Hypochloremia and Diuretic Resistance in Heart Failure: Mechanistic Insights

BACKGROUND

Recent epidemiological studies have implicated chloride, rather than sodium, as the driver of poor survival previously attributed to hyponatremia in heart failure. Accumulating basic science evidence has identified chloride as a critical factor in renal salt sensing. Our goal was to probe the physiology bridging this basic and epidemiological literature.

METHODS AND RESULTS

Two heart failure cohorts were included: (1) observational: patients receiving loop diuretics at the Yale Transitional Care Center (N=162) and (2) interventional pilot: stable outpatients receiving ≥80 mg furosemide equivalents were studied before and after 3 days of 115 mmol/d supplemental lysine chloride (N=10). At the Yale Transitional Care Center, 31.5% of patients had hypochloremia (chloride ≤96 mmol/L). Plasma renin concentration correlated with serum chloride (r=-0.46; P<0.001) with no incremental contribution from serum sodium (P=0.49). Hypochloremic versus nonhypochloremic patients exhibited renal wasting of chloride (P=0.04) and of chloride relative to sodium (P=0.01), despite better renal free water excretion (urine osmolality 343±101 mOsm/kg versus 475±136; P<0.001). Hypochloremia was associated with poor diuretic response (odds ratio, 7.3; 95% confidence interval, 3.3-16.1; P<0.001). In the interventional pilot, lysine chloride supplementation was associated with an increase in serum chloride levels of 2.2±2.3 mmol/L, and the majority of participants experienced findings such as hemoconcentration, weight loss, reduction in amino terminal, pro B-type natriuretic peptide, increased plasma renin activity, and increased blood urea nitrogen to creatinine ratio.

CONCLUSIONS

Hypochloremia is associated with neurohormonal activation and diuretic resistance with chloride depletion as a candidate mechanism. Sodium-free chloride supplementation was associated with increases in serum chloride and changes in several cardiorenal parameters.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02031354.

Reduced Cardiac Index Is Not the Dominant Driver of Renal Dysfunction in Heart Failure

BACKGROUND

It is widely believed that a reduced cardiac index (CI) is a significant contributor to renal dysfunction in patients with heart failure (HF). However, recent data have challenged this paradigm.

OBJECTIVES

This study sought to determine the relationship between CI and renal function in a multicenter population of HF patients undergoing pulmonary artery catheterization (PAC).

METHODS

Patients undergoing PAC in either the randomized or registry portions of the ESCAPE (Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness) trial were included (n = 575). We evaluated associations between CI and renal function across multiple subgroups and assessed for nonlinear, threshold, and longitudinal relationships.

RESULTS

There was a weak but significant inverse correlation between CI and estimated glomerular filtration rate (eGFR), such that higher CI was paradoxically associated with worse eGFR (r = -0.12; p = 0.02). CI was not associated with blood urea nitrogen (BUN) or the BUN to creatinine ratio. Similarly, no associations were observed between CI and better renal function across multiple subgroups defined by indications for PAC or hemodynamic, laboratory, or demographic parameters. A nonlinear or threshold effect could not be identified. In patients with serial assessments of renal function and CI, we were unable to find within-subject associations between change in CI and eGFR using linear mixed modeling. Neither CI nor change in CI was lower in patients developing worsening renal function (p ≥ 0.28).

CONCLUSIONS

These results reinforce evidence that reduced CI is not the primary driver for renal dysfunction in patients hospitalized for HF, irrespective of the degree of CI impairment or patient subgroup analyzed.

Renal tubular resistance is the primary driver for loop diuretic resistance in acute heart failure

BACKGROUND

Loop diuretic resistance is a common barrier to effective decongestion in acute heart failure (AHF), and is associated with poor outcome. Specific mechanisms underlying diuretic resistance are currently unknown in contemporary AHF patients. We therefore aimed to determine the relative importance of defects in diuretic delivery vs. renal tubular response in determining diuretic response (DR) in AHF.

