Acute hydration status and micro‐vascular function in healthy human volunteers (LB363)

Abstract

Introduction: Water is critical for most physiological functions and dehydration can be pathological. There is evidence that long‐term hydration impacts cardiac reactivity, however, there is little data on acute hydration status and micro‐vascular function. Aim: To investigate whether hydration status impacts capillary blood flow and endothelial function in healthy human volunteers. Methods: Hydration status was measured in 20 subjects (45.1±7.4y; 9 M; 11 F) using osmometry for urine osmolality and dipstick for urine specific gravity (USG). Micro‐vascular function was measured using controlled Laser Doppler Iontophoresis (Moor LDI), with acetylcholine (ACh) and sodium nitroprusside (SNP), delivered to dermal forearm vessels using graded currents (0µA x 5s; 40µA x 10s; 60 µA x 30s; 100 µA x 60s). Results: Mean urine osmolality was 271.5 mOsm/kg and mean USG 1006.9. No correlations were found (p>0.05) between urine osmolality and ACh or SNP at any current, using linear regression. Similarly, no correlation was found between USG and ACh. A small but significant relationship was found between USG and SNP at 40µA (p=0.048). Conclusion: Based on these results, it appears that acute hydration status may not be a strong predictor of micro‐circulatory response to SNP and ACh. However, as SNP at 40 µA is correlated with USG, larger studies are needed to investigate further and explore whether USG is a more sensitive hydration marker in a micro‐circulatory/endothelial context.