Show notes
CardioNerds, Amit Goyal and Daniel Ambinder, join Duke University CardioNerds Ambassador and Correspondent, Dr. Kelly Arps for the diuretic showdown of a lifetime. Join us for this Cardiology vs. Nephrology discussion and respective approach to volume overload and diuretic strategies with Dr. Michael Felker (Professor of Medicine with tenure in the Division of Cardiology at Duke University School of Medicine), and Dr. Matt Sparks (Founding member of the Nephrology Social Medial Collective and #NephJC and Associate Professor of Medicine and Program Director for the Nephrology Fellowship Program at Duke University School of Medicine). Episode introduction, audio editing and Approach to Diuretic Resistance infographic by Dr. Gurleen Kaur (Director of the CardioNerds Internship).
Volume overload is a common indication for hospitalization in patients with heart failure. Loop diuretics are first line therapy for volume overload in heart failure, with assessment for adequate response within 3-6 hours after administration. Elevation in creatinine is common with venous congestion as well as during decongestion. While other causes of renal injury should be considered, an elevated creatinine in this context should not automatically trigger avoidance or cessation of diuresis. Diuretic resistance is an exaggerated form of natural safety mechanisms in the face of diuresis. Strategies for addressing diuretic resistance include optimizing dose and frequency of loop diuretic administration, adding adjunctive medication for sequential nephron blockade (i.e., thiazide diuretic, potassium sparing diuretic, acetazolamide, tolvaptan, SGLT2 inhibitor), and, in refractory cases, hemodialysis with ultrafiltration. In the outpatient setting, transition to a more potent loop diuretic (i.e., torsemide or bumetanide from furosemide), addition of a mineralocorticoid antagonist, or intermittent dosing of thiazide diuretic may augment maintenance diuretic therapy for patients with diminished response to loop diuretics.
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Pearls - Cardiology vs Nephrology: A Diuretic Showdown
Elevation in creatinine is expected in both congested states and during diuresis. Do not avoid or stop diuresis in a patient who is clearly volume overloaded based on an elevated creatinine. There may be a role for right heart catheterization if the fluid and/or hemodynamic status is unclear. Alkalosis in the setting of loop diuretic administration and diuretic resistance may represent a natural response to loop diuretics and not volume depletion. Ensure adequate potassium repletion and try using a mineralocorticoid antagonist to correct this alkalosis. Acetazolamide is rarely necessary but may be of use.Currently available evidence does not support extreme fluid or salt restriction in hospitalized patients with volume overload. Consider permissive restrictions and focus on choosing appropriate diuretic dosing for each individual patient. Diuretic resistance is an exaggerated form of diuretic braking, the kidney’s natural response to prevent dangerous degrees of sodium loss from the NKCC2-blocking effects of loop diuretics. Torsemide has improved bioavailability and duration of action compared to furosemide and may be a good choice for outpatient therapy in patients with limited diuretic response.
Quotable - Cardiology vs Nephrology: A Diuretic Showdown
Permissive hypercreatinemia
Eventually the…body recognizes that, Hey, if we're going to live without this very important, cotransporter in KCC2, we're going to have to kick on things in the distal nephron to basically have a steady state. - Dr. Sparks
I would rather the patient feel good with a creatinine of 2 than terrible with creatinine of 1 and a half. - Dr. Felker
I think it's pretty clear that in the long run, if they're accompanied by effective decongestion, [minor elevations in creatinine] are actually if anything, a favorable prognostic indicator in terms of heart failure, prognosis, as opposed to an adverse one. - Dr. Felker
I think we hit a record for that. The most number of times a cardiologist has mentioned urine and measuring something in the urine. - Dr. Sparks
I can tell you my experience and it's biased because I take care of people with pretty bad heart failure, but nine times out of 10, if we do a right-heart cath, because we're not sure if the patient is still volume overloaded, they still are. - Dr. Felker
The more, when you look at the data, the more high quality, the study design, so randomized versus non-randomized, uh, the worst sodium and fluid restriction look. The one thing we are guaranteed to do though, is create unhappy patients. - Dr. Felker
Show notes - Cardiology vs Nephrology: A Diuretic Showdown
1. Approach to diuretic therapy for inpatients with volume overload
Evaluate for non-cardiac sources of edema (nephrotic syndrome, hepatic dysfunction, VTE, etc).Choose a starting dose of loop diuretic. The effective home dose is a helpful guide.Evaluate diuretic response within 2-3 hours of each dose. If inadequate response, double the next dose of loop diureticIf inadequate or diminishing response to high-dose loop diuretic, consider additional pharmacotherapies (discussed below) Consider right heart catheterization whenConcerned for low output state Exam is unclear for volume status
2. Initial dose of diuretic therapy for hospitalized patients
The kidney alters its compensatory mechanisms to avoid being poisoned by too much blockade of important transporters like NKCC-2 (loop diuretic) and NCC (thiazide diuretics).
