History:A 68-year-old man with chronic renal failure was in the
hospital in serious condition recovering from a heart attack. He had just
undergone "balloon angioplasty" to redilate his left coronary artery,
and was thus on an "npo" diet (i.e. he was not allowed to have food or
drink by mouth). He received fluid through an intravenous (IV) line.
Late one night, a weary nurse who was on the 11th hour of a 12-hour shift
came into the patient's room to replace the man's empty IV bag with a
new one. Misreading the physician's orders, he hooked up a fresh bag of
IV fluid that was "twice-normal" saline rather than "half-normal" saline
(in other words, the patient starting receiving a fluid that was four
times saltier than it should have been). This mistake was not noticed
until the following morning. At that time, the man had marked pitting
edema around the sacral region and had inspiratory rales ("wet-sounding
crackles") at the bases of the lungs on each side. He complained that
it was difficult to breathe as well. Blood was drawn, revealing the following:
A chest x-ray revealed interstitial edema in the lungs.
1. Most dissolved
substances in the blood plasma can easily move out of the bloodstream
and into the interstitial fluid surrounding the cells. A. Will the nurse's mistake increase or decrease the "saltiness" of the interstitial fluid?
B. Given your knowledge
of osmosis, will this cause the cells in the body to increase or decrease
in size? Explain your answer. 2. Why does this patient
have pitting edema and inspiratory rales?
3. How would this
increase in salt load affect the patient's blood-aldosterone level? In
your answer, explain the function of the hormone aldosterone.
Answer
5.
What symptoms might result from hypernatremia ("high blood-sodium" level)?
6. How is this patient's
interstitial edema in the lungs affected by his already-weakened heart?
Chief
Complaint:68-year-old man with breathing problems
Na+
157 mEq / liter (Normal = 136-145 mEq / liter)
K+
4.7 mEq / liter (Normal = 3.5-5.0 mEq / liter)
C1-
101 mEq / liter (Normal = 96-106 mEq / liter)
4. Can you think of any other normal mechanisms that the body has to control
salt and water balance? How might they react in this situation?
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