Renal Stress Responses To Work In The Heat Comparing Different Hydration Regimens

Abstract

Workplace safety organizations recommend that workers predicted to incur heavy sweat loss should consume a ‘sport drink’ during work. These sugar-sweetened beverages (SSB) often include fructose, which can lead to acute kidney injury (AKI), especially when combined with hypohydration. PURPOSE: Investigate the effect of SSB on renal stress in response to simulated industrial work in the heat, while maintaining euhydration. METHODS: Twenty male participants (24 ± 2y, 179 ± 6cm, 24.7 ± 9.0% body fat) completed two randomized, matched trials of simulated industrial work (2-hr total; two 45-min work and two 15-min rest bouts) in the heat (30oC, 55% RH). Equal amounts of SSB or placebo were provided during rest and within 2-hr of completing work. Urine specific gravity (USG), heart rate (HR), and rectal temperature (Trec) were monitored throughout trials. Serum [Na+], hemoglobin, and hematocrit levels were measured at baseline, pre- and post-work, and 16-hr post-work. Urinary kidney injury molecule-1 (uKIM-1) and urinary neutrophil gelatinase-associated lipocalin (uNGAL) were measured pre- and post-work, 3-hr and 16-hr post-work. Total urine volume was measured for 16-hrs following work. Change in plasma volume (ΔPV) was calculated using the Dill & Costill equation. RESULTS: There was no significant trial difference in USG (p=.277) or HR (p=.209), but post-work (p≤.011) and 16-hr post-work USG were elevated compared to baseline (p=.043) and 3-hr post-work (p=.001). There was no difference in maximum Trec achieved between trials (SSB 38.84 ± 0.52oC; placebo 38.68 ± 0.40oC; p=.330). Serum [Na+] was elevated post-work compared to baseline and 16-hr post-work (p=.006), but there was no trial difference (p=.612). There was no trial difference in hemoglobin (p=.650) or hematocrit (p=.637). uKIM-1 was elevated post-work and 16-hr post-work compared to baseline (p≤.028) and 3-hr post-work (p≤.009), but showed no trial difference (p=.126). uNGAL 3-hr post-work was significantly lower than baseline (p=.011), but showed no trial difference (p=.992). There was no significant trial difference in total urine volume (p=.277) or ΔPV (p=.098). CONCLUSION: These findings indicate that beverage type did not affect renal stress biomarkers following simulated industrial work in the heat when euhydration was maintained.