Markers of diuretic resistance in emergency department patients with acute heart failure

A Phenomapping Tool and Clinical Score to Identify Low Diuretic Efficiency in Acute Decompensated Heart Failure

BACKGROUND

Individuals with acute decompensated heart failure (ADHF) have a varying response to diuretic therapy. Strategies for the early identification of low diuretic efficiency to inform decongestion therapies are lacking.

OBJECTIVES

The authors sought to develop and externally validate a machine learning-based phenomapping approach and integer-based diuresis score to identify patients with low diuretic efficiency.

METHODS

Participants with ADHF from ROSE-AHF, CARRESS-HF, and ATHENA-HF were pooled in the derivation cohort (n = 794). Multivariable finite-mixture model-based phenomapping was performed to identify phenogroups based on diuretic efficiency (urine output over the first 72 hours per total intravenous furosemide equivalent loop diuretic dose). Phenogroups were externally validated in other pooled ADHF trials (DOSE/ESCAPE). An integer-based diuresis score (BAN-ADHF score: blood urea nitrogen, creatinine, natriuretic peptide levels, atrial fibrillation, diastolic blood pressure, hypertension and home diuretic, and heart failure hospitalization) was developed and validated based on predictors of the diuretic efficiency phenogroups to estimate the probability of low diuretic efficiency using the pooled ADHF trials described earlier. The associations of the BAN-ADHF score with markers and symptoms of congestion, length of stay, in-hospital mortality, and global well-being were assessed using adjusted regression models.

RESULTS

Clustering identified 3 phenogroups based on diuretic efficiency: phenogroup 1 (n = 370; 47%) had lower diuretic efficiency (median: 13.1 mL/mg; Q1-Q3: 7.7-19.4 mL/mg) than phenogroups 2 (n = 290; 37%) and 3 (n = 134; 17%) (median: 17.8 mL/mg; Q1-Q3: 10.8-26.1 mL/mg and median: 35.3 mL/mg; Q1-Q3: 17.5-49.0 mL/mg, respectively) (P < 0.001). The median urine output difference in response to 80 mg intravenous twice-daily furosemide between the lowest and highest diuretic efficiency group (phenogroup 1 vs 3) was 3,520 mL/d. The BAN-ADHF score demonstrated good model performance for predicting the lowest diuretic efficiency phenogroup membership (C-index: 0.92 in DOSE/ESCAPE validation cohort) that was superior to measures of kidney function (creatinine or blood urea nitrogen), natriuretic peptide levels, or home diuretic dose (DeLong P < 0.001 for all). Net urine output in response to 80 mg intravenous twice-daily furosemide among patients with a low vs high (5 vs 20) BAN-ADHF score was 2,650 vs 660 mL per 24 hours, respectively. Participants with higher BAN-ADHF scores had significantly lower global well-being, higher natriuretic peptide levels on discharge, a longer in-hospital stay, and a higher risk of in-hospital mortality in both derivation and validation cohorts.

CONCLUSIONS

The authors developed and validated a phenomapping strategy and diuresis score for individuals with ADHF and differential response to diuretic therapy, which was associated with length of stay and mortality.

Therapeutic approach in heart failure with poor diuretic response: peripheral ultrafiltration vs. conventional treatment

AIMS

Patients with heart failure (HF) admitted for decompensation often require high doses of intravenous diuretics. This study aims to analyse whether the use of peripheral ultrafiltration (UF) in patients hospitalized for acute HF with systemic-predominant congestion results in better hydric control, renal protection, and reduction of hospital stay compared with conventional treatment.

METHODS AND RESULTS

This study was a retrospective, comparative, single-centre study of 56 patients admitted for HF with systemic congestion with a poor diuretic response after diuretic escalation. One group underwent peripheral UF (35 patients) and others were maintained on intense diuretic treatment (control group, 21 patients). The diuretic response and days of hospital stay were compared between and within groups. The baseline characteristics of both groups were similar: males with right ventricular failure and renal dysfunction. The inter-group analysis showed that patients who received UF had better glomerular filtration rate (GFR; UF: 39.2 ± 18.2 vs. control: 28.7 ± 13.4 mL/min; P = 0.031) and higher diuresis (UF: 2184 ± 735 vs. control: 1335 ± 297 mL; P = 0.0001) at hospital discharge despite less need for diuretic drugs. Days of hospital stay were shorter in the UF group (UF: 11.7 ± 10.1 vs. control: 19.1 ± 14.4 days; P = 0.027). Intra-group analysis showed that patients receiving UF improved GFR, increased diuresis, and reduced weight at discharge (P < 0.001), whereas patients on conventional treatment only experienced improved weight but worsening renal function at discharge.

