity after the infusion mixed with her plasma butbefore any water ebtered the red blood cells.Hint: what wasthe total # of mOsm in her plasma before infusion? Once the plasmavolume is increased by 1 liter, the total # of mOsm remains thesame but the volume has changed. Now what is the new osmolarity(mOsm/L?)
Ed Rivers, a 3rd year medical student, was alone in the hospitalER one night. It was unusually quiet that night, and the residentwas getting some much needed sleep. A patient, Mrs. X, was broughtin showing signs of serious dehydration. Ed tried to give herewater, but she vomited this back up. Feeling he must try something,and not wanting to wake the resident, Ed administered 1 liter ofsterile distilled water IV. Assume for simplicity that the redblood cells contain only solutes to which the rbc membrane isimpermeable, and that the rbcs and plasma are in osmoticequilibrium when the patient is brought in. The osmolarity of therbc is 300 mOsm/L.
The volume of Mrs.X's plama was 3 liters before Ed administeredthe IV. Assume there was a complete mixing of the administeredwater with her plasma but no mixing with her interstitialfluid.
Calculate Mrs.X's plasma osmolarity after the infusion mixed with her plasma butbefore any water ebtered the red blood cells.Hint: what wasthe total # of mOsm in her plasma before infusion? Once the plasmavolume is increased by 1 liter, the total # of mOsm remains thesame but the volume has changed. Now what is the new osmolarity(mOsm/L?)
