Empagliflozin in Heart Failure: Regional Nephron Sodium Handling Effects.

SIGNIFICANCE STATEMENT: The effect of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on regional tubular sodium handling is poorly understood in humans. In this study, empagliflozin substantially decreased lithium reabsorption in the proximal tubule (PT) (a marker of proximal tubular sodium reabsorption), a magnitude out of proportion to that expected with only inhibition of sodium-glucose cotransporter-2. This finding was not driven by an "osmotic diuretic" effect; however, several parameters changed in a manner consistent with inhibition of the sodium-hydrogen exchanger 3. The large changes in proximal tubular handling were acutely buffered by increased reabsorption in both the loop of Henle and the distal nephron, resulting in the observed modest acute natriuresis with these agents. After 14 days of empagliflozin, natriuresis waned due to increased reabsorption in the PT and/or loop of Henle. These findings confirm in humans that SGLT2i have complex and important effects on renal tubular solute handling. BACKGROUND: The effect of SGLT2i on regional tubular sodium handling is poorly understood in humans but may be important for the cardiorenal benefits. METHODS: This study used a previously reported randomized, placebo-controlled crossover study of empagliflozin 10 mg daily in patients with diabetes and heart failure. Sodium handling in the PT, loop of Henle (loop), and distal nephron was assessed at baseline and day 14 using fractional excretion of lithium (FELi), capturing PT/loop sodium reabsorption. Assessments were made with and without antagonism of sodium reabsorption through the loop using bumetanide. RESULTS: Empagliflozin resulted in a large decrease in sodium reabsorption in the PT (increase in FELi=7.5%±10.6%, P = 0.001), with several observations suggesting inhibition of PT sodium hydrogen exchanger 3. In the absence of renal compensation, this would be expected to result in approximately 40 g of sodium excretion/24 hours with normal kidney function. However, rapid tubular compensation occurred with increased sodium reabsorption both in the loop ( P < 0.001) and distal nephron ( P < 0.001). Inhibition of sodium-glucose cotransporter-2 did not attenuate over 14 days of empagliflozin ( P = 0.14). However, there were significant reductions in FELi ( P = 0.009), fractional excretion of sodium ( P = 0.004), and absolute fractional distal sodium reabsorption ( P = 0.036), indicating that chronic adaptation to SGLT2i results primarily from increased reabsorption in the loop and/or PT. CONCLUSIONS: Empagliflozin caused substantial redistribution of intrarenal sodium delivery and reabsorption, providing mechanistic substrate to explain some of the benefits of this class. Importantly, the large increase in sodium exit from the PT was balanced by distal compensation, consistent with SGLT2i excellent safety profile. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: ClinicalTrials.gov ( NCT03027960 ).

External Validation of an Electronic Health Record-Based Diagnostic Model for Histological Acute Tubulointerstitial Nephritis.

BACKGROUND: Accurate diagnosis of acute tubulointerstitial nephritis (AIN) often requires a kidney biopsy. We previously developed a diagnostic statistical model for predicting biopsy-confirmed AIN by combining four laboratory tests after evaluating over 150 potential predictors from the electronic health record. Here, we validate this diagnostic model in two biopsy-based cohorts at Johns Hopkins Hospital (JHH) and Yale, which were geographically and temporally distinct from the development cohort, respectively. METHODS: We analyzed patients who underwent kidney biopsy at JHH and Yale University (2019-2023). We assessed discrimination (AUC) and calibration using previously derived model coefficients and recalibrated the model using an intercept correction factor that accounted for differences in baseline prevalence of AIN between development and validation cohorts. RESULTS: We included 1982 participants: 1454 at JHH and 528 at Yale. JHH (5%) and Yale (17%) had lower proportions of biopsies with AIN than the development set (23%). The AUC was 0.73 (0.66-0.79) at JHH and 0.73 (0.67-0.78) at Yale, similar to the development set (0.73 (0.64-0.81)). Calibration was imperfect in validation cohorts, particularly at JHH, but improved with application of an intercept correction factor. The model increased AUC of clinicians' prebiopsy suspicion for AIN by 0.10 to 0.77 (0.71-0.82). CONCLUSIONS: An AIN diagnostic model retained discrimination in two validation cohorts but needed recalibration to account for local AIN prevalence. The model improved clinicians' ability to predict AIN.

Using Overlap Weights to Address Extreme Propensity Scores in Estimating Restricted Mean Counterfactual Survival Times.

While inverse probability of treatment weighting (IPTW) is a commonly used approach for treatment comparisons in observational data, the resulting estimates may be subject to bias and excessively large variance under lack of overlap. By smoothly down-weighting units with extreme propensity scores, i.e., those that are close (or equal) to zero or one, overlap weighting (OW) can help mitigate the bias and variance issues associated with IPTW. Although theoretical and simulation results have supported the use of OW with continuous and binary outcomes, its performance with survival outcomes remains to be further investigated, especially when the target estimand is defined based on the restricted mean survival time (RMST). We combine propensity score weighting and inverse probability of censoring weighting to estimate the restricted mean counterfactual survival times, and provide computationally-efficient variance estimators when the propensity scores are estimated by logistic regression and the censoring process is estimated by Cox regression. We conduct simulations to compare the performance of weighting methods in terms of bias, variance, and 95% interval coverage, under various degrees of overlap. Under moderate and weak overlap, we demonstrate the advantage of OW over IPTW, trimming and truncation, with respect to bias, variance, and coverage when estimating RMST.

