Tuesday morning report at the VA was all about diuretics. We presented a case of a 73-year-old man with history of CHF, CKD and T2DM who presented with progressive dyspnea, bilateral lower extremity swelling, orthopnea, and abdominal distension. Physical exam showed evidence of volume overload with 3+ pitting edema, elevated JVD, and bibasilar pulmonary crackles. We considered various common triggers of heart failure exacerbation before diving into a discussion of diuretics.
Key points that we highlighted:
- Decongestion with resolution of symptoms and edema is achieved through “diuresis” = loss of sodium (natriuresis) + loss of water (diuresis). That is why sodium-limited diet is crucial in treatment of fluid overload.
- Loop diuretics function as “threshold” drugs that need to achieve a sufficient concentration in order to work. The natriuretic threshold is higher in patients with acute CHF than in healthy persons. That is why hospitalized patients require loop diuretic doses that are higher than stable outpatient doses.
- Loop diuretics exhibit a “ceiling” effect and doses above the ceiling will not increase the amount of natriuresis. Acute CHF shifts the relation between plasma diuretic concentration and sodium excretion to the right and reduces the “ceiling.”
- Patients with chronic diuretic use develop post-diuretic sodium retention and decreased efficacy with each subsequent loop diuretic dose. That is why loop diuretics are dosed multiple times daily and why patients need a net negative sodium balance each day.
- Chronic loop diuretic use leads to distal tubular hypertrophy and once maximum loop diuretic effect is reached, auxiliary diuretics are sometimes used (thiazide, aldosterone antagonists, carbonic anhydrase inhibitors). We discussed specific situations you may consider using these agents.
- Ethacrynic acid is the loop diuretic of choice in patients with sulfa allergy.
For further reading, check out this review from the NEJM:
Ellison DH, Felker GM. Diuretic Treatment in Heart Failure. N Engl J Med. 2017 Nov 16;377(20):1964-1975.