CONCLUSIONS

In patients with acute HF with systemic congestion and diuretic resistance, UF compared with conventional treatment produces greater decongestion and renal protection, reduces the total diuretic load, and shortens the length of hospital stay.

Spot Urinary Sodium Measurements: the Future Direction of the Treatment and Follow-up of Patients with Heart Failure

PURPOSE OF REVIEW

Heart failure is characterized by episodes of congestion with need for hospitalization. The current metrics lack the accuracy to predict and prevent episodes of congestion and to guide diuretic titration to reach euvolemia in case of decompensation. This article aims to provide answers to the role of urinary sodium measurements in acute and chronic heart failure.

RECENT FINDINGS

In acute heart failure, urinary sodium concentrations at the moment of admission and after diuretic administration are correlated with short- and long-term outcome. As this is a reflection of the degree of sodium retention, it can be used as a guide in the diuretic titration. In chronic heart failure, it might be used to predict and consequently prevent episodes of decompensation. Urinary sodium measurements hold great promises to be a novel diagnostic and therapeutic parameter in patients with acute and chronic heart failure. However, more research is needed.

A Machine Learning Model to Predict Diuretic Resistance

BACKGROUND

Volume overload is a common complication encountered in hospitalized patients, and the mainstay of therapy is diuresis. Unfortunately, the diuretic response in some individuals is inadequate despite a typical dose of loop diuretics, a phenomenon called diuretic resistance. An accurate prediction model that predicts diuretic resistance using predosing variables could inform the right diuretic dose for a prospective patient.

METHODS

Two large, deidentified, publicly available, and independent intensive care unit (ICU) databases from the United States were used-the Medical Information Mart for Intensive Care III (MIMIC) and the Philips eICU databases. Loop diuretic resistance was defined as <1400 ml of urine per 40 mg of diuretic dose in 24 hours. Using 24-hour windows throughout admission, commonly accessible variables were obtained and incorporated into the model. Data imputation was performed using a highly accurate machine learning method. Using XGBoost, several models were created using train and test datasets from the eICU database. These were then combined into an ensemble model optimized for increased specificity and then externally validated on the MIMIC database.

RESULTS

The final ensemble model was composed of four separate models, each using 21 commonly available variables. The ensemble model outperformed individual models during validation. Higher serum creatinine, lower systolic blood pressure, lower serum chloride, higher age, and female sex were the most important predictors of diuretic resistance (in that order). The specificity of the model on external validation was 92%, yielding a positive likelihood ratio of 3.46 while maintaining overall discrimination (C-statistic 0.69).

CONCLUSIONS

A diuretic resistance prediction model was created using machine learning and was externally validated in ICU populations. The model is easy to use, would provide actionable information at the bedside, and would be ready for implementation in existing electronic medical records. This study also provides a framework for the development of future machine learning models.

Toward quantification of loop diuretic responsiveness for congestive heart failure

Diuretics, such as furosemide, are routinely administered to dogs with congestive heart failure (CHF). Traditionally, dose and determination of efficacy primarily are based on clinical signs rather than quantitative measures of drug action. Treatment of human CHF patients increasingly is guided by quantification of urine sodium concentration (uNa) and urine volume after diuretic administration. Use of these and other measures of diuretic responsiveness is associated with decreased duration of hospitalization, complication rates, future rehospitalization, and mortality. At their core, loop diuretics act through natriuresis, and attention to body sodium (Na) stores and handling offers insight into the pathophysiology of CHF and pharmacology of diuretics beyond what is achievable from clinical signs alone. Human patients with low diuretic responsiveness or diuretic resistance are at risk for difficult or incomplete decongestion that requires diuretic intensification or other remedial strategies. Identification of the specific etiology of resistance in a patient can help tailor personalized interventions. In this review, we advance the concept of loop diuretic responsiveness by highlighting Na and natriuresis. Specifically, we review body water homeostasis and congestion in light of the increasingly recognized role of interstitial Na, propose definitions for diuretic responsiveness and resistance in veterinary subjects, review relevant findings of recent studies, explain how the particular cause of resistance can guide treatment, and identify current knowledge gaps. We believe that a quantitative approach to loop diuretic usage primarily involving natriuresis will advance our understanding and care of dogs with CHF.

