RENAL STRESS AND ELECTROLYTE RESPONSES DURING THE BOSTON MARATHON

Marathon running is known to increase the risk for acute kidney injury (AKI), due to high levels of muscle damage, dehydration, reduced renal filtration and heat stress. The Boston Marathon provides a unique combination of stress for the kidneys due to the net downhill course, variable environmental conditions, and faster finish times compared to other marathon events. PURPOSE: Observe hydration, electrolyte and renal stress biomarkers pre- and post-race. METHODS: Thirty-seven males (52 ± 11 y, 1.72 ± 0.1 m, 3.69 ± .63 hr), and thirty-eight females (38 ± 12 y, 1.67 ± 0.08 m, 3.78 ± .58 hr) provided blood at marathon expo (1-2 days prior to race), urine and body mass pre-race (within 1 hr) and immediately post-race (within 30 min of finishing). Blood samples were analyzed via i-stat CHEM8+ cartridges. Urine was analyzed for specific gravity (USG) via refractometry. Pre- versus post-race differences were evaluated using paired samples t-tests and correlations were run between variables. Significance was set a priori as p < .05. RESULTS: There were significant differences between pre- versus post-race for serum sodium [Na+] (pre: 140 ± 2; post: 142 ± 2 mEq/L), [Cl-] (pre: 101 ± 2; post: 103 ± 3 mEq/L), BUN (pre: 17 ± 4; post: 20 ± 5 mmol/L), creatinine (pre: 0.9 ± 0.2; post: 1.5 ± 0.4 mg/dL), USG (pre: 1.009 ± 0.007; post: 1.016 ± 0.015), and body mass (pre: 64.5 ± 9.8; post: 62.5 ± 9.1 kg) (all p < .001). Serum [K+] was similar at pre- (4.2 ± 0.4 mEq/L) and post-race (4.6 ± 4.0 mEq/L; p = .403). Serum creatinine increased by at least 0.3 mg/dL 69% of our participants. We did not detect sex differences in markers of hydration, electrolytes, or renal stress (all p > 0.08). CONCLUSION: Our data demonstrate increases in markers of renal stress and hypohydration with minor alterations in serum electrolyte balance during the Boston Marathon. Future work is needed to explore AKI risk using more specific, urine-based biomarkers and methods to facilitate recovery following the race. Supported by: This study was funded by the Boston Athletic Association Medical Research Grant Program.