Early, Individualized Recommendations for Hospitalized Patients With Acute Kidney Injury: A Randomized Clinical Trial.

Importance: Acute kidney injury (AKI) is a common complication during hospitalization and is associated with adverse outcomes. Objective: To evaluate whether diagnostic and therapeutic recommendations sent by a kidney action team through the electronic health record improve outcomes among patients hospitalized with AKI compared with usual care. Design, Setting, and Participants: Randomized clinical trial conducted at 7 hospitals in 2 health systems: in New Haven, Bridgeport, New London, and Waterbury, Connecticut, and Westerly, Rhode Island; and in Baltimore, Maryland. Hospitalized patients with AKI were randomized between October 29, 2021, and February 8, 2024. Final follow-up occurred February 22, 2024. Intervention: An alert about AKI was sent to the kidney action team, consisting of a study physician and study pharmacist, which sent personalized recommendations through the electronic health record in 5 major categories (diagnostic testing, volume, potassium, acid base, and medications) within 1 hour of AKI detection. The note was immediately visible to anyone with access to the electronic health record. Randomization to the intervention or usual care occurred after the recommendations were generated, but the note was only delivered to clinicians of patients randomized to the intervention group. Main Outcomes and Measures: The primary outcome was a composite outcome consisting of AKI progression to a higher stage of AKI, dialysis, or mortality occurring while the patient remained hospitalized and within 14 days from randomization. Results: Of the 4003 patients randomized (median age, 72 years [IQR, 61-81 years), 1874 (47%) were female and 931 (23%) were Black patients. The kidney action team made 14 539 recommendations, with a median of 3 (IQR, 2-5) per patient. The primary outcome occurred in 19.8% of the intervention group and in 18.4% in the usual care group (difference, 1.4%, 95% CI, -1.1% to 3.8,% P = .28). Of 6 secondary outcomes, only 1 secondary outcome, rates of recommendation implementation, significantly differed between the 2 groups: 2459 of 7270 recommendations (33.8%) were implemented in the intervention group and 1766 of 7269 undelivered recommendations (24.3%) were implemented in the usual care group within 24 hours (difference, 9.5%; 95% CI, 8.1% to 11.0%). Conclusions and Relevance: Among patients hospitalized with AKI, recommendations from a kidney action team did not significantly reduce the composite outcome of worsening AKI stage, dialysis, or mortality, despite a higher rate of recommendation implementation in the intervention group than in the usual care group. Trial Registration: ClinicalTrials.gov Identifier: NCT04040296.

Evaluation of Plasma Biomarkers to Predict Major Adverse Kidney Events in Hospitalized Patients With COVID-19.

RATIONALE & OBJECTIVE: Patients hospitalized with COVID-19 are at increased risk for major adverse kidney events (MAKE). We sought to identify plasma biomarkers predictive of MAKE in patients hospitalized with COVID-19. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: A total of 576 patients hospitalized with COVID-19 between March 2020 and January 2021 across 3 academic medical centers. EXPOSURE: Twenty-six plasma biomarkers of injury, inflammation, and repair from first available blood samples collected during hospitalization. OUTCOME: MAKE, defined as KDIGO stage 3 acute kidney injury (AKI), dialysis-requiring AKI, or mortality up to 60 days. ANALYTICAL APPROACH: Cox proportional hazards regression to associate biomarker level with MAKE. We additionally applied the least absolute shrinkage and selection operator (LASSO) and random forest regression for prediction modeling and estimated model discrimination with time-varying C index. RESULTS: The median length of stay for COVID-19 hospitalization was 9 (IQR, 5-16) days. In total, 95 patients (16%) experienced MAKE. Each 1 SD increase in soluble tumor necrosis factor receptor 1 (sTNFR1) and sTNFR2 was significantly associated with an increased risk of MAKE (adjusted HR [AHR], 2.30 [95% CI, 1.86-2.85], and AHR, 2.26 [95% CI, 1.73-2.95], respectively). The C index of sTNFR1 alone was 0.80 (95% CI, 0.78-0.84), and the C index of sTNFR2 was 0.81 (95% CI, 0.77-0.84). LASSO and random forest regression modeling using all biomarkers yielded C indexes of 0.86 (95% CI, 0.83-0.89) and 0.84 (95% CI, 0.78-0.91), respectively. LIMITATIONS: No control group of hospitalized patients without COVID-19. CONCLUSIONS: We found that sTNFR1 and sTNFR2 are independently associated with MAKE in patients hospitalized with COVID-19 and can both also serve as predictors for adverse kidney outcomes. PLAIN-LANGUAGE SUMMARY: Patients hospitalized with COVID-19 are at increased risk for long-term adverse health outcomes, but not all patients suffer long-term kidney dysfunction. Identification of patients with COVID-19 who are at high risk for adverse kidney events may have important implications in terms of nephrology follow-up and patient counseling. In this study, we found that the plasma biomarkers soluble tumor necrosis factor receptor 1 (sTNFR1) and sTNFR2 measured in hospitalized patients with COVID-19 were associated with a greater risk of adverse kidney outcomes. Along with clinical variables previously shown to predict adverse kidney events in patients with COVID-19, both sTNFR1 and sTNFR2 are also strong predictors of adverse kidney outcomes.

