Estimation of Plasma Renin Activity on the Basis of Serum and Urinary Chloride Concentrations versus Sodium Concentrations

INTRODUCTION

The present study examined the possible estimation of plasma renin activity (PRA) by serum and urinary concentrations of chloride versus sodium in acute and chronic heart failure (HF).

METHODS

Data from 29 patients with acute HF (48% men; 80.3 ± 12 years) and 26 patients with recovery of HF after decongestive therapy (50% men; 81.2 ± 12 years) were analyzed. Blood and urine samples were obtained immediately before decongestive therapy in acute HF patients. Clinical tests included peripheral blood tests, serum and spot urinary electrolytes, and plasma neurohormones. Sodium- or chloride-related indices included serum ([sNa+] or [sCl-]) and urinary ([uNa+] or [uCl-]) concentrations, their differences, and their ratio. Linear regression analysis was used for correlation coefficients.

RESULTS

PRA levels higher than the normal range were detected in only 5 (17%) of 29 patients with acute HF, but in as many as 11 (42%) of 26 patients with chronic HF. In the 29 patients with acute HF, all the chloride- and sodium-related indices except for [sNa+] were correlated with PRA: the [sCl-]/[uCl-] ratio was best correlated with PRA (R2 = 0.84, p < 0.0001) followed by the [sNa+]/[uNa+] ratio (R2 = 0.64, p < 0.0001). In the 26 patients with chronic HF, however, both the [sCl-] (R2 = 0.36, p = 0.001) and [sNa+] (R2 = 0.22, p = 0.016) were only weakly correlated with PRA.

CONCLUSION

In acute HF, chloride-related indices derived from serum and urinary concentrations were firmly associated with PRA or better than sodium-related indices. In chronic HF, either chloride- or sodium-related indices were not firmly associated with PRA, presumably due to influence of cardiovascular medication.

Rationale and validation of predicting high sodium intake by spot urinary chloride in patients with chronic kidney disease

OBJECTIVE

To analyze the rationale and evaluate the validity of spot urinary chloride or derived formulas to predict high sodium intake in patients with chronic kidney disease (CKD).

METHODS

We collected consecutive CKD patients at stages 1-4 who were admitted to our Nephrology department in a single center from January 01, 2014, to December 31, 2017, and tested spot and 24-hour urinary analysis on the same day. The feasibility of urinary chloride to predict urinary sodium was firstly analyzed by calculating their correlations. The validity of predicting excessive sodium intake by spot urinary sodium and chloride, two derived formulas based on spot urinary sodium or chloride, and our previous "CKDSALT" equation were accessed. We finally conducted Receiver operating characteristic (ROC) curves to compare their performance in detecting high sodium intake.

RESULTS

All 5204 patients were eventually analyzed. In the derivation cohort (n = 2447), a strong positive linear correlation existed between urinary sodium and chloride in both spot urine (R² = 0.804) and 24-hour urine samples (R² = 0.905), and two predictive equations based on spot urinary sodium or chloride were derived. In the validation cohort (n = 2757), spot urinary sodium and chloride only showed "fair" performance. However, both urinary sodium and chloride equations had a "good" performance in ICC, Pearson's correlation, Bland-Altman plots, and ROC curves, while and CKDSALT equation showed the best performance.

CONCLUSIONS

Spot urinary chloride is a feasible method to predict and monitor high sodium intake in CKD patients, while a novel derived formula could elevate its diagnostic accuracy.

Evaluation of urinary chloride dipsticks for the rapid estimation of hydration status in patients receiving artificial nutrition: Feasibility study

BACKGROUND AND AIMS

The home parenteral nutrition (HPN) population face many challenges, especially with respect to fluid balance management. A low urinary sodium concentration of <20 mmol/L is commonly used as an indicator of dehydration that requires clinical assessment in these patients. The Quantab titrator dipstick measures chloride concentration of a solution and correlates with sodium concentration. We assessed whether it would be feasible to use the Quantab dipstick in the HPN population and explored relationships between Quantab dipstick estimated chloride concentration and quality of life (QOL).