Start with at least double the patient’s maintenance dose of diuretic Patients on chronic high-dose diuretics need higher initial IV dosesPatients with CKD need higher doses of diuretic
3. Evaluating for adequate response to diuretic in a hospitalized patient
2-3 hours after the dose: Urine output: should be >150 mL / hour in the 2-3 hours after an adequate diuretic dose. Spot urine sodium: should be >50-70 mmol/L after an adequate diuretic dose
Daily: assess for improvement in jugular venous distension, lower extremity edema, weight, calculated ratio of fluid intake to output, and symptoms (orthopnea, dyspnea on exertion).
4. Approach to elevated creatinine in a volume overloaded patient
Evaluate for alternative causes of hypercreatinemia: urinary obstruction, nephrotoxic agents (i.e. IV contrast, antibiotics, NSAIDs).
If exam and/or invasive hemodynamic data are consistent with volume overload, renal vascular congestion may be contributing to elevated creatinine, and is expected to improve with euvolemia.
5. Approach to ‘contraction alkalosis’ in a patient undergoing diuresis
Alkalosis in the setting of loop diuretic administration and diuretic resistance may not indicate volume depletion.
Diuretics increase delivery of sodium to the distal nephron, which accelerates potassium and proton secretion and results in bicarbonate reclamation, resulting in hypokalemic metabolic alkalosis. Diuresis triggers activation of the renin-angiotensin system, which increases apical ATPase activity, increasing hydrogen ion secretion into the urine. Repleting potassium (with potassium chloride, not potassium citrate) can correct metabolic alkalosis. Use of mineralocorticoid receptor antagonists can improve this metabolic alkalosis.Acetazolamide may be used in refractory cases with severe metabolic alkalosis.
6. Approach to hyponatremia in heart failure
Consider reasonable degree of fluid restriction (available evidence does not support extreme fluid restriction. Pharmacotherapy options for extreme hyponatremia includes urea and tolvaptan.
7. Causes of diuretic resistance
Processes outside the nephron: venous congestion, low-output heart failure, hypoalbuminemia, increased intraabdominal pressureIntra-renal causes (response to sodium loss, caused by NKCC2 blockade by loop diuretics): reflexive upregulation of sodium intake in the proximal tubule, increased expression of sodium reabsorption channels (e.g., ENAC, NCC, pendrin)
8. Treatment options for diuretic resistance
Increase dose +/- frequency of loop diureticThiazide diuretic (and monitor electrolytes closely)Potassium sparing diuretic (i.e., spironolactone, amiloride)Tolvaptan SGLT2 inhibitor (“a diuretic enabler”)
Oral loop diuretics
FurosemideBumetanideTorsemidePO: IV conversion~2:11:11:1Dose ratio (to furosemide)---1:401:2Bioavailability in oral dosingWidely variableNearly 100%Nearly 100%
References - Cardiology vs Nephrology: A Diuretic Showdown
Reviews
Ellison DH, Felker GM. Diuretic Treatment in Heart Failure [published correction appears in N Engl J Med. 2018 Feb 1;378(5):492]. N Engl J Med. 2017;377(20):1964-1975. doi:10.1056/NEJMra1703100
Felker GM, Ellison DH, Mullens W, Cox ZL, Testani JM. Diuretic Therapy for Patients With Heart Failure: JACC State-of-the-Art Review. J Am Coll Cardiol. 2020;75(10):1178-1195. doi:10.1016/j.jacc.2019.12.059
Trials
3T trial: Cox ZL, Hung R, Lenihan DJ, Testani JM....
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