Deep learning prediction of hospital readmissions for asthma and COPD.

QUESTION: Severe asthma and COPD exacerbations requiring hospitalization are linked to increased disease morbidity and healthcare costs. We sought to identify Electronic Health Record (EHR) features of severe asthma and COPD exacerbations and evaluate the performance of four machine learning (ML) and one deep learning (DL) model in predicting readmissions using EHR data. STUDY DESIGN AND METHODS: Observational study between September 30, 2012, and December 31, 2017, of patients hospitalized with asthma and COPD exacerbations. RESULTS: This study included 5,794 patients, 1,893 with asthma and 3,901 with COPD. Patients with asthma were predominantly female (n = 1288 [68%]), 35% were Black (n = 669), and 25% (n = 479) were Hispanic. Black (44 vs. 33%, p = 0.01) and Hispanic patients (30 vs. 24%, p = 0.02) were more likely to be readmitted for asthma. Similarly, patients with COPD readmissions included a large percentage of Blacks (18 vs. 10%, p < 0.01) and Hispanics (8 vs. 5%, p < 0.01). To identify patients at high risk of readmission index hospitalization data of a subset of 2,682 patients, 777 with asthma and 1,905 with COPD, was analyzed with four ML models, and one DL model. We found that multilayer perceptron, the DL method, had the best sensitivity and specificity compared to the four ML methods implemented in the same dataset. INTERPRETATION: Multilayer perceptron, a deep learning method, had the best performance in predicting asthma and COPD readmissions, demonstrating that EHR and deep learning integration can improve high-risk patient detection.

Optimizing the Design and Analysis of Future AKI Trials.

AKI is a complex clinical syndrome associated with an increased risk of morbidity and mortality, particularly in critically ill and perioperative patient populations. Most AKI clinical trials have been inconclusive, failing to detect clinically important treatment effects at predetermined statistical thresholds. Heterogeneity in the pathobiology, etiology, presentation, and clinical course of AKI remains a key challenge in successfully testing new approaches for AKI prevention and treatment. This article, derived from the "AKI" session of the "Kidney Disease Clinical Trialists" virtual workshop held in October 2021, reviews barriers to and strategies for improving the design and implementation of clinical trials in patients with, or at risk of, developing AKI. The novel approaches to trial design included in this review span adaptive trial designs that increase the knowledge gained from each trial participant; pragmatic trial designs that allow for the efficient enrollment of sufficiently large numbers of patients to detect small, but clinically significant, treatment effects; and platform trial designs that use one trial infrastructure to answer multiple clinical questions simultaneously. This review also covers novel approaches to clinical trial analysis, such as Bayesian analysis and assessing heterogeneity in the response to therapies among trial participants. We also propose a road map and actionable recommendations to facilitate the adoption of the reviewed approaches. We hope that the resulting road map will help guide future clinical trial planning, maximize learning from AKI trials, and reduce the risk of missing important signals of benefit (or harm) from trial interventions.

Does This Child With High Blood Pressure Have Secondary Hypertension?: The Rational Clinical Examination Systematic Review.

Importance: Guidelines recommend that all children and adolescents with hypertension undergo evaluation for secondary causes. Identifying clinical factors associated with secondary hypertension may decrease unnecessary testing for those with primary hypertension. Objective: To determine the utility of the clinical history, physical examination, and 24-hour ambulatory blood pressure monitoring for differentiating primary hypertension from secondary hypertension in children and adolescents (aged ≤21 years). Data Sources and Study Selection: The databases of MEDLINE, PubMed Central, Embase, Web of Science, and Cochrane Library were searched from inception to January 2022 without language limits. Two authors identified studies describing clinical characteristics in children and adolescents with primary and secondary hypertension. Data Extraction and Synthesis: For each clinical finding in each study, a 2 × 2 table was created that included the number of patients with and without the finding who had primary vs secondary hypertension. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool. Main Outcomes and Measures: Random-effects modeling was used to calculate sensitivity, specificity, and likelihood ratios (LRs). Results: Of 3254 unique titles and abstracts screened, 30 studies met inclusion criteria for the meta-analysis and 23 (N = 4210 children and adolescents) were used for pooling in the meta-analysis. In the 3 studies conducted at primary care clinics or school-based screening clinics, the prevalence of secondary hypertension was 9.0% (95% CI, 4.5%-15.0%). In the 20 studies conducted at subspecialty clinics, the prevalence of secondary hypertension was 44% (95% CI, 36%-53%). The demographic findings most strongly associated with secondary hypertension were family history of secondary hypertension (sensitivity, 0.46; specificity, 0.90; LR, 4.7 [95% CI, 2.9-7.6]), weight in the 10th percentile or lower for age and sex (sensitivity, 0.27; specificity, 0.94; LR, 4.5 [95% CI, 1.2-18]), history of prematurity (sensitivity range, 0.17-0.33; specificity range, 0.86-0.94; LR range, 2.3-2.8), and age of 6 years or younger (sensitivity range, 0.25-0.36; specificity range, 0.86-0.88; LR range, 2.2-2.6). Laboratory studies most associated with secondary hypertension were microalbuminuria (sensitivity, 0.13; specificity, 0.99; LR, 13 [95% CI, 3.1-53]) and serum uric acid concentration of 5.5 mg/dL or lower (sensitivity range, 0.70-0.73; specificity range, 0.65-0.89; LR range, 2.1-6.3). Increased daytime diastolic blood pressure load combined with increased nocturnal systolic blood pressure load on 24-hour ambulatory blood pressure monitoring was associated with secondary hypertension (sensitivity, 0.40; specificity, 0.82; LR, 4.8 [95% CI, 1.2-20]). Findings associated with a decreased likelihood of secondary hypertension were asymptomatic presentation (LR range, 0.19-0.36), obesity (LR, 0.34 [95% CI, 0.13-0.90]), and family history of any hypertension (LR, 0.42 [95% CI, 0.30-0.57]). Hypertension stage, headache, and left ventricular hypertrophy did not distinguish secondary from primary hypertension. Conclusions and Relevance: Family history of secondary hypertension, younger age, lower body weight, and increased blood pressure load using 24-hour ambulatory blood pressure monitoring were associated with a higher likelihood of secondary hypertension. No individual sign or symptom definitively differentiates secondary hypertension from primary hypertension.