The association between urinary sodium concentration (UNa) and outcomes of acute heart failure: a systematic review and meta-analysis

AIMS

Urinary sodium concentration (UNa) is a simple test advocated to assess diuretics efficacy and predict outcomes in acute heart failure (AHF). We performed a systematic review and meta-analysis to examine the association of UNa with outcomes of AHF.

METHODS AND RESULTS

We searched Embase and Medline for eligible studies that reported the association between UNa and outcomes of urinary output, weight loss, worsening renal function, length of hospital stay, re-hospitalization, worsening heart failure, and all-cause mortality in AHF. Nineteen observational studies out of 1592 screened records were included. For meta-analyses of outcomes, we grouped patients into high vs. low UNa, with most studies defining high UNa as &gt;48-65 mmol/L. In the high UNa group, pooled data showed a higher urinary output (mean difference 502 mL, 95% CI 323-681, P &lt; 0.01), greater weight loss (mean difference 1.6 kg, 95% CI 0.3-2.9, P = 0.01), and a shorter length of stay (mean difference -1.4 days, 95% CI -2.8 to -0.1, P = 0.03). There was no significant difference in worsening kidney function (OR 0.54, 95% CI 0.25-1.16, P = 0.1). Due to the small number of studies, we did not report pooled estimates for re-hospitalization and worsening heart failure. High UNa was associated with lower odds of 30-day (OR 0.27; 95% CI 0.14-0.49, P &lt; 0.01), 90-day (OR 0.39,95% CI 0.25-0.59, P &lt; 0.01) and 12-month (OR 0.35; 95% CI 0.20-0.61, P &lt; 0.01) mortality.

CONCLUSION

High UNa after diuretic administration is associated with higher urinary output, greater weight loss, shorter length of stay, and lower odds of death. UNa is a promising marker of diuretic efficacy in AHF which should be confirmed in randomized trials.

Pharmacokinetic and pharmacodynamic properties of orally administered torasemide in healthy cats

BACKGROUND

In people and dogs, torasemide has higher bioavailability, longer half-life, and longer duration of action than equivalent doses of furosemide but data regarding pharmacological properties of torasemide in cats are limited.

OBJECTIVE

To assess pharmacokinetic and pharmacodynamic parameters of torasemide in healthy cats, and to investigate the effects of a single administration of torasemide on indicators of diuresis, plasma creatinine concentration, blood pressure, electrolyte concentrations and markers of the renin-angiotensin-aldosterone system (RAAS).

ANIMALS

Six clinically healthy adult European shorthair cats.

METHODS

Randomized 4-period crossover design with 3 groups and 4 treatments. Pharmacokinetic parameters were obtained using a noncompartmental analysis, and the clinically effective dose was assessed using a Hill model.

RESULTS

Mean absolute bioavailability was estimated at 88.1%. Mean total body clearance was 3.64 mL/h/kg and mean terminal half-life was 12.9 hours. Urine output significantly increased after torasemide administration (P < .001). The urine sodium : potassium ratio (uNa : uK) paralleled and was statistically correlated to urine output (P < .001). Administration of a single torasemide dose led to a significant dose-dependent increase in urine aldosterone : creatinine ratio (uAldo : C; P < .001) and a transient decrease in plasma potassium concentration (P < .001) but did not affect blood pressure or plasma creatinine concentration.

CONCLUSIONS AND CLINICAL IMPORTANCE

A single torasemide dose leads to a significant increase in diuresis and renin-angiotensin-aldosterone system (RAAS) activation in healthy cats, with high absolute bioavailability, and without clinically relevant adverse effects. Pharmacokinetic parameters indicate that once daily dosing of 0.27 mg/kg may be appropriate in a clinical setting.

Clinical relevance of serum electrolytes in dogs and cats with acute heart failure: A retrospective study

Background

Hypochloremia is a strong negative prognostic factor in humans with congestive heart failure (CHF), but the implications of electrolyte abnormalities in small animals with acute CHF are unclear.