METHODS AND RESULTS

Fifty AHF patients treated with intravenous bumetanide underwent a 6-h timed urine collection for sodium and bumetanide clearance. Whole-kidney DR was defined as sodium excreted per doubling of administered loop diuretic and represents the sum of defects in drug delivery and renal tubular response. Tubular DR, defined as sodium excreted per doubling of renally cleared (urinary) loop diuretic, captures resistance specifically in the renal tubule. Median administered bumetanide dose was 3.0 (2.0-4.0) mg with 52 (33-77)% of the drug excreted into the urine. Significant between-patient variability was present as the administered dose only explained 39% of variability in the quantity of bumetanide in urine. Cumulatively, factors related to drug delivery such as renal bumetanide clearance, administered dose, and urea clearance explained 28% of the variance in whole-kidney DR. However, resistance at the level of the renal tubule (tubular DR) explained 71% of the variability in whole-kidney DR.

CONCLUSION

Defects at the level of the renal tubule are substantially more important than reduced diuretic delivery in determining diuretic resistance in patients with AHF.

Informing etiologic research priorities for squamous cell esophageal cancer in Africa: A review of setting-specific exposures to known and putative risk factors

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers in most Eastern and Southern African countries, but its etiology has been understudied to date. To inform its research agenda, we undertook a review to identify, of the ESCC risk factors which have been established or strongly suggested worldwide, those with a high prevalence or high exposure levels in any ESCC-affected African setting and the sources thereof. We found that for almost all ESCC risk factors known to date, including tobacco, alcohol, hot beverage consumption, nitrosamines and both inhaled and ingested PAHs, there is evidence of population groups with raised exposures, the sources of which vary greatly between cultures across the ESCC corridor. Research encompassing these risk factors is warranted and is likely to identify primary prevention strategies.

Impact of the use of a rapid diagnostic test for visceral leishmaniasis on clinical practice in Ethiopia: a retrospective study

Background

Diagnostic guidelines for Visceral Leishmaniasis (VL) in the East African region are complex. Patients meeting the VL clinical case definition should be tested by rK39 rapid diagnostic test (RDT) followed by the Direct Agglutination Test (DAT) or tissue aspiration if RDT-negative. Otherwise, RDT-positive patients should be started on VL treatment. We evaluated how this guideline is adhered to by assessing the routine clinical practice in a university hospital in North-West Ethiopia.

Methods

Retrospective record analysis was done for all patients who had an rK39-RDT done at University of Gondar (UoG) Hospital between June 2012 and June 2013. We described the diagnostic work-up performed and the proportion initiated on VL treatment by test result.

Results/Findings

From a total of 928 patients tested, 308 (33.2%) were rK39 RDT-positive. Spleen or bone marrow aspiration was done for 237 (77.2%) RDT-positive patients. Of these, 165 were confirmed parasitologically, yielding a positive predictive value of 69.6%. Only 126 (20.3%) of the 620 patients with a negative rK39 test underwent further testing by tissue aspiration, of which 22 (17.5%) were also parasitology positive. HIV test results were available for 570 (61.4%) patients and 36 (6.3%) were HIV-infected. Of the 187 parasitologically confirmed patients, 182 (97.3%) were started on VL treatment.

Conclusions / Discussion

A negative rK39 test was often not followed by further testing and a positive rK39 test result was followed by tissue aspiration in three out of four cases. Further research is required to understand why the diagnostic work-up did not comply with the guidelines, including evaluating adherence to the VL clinical case definition and quality of rK39-RDT testing.

The introduction of RDTs is one of the major advancements in leishmaniasis control programs. While the variability in performance from one endemic region to the other is well recognized, the utilization of these RDTs in the routine clinical setting has not been evaluated to date. In this study, we showed that the RDT use in routine practice setting has large deviations from the guidelines. Clinical suspicion of VL should be based on the full criteria of case definition as is recommended in the guidelines and the presence of the criteria should be checked by clinicians before requesting the RDT. Not respecting these clinical criteria can lead to low pretest probability of the disease and eventually low positive predictive value of the test used. Additionally, introducing regular monitoring activities with training and quality assurance system for leishmania RDTs is very important.