Rationale and design of a pragmatic trial aimed at improving treatment of hyperlipidemia in outpatients with very high risk atherosclerotic cardiovascular disease: A pragmatic trial of messaging to providers about treatment of hyperlipidemia (PROMPT-LIPID).

BACKGROUND: Despite guideline recommendations to optimize low-density lipoprotein cholesterol (LDL-C) reduction with intensification of lipid-lowering therapy (LLT) in patients with atherosclerotic cardiovascular disease (ASCVD), few of these patients achieve LDL-C < 70 mg/dL in practice. PURPOSE: We developed a real-time, targeted electronic health record (EHR) alert with embedded ordering capability to promote intensification of evidence based LLT in outpatients with very high risk ASCVD. METHODS: We designed a pragmatic, multicenter, single-blind, cluster randomized trial to test the effectiveness of an EHR-based LLT intensification alert. The study will enroll about 100 providers who will be randomized to either receive the alert or undergo usual care for outpatients with high risk ASCVD with LDL-C > 70 mg/dL. Total enrollment will include 2,500 patients. The primary outcome will be the proportion of patients with LLT intensification at 90 days. Secondary outcomes include achieved LDL-C at 6 months and the proportion of patients with LDL-C < 70 mg/dL or < 55 mg/dL at 6 months. RESULTS: Enrollment of 1,250 patients (50% of goal) was reached within 47 days (50% women, mean age 72, median LDL-C 91). At baseline, 71%, 9%, and 3% were on statins, ezetimibe, or proprotein convertase subtilisin/kexin type 9 inhibitors, respectively. CONCLUSIONS: PRagmatic Trial of Messaging to Providers about Treatment of HyperLIPIDemia has rapidly reached 50% enrollment of patients with very high risk ASCVD, demonstrating low baseline LLT utilization. This pragmatic, EHR-based trial will determine the effectiveness of a real-time, targeted EHR alert with embedded ordering capability to promote LLT intensification. Findings from this low-cost, widely scalable intervention to improve LDL-C may have important public health implications. TRIAL REGISTRATION: clinicaltrials.gov NCT04394715.

Rationale and design of a cluster-randomized pragmatic trial aimed at improving use of guideline directed medical therapy in outpatients with heart failure: PRagmatic trial of messaging to providers about treatment of heart failure (PROMPT-HF).

Heart failure with reduced ejection fraction (HFrEF) is one of the most common chronic illnesses in the United States and carries significant risk of morbidity and mortality. Use of guideline-directed medical therapy (GDMT) for patients with HFrEF has been shown to dramatically improve outcomes, but adoption of these treatments remains generally low. Possible explanations for poor GDMT uptake include lack of knowledge about recommended management strategies and provider reluctance due to uncertainties regarding application of said guidelines to real-world practice. One way to overcome these barriers is by harnessing the electronic health record (EHR) to create patient-centered "best practice alerts" (BPAs) that can guide clinicians to prescribe appropriate medical therapies. If found to be effective, these low-cost interventions can be rapidly applied across large integrated healthcare systems. The PRagmatic Trial Of Messaging to Providers about Treatment of Heart Failure (PROMPT-HF) trial is a pragmatic, cluster randomized controlled trial designed to test the hypothesis that tailored and timely alerting of recommended GDMT in heart failure (HF) will result in greater adherence to guidelines when compared with usual care. PROMPT-HF has completed enrollment of 1,310 ambulatory patients with HFrEF cared for by 100 providers who were randomized to receive a BPA vs usual care. The BPA alerted providers to GDMT recommended for their patients and displayed current left ventricular ejection fraction (LVEF) along with the most recent blood pressure, heart rate, serum potassium and creatinine levels, and estimated glomerular filtration rate. It also linked to an order set customized to the patient that suggests medications within each GDMT class not already prescribed. Our goal is to examine whether tailored EHR-based alerting for outpatients with HFrEF will lead to higher rates of GDMT at 30 days post randomization when compared with usual care. Additionally, we are assessing clinical outcomes such as hospital readmissions and death between the alert versus usual care group. Trial Registration: Clinicaltrials.gov NCT04514458.