METHODS

Patients on HPN were asked to collect urine samples at 5 specific times points (day 0,7,14, 21 and 28) to send to the laboratory for formal electrolyte analysis. The participant and a member of laboratory staff tested these samples with the Quantab dipstick to estimate urinary chloride concentration. Participants were instructed to complete a QOL questionnaire at each of the 5 time-points in addition to a baseline demographic questionnaire and an end-of-study questionnaire. Six participants completed an interview at the end of the study period. The relationship between participant-derived and laboratory-derived data was assessed using rank correlation coefficients. QOL assessment was correlated with urine dipstick measurements.

RESULTS

10 patients on HPN completed the study. Data on chloride concentration as estimated by the dipstick (assessed by participants and by the laboratory) and sodium concentration from the laboratory were available for 47 urine samples. There was a positive relationship between participant dipstick estimated chloride concentration and laboratory sodium (Kendall's τ = 0.45; P < 0.001; Spearman's r_s = 0.58 P < 0.001; 47 pairs). There was a strong correlation between chloride concentrations estimated by dipstick in the laboratory and by participants (Kendall 0.58 p < 0.001, Spearman's 0.69 p < 0.001; 47 pairs). In exploratory analyses, there was no relationship between QOL and dipstick estimated chloride concentration. Participants had no issues collecting urine samples but some difficulties were reported with determining the dipstick reading.

CONCLUSIONS

Patients on HPN are able to collect urine specimens, complete QOL questionnaires, and are capable of using the Quantab dipstick to estimate urinary chloride concentration. The Quantab dipstick correlates with laboratory measured sodium and chloride concentrations. Further work is required to fully establish whether this point-of-care test could be used to guide fluid balance management in the HPN population.

Real-time urinary electrolyte monitoring after furosemide administration in surgical ICU patients with normal renal function

Background

Although the loop-diuretic furosemide is widely employed in critically ill patients with known long-term effects on plasma electrolytes, accurate data describing its acute effects on renal electrolyte handling and the generation of plasma electrolyte alterations are lacking. We hypothesized that the long-term effects of furosemide on plasma electrolytes and acid–base depend on its immediate effects on electrolyte excretion rate and patient clinical baseline characteristics. By monitoring urinary electrolytes quasi-continuously, we aimed to verify this hypothesis in a cohort of surgical ICU patients with normal renal function.

Methods

We retrospectively enrolled 39 consecutive patients admitted to a postoperative ICU after major surgery, and receiving single low-dose intravenous administration of furosemide. Urinary output, pH, sodium [Na⁺], potassium [K⁺], chloride [Cl⁻] and ammonium [NH₄⁺] concentrations were measured every 10 min for three to 8 h. Urinary anion gap (AG), electrolyte excretion rate, fractional excretion (Fe) and time constant of urinary [Na⁺] variation (τNa⁺) were calculated.

Results

Ten minutes after furosemide administration (12 ± 5 mg), urinary [Na⁺] and [Cl⁻], and their excretion rates, increased to similar levels (P < 0.001). After the first hour, urinary [Cl⁻] decreased less rapidly than [Na⁺], leading to a reduction in urinary AG and pH and an increment in urinary [NH₄⁺] (P < 0.001). Median urinary [Cl⁻] over the first 3-h period was higher than baseline urinary and plasmatic [Cl⁻] (P < 0.001). During the first 2 h, difference between FeCl⁻ and FeNa⁺ increased (P < 0.05). Baseline higher values of central venous pressure and FeNa⁺ were associated with greater increases in FeNa⁺ after furosemide (P = 0.03 and P = 0.007), whereas higher values of mean arterial and central venous pressures were associated with a longer τNa⁺ (P < 0.05). In patients receiving multiple administrations (n = 11), arterial pH, base excess and strong ion difference increased, due to a decrease in plasmatic [Cl⁻].

Conclusions

Low-dose furosemide administration immediately modifies urinary electrolyte excretion rates, likely in relation to the ongoing proximal tubular activity, unveiled by its inhibitory action on Henle’s loop. Such effects, when cumulative, found the bases for the long-term alterations observed. Real-time urinary electrolyte monitoring may help in tailoring patient diuretic and hemodynamic therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-016-0168-y) contains supplementary material, which is available to authorized users.