Poor symptomatic tuberculosis screening practices in a quarter of health centres in Amhara Region, Ethiopia

SETTING

In 2011, Ethiopia introduced a strategy of symptomatic tuberculosis (TB) screening for patients attending out-patient services to increase identification of presumptive TB.

OBJECTIVE

To assess implementation and factors affecting symptomatic TB screening at out-patient departments in health centres in the Amhara Region, Ethiopia.

DESIGN

Using a cross-sectional study design, 86 randomly selected public health centres providing DOTS were included in the study. Data were captured by reviewing TB registers and interviewing key informants at out-patient services.

RESULTS

Of 86 health centres, 24 (28%) had poor symptomatic TB screening practices, defined as screening <80% of attending out-patients. Having an actively functioning multidisciplinary health centre team to assess TB services (aOR 2.29, 95%CI 2.23-30.80) and partner support for TB activities (aOR 4.84, 95%CI 1.05-22.40) were associated with higher TB screening rates, whereas availability of antiretroviral therapy was negatively associated. In all health centres combined, 1.6% of out-patient department attendees were identified as having presumptive TB.

CONCLUSION

A quarter of health centres had poor symptomatic TB screening practices in the out-patient services in this study. Strengthening multidisciplinary teams and expanding partner support are recommended to improve TB screening practices at out-patient services in Ethiopia.

Mathematical Modeling Of Glioma Proliferation And Diffusion

Gliomas, the most common of primary brain tumors, are known for their widespread invasion of tissue near the gross tumor mass. My research was based on my mentor's focus on developing mathematical models for the growth of gliomas within the central nervous system (CNS). The model focuses on two key parameters: D, the spread of glioma cells to tissues within the central nervous system, and ρ, the net proliferation rate of glioma cells. The model was created to account for the fact that even after gross total resection of portions of the tumor detectable on magnetic resonance imaging (MRI) scans, invasive glioma cells are found in tissues surrounding the area of resection. Additionally, this model considers the location of the tumor within the CNS because tumor cells are known to diffuse at a faster pace in white matter compared to grey matter. As a result a more accurate prediction of the patient's longevity and the time period of the tumor's inevitable recurrence can be made. This accuracy will allow physicians to make improved diagnosis and treatment of gliomas, thereby extending the patients' survival.

Aetiology and outcome of non-traumatic altered states of consciousness in north western Ethiopia

Awareness of the relative prevalence of diseases causing altered states of consciousness (ASC) in a particular geographic locality could greatly facilitate the approach to patient management. This prospective study has, therefore, evaluated 202 patients with ASC admitted to the medical wards of GCMS teaching hospital in a two year period, between January 1994 and December 1995. ASC was defined as a clinical state manifested by conditions ranging from confusion and disorientation in person, place and time to stupor and deep coma. History, physical examination, limited laboratory tests and course of the patient in the hospital were used to identify the aetiology. There were 122 (60.4%) males and 80 (39.6%) females with male to female ratio of 3:2. Most of the patients, 122 (60.4%), belong to the age group below 40 years and the median age was 33 years (range = 15.84). The median duration of hospital stay was six days (range = 1-90). The commonest cause was infections, 111 (55%) followed by metabolic disorders, 45 (22.3%), structural lesions, 30 (14.9%) and poisoning, seven (3.5%). The aetiology was not identified in nine (4.5%) of the patients. Cerebral malaria was the commonest infectious cause followed by chronic meningitis and/or encephalitis. In hospital mortality rate was 60.4%. Unknown diagnosis, structural neurologic and metabolic causes were associated with increased mortality rate, with p values of 0.002, 0.009 and 0.015, respectively. The same was true for presence of HIV infection, P = 0.02. Since infectious causes are the commonest causes in our series, of which most are treatable with a relatively favourable outcome, critical evaluation for infections and early intervention is recommended. In addition, diagnostic facilities, especially for structural central nervous system lesions has to be improved because successful treatment and prognosis depends on the identification of a specific aetiology.