THE EFFECT OF SODIUM BICARBONATE ON ACUTE KIDNEY INJURY MARKERS DURING PHYSICAL WORK IN THE HEAT

Abstract

Sodium bicarbonate supplementation (NaHCO3) before physical work in the heat may reduce the risk of developing acute kidney injury (AKI). Purpose: To determine the effects of NaHCO3 supplementation before a prolonged bout of physical work in the heat on AKI markers and kidney function. Method: A randomized, cross-over, double blinded design was conducted on 8 participants (3 females) who consumed NaHCO3 (0.2 g/kg body weight) or placebo (CON) before prolonged (120 minutes) moderate intensity (~65% of maximal heart rate) physical work in the heat (40℃ and 23% relative humidity (RH)). Blood and urine samples were collected pre, post, and 1hr post exercise. Core temperature (Tc) and heart rate (HR) were measured every three minutes, and perceptual variables [i.e., rating of perceived exertion (RPE), thermal sensation (TS), and comfort scale (CS)] were measured every 6 minutes. Gastrointestinal discomfort (GI) was evaluated pre- and post NaHCO3 or placebo (CON) ingestion, within 1hr of the physical work, post physical work, and 1hr post physical work. Urine flow rate (UFR) was calculated pre and 1hr post physical work. Urine osmolality (Uosm) and creatinine (uCr) and plasma osmolality (Posm) were assessed pre, post, and 1hr post physical work. Insulin-like growth factor binding protein 7 (IGFBP7), tissue inhibitor of metalloproteinase 2 (TIMP-2), and neutrophil gelatinase-associated lipocalin (NGAL) were measured in the urine pre and 1hr post physical work. Results: Physiological, perceptual, and GI parameters increased over time (p < 0.05), but they were not different between conditions (p > 0.05). Uosm was higher in CON compared to NaHCO3 (p = 0.011) post exercise. UFR was lower in CON compared to NaHCO3 at 1 hour post exercise (p = 0.042). Urine TIMP-2 corrected for UFR was higher in CON compared to NaHCO3 (p =0.040). IGFBP-7 × TIMP-2 corrected for UFR trended to be lower in NaHCO3 (p = 0.062). Conclusion: NaHCO3 72 ingestion pre-physical work in the heat reduced markers of AKI and increased UFR suggesting less stress to the kidneys.