Objectives

To document electrolyte abnormalities present upon admission of small animals with acute CHF, and to assess the relationship between electrolyte concentrations and diuretic dose, duration of hospitalization and survival time.

Animals

Forty‐six dogs and 34 cats with first onset of acute CHF.

Methods

Retrospective study. The associations between electrolyte concentrations and diuretic doses were evaluated with Spearman rank correlation coefficients. Relationship with duration of hospitalization and survival were assessed by simple linear regression and Cox proportional hazard regression, respectively.

Results

The most commonly encountered electrolyte anomaly was hypochloremia observed in 24% (9/46 dogs and 10/34 cats) of cases. In dogs only, a significant negative correlation was identified between serum chloride concentrations at admission (median 113 mmol/L [97‐125]) and furosemide doses both at discharge (median 5.2 mg/kg/day [1.72‐9.57]; r = −0.59; P < .001) and at end‐stage heart failure (median 4.7 mg/kg/day [2.02‐7.28]; r = −0.62; P = .005). No significant hazard ratios were found for duration of hospitalization nor survival time for any of the electrolyte concentrations.

Conclusions and Clinical Importance

The observed association between serum chloride concentrations and diuretic doses suggests that hypochloremia could serve as a marker of disease severity and therapeutic response in dogs with acute CHF.

Effect of spironolactone and benazepril on furosemide-induced diuresis and renin-angiotensin-aldosterone system activation in normal dogs

Background

Diuretic braking during furosemide continuous rate infusion (FCRI) curtails urine production.

Hypothesis

Renin‐angiotensin‐aldosterone system (RAAS) activation mediates braking, and RAAS inhibition will increase urine production.

Animals

Ten healthy purpose‐bred male dogs.

Methods

Dogs received placebo, benazepril, or benazepril and spironolactone PO for 3 days before a 5‐hour FCRI (0.66 mg/kg/h) in a 3‐way, randomized, blinded, cross‐over design. Body weight (BW), serum creatinine concentration (sCr), serum electrolyte concentrations, PCV, and total protein concentration were measured before PO medications, at hours 0 and 5 of FCRI, and at hour 24. During the FCRI, water intake, urine output, urine creatinine concentration, and urine electrolyte concentrations were measured hourly. Selected RAAS components were measured before and after FCRI. Variables were compared among time points and treatments.

Results

Diuretic braking and urine production were not different among treatments. Loss of BW, hemoconcentration, and decreased serum chloride concentration occurred during FCRI with incomplete recovery at hour 24 for all treatments. Although unchanged during FCRI, sCr increased and serum sodium concentration decreased at hour 24 for all treatments. Plasma aldosterone and angiotensin‐II concentrations increased significantly at hour 5 for all treatments, despite suppressed angiotensin‐converting enzyme activity during benazepril background treatment.

Conclusions

The neurohormonal profile during FCRI supports RAAS mediation of diuretic braking in this model. Background treatment with benazepril with or without spironolactone did not mitigate braking, but was well tolerated. Delayed changes in sCr and serum sodium concentration and incomplete recovery of hydration indicators caused by furosemide hold implications for clinical patients.

Pharmacotherapeutic principles of fluid management in heart failure

Introduction: Heart failure is a major public health concern that is expected to increase over the decades to come. Despite significant advances, fluid overload and congestion remain a major therapeutic challenge. Vascular congestion and neurohormonal activation are intricately linked and the goal of therapy fundamentally aims to reduce both.Areas covered: The authors briefly review a number of core concepts that elucidate the link between fluid overload and neuro-hormonal activation. This is followed by a review of heart-kidney interactions and the impact of diuresis in this setting. Following an in-depth review of currently available pharmacological agents, the rationale and evidence behind their use, the authors end with a brief note on novel agents/approaches to aid volume management in HF.Expert opinion: A number of non-pharmacological advances in the management of volume overload in heart failure, though promising - are associated with a number of shortcomings. Pharmacological therapy remains the cornerstone of volume management. A number of novel approaches, utilizing existing therapies as well as the emergence of new agents over the past decade bode well for the vulnerable HF population.

Hypochloremia Secondary to Diuretics in Preterm Infants: Should Clinicians Pay Close Attention?

