A 64-year-old woman with a history of two previous myocardial infarctions comes to the emergency room with shortness of breath. In the previous 2 weeks, she has developed dyspnoea with exertion and swelling of her legs. She sleeps on three pillows because she coughs and gets shortness of breath if she tries to lie flat. In the emergency department, she is sitting upright, appears to be in moderate respiratory distress, and is tachycardic and hypertensive. She has jugular venous distension to the angle of her jaw. On auscultation of her lungs, wet rales are heard bilaterally. She has pitting edema of both lower legs up to her knees. A chest X-Ray confirms the diagnosis of pulmonary edema. She is placed on oxygen and immediately given an IV injection of furosemide.

2.  A 64-year-old woman with a history of two previous myocardial
infarctions comes to the emergency room with shortness of
breath. In the previous 2 weeks, she has developed dyspnoea
with exertion and swelling of her legs. She sleeps on three
pillows because she coughs and gets shortness of breath if she
tries to lie flat. In the emergency department, she is sitting
upright, appears to be in moderate respiratory distress, and is
tachycardic and hypertensive. She has jugular venous distension
to the angle of her jaw. On auscultation of her lungs, wet rales
are heard bilaterally. She has pitting edema of both lower legs
up to her knees. A chest X-Ray confirms the diagnosis of
pulmonary edema. She is placed on oxygen and immediately
given an IV injection of furosemide.

3. Questions
1. What is the mechanism of action of
furosemide?
2. What electrolyte abnormalities can be caused
by furosemide?

4. Summary
 A 64-year-old woman with pulmonary
edema is prescribed furosemide.

5. Mechanism of action of
furosemide
 Inhibit active NaCl reabsorption in the
ascending limb of loop of Henle, increasing
water and electrolyte excretion

6. Potential electrolyte abnormalities
 Hypokalemia
 Hypomagnesemia
 Metabolic alkalosis because of enhanced H+
excretion