Development and double cross-validation of new spot urine sodium equation to predict 24-h urine sodium in the Malaysian population

BACKGROUND

Monitoring sodium intake through 24-h urine collection sample is recommended, but the implementation of this method can be difficult. The objective of this study was to develop and validate an equation using spot urine concentration to predict 24-h sodium excretion in the Malaysian population.

METHODS

This was a Malaysian Community Salt Study (MyCoSS) sub-study, which was conducted from October 2017 to March 2018. Out of 798 participants in the MyCoSS study who completed 24-h urine collection, 768 of them have collected one-time spot urine the following morning. They were randomly assigned into two groups to form separate spot urine equations. The final spot urine equation was derived from the entire data set after confirming the stability of the equation by double cross-validation in both study groups. Newly derived spot urine equation was developed using the coefficients from the multiple linear regression test. A Bland-Altman plot was used to measure the mean bias and limits of agreement between estimated and measured 24-h urine sodium. The estimation of sodium intake using the new equation was compared with other established equations, namely Tanaka and INTERSALT.

RESULTS

The new equation showed the least mean bias between measured and predicted sodium, - 0.35 (- 72.26, 71.56) mg/day compared to Tanaka, 629.83 (532.19, 727.47) mg/day and INTERSALT, and 360.82 (284.34, 437.29) mg/day. Predicted sodium measured from the new equation showed greater correlation with measured sodium (r = 0.50) compared to Tanaka (r =0.24) and INTERSALT (r = 0.44), P < 0.05.

CONCLUSION

Our newly developed equation from spot urine can predict least mean bias of sodium intake among the Malaysian population when 24-h urine sodium collection is not feasible.

Spot urine sodium in acute heart failure: differences in prognostic value on admission and discharge

AIMS

Most studies examined spot urine sodium's (sUNa⁺ ) prognostic utility during the early phase of acute heart failure (AHF) hospitalization. In AHF, sodium excretion is related to clinical status; therefore, we investigated the differences in the prognostic information of spot UNa⁺ throughout the course of hospitalization for AHF (admission vs. discharge).

METHODS AND RESULTS

The study population were AHF patients (n = 172), who survived the index hospitalization. We compared the relationship between early (on admission, at 24 and 48 h) and discharge sUNa⁺ measurements with post-discharge study endpoints: composite of 1 year all-cause mortality and AHF rehospitalization (with time to first event analysis) as well as with each event in separation. There were 49 (28.5%) deaths, 40 (23.3%) AHF rehospitalizations, while the composite endpoint occurred in 69 (40.1%) during 1 year follow-up. The sUNa⁺ had prognostic significance for the composite endpoint when assessed on admission, at 24 and at 48 h: hazard ratios (HRs) with 95% confidence intervals (CIs) (per 10 mmol/L) were 0.88 (0.82-0.94); 0.87 (0.81-0.91); 0.90 (0.84-0.96), all P < 0.005. In contrast to early, active decongestion phase, discharge sUNa⁺ had no prognostic significance HR (95% CI) (per 10 mmol/L): 0.99 (0.93-1.06) P = 0.79 for the composite endpoint, which was independent from the dose of oral furosemide prescribed at that timepoint (average causal mediation effects: -0.38; P = 0.71). Similarly, discharge sUNa⁺ was neither associated with 1 year mortality HR (95% CI) (per 10 mmol/L): 0.97 (0.89-1.05) P = 0.48 nor with AHF rehospitalizations HR (95% CI) (per 10 mmol/l): 1.03 (0.94-1.12), P = 0.56. The comparison of longitudinal profiles of sUNa⁺ during hospitalization showed significantly higher values within the early, active decongestive phase in those who did not experience composite endpoint when compared with those who did: admission: 94 ± 34 vs. 76 ± 35; Day 1: 85 ± 36 vs. 65 ± 37; Day 2: 84 ± 37 vs. 67 ± 35, all P < 0.005 (mmol/L), respectively. There was no difference between those groups in discharge sUNa⁺ : 73 ± 35 vs. 70 ± 35 P = 0.82 (mmol/L).

CONCLUSIONS

Spot UNa⁺ assessed at early phase of hospitalization and at discharge have different prognostic significance, which confirms that it should be always interpreted along with clinical context.

Renal profiling based on estimated glomerular filtration rate and spot urine sodium identifies high-risk acute heart failure patients

AIMS

In acute heart failure (AHF), assessment of renal function comprises estimation of glomerular filtration rate (eGFR), which does not provide any information about renal sodium/water handling. We describe the interactions between urinary sodium concentration and eGFR to better characterize AHF patients.