Prevalence of Secondary Hypertension in Otherwise Healthy Youths with a New Diagnosis of Hypertension: A Meta-Analysis.

OBJECTIVE: To estimate the prevalence of secondary hypertension among otherwise healthy children with hypertension diagnosed in the outpatient setting. STUDY DESIGN: The MEDLINE, PubMed Central, Embase, Web of Science, and Cochrane Library databases were systematically searched for observational studies reporting the prevalence of secondary hypertension in children who underwent evaluation for hypertension and had no known comorbidities associated with hypertension at the time of diagnosis. Two authors independently extracted the study-specific prevalence of secondary hypertension in children evaluated for hypertension. Prevalence estimates for secondary hypertension were pooled in a random-effects meta-analysis. RESULTS: Nineteen prospective studies and 7 retrospective studies including 2575 children with hypertension were analyzed, with a median of 65 participants (range, 9-486) in each study. Studies conducted in primary care or school settings reported a lower prevalence of secondary hypertension (3.7%; 95% CI, 1.2%-7.2%) compared with studies conducted in referral clinics (20.1%; 95% CI, 11.5%-30.3%). When stratified by study setting, there were no significant subgroup differences according to study design, country, participant age range, hypertension definition, blood pressure device, or study quality. Although the studies applied different approaches to diagnosing secondary hypertension, diagnostic evaluations were at least as involved as the limited testing recommended by current guidelines. CONCLUSIONS: The low prevalence of secondary hypertension among children with a new diagnosis of hypertension identified on screening reinforces clinical practice guidelines to avoid extensive testing in the primary care setting for secondary causes in most children with hypertension.

Prognostic Significance of Urinary Biomarkers in Patients Hospitalized With COVID-19.

RATIONALE & OBJECTIVE: Acute kidney injury (AKI) is common in patients with coronavirus disease 2019 (COVID-19) and associated with poor outcomes. Urinary biomarkers have been associated with adverse kidney outcomes in other settings and may provide additional prognostic information in patients with COVID-19. We investigated the association between urinary biomarkers and adverse kidney outcomes among patients hospitalized with COVID-19. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: Patients hospitalized with COVID-19 (n=153) at 2 academic medical centers between April and June 2020. EXPOSURE: 19 urinary biomarkers of injury, inflammation, and repair. OUTCOME: Composite of KDIGO (Kidney Disease: Improving Global Outcomes) stage 3 AKI, requirement for dialysis, or death within 60 days of hospital admission. We also compared various kidney biomarker levels in the setting of COVID-19 versus other common AKI settings. ANALYTICAL APPROACH: Time-varying Cox proportional hazards regression to associate biomarker level with composite outcome. RESULTS: Out of 153 patients, 24 (15.7%) experienced the primary outcome. Twofold higher levels of neutrophil gelatinase-associated lipocalin (NGAL) (HR, 1.34 [95% CI, 1.14-1.57]), monocyte chemoattractant protein (MCP-1) (HR, 1.42 [95% CI, 1.09-1.84]), and kidney injury molecule 1 (KIM-1) (HR, 2.03 [95% CI, 1.38-2.99]) were associated with highest risk of sustaining primary composite outcome. Higher epidermal growth factor (EGF) levels were associated with a lower risk of the primary outcome (HR, 0.61 [95% CI, 0.47-0.79]). Individual biomarkers provided moderate discrimination and biomarker combinations improved discrimination for the primary outcome. The degree of kidney injury by biomarker level in COVID-19 was comparable to other settings of clinical AKI. There was evidence of subclinical AKI in COVID-19 patients based on elevated injury biomarker level in patients without clinical AKI defined by serum creatinine. LIMITATIONS: Small sample size with low number of composite outcome events. CONCLUSIONS: Urinary biomarkers are associated with adverse kidney outcomes in patients hospitalized with COVID-19 and may provide valuable information to monitor kidney disease progression and recovery.

Inferior Vena Cava Diameter Measurement Provides Distinct and Complementary Information to Right Atrial Pressure in Acute Decompensated Heart Failure.

BACKGROUND: Inferior vena cava (IVC) measurements correlate only modestly with right atrial pressure (RAP). Part of this inaccuracy is due to the high compliance of the venous system, where a large change in blood volume may result in only a small change in pressure. As such, the information provided by the IVC may be different rather than redundant. METHODS AND RESULTS: We analyzed patients in the ESCAPE (Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness) trial who had both pulmonary artery catheter and IVC measurements at baseline (n = 108). There was only a modest correlation between baseline RAP and IVC diameter (r = 0.41; P < 0.001). Hemoconcentration, defined as an increase in hemoglobin levels between admission and discharge, was correlated with decrease in IVC diameter (r = 0.35; P = 0.02) but not with a decrease in RAP (r = 0.01; P = 0.95). When patients had both IVC and RAP measurements that were below the median, survival rates were superior to the rates of those who had only 1 measurement below the median, and when both rates were above the median, patients fared the worst (P = 0.002). CONCLUSION: IVC and RAP have limited correlation with each another, and changes in intravascular volume appear to correlate better with IVC diameter rather than with RAP. Furthermore, complementary information is provided by pressure and volume assessments in acute decompensated heart failure.