Diuretic therapy, commonly used in the newborn intensive care unit, is associated with a variety of electrolyte abnormalities such as hyponatremia, hypokalemia, and hypochloremia. Hypochloremia, often ignored, is associated with significant morbidities and increased mortality in infants and adults. Clinicians respond in a reflex manner to hyponatremia than to hypochloremia. Hypochloremia is associated with nephrocalcinosis, hypochloremic alkalosis, and poor growth. Besides, the diuretic resistance associated with hypochloremia makes maintaining chloride levels in the physiological range even more logical. Since sodium supplementation counters the renal absorption of calcium and lack of evidence for spironolactone role in diuretic therapy for bronchopulmonary dysplasia (BPD), alternate chloride supplements such as potassium or arginine chloride may need to be considered in the management of hypochloremia due to diuretic therapy. In this review, we have summarized the current literature on hypochloremia secondary to diuretics and suggested a pragmatic approach to hypochloremia in preterm infants.

Prediction and measurement of diuretic responsiveness after oral administration of furosemide to healthy dogs and dogs with congestive heart failure

Background

In human patients, cumulative urine volume (uVol) and urine sodium (uNa) can be predicted using spot urine samples and these quantitative measures help detect low diuretic responsiveness (LDR).

Hypothesis/objectives

Formulas using spot urine samples predict cumulative uVol and uNa output after oral administration of furosemide to dogs.

Animals

Eight healthy dogs, 6 dogs with congestive heart failure (CHF).

Methods

Prospective interventional study. Spot urine samples at 180 and 270 minutes after furosemide (3 mg/kg PO) were used to predict cumulative uVol and uNa output over 7 hours. Differentiation of dogs fulfilling predefined criteria for LDR was examined using receiver operating characteristic (ROC) curves.

Results

Predicted uNa output at 180 minutes (r_s = 0.763, [95% confidence interval [CI], 0.375‐0.923], P = .002) and 270 minutes (r = 0.816, [95% CI, 0.503‐0.940], P < .001) was highly correlated to 7‐hour uNa output. Predicted uVol at 180 minutes (r = 0.598, [95% CI, 0.098‐0.857], P = .02) and 270 minutes (r = 0.791, [95% CI, 0.450‐0.931], P < .001) was moderately correlated to 7‐hour uVol. Predicted uNa using 180‐minute (area under the curve [AUC], 0.933 [95% CI, 0.804‐1.000]) and 270‐minute (AUC, 0.911 [95% CI, 0.756‐1.000]) samples identified dogs with LDR (n = 5) with high accuracy.

Conclusions and Clinical Importance

Urinary Na excretion and uVol are complementary but distinct aspects of diuretic responsiveness in dogs. Quantification of diuretic responsiveness in the clinical setting opens new diagnostic, treatment, and monitoring strategies.

The value of urinary sodium assessment in acute heart failure

Acute heart failure (AHF) is a frequent medical condition that needs immediate evaluation and appropriate treatment. Patients with signs and symptoms of volume overload mostly require intravenous loop diuretics in the first hours of hospitalization. Some patients may develop diuretic resistance, resulting in insufficient and delayed decongestion, with increased mortality and morbidity. Urinary sodium measurement at baseline and/or during treatment has been proposed as a useful parameter to tailor diuretic therapy in these patients. This systematic review discusses the current sum of evidence regarding urinary sodium assessment to evaluate diuretic efficacy in AHF. We searched Medline, Embase, and Cochrane Clinical Trials Register for published studies that tested urinary sodium assessment in patients with AHF.

Diuretic Resistance in Heart Failure

Decompensated heart failure accounts for approximately 1 million hospitalizations in the United States annually, and this number is expected to increase significantly in the near future. Diuretics provide the initial management in most patients with fluid overload. However, the development of diuretic resistance remains a significant challenge in the treatment of heart failure. Due to the lack of a standard definition, the prevalence of this phenomenon remains difficult to determine, with some estimates suggesting that 25-30% of patients with heart failure have diuretic resistance. Certain characteristics, including low systolic blood pressures, renal impairment, and atherosclerotic disease, help predict the development of diuretic resistance. The underlying pathophysiology is likely multifactorial, with pharmacokinetic alterations, hormonal dysregulation, and the cardiorenal syndrome having significant roles. The therapeutic approach to this common problem typically involves increases in the diuretic dose and/or frequency, sequential nephron blockade, and mechanical fluid movement removal with ultrafiltration or peritoneal dialysis. Paracentesis is potentially useful in patients with intra-abdominal hypertension.

