Podcast #141 - Furosemide (Frusemide) Mythbusting

Furosemide (frusemide) is a commonly used loop diuretic.  Also known by the commercial name, Lasix, it is well established drug but is prone to some common myths.  To help kill the dogma, we review a recently published paper discussing 10 myths regarding this frequently used medication.

Check out the paper published in Intensive Care Medicine on January 14, 2019 titled 10 Myths About Frusemide.  Surprisingly, this article did not get much attention by the #FOAMed world, but here is a brief summary of an already succinct article.

#1 - Furosemide causes AKI
Inappropriate used of diuretics in hypovolemic patients can contribute to the development of acute kidney injury (AKI), but when used in appropriate patients with fluid overload it can help improve or resolve the patient's AKI.  The rationale for this includes multiple bodies of evidence where diuretics can prevent tubular obstruction, reduce medullary oxygen consumption and increase renal blood flow as well as reduce fluid overload and venous congestion.

#2 -  Furosemide and fluids together can prevent AKI in high-risk patients
Although it is commonly believed that giving both furosemide and fluids together will avoid hypovolemia and thus AKI, it has not been demonstrated to be the case in actual evidence.  Fluids should be used for intravascular hypovolemia and diuretics for those with intravascular hypervolemia.

#3 - Furosemide is contraindicated in AKI
Tying in with the points above, this is also a myth.  This medication plays several roles.  It may require even higher doses especially in severe AKI.  Furosemide plays a role in managing hyperkalemia and as a stress test to assess tubular function and risk of progression to higher stages of AKI.

#4 - Furosemide can kick-start kidney function
While furosemide can lead to significant diuresis, this reflects functioning tubular cells and not the drug's effect on renal function.  Patients not responsive to diuretics but with fluid overload should not be given repeat doses.

#5 - Furosemide works better if given together with albumin
Evidence is sparse, but furosemide is highly protein-bound and with severely low levels of albumin this could impair secretion of this medication into the tubular lumen.  A meta-analysis did find better fluid balance with co-administration in those with a low albumin, but some evidence is less convincing especially in those with normal albumin levels.

#6 - Furosemide infusion is more effective than furosemide boluses
While sustained diuresis is easier to achieve with continuous infusion, it does not appear to result in better outcomes for patients.

#7 - Furosemide can prevent renal replacement therapy (RRT)
A systematic review and meta-analysis did demonstrate that loop diuretics such as furosemide were associated with a shorter duration of RRT and increased urine output but did not improve mortality or the rate of independence from RRT.  The SPARK study also demonstrated it does not help patients with early AKI needing RRT or having further worsening of their AKI.

#8 - Furosemide helps to wean anuric patients from RRT
Given the risk of ototoxicity, especially in anuric patients with increased risk of furosemide accumulation, diuretics do not appear to be effective at improving creatinine clearance or inducing renal recovery. 

#9 - Furosemide-induced diuresis after AKI implies full renal recovery
Furosemide can lead to increased urinary output in AKI, but this is not a sign of full or permanent recovery as there remains an increased risk of chronic kidney disease and increased mortality.

#10 - Furosemide ​ should be stopped if serum creatinine is increasing, indicating worsening renal function
This one can be confusing, but since creatinine is measured as a concentration in serum, and isolated increase in combination with a rise in hematocrit can be a sign of reduction in intravascular volume and effective decongestion.  The FACTT trial further supported this claim where RRT was lower in the group with increased serum creatinine with high diuretic dosing.

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