Development and external validation of a diagnostic model for biopsy-proven acute interstitial nephritis using electronic health record data.

BACKGROUND: Patients with acute interstitial nephritis (AIN) can present without typical clinical features, leading to a delay in diagnosis and treatment. We therefore developed and validated a diagnostic model to identify patients at risk of AIN using variables from the electronic health record. METHODS: In patients who underwent a kidney biopsy at Yale University between 2013 and 2018, we tested the association of >150 variables with AIN, including demographics, comorbidities, vital signs and laboratory tests (training set 70%). We used least absolute shrinkage and selection operator methodology to select prebiopsy features associated with AIN. We performed area under the receiver operating characteristics curve (AUC) analysis with internal (held-out test set 30%) and external validation (Biopsy Biobank Cohort of Indiana). We tested the change in model performance after the addition of urine biomarkers in the Yale AIN study. RESULTS: We included 393 patients (AIN 22%) in the training set, 158 patients (AIN 27%) in the test set, 1118 patients (AIN 11%) in the validation set and 265 patients (AIN 11%) in the Yale AIN study. Variables in the selected model included serum creatinine {adjusted odds ratio [aOR] 2.31 [95% confidence interval (CI) 1.42-3.76]}, blood urea nitrogen:creatinine ratio [aOR 0.40 (95% CI 0.20-0.78)] and urine dipstick specific gravity [aOR 0.95 (95% CI 0.91-0.99)] and protein [aOR 0.39 (95% CI 0.23-0.68)]. This model showed an AUC of 0.73 (95% CI 0.64-0.81) in the test set, which was similar to the AUC in the external validation cohort [0.74 (95% CI 0.69-0.79)]. The AUC improved to 0.84 (95% CI 0.76-0.91) upon the addition of urine interleukin-9 and tumor necrosis factor-α. CONCLUSIONS: We developed and validated a statistical model that showed a modest AUC for AIN diagnosis, which improved upon the addition of urine biomarkers. Future studies could evaluate this model and biomarkers to identify unrecognized cases of AIN.

First-in-Human Experience With Peritoneal Direct Sodium Removal Using a Zero-Sodium Solution: A New Candidate Therapy for Volume Overload.

BACKGROUND: Loop diuretics have well-described toxicities, and loss of response to these agents is common. Alternative strategies are needed for the maintenance of euvolemia in heart failure (HF). Nonrenal removal of sodium directly across the peritoneal membrane (direct sodium removal [DSR]) with a sodium-free osmotic solution should result in extraction of large quantities of sodium with limited off-target solute removal. METHODS: This article describes the preclinical development and first-in-human proof of concept for DSR. Sodium-free 10% dextrose was used as the DSR solution. Porcine experiments were conducted to investigate the optimal dwell time, safety, and scalability and to determine the effect of experimental heart failure. In the human study, participants with end-stage renal disease on peritoneal dialysis (PD) underwent randomization and crossover to either a 2-hour dwell with 1 L DSR solution or standard PD solution (Dianeal 4.25% dextrose, Baxter). The primary end point was completion of the 2-hour dwell without significant discomfort or adverse events, and the secondary end point was difference in sodium removal between DSR and standard PD solution. RESULTS: Porcine experiments revealed that 1 L DSR solution removed 4.1±0.4 g sodium in 2 hours with negligible off-target solute removal and overall stable serum electrolytes. Increasing the volume of DSR solution cycled across the peritoneum increased sodium removal and substantially decreased plasma volume (P=0.005). In the setting of experimental heart failure with elevated right atrial pressure, sodium removal was ≈4 times greater than in healthy animals (P<0.001). In the human proof-of-concept study, DSR solution was well tolerated and not associated with significant discomfort or adverse events. Plasma electrolyte concentrations were stable, and off-target solute removal was negligible. Sodium removal was substantially higher with DSR (4.5±0.4 g) compared with standard PD solution (1.0±0.3 g; P<0.0001). CONCLUSIONS: DSR was well tolerated in both animals and human subjects and produced substantially greater sodium removal than standard PD solution. Additional research evaluating the use of DSR as a method to prevent and treat hypervolemia in heart failure is warranted. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03801226.

Empagliflozin in Heart Failure: Diuretic and Cardiorenal Effects.

