How to become a diuretic ninja

by Sharad Patel August 23, 2020

Reading Time: 2 minutes

Professional Intensivist/Nephrologist/Dad, and very amateur surfer and coder.

Sam Epstein • Illustrator

Aspiring Medical Student and current Critical Care RN. Enjoys everything outdoors but can also be found inside nerding out on her medical education artwork

The Pre-brief

Strategies of diuresis are not created equal. This post will discuss different ways to diurese patients depending on the desired clinical outcome.

A little history…

55-year-old male with a history of CHF (EF of 20%) presents with dyspnea on exertion, an 8 kg weight gain, and evidence of pulmonary edema on chest Xray. On day 3 of admission, the patient is 3 liters negative but ultrasound assessment indicates ongoing venous congestion; further diuresis is needed. Assuming that a “Multiverse” exists, here are 4 alternate universes with differing electrolyte anomalies and the best strategy for each scenario.

Goal #1: Attain negative sodium and fluid balance while augmenting the correction of hyperkalemia and acidemia.

Mechanism: Furosemide (loop diuretic) and Metolazone (Thiazide diuretic) act synergistically to increase the distal delivery of sodium to the collecting duct(CD). Increased sodium at the CD leads to increased potassium and hydrogen excretion.
Net Result: Increased sodium and fluid excretion whilst alleviating the hyperkalemia and acidemia.

Goal #2: Attain negative sodium and fluid balance correcting hyponatremia and acidemia

Furosemide monotherapy blocks sodium reabsorption within the Loop of Henle but there will be subsequent reabsorption of sodium at the Distal Convuluted Tubule (DCT) and CD. The net result will be urine that is hypotonic to the serum which results in a rise in serum sodium. Increased sodium delivery to the CD increases potassium and hydrogen excretion.
The net result is a negative fluid balance with improvements in hyponatremia, hyperkalemia, and acidemia.

Goal #3: Achieve a negative sodium balance while preventing further hypokalemia and alkalemia

Furosemide and a potassium-sparing diuretic (Amiloride or Spironolactone) work synergistically to increase natriuresis by blocking sodium reabsorption at the CD. Potassium and hydrogen excretion will be reduced.
The net result is a negative sodium balance with potential improvements in hypokalemia and alkalemia.

Goal #4: Achieve negative sodium balance while preventing further hypokalemia, alkalemia, and hypernatremia

Furosemide and a potassium-sparing diuretic (Amiloride or Spironolactone) work synergistically to increase natriuresis by blocking sodium reabsorption at the CD. Potassium and hydrogen excretion will be reduced. Urine output is more isotonic as compared to Lasix monotherapy which reduces free water loss, therefore, making free water replacement more effective. (If potassium is normal or high, acetazolamide is the ideal agent).
The net result-negative sodium balance with the stability of the hypernatremia, hypokalemia, and alkalemia.