RenalGuard-Guided Diuretic Dosing in ADHF Intrigues, Challenges Practice

May 30, 2018

VIENNA — A novel device–based technique for guided diuretic dosing might avoid some pitfalls of aggressive diuresis in patients with acute decompensated heart failure (ADHF), results of a small feasibility study suggest.

The idea, which some observers here at the European Society of Cardiology Heart Failure (ESC-HF) 2018 sessions met with cautious optimism, others with skepticism, is to use the RenalGuard system (RenalGuard Solutions) to guide clinicians in titrating intravenous (IV) diuretic administration to a preset urine-output target.

To that end, the device, originally designed to minimize contrast-induced nephropathy at angiography, constantly measures urine output and, as needed, can hydrate the patient in a measured way through a fixed IV line.   

Hopes are that RenalGuard guidance can optimize diuretic efficiency in ADHF by achieving robust diuresis at a reduced overall dosage, avoiding diuretic resistance while preserving intravascular fluid volume enough to support cardiac output.

The process was feasible and safe in the nine reported patients, and their symptom and biomarker responses over 24 hours were at least promising for the technique, Piotr Ponikowski, MD, PhD, Medical University, Wroclaw, Poland, reported here.

In practice, it's hard to get the right IV diuretic dosing to achieve the best degree of diuresis for individual patients, Ponikowski explained to | Medscape Cardiology. Too much diuretic administration can rapidly deplete intravascular fluid volume, triggering hormonal mechanisms that preserve sodium and water, leading to diuretic resistance — or so he and some others believe, he said.

The RenalGuard system automatically provides fluid through a standing IV line based on measured urine output to achieve a degree of net volume loss that may not lead to diuretic resistance.

Giving any more fluid is at odds with the accepted paradigm in volume-overloaded dyspneic patients with acute decompensation, but "it is the paradigm that we are challenging," Ponikowski said.

The current study, which compared patients on diuretics before and after institution of RenalGuard, was designed simply "to prove the concept that we are able to increase urine production with the device," he said. It can be done safely in congested patients, the experience suggests, and "we believe that it is due to better control of intravascular function."

It's not ready to replace standard IV diuretic dosing practice or ultrafiltration in ADHF, "but I do think there is something to this technology," Maria Rosa Costanzo, MD, Midwest Heart Specialists, Naperville, Illinois, told | Medscape Cardiology.

"I think that ultimately, the value of this technology will be in increasing diuretic efficiency, that is, how much fluid can you take out per milligram of any given diuretic," she said.

"And I think that in future studies it will be essential to measure urinary sodium. If the concept works, you should be seeing more sodium in the urine as the therapy is delivered," said Costanzo, who wasn't involved in the current patient series.

"It has some theoretical appeal but I'm not sure how much practical appeal it has," said G. Michael Felker, MD, Duke University, Durham, North Carolina, in an interview here.

"There probably are patients who get diuresed too fast," but in practice, filling pressures are almost never low, said Felker, a primary investigator with the DOSE trial. "So I'm not sure how often true intravascular volume depletion occurs."

As assigned discussant after Ponikowski's presentation of the study, Veli-Pekka Harjola, MD, PhD, Helsinki University Central Hospital, Finland, agreed that RenalGuard-guided diuretic dosing "challenges the concept of trying to minimize volume input during the management of acute heart failure."

But most patients with ADHF are fluid-overloaded, so "we should not be afraid of this overdiuresis and intravascular depletion."

Still, Harjola said, the current study "opens a door in the field of acute heart failure management. We still don't know where the door leads to, and how big a room is waiting there, but it truly needs a randomized controlled trial approach and further testing of this elegant hypothesis."

The study entered eight men and one woman with ADHF by symptoms and natriuretic-peptide elevations. Their estimated glomerular filtration rates (eGFR) ranged from 25 to 90 mL/min/1.73 m2.

They were managed conventionally for at least 24 hours, after which RenalGuard was engaged. Patients were given a 40-mg IV bolus of furosemide and managed by standard practice for the first hour.

Thereafter, clinicians gave diuretics according to their judgment to keep the RenalGuard-monitored balance of urine output and IV infusion aimed at a net fluid output of 100 mL/h. Diuretic dosing and even the target net fluid loss could be tweaked based on clinician evaluation of the patient's symptoms.

Throughout 24 hours of RenalGuard-guided management, all patients showed significant improvements in dyspnea scores, jugular venous pressure, and degree of peripheral edema compared to how they fared in the prior 24 hours, Ponikowski said. Urine output was sharply higher, and diuretic efficiency also improved significantly.

Table. Diuretic Use and Volume Changes During 24 Hours Before RenalGuard vs First 24 Hours on RenalGuard

Parameter 24 h Before RenalGuard First 24 h on RenalGuard P Value
Total furosemide dose (mg) 82 125 <.05
24-h urine output (mL) 1961 4771 <.01
Net fluid lossa (mL) 1754 1597 NS
Diuretic efficiency (mL urine output per 40 mg furosemide) 998 1650 <.05
aVolume infused minus urine output.

NS = not significant.


Mean creatinine fell from 1.31 mg/dL at baseline to 1.17 mg/dL after 24 hours on RenalGuard, to 1.19 mg/dL by hospital discharge,  it then rose to 1.28 mg/dL by 30 days.

The mean eGFR rose from 64 to 66 mL/min/1.73 m2 from baseline to discharge, but individual changes in this small patient sample ranged from an increase of 42% to a decrease of 22%.

"It would be unfair to say that there's no risk" because there's always at least some risk with an IV line and Foley catheter, Ponikowski said, but there were no cases of hypovolemia, electrolyte imbalance, renal dysfunction, infection, or device malfunction. "No problems whatsoever," he said.

"I'm a little skeptical about the long-term ability of this to decongest patients better than we do with the normal methods," Felker said. But, he continued, "I think we need more innovation in this space, and I'm willing to be open to innovation."

Ponikowsi  discloses receiving fees for consulting from Cibiem and RenalGuard Solutions. Harjola and Felker had no relevant disclosures. Costanza recently disclosed that her institution received research grants through her from Baxter, Cardiokinetix, Impulse Dynamics, St Jude Medical, Novartis, and Respicardia and that she has consulted for St Jude Medical, Medtronic, and Respicardia.

European Society of Cardiology Heart Failure (ESC-HF) 2018. Late Breaking Trial I – Acute Heart Failure. Presented May 26, 2018.

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