BACKGROUND: Sodium-glucose cotransporter-2 inhibitors improve heart failure-related outcomes. The mechanisms underlying these benefits are not well understood, but diuretic properties may contribute. Traditional diuretics such as furosemide induce substantial neurohormonal activation, contributing to the limited improvement in intravascular volume often seen with these agents. However, the proximal tubular site of action of the sodium-glucose cotransporter-2 inhibitors may help circumvent these limitations. METHODS: Twenty patients with type 2 diabetes mellitus and chronic, stable heart failure completed a randomized, placebo-controlled crossover study of empagliflozin 10 mg daily versus placebo. Patients underwent an intensive 6-hour biospecimen collection and cardiorenal phenotyping at baseline and again after 14 days of study drug. After a 2-week washout, patients crossed over to the alternate therapy with the above protocol repeated. RESULTS: Oral empagliflozin was rapidly absorbed as evidenced by a 27-fold increase in urinary glucose excretion by 3 hours (P<0.0001). Fractional excretion of sodium increased significantly with empagliflozin monotherapy versus placebo (fractional excretion of sodium, 1.2±0.7% versus 0.7±0.4%; P=0.001), and there was a synergistic effect in combination with bumetanide (fractional excretion of sodium, 5.8±2.5% versus 3.9±1.9%; P=0.001). At 14 days, the natriuretic effect of empagliflozin persisted, resulting in a reduction in blood volume (-208 mL [interquartile range, -536 to 153 mL] versus -14 mL [interquartile range, -282 to 335 mL]; P=0.035) and plasma volume (-138 mL, interquartile range, -379 to 154±453 mL; P=0.04). This natriuresis was not, however, associated with evidence of neurohormonal activation because the change in norepinephrine was superior (P=0.02) and all other neurohormones were similar (P<0.34) during the empagliflozin versus placebo period. Furthermore, there was no evidence of potassium wasting (P=0.20) or renal dysfunction (P>0.11 for all biomarkers), whereas both serum magnesium (P<0.001) and uric acid levels (P=0.008) improved. CONCLUSIONS: Empagliflozin causes significant natriuresis, particularly when combined with loop diuretics, resulting in an improvement in blood volume. However, off-target electrolyte wasting, renal dysfunction, and neurohormonal activation were not observed. This favorable diuretic profile may offer significant advantage in the management of volume status in patients with heart failure and may represent a mechanism contributing to the superior long-term heart failure outcomes observed with these agents. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03027960.

Renal negative pressure treatment as a novel therapy for heart failure-induced renal dysfunction.

Congestion is the primary pathophysiological lesion in most heart failure (HF) hospitalizations. Renal congestion increases renal tubular pressure, reducing glomerular filtration rate (GFR) and diuresis. Because each nephron is a fluid-filled column, renal negative pressure therapy (rNPT) applied to the urinary collecting system should reduce tubular pressure, potentially improving kidney function. We evaluated the renal response to rNPT in congestive HF. Ten anesthetized ∼80-kg pigs underwent instrumentation with bilateral renal pelvic JuxtaFlow catheters. GFR was determined by iothalamate clearance (mGFR) and renal plasma flow (RPF) by para-aminohippurate clearance. Each animal served as its own control with randomization of left versus right kidney to -30 mmHg rNPT or no rNPT. mGFR and RPF were measured simultaneously from the rNPT and no rNPT kidney. Congestive HF was induced via cardiac tamponade maintaining central venous pressure at 20-22.5 mmHg throughout the experiment. Before HF induction, rNPT increased natriuresis, diuresis, and mGFR compared with the control kidney (P < 0.001 for all). Natriuresis, diuresis, and mGFR decreased following HF (P < 0.001 for all) but were higher in rNPT kidney versus control (P < 0.001 for all). RPF decreased during HF (P < 0.001) without significant differences between rNPT treatments. During HF, the rNPT kidney had similar diuresis and natriuresis (P > 0.5 for both) and higher fractional excretion of sodium (P = 0.001) compared with the non-rNPT kidney in the no HF period. In conclusion, rNPT resulted in significantly increased diuresis, natriuresis, and mGFR, with or without experimental HF. rNPT improved key renal parameters of the congested cardiorenal phenotype.

Changes in Body Composition, Muscle Strength, and Fat Distribution Following Kidney Transplantation.

RATIONALE & OBJECTIVE: Low muscle mass relative to fat mass (relative sarcopenia) has been associated with mortality and disability but has not been examined after kidney transplantation. We studied how measures of body composition change after receipt of a kidney allograft. STUDY DESIGN: Prospective longitudinal cohort study. SETTING & PARTICIPANTS: 60 kidney transplant recipients, aged 20-60 years, at the University of Pennsylvania. EXPOSURE: Kidney transplantation. OUTCOME: Dual-energy x-ray absorptiometry measures of fat mass index (FMI) and appendicular lean mass index (ALMI, representing muscle mass), computed tomography measures of muscle density (low density represents increased intramuscular adipose tissue), dynamometer measures of leg muscle strength, and physical activity. ALMI relative to FMI (ALMFMI) is an established index of relative sarcopenia. ANALYTICAL APPROACH: Measures expressed as age, sex, and race-specific z scores for transplant recipients were compared with 327 healthy controls. Regression models were used to identify correlates of change in outcome z scores and compare transplant recipients with controls. RESULTS: At transplantation, ALMI, ALMIFMI, muscle strength, and muscle density z scores were lower versus controls (all P≤0.001). Transplant recipients received glucocorticoids throughout. The prevalence of obesity increased from 18% to 45%. Although ALMI increased after transplantation (P<0.001) and was comparable with the controls from 6 months onward, gains were outpaced by increases in FMI, resulting in persistent ALMIFMI deficits (mean z score of-0.31 at 24 months; P=0.02 vs controls). Muscle density improved after transplantation despite gains in FMI (P=0.02). Muscle strength relative to ALMI also improved (P=0.04) but remained low compared with controls (P=0.01). Exercise increased in the early months after transplantation (P<0.05) but remained lower than controls (P = 0.02). LIMITATIONS: Lack of muscle biopsies precluded assessment of muscle histology and metabolism. CONCLUSIONS: The 2-year interval after kidney transplantation was characterized by gains in muscle mass and strength that were outpaced by gains in fat mass, resulting in persistent relative sarcopenia.

