Chloride dipstick to rapidly estimate urine sodium during diuresis in acute heart failure.

Background: Rapid assessment of diuretic efficacy is necessary in the treatment of acute decompensated heart failure. European guidelines advocate for the use of spot urinary sodium measurements, but recent data suggest urinary chloride is the better marker. Laboratory turnaround, however, delays clinical decision-making. We tackle this by using a commercially available chloride urinary dipstick to estimate sodium and measure chloride.

Methods: This was a prospective pilot study involving patients hospitalized at the University of Michigan for acute decompensated heart failure (ADHF) with an indication for intravenous diuresis; patients were eligible for enrollment within 24 h of admission. Patients with end-stage kidney disease or receiving continuous loop diuretic infusions or thiazide-type diuretics were excluded. A spot urine sample was collected after the loop diuretic dose. A chloride dipstick was used, and results were compared against laboratory-obtained measurements of urinary chloride and sodium.

Results: In a total of 22 patients (mean age 62.2 ± 11.8 years, 50% female, and LVEF 31.8 ± 17.4%), dipstick chloride concentrations correlated highly with laboratory-measured urine chloride (r = 0.98, p < 0.001) with slight overestimation across the physiological range and with laboratory-measured urine sodium (r = 0.86, p < 0.001), although with greater variation. Dipstick interpretation preceded laboratory results by a median of 136 minutes (IQR 103-170, p < 0.001).

Conclusions: The chloride dipstick rapidly and accurately assessed urine chloride almost 2 h faster than traditional laboratory output in patients undergoing diuresis for ADHF. It may be a new tool to evaluate loop diuretic treatment for ADHF. However, more studies are needed to assess its impacts on clinical outcomes.