Jared Swollen, suffering from chronic renal failure, was in the hospital in seri

Question

Jared Swollen, suffering from 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.
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.
c)      Why does this patient have pitting edema?
d)      What symptoms might result from hypernatremia (high blood-sodium level)?
e)      How is this patient's interstitial edema in the lungs affected by his already-weakened heart?

Explanation / Answer

a) The intravenous fluid given to the patient contained high concentrations of sodium and chloride. As both sodium and potassium ions can diffuse freely between plams and interstitial fluid, therefore any increase in the level of sodium and potassium concentration of plasma will lead to an increase in the sodium and potassium concentration of interstitial fluid. Therefore, the nurse's mistake will lead to tncrease in the saltiness of the interstitial fluid.

b) As the interstitial fluid has become hypertonic in relation to intracellular fluid, it will lead to exosmosis which will cause water to move out of the cells into interstitial fluid. Therefore osmosis will cause shrinkage of the cells. Due to this, there might be lead to distortion of the vital organelles required for appropriate cell functioning.

c) Due to hypertonic saline, the sodium concentration of the plasma and interstitial fluid increased in level. Increase in sodium concentration of the plasma leads to passive osmosis, due to which water moves from the kidney tubules to the peritubular capillaries of the kidneys. The blood volume and the blood pressure increases which leads to movement of water from the plasma to the interstial spaces. This results in the patient developing pitting edema.

d) Hypernatremia laeds to osmotic shrinkage of the cells due to which there is shrinkage of the brain and symptoms associated with the central nervous system. Therefore the patient might experience lethargy, convulsions, coma and confusion.

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