Spot urinary sodium in acute decompensation of advanced heart failure and dilutional hyponatremia: insights from DRAIN trial

BACKGROUND

Diuretic resistance portends a poor prognosis in acute heart failure, especially in advanced stages. Early identification of a poor response to diuretics may help to improve treatment and outcomes. Spot natriuresis (UNa⁺) at 2 h from the start of intravenous furosemide has been proposed as an early indicator of diuretic response. Our paper aimed to determine the role of early natriuresis in patients hospitalized with advanced chronic heart failure (ACHF) and high risk of diuretic resistance.

METHODS AND RESULTS

We performed a sub-analysis of the DRAIN trial, a randomized clinical trial on 80 patients with acute decompensation of ACHF (NYHA IV, EF ≤ 30%) with low systolic blood pressure (≤ 110 mmHg) and dilutional hyponatremia (sodium ≤ 135 mMol/L) at admission. Patients were divided into two groups according to spot urinary sodium excretion (high: UNa⁺  > 50 or low: ≤ 50 mEq/L) at 2 h from furosemide administration. Twenty-eight patients (35%) showed a low natriuretic response. As compared to the other patients, this group showed lower daily urinary output (2275 ± 790 vs 3849 ± 2034 mL, p < 0.001), lower body weight reduction after 48 h (1.55 ± - 1.66 vs - 3.55 ± - 2.93 kg, p < 0.001), higher incidence of worsening renal function (32% vs 10%, p 0.02) and increasing rather than reducing NT-proBNP at 72 h (p 0.02).

CONCLUSIONS

In patients with ACHF and dilutional hyponatremia, low natriuresis after furosemide is an early marker of poor diuretic response and correlates with higher NT-proBNP and higher incidence of worsening renal function at 72 h.

Role of electrolyte concentrations and renin-angiotensin-aldosterone activation in the staging of canine heart disease

Background

Refractory congestive heart failure (CHF) and associated diuretic resistance are not well defined.

Objectives

To characterize renal function, electrolyte concentrations, indices of diuretic efficacy, and renin‐angiotensin‐aldosterone system (RAAS) activation in dogs with naturally occurring heart disease (HD) in American College of Veterinary Internal Medicine stages B1, B2, C, and D and to determine their usefulness in defining HD stages.

Animals

Group 1:149 dogs with HD stages B1, B2, C, and D. Group 2:22 dogs with HD stages C and D.

Methods

Group 1: Renal parameters, serum and urine electrolyte and diuretic concentrations, and urine aldosterone concentrations were measured. Medication dosages and measured variables were compared among stages. Correlation of furosemide dosages to serum concentrations was explored. Group 2: Angiotensin‐converting enzyme activity and RAAS components were measured and compared among CHF stages.

Results

Serum chloride concentration was the best differentiator of HD stage. Furosemide PO dosages (≤6 mg/kg/day) were weakly correlated with serum furosemide concentrations, whereas higher dosages were not significantly correlated. Angiotensin‐converting enzyme inhibitor dosage and RAAS inhibition were greater in stage D, compared to stage C dogs.

Conclusions and Clinical Importance

Hypochloremia is a useful marker for stage D HD in dogs. Poor furosemide dosage correlation to serum concentration may indicate variable and poor absorption, especially at higher dosages, advanced disease, or both. A small number of stage D dogs met proposed criteria for diuretic resistance. Greater RAAS inhibition in stage D versus stage C indicates effectiveness of RAAS‐suppressive treatments in this group of dogs with refractory CHF.

Early urine electrolyte patterns in patients with acute heart failure

Aims

We conducted a prospective study of emergency department (ED) patients with acute heart failure (AHF) to determine if worsening HF (WHF) could be predicted based on urinary electrolytes during the first 1–2 h of ED care. Loop diuretics are standard therapy for AHF patients. A subset of patients hospitalized for AHF will develop a blunted natriuretic response to loop diuretics, termed diuretic resistance, which often leads to WHF. Early detection of diuretic resistance could facilitate escalation of therapy and prevention of WHF.