METHODS AND RESULTS

In 219 patients with AHF, spot urine sodium (UNa⁺ ) and eGFR were assessed on admission, day 1 and day 2 of hospitalization. We found no correlation between UNa⁺ and eGFR (calculated on each consecutive day, as an average of all three values, and as changes from baseline; all P > 0.05). The population was subsequently divided into four profiles based on eGFR (preserved vs. impaired; cutoff of 60 mL/min/1.73 m² ) and UNa⁺ (sodium excreter vs. non-excreter; cutoff of 60 mmol/L). At day 1, there were 70 (31.9%) patients classified as preserved eGFR/sodium excreter, 37 (16.8%) as impaired eGFR/sodium non-excreter, 72 (32.9%) as impaired eGFR/sodium excreter, and 40 (18%) as preserved eGFR/sodium non-excreter. Both sodium non-excreter profiles were associated with an increased risk of in-hospital heart failure worsening [odds ratio (OR) 2.8, 95% confidence interval (CI) 1.3-6.4], inotrope use (OR 2.6, 95% CI 1.1-6.7) and rehospitalization due to AHF (OR 3.2, 95% CI 1.6-6.2; all P < 0.05). The preserved eGFR/sodium non-excreter profile was associated with highest 1-year mortality (52.5%) and remained an independent prognosticator after adjustment for other prognosticators (hazard ratio 2.9, 95% CI 1.7-5.2; P < 0.0005).

CONCLUSIONS

In AHF, values of spot UNa⁺ and eGFR are not interrelated. Concomitant assessment of eGFR and spot UNa⁺ may be useful for better clinical and therapeutic profiling of patients.

Elevated plasma endothelin-1 is related to low natriuresis, clinical signs of congestion, and poor outcome in acute heart failure

AIMS

Endothelin-1 (ET-1) is a potent vasoconstrictor, which regulates renal and vascular function. We aimed to relate plasma levels of ET-1 with the clinical picture and outcomes in acute heart failure (AHF).

METHODS AND RESULTS

We studied 113 patients with AHF [mean age 65 ± 13 (years), median (upper and lower quartiles) N-terminal pro-B-type natriuretic peptide, 5422 (2689; 8582) (pg/mL)], in whom plasma levels of ET-1 were serially measured at admission (10.8 ± 5.2), Day 1 (9.5 ± 3.4), and Day 2 (8.9 ± 3.8) (pg/mL). The population was divided into tertiles across baseline ET-1 levels. Patients in the highest ET-1 tertile had predominant clinical signs of peripheral congestion; however, no difference was observed in pulmonary congestion and severity of dyspnoea. They also presented lower spot urine sodium at admission (75 ± 35 vs. 99 ± 43 vs. 108 ± 30), 6 h (84 ± 34 vs. 106 ± 43 vs. 106 ± 35), and Day 1 (75 ± 38 vs. 96 ± 36 vs. 100 ± 35) (mmol/L), when compared with the second and first tertile, respectively (all P < 0.05); furthermore, they received higher doses of intravenous furosemide from Day 2 and had longer intravenous diuretics, as median switch to oral furosemide was 4 (3; 4) vs. 3 (2; 4) vs. 2 (2; 3) (days), respectively, P < 0.05. There was no difference in serum creatinine, urea, and renal injury biomarkers (kidney injury molecule-1, serum cystatin C, and urine neutrophil gelatinase-associated lipocalin) between the ET-1 tertiles. Higher values of ET-1 measured at each time point were related with a higher risk of 1 year mortality.

CONCLUSIONS

Elevation of ET-1 is related to clinical signs of peripheral congestion, low urine sodium excretion, and poor outcome in AHF.

Diuretic Resistance in Heart Failure

Purpose of review:

Diuretic resistance (DR) occurs along a spectrum of relative severity and contributes to worsening of acute heart failure (AHF) during an inpatient stay. This review gives an overview of mechanisms of DR with a focus on loop diuretics and summarizes the current literature regarding the prognostic value of diuretic efficiency and predictors of natriuretic response in AHF.

Recent findings:

The pharmacokinetics of diuretics are impaired in chronic heart failure, but little is known about mechanisms of DR in AHF. Almost all diuresis after administration of a loop diuretic dose occurs in the first few hours after administration and within-dose DR can develop. Recent studies suggest that DR at the level of the nephron may be more important than defects in diuretic delivery to the tubule. Because loop diuretics induce natriuresis, urine sodium (UNa) concentration may serve as a functional, physiologic and direct measure for diuretic responsiveness to a given loop diuretic dose.

Summary:

Identifying and targeting individuals with DR for more aggressive, tailored therapy represents an important opportunity to improve outcomes. A better understanding of the mechanistic underpinnings of DR in AHF is needed to identify additional biomarkers and guide future trials and therapies.