The Association of COVID-19 With Acute Kidney Injury Independent of Severity of Illness: A Multicenter Cohort Study.

RATIONALE & OBJECTIVE: Although coronavirus disease 2019 (COVID-19) has been associated with acute kidney injury (AKI), it is unclear whether this association is independent of traditional risk factors such as hypotension, nephrotoxin exposure, and inflammation. We tested the independent association of COVID-19 with AKI. STUDY DESIGN: Multicenter, observational, cohort study. SETTING & PARTICIPANTS: Patients admitted to 1 of 6 hospitals within the Yale New Haven Health System between March 10, 2020, and August 31, 2020, with results for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing via polymerase chain reaction of a nasopharyngeal sample. EXPOSURE: Positive test for SARS-CoV-2. OUTCOME: AKI by KDIGO (Kidney Disease: Improving Global Outcomes) criteria. ANALYTICAL APPROACH: Evaluated the association of COVID-19 with AKI after controlling for time-invariant factors at admission (eg, demographic characteristics, comorbidities) and time-varying factors updated continuously during hospitalization (eg, vital signs, medications, laboratory results, respiratory failure) using time-updated Cox proportional hazard models. RESULTS: Of the 22,122 patients hospitalized, 2,600 tested positive and 19,522 tested negative for SARS-CoV-2. Compared with patients who tested negative, patients with COVID-19 had more AKI (30.6% vs 18.2%; absolute risk difference, 12.5% [95% CI, 10.6%-14.3%]) and dialysis-requiring AKI (8.5% vs 3.6%) and lower rates of recovery from AKI (58% vs 69.8%). Compared with patients without COVID-19, patients with COVID-19 had higher inflammatory marker levels (C-reactive protein, ferritin) and greater use of vasopressors and diuretic agents. Compared with patients without COVID-19, patients with COVID-19 had a higher rate of AKI in univariable analysis (hazard ratio, 1.84 [95% CI, 1.73-1.95]). In a fully adjusted model controlling for demographic variables, comorbidities, vital signs, medications, and laboratory results, COVID-19 remained associated with a high rate of AKI (adjusted hazard ratio, 1.40 [95% CI, 1.29-1.53]). LIMITATIONS: Possibility of residual confounding. CONCLUSIONS: COVID-19 is associated with high rates of AKI not fully explained by adjustment for known risk factors. This suggests the presence of mechanisms of AKI not accounted for in this analysis, which may include a direct effect of COVID-19 on the kidney or other unmeasured mediators. Future studies should evaluate the possible unique pathways by which COVID-19 may cause AKI.

Characteristics and Outcomes of Individuals With Pre-existing Kidney Disease and COVID-19 Admitted to Intensive Care Units in the United States.

RATIONALE & OBJECTIVE: Underlying kidney disease is an emerging risk factor for more severe coronavirus disease 2019 (COVID-19) illness. We examined the clinical courses of critically ill COVID-19 patients with and without pre-existing chronic kidney disease (CKD) and investigated the association between the degree of underlying kidney disease and in-hospital outcomes. STUDY DESIGN: Retrospective cohort study. SETTINGS & PARTICIPANTS: 4,264 critically ill patients with COVID-19 (143 patients with pre-existing kidney failure receiving maintenance dialysis; 521 patients with pre-existing non-dialysis-dependent CKD; and 3,600 patients without pre-existing CKD) admitted to intensive care units (ICUs) at 68 hospitals across the United States. PREDICTOR(S): Presence (vs absence) of pre-existing kidney disease. OUTCOME(S): In-hospital mortality (primary); respiratory failure, shock, ventricular arrhythmia/cardiac arrest, thromboembolic events, major bleeds, and acute liver injury (secondary). ANALYTICAL APPROACH: We used standardized differences to compare patient characteristics (values>0.10 indicate a meaningful difference between groups) and multivariable-adjusted Fine and Gray survival models to examine outcome associations. RESULTS: Dialysis patients had a shorter time from symptom onset to ICU admission compared to other groups (median of 4 [IQR, 2-9] days for maintenance dialysis patients; 7 [IQR, 3-10] days for non-dialysis-dependent CKD patients; and 7 [IQR, 4-10] days for patients without pre-existing CKD). More dialysis patients (25%) reported altered mental status than those with non-dialysis-dependent CKD (20%; standardized difference=0.12) and those without pre-existing CKD (12%; standardized difference=0.36). Half of dialysis and non-dialysis-dependent CKD patients died within 28 days of ICU admission versus 35% of patients without pre-existing CKD. Compared to patients without pre-existing CKD, dialysis patients had higher risk for 28-day in-hospital death (adjusted HR, 1.41 [95% CI, 1.09-1.81]), while patients with non-dialysis-dependent CKD had an intermediate risk (adjusted HR, 1.25 [95% CI, 1.08-1.44]). LIMITATIONS: Potential residual confounding. CONCLUSIONS: Findings highlight the high mortality of individuals with underlying kidney disease and severe COVID-19, underscoring the importance of identifying safe and effective COVID-19 therapies in this vulnerable population.