Methods and results

Patients were eligible if they had an ED AHF diagnosis, had not yet received intravenous diuretics, had a systolic blood pressure > 90 mmHg, and were not on dialysis. Urine electrolytes and urine output were collected at 1, 2, 4, and 6 h after diuretic administration. Worsening HF was defined as clinically persistent or WHF requiring escalation of diuretics or administration of intravenous vasoactives after the ED stay. Of the 61 patients who qualified in this pilot study, there were 10 (16.3%) patients who fulfilled our definition of WHF. At 1 h after diuretic administration, patients who developed WHF were more likely to have low urinary sodium (9.5 vs. 43.0 mmol; P < 0.001) and decreased urine sodium concentration (48 vs. 80 mmol/L; P = 0.004) than patients without WHF. All patients with WHF had a total urine sodium of <35.4 mmol at 1 h (100% sensitivity and 60% specificity).

Conclusions

One hour after diuretic administration, a urine sodium excretion of <35.4 mmol was highly suggestive of the development of WHF. These relationships require further testing to determine if early intervention with alternative agents can prevent WHF.

Editor's Choice-Diuretic resistance in acute heart failure

Diuretic resistance is a powerful predictor of adverse outcome in acute heart failure (AHF), irrespectively of underlying glomerular filtration rate. Metrics of diuretic efficacy such as natriuresis, urine output, weight loss, net fluid balance, or fractional sodium excretion, differ in their risk for measurement error, convenience, and biological plausibility, which should be taken into account when interpreting their results. Loop diuretic resistance in AHF has multiple causes including altered drug pharmacokinetics, impaired renal perfusion and effective circulatory volume, neurohumoral activation, post-diuretic sodium retention, the braking phenomenon and functional as well as structural adaptations in the nephron. Ideally, these mechanisms should guide specific treatment decisions with the goal of achieving complete decongestion. Therefore, volume overload needs to be identified correctly to avoid poor diuretic response due to electrolyte depletion or dehydration. Next, renal perfusion should be optimised if possible and loop diuretics should be prescribed above their threshold dose. Addition of thiazide-type diuretics should be considered when a progressive decrease in loop diuretic efficacy is observed with prolonged use (i.e., the braking phenomenon). Furthermore, thiazide-type diuretics are a useful addition in patients with low glomerular filtration rate. However, they limit free water excretion and are relatively contraindicated in cases of hypotonic hyponatremia, where acetazolamide is the better option. Finally, ultrafiltration should be considered in patients with refractory diuretic resistance as persistent volume overload after decongestive treatment is associated with worse outcomes. Whether more upfront use of any of these individually tailored decongestion strategies is superior to monotherapy with loop diuretics remains to be shown by adequately powered randomised clinical trials.

Pharmacodynamic assessment of diuretic efficacy and braking in a furosemide continuous infusion model

INTRODUCTION

Diuretic failure is a potential life-ending event but is unpredictable and poorly understood. The objectives of this study were to evaluate pharmacodynamic markers of furosemide-induced diuresis and to investigate mechanisms of diuretic braking in dogs receiving constant rate infusion (CRI) of furosemide.

ANIMALS

Six healthy male dogs.

METHODS

Raw data and stored samples from one arm of a previously published study were further analyzed to mechanistically investigate causes of diuretic braking in these dogs. Urine volume was recorded hourly during a 5-h furosemide CRI. Urine and blood samples were collected hourly to measure serum and urine electrolytes, urine aldosterone, and plasma and urine furosemide. Serum electrolyte fractional excretion was calculated. Urine sodium concentration was indexed to urine potassium (uNa:uK) and urine furosemide (uNa:uFur) concentrations, plasma furosemide concentration was indexed to urine furosemide concentration (pFur:uFur), and urine aldosterone was indexed to urine creatinine (UAldo:C). Temporal change and the relationship to urine volume were evaluated for these measured and calculated variables.

RESULTS

Urine volume was significantly correlated with urine electrolyte amounts and with uNa:uK. The ratio of pFur:uFur decreased during the infusion, whereas furosemide excretion was unchanged.

CONCLUSIONS

There was a strong relationship between urine volume and absolute urine electrolyte excretion. Urine volume was strongly correlated to uNa:uK, giving it potential as a spot indicator of urine production during diuresis. The decrease in uNa:uK over time during the infusion is consistent with mineralocorticoid modification of urinary electrolyte excretion, supporting renin-angiotensin-aldosterone activation as a cause of diuretic braking in this model.